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PUBLICATIONS

RAPID

SOLIDIFICA TION

TECHNOLOGY

Report of the First Workshop

Edited by

Robert Mehrabian and

Jerome Persh

This document contains information which is subject to special

export controls. It should not be transferred to foreign nationals

in the U.S. or abroad without a validated export license.

(Reference Export Administration Regulations, Section 387.1,

1 October 1980 and Federal Register, 1 October 1980,

Volume 45, No. 192, Page 65014.)

Sponsored by

Committee on Materials (COMAT)

Ad Hoc Working Group on RST

Hosted By

National Measurement Laboratory

National Bureau of Standards

NATIONAL EUSEAU

OF STANDARDS UBRARt MAY I ,' j /lot

RAPID

SOLIDIFICATION

TECHNOLOGY

Report of the First Workshop

NATIONAL BUREAU OF STANDARDS

GAITHERSBURG, MARYLAND

July 1-2, 1981

Sponsored by

Committee on Materials (COMAT)

Ad Hoc Working Group on RST

Hosted By

National Measurement Laboratory

National Bureau of Standards

CONTENTS

Committee on Materials Ad Hoc Working Group

on Rapid Solidification Technology iv

BriefingA^orkshop Organizing Committee v

Introduction 1

Ferrous and Specialty Materials 5

Light Alloys 19

Superalloys 31

Appendix 47

iii

Coimnittee on Materials

Ad Hoc Working Group on

RAPID SOLIDIFICATION TECHNOLOGY

Chairman; J. Persh, COMAT/RST, OSD/OUSD R and E

(ET) , The Pentagon, Washington, DC

Members; J. I. Bryant, HQ DA/DAMA, The Pentagon,

Washington, DC

M. Greenfield, National Aeronautics and

Space Administration, Washington, DC

L. C. lanniello, U.S. Dept, of Energy,

Washington, DC

T. Jacobs, Office of Assistant Secretary

of Navy [RES] , Washington, DC

R. Kagarise, National Science Foundation,

Washington, DC

R. Mehrabian, National Bureau of

Standards, Washington, DC

K. W. Mlynarski, Bureau of Mines,

Washington, DC

Col. J. Morgan, Air Force Systems Command,

Andrews Air Force Base, Maryland

R. Schmidt, Naval Air Systems Command,

Washington, DC

E. C. van Reuth, Defense Advanced Research

Projects Agency, Arlington, VA

J. Wachtman, Jr., National Bureau of

Standards, Washington, DC

R. Woody, Dept, of State, Washington, DC

IV
BRIEFINGA^3RKSH0P

Organizing Committee

Chairman: R. Mehrabian, National Bureau of Standards,

Washington, DC

Members: A. Adair, Air Force Wright Aeronautical

Laboratories, Materials Laboratory,

Wright Patterson AFB, OH

M. Greenfield, National Aeronautics and

Space Administration, Washington, DC

S. Isserow, AMMRC, Watertown, MA

Lt. Col. L. Jacobson, Defense Advanced

Research Projects Agency, Arlington, VA

R. Kagarise, National Science Foundation,

Washington, DC

J. R. Manning, National Bureau of

Standards, Washington, DC

K. W. Mlynarski, Bureau of Mines,

Washington, DC

J. Persh, OSD/OUSD R and F (FT) , The

Pentagon, Washington, DC

D. F. Polk, Office of Naval Research,

Arlington, VA

Major F. Ross, Air Force Systems Command,

Andrews Air Force Base, Maryland

R. Schmidt, Naval Air Systons Command,

Washington, DC

D. P. Voss, Air Force Wright Aeronautical

Laboratories, Materials Laboratory,

Wright Patterson AFB, OH

J. Waldman, U.S. Army Armament R and D

Command, Dover, NJ

S. M. Wolf, U.S. Dept, of Energy,

Washington, DC

V
INTRODUCTION

The first BriefingA^orkshop on Rapid Solidification

Technology (RST) was convened on July 1-2, 1981 at the

National Bureau of Standards in Gaithersburg, Maryland.

It was sponsored by the Office of Science and Technology

Policy Cornmittee on Materials (COIAT) /Rapid

Solidification Technology Ad Hoc Working Group.* The

aim of this Briefing/Workshop was to first provide the

private sector with the government-wide implementation

strategy for RST in the next five years; and second, to

seek industry/university input and involvement in order

to effect a wider range of applications of this

technology-based "breakthrough." This report is the

proceedings of the deliberations from the Workshop

portion of the meeting. The material was obtained from

detailed notes and summaries given to us by the

Recorders and Moderators of the three different Workshop

Task Groups. A preliminary draft of proce^ings was

forwarded to the Moderators, the Briefing/Workshop

Coordinating Committee* and the CCMAT Ad Hoc Working

Group for their comments and suggestions. The inputs

received are incorporated in the final version of the

report presented here.

The major attention of RST has been directed toward the

development of processes which would permit achievement

of fast cooling rates from the pre-alloyed liquid state.

Such processes have typically involved: (a)

solidification of small droplets, followed by their

subsequent consolidation via powder-metallurgy

techniques into bulk-pieces and net shapes, or (b) the

melt spinning of continuous or discontinuous lengths of

filaments and thin ribbons, or (c) the in situ melting,

sometimes coupled with alloying and compositing, of

metallic surface layers.

*Lists of the members of the Ad Hoc Working Group and

the Briefing/Workshop Coordinating Committee are given

on pages iv and v, respectively.

1
There is ample evidence that rapid solidification of

pre-alloyed liquids leads to improved homogeneity,

structural refinement, control of grain size and

precipitate distributions in the resulting solid. For

certain alloy compositions, the solid forming is

amorphous and possesses exceptional magnetic

properties. A further important aspect of this new

technology is the development of new alloys with reduced

segregation which will lead to cost-beneficial

properties in final shapes or coatings of technological

importance.

The advent of RST has catalyzed new ideas across the

wide spectrum of alloy structures, properties, and

performance. A number of useful new alloys and products

have already emerged from this rapidly evolving field.

At the same time, striking advances have been made in our understanding of the phenomena associated with rapid

solidification, which promises to further expand the areas of applications.

This Brief ingA^orkshop stemmed from our recognition that

in order to achieve a wide-scale exploitation of this

new technology university/industry input, involvement

and support should go along with the implementation of

the government-wide program. A number of U.S. firms are already conducting in-house research and developi^nt

programs directed at their product lines. Some

industrial laboratories are investing in new methods for

producing rapidly solidified alloys. It is much too

early to predict which methods will best produce

superior products in a cost-effective way, but it is

safe to assume that a variety of techniques will emerge

which are tailored to specific manufacturing processes.

During the first day of the meeting, coordinated

briefings were given of the government-wide program and

implementation strategy. The specific lectures for the

2
Briefing were prepared jointly by the Coordinating

Committee of the Briefing/Workshop. The program for

both the Briefing and the Workshop is given in the

Appendix to this report.

A Workshop/Task Group format, organized by industry

sectors (i.e., ferrous and specialty materials, light

alloys, and superalloys industries ) was followed on the

late afternoon of the first day and throughout the

second day to permit a wide range of inputs from the

attendees. The majority, of the two hundred and seventy

five Workshop participants were from industry. The

actual percentages were: 68 percent from industry, 11

percent from academia and 21 percent from government.

These percentages also reflect a fair representation of

participation in the three Workshop Task Groups. The

number of participants in the Task Groups were: 102 in

Ferrous and Specialty Materials, 75 in Light Alloys, and

98 in Superalloys.

Two to three Moderators ( from outside the government) were assigned to each Workshop Task Group. The

Moderators first discussed pre-selected questions to be

addressed by the Workshop. Input was sought from the

participants on other questions of importance for the

Workshop agenda. For example, two of the pre-selected

questions were modified in the Superalloy Workshop and

four new questions were added at the suggestion of the

participants. An assigned speaker initiated the

discussion on each question with a five- to ten-minute

presentation, thus opening avenues for further

deliberations. At the end of the apportioned time for

the question, the Moderators summarized the conclusions

and recommendations emanating from the discussion and

moved on to a new subject. At the end of the second day

the Moderators of each Workshop Task Group reported the

findings to all the attendees in a joint final session.

3
4
FERROUS AND SPECIALTY MATERIALS

The participants in this Workshop proved to have a wide

range of interests, reflecting the differently oriented

constituencies in crystalline vs amorphous materials, in

structural vs magnetic materials, and in the disparate

nature of the ferrous metallurgy field as it is

beginning to learn about RST. The available time for

this Workshop was divided between crystalline ferrous

materials and amorphous alloys.

Moderators; M. Cohen, M.I.T.

L. A. Davis, Allied Corporation

E. J. Dulis, Crucible Research Center

Recorders; D. E. Polk, ONR

S. Isserow, AMMRC

S. Wolf, U.S. Dept, of Energy

Speakers; M. Cohen, M.I.T.

A. Lawley, Drexel University

E. J. Dulis, Crucible Research Center

T. E. Tietz, National Academy of Sciences

L. A. Davis, Allied Corporation

L. A. Johnson, General Electric Corporation

P. R. Strutt, University of Connecticut

J. Dickson, Allied Corporation

5
1, What are the main principles and guidelines which

have now emerged regarding the rapid solidification

of crystalline ferrous alloys? • Refined segregate structures and compositionally

more uniform structures are produced. • Second-phase disperse ids are refined, and sometimes new phases are formed. • The range of useful alloy compositions is expanded,

for example, through extended solid solubility of

solute elements. • Grain size is reduced, but this also depends on subsequent processing. Resistance to grain growth

at high austenitizing temperatures has been noted

through pinning of grain boundaries by finely

dispersed second-phase particles. Thus,

second-phase particles can play an important role in

achieving a combination of strength and toughness. • Mechanical and chemical properties are improved in

specific alloy systems. • Advantages and disadvantages are noted when the

powder metallurgy route is followed, for example, in

applications based on mechanical properties.

Other comments of relevance included the following: • Alloy design can be aided by considering the

thermodynamics of second-phases, so that extremely

stable second-phase particles can be incorporated.

The role of fine second-phase particles on the

kinetics of grain coarsening can be related to

Ostwald ripening of the particles. Thus,

thermodynamic data for solubility products and

diffusivities of the operative elements are needed

for estimating the stability of second-phase

particles.

6
• Some of the principles outlined can be equally

applied to other alloy systems, and the potential

benefit of stable distributions of fine precipitates

need not be limited to pinning of grain boundaries.

For example, large volume fractions of fine

precipitates can be effective for dispersion

strengthening. • More work is needed to establish the relationships

between alloy composition and process variables on

the formation and stability of second-phase

particles. • Additional fundamental and engineering data are needed in several areas; these include welding,

secondary recrystallization, ability to exploit the

high austenitizing temperatures, and critical

element substitutibility. • A present bottleneck to fundamental and

developmental studies is the availability of

adequate amounts of high-quality rapidly solidified

materials. Facilities for research materials, if

established, should use several particulate

production methods.

7
2 . What are the important needs for further research on

the various steps from rapid-solidification and

particulate-consolidation methods to final

properties in order to move toward the engineering

application of ferrous RST?

# Attainment of microcrystalline, segregation-free

solids by rapid solidification is influenced by both

the heat extraction rate and the degree of

undercooling. The role of heterogeneities,

endogenous (melt composition and cleanliness) or exogenous (melt reactions with crucible or quench

medium) , on nucleation rate and achievable

undercooling should be investigated more

systematically.

# Attention should be given to single-variable rapid

solidification experiments to establish the effects

of different atomization processes and powder sizes

on microstructure and properties.

# Work is required to delineate the influence and

relative importance of powder production method,

consolidation method, and process variables, as well

as the effect of post consolidation heat treatments

on the structure and properties of the final

product.

# Work is needed on new consolidation approaches, in

particular high-rate, low-temperature and direct

dens ificat ion techniques.

# Melt spinning of crystalline ferrous alloys, the

product of which is subsequently broken into fine

particles, should be studied. Advantages could

include more uniform cooling conditions (for a given

melt composition and cleanliness) and easier quality

control. Possible contamination from the chill

material could be a disadvantage.

8
• The effect of particulate size and geometry

(including melt-spun particulates) on packing

density and densification mechanisms should be

investigated.

9
3. What are the prospects for the engineering

application of RST to typical ferrous products, such

as tool steels, bearing steels, corrosion- and

oxidation-resisting steels, etc.? What are the

present roadblocks? • The principal current application of RST in

crystalline ferrous alloys is in high-speed tool

steels, which commands less than 5% of the market.

Conventional alloys have been improved through RST

by reducing micro-segregation and carbide size. • New ferrous alloys, unique to RST, are being

developed which have the advantage of critical

materials substitutibility or superior performance.

Examples include the development of cobalt-free

high-speed steel replacements for M42 and T15, high

chromium- and vanadium-containing alloys with

improved corrosion and wear resistance, and high

vanadium tool steels with unusually high wear

resistance. • Cost has an important bearing on broader acceptance

of various low alloy ferrous RST products. The

prices of current RS and conventionally produced

high-speed tool steels are about the same. • Cost and quality-control considerations pose

roadblocks for other engineering applications. The

value-added concept - including costA>enef its of the

entire component based on its life cycle and not

just the initial cost of material - should improve

competitive pricing of RST materials. Strict

quality-control procedures are needed. • Production of large net shapes, hollow shapes, and

composites have engineering advantages for RST that

could be exploited.

10
4. What are the prospects for scaling-up rapid

solidification techniques for cost-effective

production? • Prospects for scale-up appear very good. Production

facilities are presently available which are capable

of producing several hundred tons/month of

intermediate cooling-rate atomized particulates. • A principal roadblock here involves convincing

companies that there is a demand for RST products

and that the demand will be lasting. Technical and

economic information must be generated which will

convince producer and user management that

investment in RST is sound business. • NMAB is currently conducting a study (1) to survey

existing facilities for rapid solidification and

subsequent consolidation, and (2) to assess the

potential of new emerging processes. • The experience gained by industry in the melt

spinning of amorphous materials suggests that this

method of rapid solidification should also be

investigated for crystalline alloys. Thorough

comparisons should be made with the atanizing

approach from the standpoints of both the quality of

the rapidly solidified materials produced and the

efficiency of the subsequent consolidation steps.

These considerations are also relevant to future

decisions concerning scale-up and cost-effectiveness. • Based on the current commercialization of RST for

tool steels, the eventual technology-transfer to

industry for many other ferrous applications looks

favorable particularly for specialty alloys.

11
5. Are the conclusions and recommendations put forth in

the NMAB report adequate as guidelines for

establishing national policy regarding development

of rapidly solidified amorphous alloys technology?

# The study did not aim to establish such guidelines.

It was too broad in scope and most of its

conclusions/recommendations dealt with crystalline

materials. Furthermore, the study was conducted in

1979 and is therefore slightly out-of-date.

# Up to now, most of the funding for R and D on

amorphous alloys in the United States has come from

industry rather than from the government. In Japan,

the trend appears to be the opposite. For example,

Nippon Steel was recently awarded a $9 million

contract to develop amorphous-alloy sheet for

transformers.

# A plea was made for a strong governmental program in

the design and manufacture of new transformers that

would take full advantage of the lower core losses

of amorphous alloys. The prevailing weak

transformer market in the United States coupled with

strong cooperation between government and industry

in Japan could lead to a world market dominated by

Japanese manufacturers.

12
6. What are the economic and other driving forces and

barriers for application of amorphous alloys?

# In the past decade, significant progress has been

made in process development, alloy design and

characterization of amorphous alloys. The broad

spectrum of activity in this field is evidenced by

the approximately 400 papers presented at the 1981

Fourth International Conference on Rapidly Quenched

Metals in Japan.* • Largest current potential use of amorphous alloys is

in electromagnetic applications. For example,

alloys have been formulated which exhibit ^vl/4 of the core losses of Fe-3%Si, which is the standard

magnetic core material in power-distribution transformers. • Potential energy savings provide the economic

driving force for the use of amorphous alloys to

replace Fe-Si. One estimate predicts a $30 billion

saving over the next 15 years - this includes

savings which would accrue due to reduced need for

new generating capacity, amounting to seven 1000-megawatt stations.

# In addition to soft magnetic properties and low core

loss, metallic glasses exhibit other notable

magnetic properties, such as high magnetostriction,

low acoustic loss, high permeability, high corrosion

resistance, and temperature-dependent permeability.

Thus, they have the potential for myriad of

applications in devices, including magnetostrictive

transducers, load cells, electric motors, magnetic

amplifiers and phase shifters, magnetic separators.

*This information became available subsequent to this

Workshop.

13
magnetic shielding, thermosensor, magnetic recording

heads (audio, video, digital) , and others. Efforts

in the latter areas are primarily conducted by

device manufacturers in Japan.

# Barriers to application of amorphous alloys are primarily economic and institutional rather than

technical. They include: cost of materials (boron

dominates raw material cost, 85%) , cost to develop

a new design and the corresponding manufacturing

technology, availability of lower-cost competing

technologies, and lack of multiple suppliers. On

the other hand, the driving force in Japan is

stronger due to the higher cost of energy - several

times higher than in the U.S.

# Some cost/production questions are being answered at

the 0-5, 000 ton/year facility at Allied Corporation.*

# Other potential applications of amorphous alloys are envisioned due to their special engineering

properties. These include: brazing materials

(already commercialized in the U.S.), razor blades,

radiation shielding, corrosion-resistant pipes or sheets, etc.

*A major joint Allied Corporation - Japan amorphous

alloys venture was announced subsequent to the July 1-2,

1981 Workshop. The joint venture with four Japanese

companies of the Mitsui Group, led by Mitsui

Petrochemical (and including Toshiba) , resulted in the

formation of a new company NAMCO (50 percent shared by

Allied) and an exclusive Asia license to same for the

technology and patents.

14
7. What are the prospects for surface treatments by

rapid solidification methods for both crystalline

ferrous and metallic glasses? What are the present

roadblocks?

# There is good evidence that rapid solidification by

directed high-energy sources confers significant

resistance to oxidation, corrosion and wear through

surface melting, alloying and compositing.

# Studies are needed to better define specific

processing/structure relationships and to determine

mechanisms for the enhancement of surface properties.

# Directed energy beam characterization and control

issues coupled with a lack of predictive models

relating processing/structure/properties pose strong

barriers to applications at the present time.

# There is the prospect that surface melting can be

automated and coupled to other surface treatments

such as plasma spraying. Cost saving could thus be

realized by imparting superior surface performance

to inexpensive bulk materials.

# More service testing of surface-modified components

is needed.

15
8. What are the prospects and roadblocks for the

development of bulk rapidly solidified components

using the glassy state as a "pathway" to

microcrystalline structures? • Amorphous alloy formation is already being

investigated as an alternative "pathway" to the

formation of crystalline structures. Bulk

microcrystalline structures are being synthesized

through crystallization and consolidation of new

families of amorphous alloys specifically designed

for this purpose. • Devitrification of amorphous alloys produces a fine

mixture of metallic phases and borides.

Investigations are underway to test the consolidated

materials in a variety of tool, die and

wear-resistant applications. • Thus far, this route appears to generate a finer

grain size than that obtained by rapid

solidification directly to the crystalline state.

On the other hand, compositional ranges are limited

to those that can avoid crystallization under the

available cooling rates from the liquid state, as well as to those that do not weld to or damage the

chilling substrate. • Comparison of properties should be performed on RS

alloys of the same composition formed by alternative

methods. For example, one would be devitrification

of an amorphous alloy while the other would be

direct microcrystalline solidification. • The mechanism of wetting/adherence, important in

melt spinning, is not sufficiently understood and

needs further study if the process is to be applied

to a wider range of alloys, including those that

solidify in the crystalline mode.

16
9. What is necessary in order for the government-wide

programs on rapid solidification (a) to stimulate

increased research efforts in industry and in

academia, and (b) to encourage the commercialization

of RST? What are the barriers to overcome?

# The government does not yet have a coordinated and

viable program in the RST of ferrous alloys, as is

already the case for aluminum alloys nor is it as well supported as is work in superalloys. The

overall potential for steels is at least as great as

for the other two classes of materials. Indeed, the

latter two programs provide prototypes for what

needs to be done in the way of coordination, goal

setting, and funding for the RST of ferrous alloys.

# The steel industry seems to be quite curious about

RST, but it is not yet particularly excited about

it. While there was considerable "diffusion" of new

information to the ferrous segment of the audience,

this was apparently not sufficient to stimulate the

start-up of research programs "back home". The

general attitude remained one of "we will still wait

and see". • The problem of easier access to rapidly solidified

as well as to consolidated ferrous materials was

expressed over and over again, but it was clear that

the intended applications will be extremely varied

and multiple facilities will be needed to cope with

the supply problem. • There is a need for concrete evidence of improved

properties via RST all the way to "prototype"

demonstration. This will help stimulate a market

pull for RST products.

17
• The steel industry is more "diffuse" in comparison

to light alloys and superalloys. The tool steel and

amorphous alloy technology commitments were made by

companies with little or no governmental support.

Improved communication between users and suppliers

of ferrous materials will aid in identifying

specific products which could gain from RS

manufacturing methods. • There is now ample evidence that Japan is making a strong commitment to commercialization of amorphous

alloy products - see questions 5 and 6. The

prevailing trend is likely to lead to another new

technological market dominated by Japanese products.

18
LIGHT ALLOYS

Moderators

:

Recorders;

Speakers;

R. Spear, ALCOA

R. V. Carter, Boeing Commercial Airplane Co.

D. P. Voss, ATWAL

M. Greenfield, NASA

J. Waldman, U.S. Army Armament R and D

Command

R. Athey, Pratt and Whitney Aircraft

R. V. Carter, Boeing Commercial Airplane Co.

W. S. Cebulak, ALCOA

N. J. Grant, M.I.T.

G. E. Spangler, Reynolds Metals Co.

19
1. (a) Are the conclusions and recommendations put

forth in the NMAB report adequate as guidelines

for establishing national policy regarding

rapidly solidified (RS) aluminum alloy

development? • Yes. However, some of the conclusions paint too

optimistic a picture of aluminum alloy RST without

an adequate data-base. • No RS aluminum alloy has yet attained commercial

production status. • Near term opportunities for commercial applications

are limited to the aerospace industry. • There has been no in-service experience for RS

aluminum alloys. Such experience is needed on a variety of components, especially where superior

performance and/or total life-cycle cost savings are expected

.

• Insufficient number of new alloys have been

developed and studied to date.

1. (b) Is the current national program addressing the

needs stated in the recent NMAB study? • The government-wide RS aluminum alloy program has

two major thrusts: (1) near-term (by 1985)

attainment of production status for first generation

alloys, with moderate property improvements, to

develop operating and in-service use experience, and

(2) longer-range (by 1990) development of advanced

alloys, with significantly large property

improvements, coupled to generic studies to advance

the underlying science-base.

20
• More work is required to relate the

microstructure/property observations in RS aluminum

alloys to thermodynamic, kinetic and heat flow

concepts. • Cost versus performance analysis is required for

specific commercial aircraft components. • Programs are needed aimed at in-service experience

and round robin tests on RS aluminum alloy products

by various aerospace ccanpanies. • Impetus is needed for producers to make different RS

aluminum alloy products available for user evaluation.

21
2. What are the envisioned applications of rapidly

solidified aluminum alloys?

(a) In the aerospace industries?

(b) In other than aerospace industries?

# In general, the extent of applications for RS

aluminum alloys will depend on the total life-cycle

cost, property improvements achieved, demonstrated

in-service performance and availability of

production quantities of quality material.

# Near-term opportunities for commercial applications

are limited to the aerospace industry. Significant

other commercial applications have yet to be

identified.

# Cost-competitiveness with respect to improved ingot

metallurgy aluminum alloys, titanium alloys and

composites is an important consideration in

aerospace applications.

# The driving forces for aerospace application are improvements in modulus-and/or strength-to-weight

ratio, resistance to stress corrosion cracking,

general corrosion, fatigue and fracture toughness.

# RS aluminum alloy suppliers need input from the

marketplace (the user industries) on their property

goals, volume and the product form needs.

# There has been little in-service experience for RS

aluminum alloys. Such experience is needed, even if

it is on non-critical components, in order to

instill confidence in the user community.

22
# In the near-term, substitution for components in

existing aerospace systems should be emphasized. It

is not likely that the design of new systems will

include untested materials which have not achieved

production status.

# The value of weight saved in a component may depend

on the location and application of the component in an aircraft.

# Non-aerospace applications of RS aluminum alloys are

almost entirely in the transportation industry (e.g.,

connecting rods in internal combustion engines)

.

Cost-effectiveness in non-military applications will

be the critical factor.

23
3. What are the critical issues in early

commercialization of rapidly solidified aluminum

alloy products:

(a) with respect to production of large quantities

of particulate of uniform quality?

# In the near-term, there is no forseeable problem in

the production of large quantities of relatively

uniform quality RS X7090 and X7091 aluminum alloys.

# Process R and D is needed to address observed

microstructural variations, especially variations in

second phase particle size, in other RS aluminum

alloys.

# The production of lithium-containing RS aluminum

alloy particulate will present special problems due

to the reactivity of this element.

(b) in the cost effective manufacture of billet,

sheet and plate? • The production cost of RS aluminum alloy products

will have a great influence on their ultimate

utilization. • Scale-up of RS aluminum alloy billet, plate and

sheet production is difficult and costly - it

requires new facilities and the particulate is

reactive. This is a critical aspect of the

near-term problem in commercialization. • Total life-cycle cost savings in existing systems

need to be identified based on improved performance

- durability and/or reduced density. This will

stimulate early demonstration/application of RS

aluminum alloys.

24
# Work is needed on new consolidation approaches for

aluminum RST. For example, siqnificant cost savings

will be realized by eliminating encapsulation during

billet processing. Manufacture of preform billets

for subsecfuent net-shape forging may be another

approach. • Investment in new facilities for billet manufacture

(e.g., cold and vacuum hot pressing) needs to be

justified on the basis of an available,

cost-effective, market for the RS aluminum alloy

products.

# Vacuum pre-heating, with its attendant cost penalty,

has been shown to have a major positive effect on fracture toughness (especially short transverse) of

RS X7090 and X7091 alloys. • Appropriate billet sizes and geometries have to be

identified for extrusion, forging, plate, sheet and

other products.

25
4. What are the key technical considerations in the

consolidation processes and thermonechanical

treatments, with respect to the control of

metastability and 100% densif ication? • In the near-term, adequate thermomechanical

treatments (IMT's) are available for RS X7090 and

X7091 aluminum alloys. • Conventional IMT practice may not be applicable to

the perservation of metastable structures obtained

in other RS aluminum alloys. In the long term,

development of special IMT's may be required to

fully utilize RST alloys. • The effect of heat treatment on the microstructure

of aluminum alloy particulates should be studied

with and without the influence of the consolidation

operations. • Direct HIP to final product is not currently a viable approach for RS aluminum alloys due to

particulate surface contamination. • Studies are needed on the effect of alloy

composition and solidification variables

(undercooling, liquid/solid interface velocity,

etc.) on the formation and stability of

supersaturated matrices and second phase particles. • Detailed quantitative microstructural analysis of RS

aluminum alloys and failure modes are needed. For

example, coarsening of fine second phase particles,

their role on pinning of grain boundaries, and crack

initiation and propagation in fatigue needs to be

studied.

26
• Guidelines need to be developed for the design of

"ideal" microstructures for RS aluminum alloys to

achieve desired properties. • Many RS aluminum alloys represent incremental

changes of conventional wrought or cast alloys.

More attention should be given to radical departures

in alloy design to produce

microstructures noted above.

the "ideal"

Studies are needed on the

characteristics of RS aluminum alloys.

hot working

27
5. (a) Is there a need for improved sources of high

quality, research quantity, rapidly solidified

particulate? Should this be supplied by

government supported central facilities? • Sources for high quality, research quantity, RS

aluminum alloy particulate are needed. • There is also a need in the community for a variety

of RS aluminum alloy billets and mill products for

characterization and performance analysis. • Intermediate size extrusions of two RS aluminum

alloys are now available. More sources are needed

including those using the direct powder-to-mill

product route. • Users should not be dependent on a single government

or other source for RS aluminum alloys. Industrial

and other facilities should be encouraged to

participate in the supply of particulate and

consolidated materials.

5. (b) Will the government-wide program stimulate

strong university/industry involvement, as well

as industry investment? If not, why not? What

other actions are deemed desirable to achieve

this objective? • Yes. The government-wide program does stimulate

participation and investment. • In the near-term, more government support is needed

for component demonstration programs.

28
• In the long-term, sponsorship of more fundamental

programs is encouraged in the areas of phase

stability and microstructure control during

solidification and TMT.

29

SUPERALLOYS

Moderators:

Recorders;

Speakers:

A. L. Bement, Jr., TRW, Inc.

H. J. Klein, Cabot Corporation

A. M. Adair, AFWAL

L. A. Jacobson, DARPA

J. R. Manning, NBS

E. M. Breinan, United Technologies Research Ctr.

W. H. Couts, Jr., Wyman-Gordon Co.

A. Lawley, Drexel University

D. Maxwell, TRW, Inc.

J. B. Moore, Pratt and Whitney Aircraft

S. H. Reichman, Special Metals Corporation

R. G. Rowe, General Electric Company

. C. Williams, Carnegie Mellon University

R. F. Wojcieszak, General Electric Company

31
1. (a) Are the conclusions and recommendations put

forth in the NMAB report adequate as guidelines for establishing national policy

regarding rapidly solidified superalloy

development? • The emphasis of the NMAB study was on superalloy

turbine disk applications. Therefore, the report

is not broad enough in scope to be used as a guideline for other RS superalloy applications. • Some of the conclusions and recommendations of the

NMAB report; for example, those dealing with the

fundamental aspects of RST, the need for low cycle

fatigue (LCF) data, and the problems associated

with ceramic inclusions and quality assurance (QA)

,

were discussed during this Workshop. Consensus

reached during the deliberations are noted in the

various segments of this summary. • Recommendations should be prioritized in future

NMAB reports on RST.

1. (b) Is the current national program addressing

the needs stated in the recent NMAB study?

# This question was not directly addressed due to

lack of relevant data. However, there was discussion about what the government should do.

# For disk applications, data from standardized test

procedures for LCF are needed. Furthermore,

factors that affect crack initation and propagation

should be identified in order to assess the

influence of RS on LCF.

# Government support is needed to develop fatigue

resistant alloys and melting methods for powder

production that avoid melt contact with ceramics.

32
# Superalloy powder materials for disk applications

offer higher strength than can be obtained from

cast and wrought products; however, a trade-off

must often be made between higher strength and

defect tolerance. Powder cleanliness is a key

issue that should be addressed in conjunction with

QA.

# Proposed government programs put too much emphasis

on powder production methods and not nearly enough

effort on consolidation techniques. The latter is

important and should be fully addressed.

33
2. Is there a need for more work on structure-property

relationships and the effect of heat treatment on stability in rapidly soldified superalloys? • Yes. Furthermore, it is important that an exploratory attitude be maintained regarding

opportunities for development of new RS sup^eralloy

microstructures

.

• RST opportunities for microstructure development are much broader than conventional practice. Work on computer-based phase stability data compilation

coupled to predictive models could provide a better

description of phase relations (both equilibrium and

metastable) for design of new alloys and

microstructures

.

• There is a need to systematically determine how

consolidation and subsequent thermomechanical

processing variables affect the structure-prop>erty

relationships in specific component parts. • There is a need to define and conduct spiecific

research programs in the structure-property area. Guidance and participation should be sought from a spectrum of qualified scientific experts in the

f ield

.

• Fundamental work is required on the high temperature

stability of RS superalloys. Instability has been

observed in the form of discontinuous y' coarsening

at the grain boundaries of a number of consolidated

RS nickel base alloys. The mechanisms responsible

for this phenomenon are not yet understood. • Research is needed to provide thermodynamic data for

solubility products important in estimating the

stability of primary and secondary phases in RS

superalloys

.

34
• Guidelines are needed based on kinetic and

thermodynamic solidification theory for alloy

design, prediction of phase sequences and control of

processes and microstructures.

35
3. Is the lack of suitable techniques for detection and

separation of non-metallic and other foreign

inclusions from metallic powder a major roadblock to

useful application of superalloy powders?

What can be done to correct this problem?

# It is a serious matter and of prime concern, but not

a major roadblock. Many components made from

complex superalloy powders have been flying

successfully. Specific information should be

documented on the highest number of engine cycles

exper ienced

.

# Non-metallic and other foreign inclusions have been

shown to reduce the fatigue life of superalloy P/M

material depending on the size, composition and the

volume fraction of the inclusions.

# Inclusions may originate from both master melt

contamination and the powder production process.

Improved powder processing techniques and better

methods for the detection and separation of

inclusions are needed to extend the range of

applications for RS superalloy parts and/or to

improve their performance. • Improved powder processing techniques can include

cleaner feedstock, better melting practice, no melt

contact with ceramics and all inert powder handling. • It is important to detect and separate out

inclusions before consolidation. For example,

better refined elutriation methods are needed. • Defect appearance in failed test specimens is

related to the type of test, specimen size, strain

range, etc. In order to keep RS superalloy powder

usage an accepted technology, we must continually

explore the products for evidence of defects, and

characterize them well.

36
• on The Workshop recanmends that ASIM initiate work

cleanliness standards for RS superalloy powders. • Consideration should be given to improve defect

tolerance of RS superalloy products through changes

in alloy chemistry, production of fine powders and

thermomechanical treatments.

37
4. What policies, programs, or financial support are needed to assist producers, users, and designers in

developing confidence in RS superalloy technology? • In the long run capital expenditure by producers

depends on the civilian market. Furthermore, large

investments are necessary to requalify critical

components. Therefore, it is recommended that the

government sponsor RST programs on some non-critical

parts so that hands-on experience can be gained by

the producer and confidence can be established in

the user industries. • Data-base is needed by designers on the effect of

inclusions on properties of RS superalloys. It is

recommended that government programs be established

to measure the effect of controlled addition of

inclusions on properties using standarized test

methods. • The need for improved processing techniques, noted

under question 3 above, was reiterated. For

example, the potential use of EB or laser melting to

eliminate ceramic crucibles should be investigated. • Designer confidence in RST must be gained by

successful component testing and uniform acceptance

tests for QA. • Other options for producing "RS properties" in

superalloys should be examined in terms of process

economics.

38
5. What market sectors will benefit most over the next

ten years from rapid solidification technology?

Where are the major opportunities in superalloys?

# Markets for RS superalloys can be broadly identified

in the gas turbine engine for aircraft, ground

transport and power generation - where fuel

efficiency is of prime concern. # Disk RST is anticipated to show rapid growth in both

the military and the commercial sectors.

# No RS superalloy has yet been designed for disk - specific applications. Alloy development programs

should emphasize low cost, strategic element

content, improvements in fracture toughness and LCF.

# No application for RS superalloy airfoils is seen in

a commerical aircraft engine over the next ten

years. On the other hand, military applications are envisioned during the same period.

# Development of new RS iron-base alloys offers

potential cost savings and freedom from import

dependence if it can replace the 3.5 million pounds

of cobalt-base superalloy cast in 1980 for the

industrial machine hardware sector.

# Nickel availability and cost has been a deterrent to

serious consideration of superalloys for the

automotive turbine. The development of a new RS

iron-base alloy could have an important impact on

this technology.

# Advanced forming concepts for low cost components

for use in vehicular engines will greatly affect

market applications. For example, combined

forging/extrusion processes are needed to produce

integrally bladed turbine wheels.

39
• Applications for RS superalloys have been identified

in energy conversion systems and deep oil well

tooling. • Nickel base RS alloys are being developed for tool

and die applications. • The catalytic effectiveness of Raney nickel can be

improved significantly by rapid solidification

before leaching out the contained aluminum. This

has been shown in the synthesis of methanol from

natural gas and in other reactions of commercial

interest.

40
6. Can surface processing lead to important commercial

applications involving superalloys? • Yes. The economic analysis of surface processing

identifies the limiting problem to be energy

deposition rate. This limitation opens a window of

opportunity for high power density directed energy

processing. • The field of RST surface processing needs stronger

support to establish possible microstructure/property

improvements. Cost-benefit analysis is also needed. • RST surface processing of superalloys could make

important contributions to rework and repair of

components

.

• Cracking of high y' nickel-base superalloys is a severe problem in directed high energy processing.

Non-destructive techniques could be developed for

crack detection and on-line control of process

parameters. • RST surface processing offers the potential for

upgrading acceptability of surface coating

technology because of improvements in

microstructural uniformity. More automation will be

required to optimize process economics.

41
7. (a) Is there a need for improved sources of high

quality, research quantity, rapidly solidified

particulate?

Should this be supplied by government supported

central facilities?

# Yes. Many different needs are evident. A strong

endorsement is given to help establish this

capability at MBS as part of their overall

responsibility for Standard Reference Materials.

# It is also recommended that selected NSF funded

Materials Research Centers participate in the

production of research quantity RS particulates.

# A survey should be conducted of university and other

facilities to determine capabilities for RS

particulate production and consolidation.*

7. (b) Will the government-wide program stimulate

strong university/industry involvement as well

as industry investment? If not, why not? What

other actions are deemed desirable to achieve

this objective?

# University/industry co-participation has been stimulated by the government program.

# Contractor commitment and investment has been one of

the quid-pro-quo's in contractor selection. This is

endorsed as future policy.

# Qualified not-for-profit institutes should participate in the overall RST program.

*Such a survey is presently underway as part of a new NMAB study on RS processing.

42
• It is recomnended that CCMAT bring the Metal Powder

Industries Federation (MPIF) into their planning

activities.

43
8. How do powder production and subsequent processing

techniques interact to yield a product that is

defined as "RS"? • A good review of these interactions is given in the

paper by M. Cohen, B. H. Rear, and R. Mehrabian

"Rapid Solidification Processing: An Outlook",

Rapid Solidification Processing; Principles and

Technolog ies 1

1

, R. Mehrabian, B. H. Rear, M. Cohen,

eds., Claitor's Publishing Division, Baton Rouge, LA

( 1980 )

.

• There is a need to balance emphasis on heat

extraction rate and other factors, such as nucleation rate and undercooling governing the

attainment of unique microstructures. • In general, definition of rapid solidification

processes in terms of just high cooling rates has

led to confusion. A measure of rapid solidification

processing could be the cooling rate of an alloy at

its liquidus temperature since this rate influences

the "incubation period" available for nucleation.

On the other hand, fineness of microstructure is

usually correlated to average cooling rate during

solidification or time available for coarsening.

Finally, many structural manifestations of rapid

solidification are best correlated to the

solid-liquid interface velocity.

44
9.

How does RST compare in performance with single

crystal and mechanically alloyed products?

# It is recommended that valid comparisons be made for

competing air foil technologies. The tests could

include: ICF, creep, oxidation, cooling

effectiveness, corrosion, coating compatibility,

transverse strength and ductility, and repairability.

# It is recommended that NMAB do an equivalent study

(to the RS superalloy disk applications) on blades

and vanes, and include the comparisons noted above.

# We should consider RST for those applications where

specific advantages of the technology can be

exploited.

10.

What is the potential of RST for substitution of

critical/strategic materials? • This potential has yet to be clearly defined on a scientific basis. RST is not a panacea technology.

# A possible potential of RST may be in manufacturing

of composite components (using plasma or laser

deposition) in which critical elements are only used

in needed areas.

11.

What are the strengths and limitations of the

various consolidation processes that are used for RS

superalloy powders?

# The microstructures of RS powders are affected by

consolidation processes. This issue should be

addressed in considerable depth.

45

APPENDIX

PROGRAM

July 1-2, 1981

BRIEFING Wednesday, July 1

8:30 a.m. Registration

9:30 a.m. WELCOME — E. Ambler, Director, NBS, U.S. Department of Commerce

9:40 a.m. INTRODUCTION — J. S. Kane, Associate Director for Basic Energy Sciences, DOE

9:55 a.m. DoD MANAGEMENT OF TECHNOLOGY BASE PROGRAMS - G. P. MUlbum,

Acting Deputy Under Secretary of Defense for Research and Engineering, PentE^on

10:25 a.m. Coffee Break

10:45 a.m. GOVERNMENT-WIDE IMPLEMENTATION STRATEGY FOR RST - J. Persh,

Staff Specialist for Materials and Structures, OSD/OUSD R&E (ET), Pentagon

Session Chairman — J. Persh

11:00 a.m. RAPID SOLIDIFICATION METHODS AND GENERIC PROGRAMS -

R. Mehrabian, Chief, Metallurgy Division, NBS, U.S. Department of Commerce

11:30 a.m. LIGHT ALLOYS PROGRAM — H. M. Burte, Chief, Materials and Ceramics

Division Materials Laboratory, AFWAL/MLL, Wright-Patterson AFB

12:30 p.m. FERROUS ALLOYS PROGRAM — E. S. Wright, Director, Army Materials and

Mechanics Research Center, Watertown

1:00 p.m. Lunch

2:00 p.m. SPECIALTY MATERIALS (INCLUDING METALLIC GLASSES) PROGRAM -

R. Schmidt, Administrator, Materials Technology, Naval Air Systems Command

2:30 p.m. SUPERALLOYS PROGRAM — E. C, van Reuth, Deputy Director for Materials

Sciences, DARPA

3:30 p.m. Coffee Break

3:45 p.m. INTRODUCTION TO WORKSHOP FORMAT - L. A. Harris, Manager,

Materials and Structures, OAST, NASA

4:00 p.m. Divison of attendees into three Working Groups: Light Alloys, Ferrous and

Specialty Materials, and Superalloys. Discussion by the Moderators of the questions

to be addressed in the Workshop on the following day. Input from the participants for other items of importance for the Workshop agenda will also be sought.

5:30 p.m. ADJOURN

47
EVENING PROGRAM — Washingtonian Motel

6:30 p.m. Cocktails

7:00 p.m. Banquet

8:00 p.m. KEYNOTE SPEECH — Dr. Arden L, Bement, Vice President for

Technical Resources, TRW, Inc.

WORKSHOP Thursday, July 2

9:00 a.m. Assemble as Working Groups into specific Workshops. The general format will

be as follows:

Each Group will have two or three Moderators, and two Recorders, see list attached.

The Moderators will have previously apportioned the available time into the

number of questions to be addressed, discussed, and debated. An assigned speaker

will kick off the discussion with a five- to ten-minute presentation, thus opening

avenues for discussion. At the end of the apportioned time for that question,

the Moderators will end the discussion and move on to a new subject.

It is anticipated that during the morning session at least four to five subjects

would have been addressed with a 15-minute coffee break at 10:30 a.m.

1:00 p.m. Lunch

2:00 p.m. Workshops

3:45 p.m. Coffee Break

4:00 p.m. Report of the Workshop Findings to all attendees in a Joint Final Session.

One Moderator from each Workshop Group will report its findings to all attendees in 15 minutes and an additional 15 minutes will be allowed for

discussion.

5:30 p.m. ADJOURN

48
NBS*114A (REV. 9-78)

U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. BIBLIOGRAPHIC DATA

SHEET NBSIR 81-2439

Z, Acce$$ion Ho. January 1982

4. TITLE AND SUBTITLE 5. Publication Date Report of the First Vfork^op on Rapid Solidification

Technology

7. AUTHOR(S)

R. Mehrabian and J. Persh

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10.project/Tai*/Woik

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS fSrreer, City, state, ZIP) 13. Type of Report & Period Covered

14. Sponsoring Agency

15. SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FIPS Softw/are Summary, is attached.

16. ABSTRACT (A 200^word or teas factual summary of moat aignificant irzformation. If document includes a significant bibliography or

literature survey, mention it here,)

The aim of this BriefingAforkshop was to first provide the private sector

with the govemment--wide irrpleinentation strategy for Rapid Solidification Technology

(RST) in the next five years; and second, to seek industry/university input and

involvement in order to effect a wider range of applications of this technology

based "breakthrough”.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unleaa a proper name;

aeparated by aemicolona)

Ferrous and specialty materials; light alloys; metallic glass; rapid solidification;

workshop

18. AVAILABILITY Unlimited

For Official Distribution. Do Not Release to NTIS

I 1 Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

I I Order From National Technical Information Service (NTIS), Springfield, VA. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

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UNCLASSIFIED

21. NO. OF

PRINTED PAGES

22. Price

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