NICKEL-GADOLINIUM PHASE 

DIAGRAM 

By M. I. Copeland, M. Krug, C. E. Armantrout, 

and H. Kato 

+ + + + + + + + + + + report of investigations 6566 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Stewart L. Udall, Secretary 

BUREAU OF MINES 

Marling J. Ankeny, Director 

MSTFBBUT4OW OE THE DOCUMENT IS UNLIMITEb 1 
DISCLAIMER 

This report was prepared as an account of work sponsored by an 

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Government nor any agency Thereof, nor any of their employees, 

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Government or any agency thereof. 
DISCLAIMER 

Portions of this document may be illegible in 

electronic image products. Images are produced 

from the best available original document. 
This publication has been cataloged as follows: 

Copeland, Mark I 

Nickel-gadolinium phase diagram, by M. I. Copeland [and 

others. Washington] U. S. Dept. of the Interior, Bureau of 

Mines [19641 

24 p. illus., tables. (U. S. Bureau of Mines. Report of investigations 6566) 

Includes bibliography. 

1. Nickel alloys. 2. Gadolinium alloys. 3. Phase rule and equilibrium. I. Title. (Series) 

TN23.U7 no. 6566 622.06173 

U. S. Dept. of the Int. Library 
CONTENTS 

Page 

Abstract ................................................................. 1 

Introduction ............................................................. 1 

Experimental procedures and results ...................................... 3 

Materials and melting procedure ..................................... 3 

4 

Phase diagrams ...................................................... 5 

Melting-point determinations ........................................ 6 

Heat treatments and metallography ................................... 7 

Phases observed ..................................................... 9 

X-ray diffraction data .............................................. 9 

Discussion of results .................................................... 17 

Conclusions .............................................................. 22 

References ............................................................... 23 

Annealing treatment and hardness of alloys .......................... 

ILLUSTRATIONS 

Fig . 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

8 . 

9 . 

10 . 

11 . 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

8 . 

9 . 10 . 11 . 

Nickel-gadolinium phase diagram .................................... 5 

Nickel-gadolinium phase diagram. metallography. and thermal data ... 6 

Structure of the intermetallic compound Ni.. Gd , .................... 9 

Dendritic structure observed in an Ni-10 wt pct Gd alloy ........... 18 

Cored structure in Ni-26.4 wt pct Gd specimen developed after heat 

treatment at 1, 310. C ............................................ 18 

Structure of an Ni-37.5 wt pct Gd alloy held at 10" C above the 

peritectic isotherm occurring at 1, 270' C ........................ 19 

Cored structure in an Ni-45 wt pct Gd alloy after heat treatment at 

10" C above the peritectic isotherm occurring at 1, 180. C ........ 19 

Cored structure observed after holding at 10" C above the peritec20 

Eutectic structure observed in an Ni-70 wt pct Gd specimen held at 

10" C above the 890" C isotherm .................................. 20 

Duplex structure consisting of Ni, Gd and Ni,Gd, observed in an 

21 

21 

tic isotherm at 1. 070° C, where Ni, Gd melted incongruently ....... 

annealed Ni-39 wt pct Gd specimen ................................ NiGd and NiGd, phases observed in an Ni-80 wt pct Gd alloy ......... 

TABLES 

Selected properties of nickel and gadolinium ....................... Impurity analyses of nickel and gadolinium ......................... Analysis and hardness of alloys .................................... 

Nil,Gd, X-ray diffraction data ..................................... Ni, Gd X-ray diffraction data ....................................... 

Ni3Gd X-ray diffraction data ....................................... Ni, Gd X-ray diffraction data ....................................... NiGd X-ray diffraction data ........................................ NiGd, X-ray diffraction data ....................................... 

3 

3 

4 

8 

11 

12 

13 

14 

15 

16 

17 

Liquidus and solidus data .......................................... 

Ni,Gd, X-ray diffraction data ...................................... 
N I CKEL-GADOLIN I UM PHASE DIAGRAM 

by 

M. I. Copeland,' M. Krug12 C. E. Armantrout13 and H. Kato3 

ABSTRACT 

The investigation of the nickel-gadolinium phase diagram was undertaken 

to determine the alloying behavior of these two metals. The data from meltingpoint determinations, thermal analyses, metallographic examinations, and X-ray 

diffraction analyses revealed a phase diagram with three eutectic points and 

seven intermetallic compounds. 

other was observed. 

melted incongruently at about 1,300", 1,250", 1,180°, l,O?O", and 775" C, 

respectively. 

980" C, respectively. Four of the compounds were determined to crystallize in 

the hexagonal system: Nil,Gd,, Ni,Gd, Ni7Gd2, and Ni Gd. Ni,Gd was determined to be cubic and NiGd, orthorhombic. The crystal system of NiGd, was not 

determined. The eutectic points occurred at 13, 67, and 85 wt pct gadolinium, 

and the isotherms at 1,290", 890°, and 700" C, respectively. 

Very limited solubility of the phases in each 

The five phases, Ni, Gd,, Ni7Gd2, Ni Gd, Ni,Gd, and NiGd3, 

Ni,Gd and NiGd melted congruently at approximately 1,550' and 

INTRODUCTION 

Because of their high thermal neutron capture cross section, the possible 

utilization of a number of rare-earth elements as control rod materials in 

power-producing atomic reactors has been considered by the Atomic Energy Commission. However, the rare-earth metals of interest are very reactive, and 

they must be protected from corrosive environments or be made corrosive 

resistant. 

The search for new corrosion-resistant alloys for application in the 

atomic energy field prompted the investigation of the stainless steelgadolinium phase diagram by the Bureau of Mines. Gadolinium was one of the 

IPhysical metallurgist (research). 

"Physicist (general). 

3Supervising physical metallurgist. 

All authors are with the Albany Metallurgy Research Center, Bureau of Mines, 

Albany, Oreg. 

Work on manuscript completed May 1964. 
2 

rare-earth elements of special kterest because of its high thermal neutron 

capture cross section, about 46,000 barns (13) .4 Previous work conducted by 

the Bureau indicated that gadolinium could be easily alloyed with AIS1 type 

304 stainless steel, extra low carbon. This type of stainless steel has a 

nominal composition of 18 wt pct chromium, 8 wt pct nickel, and 74 wt pct iron. 

Shortly after the investigation of the stainless steel-gadolinium phase 

diagram was initiated, it became obvious that the identification of the multitude of phases observed was impossible with the data available. As many as 

four unknown phases in one alloy composition were observed. It soon became 

apparent that the identification of the phases in this multicomponent alloy 

would have to be based in part on data from the investigation of the binary 

alloys, Fe-Gd, Cr-Gd, and Ni-Gd. The investigation of the Fe-Gd alloy system 

was completed and reported by the Bureau of Mines (k). 

system was reported by the senior author at the Second Rare Earth Conference 

(3) as a part of the Bureau's research effort. 

tigation is presented in this report. The phase diagrams of the other possible 

binary alloys, Fe-Cr, Cr-Ni, and Fe-Ni, have been thoroughly investigated and 

reported in the literature (11). 

The chromium-gadolinium 

The Ni-Gd phase diagram invesA search of the literature revealed the existence of several compounds in 

the nickel-gadolinium alloy system. Ehdter and Klemm (E) reported the compound NisGd which is isotypic with Cu,Ca. Wernick and Geller (20) prepared 

rare earth-nickel compounds with MgCuz-type structure, one of which was Ni,Gd. 

Moriarty and Baenziger (15) reported that Ni5Gd, Ni,Gd, NiGd3, and possibly 

Ni7Gdz, Ni,Gd, and Ni3Gd exist in that alloy system. There were no references 

to metallographic studies of nickel-gadolinium alloys. 

Table 1 lists selected physical properties of nickel and gadolinium, a 

few of which were useful in constructing and evaluating nickel-gadolinium 

phase diagrams. The physical properties of nickel are well established, but 

only recently were the properties of gadolinium accurately determined and 

reported in the literature (12). 

4Underlined numbers in parentheses refer to items in the list of references at 

the end of this report. 

A review of the theories of alloying indicated little possibility of 

significant terminal solid solubility in the nickel-gadolinium phase diagram. 

The Hume-Rothery (14) rule predicts only limited solubility when the atomic 

sizes differ by more than 15 percent. The disparity of atomic radii of 

nickel, 1.245 A, and gadolinium, 1.802 A, is greater than 15 percent. According to Gschneidner (E), electronegativity also is important in determining 

solid solubility. In general, a difference of electronegativities greater 

than 0.4 between two alloying elements is the limiting value at which any 

terminal solid solubility can be expected. The difference between the electronegativities of nickel, 1.80, and gadolinium, 1.20, is greater than 0.4. 
TABLE 1. - Selected properties of nickel and gadolinium 

Property 

Atomic number................... 

Atomic weight ................... Density at 20' C...........g/cm3 

Melting point ................. C 

Boiling point ................. C 

Atomic radius..................A 

Crystal structure............... 

Electronegativity (19). ......... 

a ........................... A 0 

c0...........................A 

Thermal neutron capture cross 

section (13) ......... barns/atom 

1Up to 1,264' C. 

Nickel (18) 

28................. 

58.71.............. 

8.902.. ............ 1,453 .............. 

1.245. ............. 1.80............... 

Fac e-c en t er ed cub ic 

3.52............... 

2,730.. ............ 

................... 

Gadolinium (12) 

64. 

157.26. 

7.92. 

1,312 L 15. 

2,830. 

1.802. 

1.20. 

Hexagonal close-packed 

3.636. 

5.783. 

4.6 It 0.2 .......... 146,000 2 2,000. 

EXPERIMENTAL PROCEDURES AND RESULTS 

Materials and Melting Procedure 

Gadolinium and nickel of 99+ percent purity were used in this investigation. Analyses for impurity content of both metals are presented in table 2. 

The presence of elements other than those listed was not detected. 

TABLE 2. - Impurity analyses of nickel and gadolinium 

Impurity element I Nickel, ppm I Gadolinium, 

ppm 

Chromium.................... I ) 10- 100 

Copper ...................... >10 10- 100 

Hydrogen .................... 3 86 

Magnesium ................... >10 10- 100 

Manganese.. ................. 1 10- 100 

Nickel...................... PI 100- 1,000 

Nitrogen .................... 10 280 

Oxygen ...................... 115 1,875 

Silicon..................... 10- 100 10- 100 

Titanium.................... 100-~,000 ) 

Tungsten .................... 100-1,000 (1) 

2No analysis. 

Iron........................ 100-1,000 100-1,000 

Not detected . 

The alloy charges were melted in a nonconsumable tungsten electrode arc 

furnace on a water-cooled copper hearth. The furnace atmosphere was controlled by evacuating, backfilling with helium, and gettering with gadolinium. 

Proportioned charges of 40 to 50 grams were melted four times or more with 

inverting between each melt to promote homogeneity in the alloys. The nominal 

composition of a number of alloys and the X-ray fluorescent analyses after 
4 

melting are tabulated in table 3. Chemical analyses mentioned in this report 

are in percent by weight unless otherwise specified. 

TABLE 3. - Analysis and hardness of alloys 

Composition, wt pct 

gad1 

Nominal 

1.0 

5.0 

10.0 

15.0 

20.0 

24.0 

27.5 

30.0 

35.0 

40.0 

43.3 

45.0 

50.0 

55 .O 

57.2 

60.0 

65 .O 

70.0 

72.8 

75.0 

80.0 

85.0 

89.0 

90.0 

95.0 

99.0 

1 Not run. 

inium 

Fluorescent 

analyses 

1 

4.9 

1 

14.5 

21.7 

26.7 

30.7 

35 .O 

40.8 

43.5 

45 .O 

50.0 

55 .O 

57.3 

* (I1 

62.5 

(l1 

73.3 

1 

78.7 

85.0 

88.3 

90.0 

(1 1 

(1 ) 

Knoop 

As-cast 

1 

14 3 

281 

390 

5 04 

632 

726 

747 

577 

5 77 

529 

434 

5 29 

454 

430 

237 

228 

308 

25 1 

(l1 

237 

15 7 

119 

cI> 

irdness 

Ann e a 1 ed 

113 

15 3 

15 7 

35 6 

498 

608 

577 

624 

65 0 

475 

5 35 

498 

542 

522 

54 9 

470 

1 

374 

25 8 

237 

262 

535 

134 

64 

1 

) 

Annealing heat treatment 

- 

l,OOOo C, 3 days, furnace cooled. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

00" c, days, furnace cooled. 

600" C, 2 weeks, furnace cooled. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Homogeneous and coherent ingot buttons were difficult to obtain on all 

alloys whose composition contained large amounts of intermetallic compounds. 

Most of the buttons were made homogeneous by repeated melting of the alloys. 

However, a slight difference in composition between the top and bottom was 

observed in a few buttons. A small degree of inhomogeneity could be expected 

because of the rapidity at which the copper hearth cools the buttons. Coheren 

buttons were difficult to obtain on the majority of the alloys with high compound composition. 

an arc to them on melting, and at times on cooling. 

Shattering of the buttons was frequently noted on striking 

Annealing Treatment and Hardness of Alloys 

After removing a sample from each ingot button for metallographic examination and before proceeding further with the investigation, the as-cast 
5 

nickel-gadolinium alloys were annealed. Most of the nickel-gadolinium alloys 

were very hard and brittle, and therefore they were not amenable to any hotor cold-working procedure for homogenization or shaping procedures. The samples were annealed by heating in a tube furnace in a vacuum of 2.5 x torr 

and allowing the furnace to cool. A molybdenum boat was used to hold the 

specimen and prevent reaction between the samples and the ceramic. The annealing heat treatments and the hardness of a few alloys before and after annealing 

are tabulated in table 3. 

Phase Diagrams 

The phase diagram was determined from data obtained by conducting melting.- 

point, thermal analysis, heat treatment, metallographic examination, and X-ray 

diffraction analysis tests. Metallographic data were used as the final criterion. On the basis of the data obtained, the phase diagram as constructed is 

presented in figure 1. In figure 2, the majority of the metallographic and 

melting-point data are presented in the phase diagram. 

GADOLINIUM, atomic percent 

0 IO 

1,6001 I Ni. 

- 1,200 -- W 

Lx $ (,I 00 .- 

I- 9001 

I 

2- I 

I 

800t 

I 

7001 

K 

: IQOOt 

W 

NiI5Gd2 

Ni+Ni15Gd2 

Ni5Gd + Ni15Gd2 

N i 5G d + N i7G d,- 

600 

0 

L 

IO 20 

I 

-I 

I 

--t 

I 

I 

I 

I 

1 

I 

30 

20 30 40 50 60 70 8090100 8090100 

91,550° 2 I I II -- Ni7Gd2 - 2,800 

'4 Ni3Gd 

\A 

\ Liquid Liquid+ \ 

Ni,Gd \\Ni2Gd 

2,600 1 

I I I I Ill 

42,800 >,550° C 

-- Ni7Gd2 

'4 Ni3Gd 

\A 

Ni5Gi 

- 

-+ 

I 

40 

\ 2,400 1,312"c- 270" C. \,I 14 aoo c 

,. 

Liquid Ni73 ,-I,07O0 C 

50 60 70 80 90 100 

w 

LT 

3 

kK 

W 

a 

2 

W 

Ia 

GADOLINIUM , weigh t -percenl 

FIGURE 1. - Nickel-Gadolinium Phase Diagram. 
6 

GADOLINIUM, atomi percent 

0 IO 20 30 40 50 60 70 8090 100 

1,600 I I I 

1,500 

1,45 5 / 

- 2,800 0 Liquidus, optical 

A Transformation by 

\ thermal analysis 

\ x Melting, visible -2,600 

- 

1,400' ' / t \ -1 \ Single phase 

\ Ni2Gd 0 Two phase 

'0 "C 'J 

-A4'J800

2*070 OC 

1,800 

I 

I 1,600 

c 

W 

CK 

3 

Ia 

K 

W 

a 

I 

W 

I- 

, I by ~~L~l,400 

700 "C 1,200 

LA-x 0 P om 0 00 0 

30 70 80 90 100 

GADOLINIUM, weight-percent 

FIGURE 2. - Nickel-Gadol inium Phase Diagram, Metallography, and Thermal Data. 

Melting-Point Determinations 

Solidus and liquidus determinations were made using an optical pyrometer 

method and by thermal analyses. 

according to the thermal gradient technique suggested by Deardorff and 

Hayes (1). A small cylindrical hole was drilled in the alloy sample, the 

specimen placed on a nickel pedestal, and heated at a relatively constant 

rate. The bottom of the hole was observed with a disappearing filament optical pyrometer, and the solidus was determined when a small droplet was 

observed in the bottom of the hole. The liquidus was determined as the temperature at which the hole was completely filled with liquid. 

melting-point determinations were conducted in a vacuum of 

The specimens were heated in an induction furnace which used a tantalum susceptor as a heat source. The data were useful in determining the melting 

points of the two compounds that melted congruently (Ni,Gd and NiGd) and 

obtaining generalized information on the eutectic isotherms and peritectic 

reaction isotherms for the remaining compounds. The data were not believed 

The optical pyrometer method was conducted 

All the optical 

torr or less. 
to be adequate for accurately placing the isotherm at which the compounds 

(Ni, 5Gd2, Ni,Gd,, Ni,Gd, Ni2Gd, and NiGd ) melted peritectically, nor when 

the alloy composition was not close to tke eutectic point. 

Thermal analyses were conducted by both differential and time-temperature 

techniques. Using differential thermal analysis, one insulated ChromelAlume15 thermocouple was inserted in a hole drilled in the specimen under 

investigation and another in a hole drilled in a neutral body, molybdenum. 

A three-wire system was used. One lead wire from each thermocouple to the 

outside of the furnace was alumel. The common lead wire between the thermocouples was chrome1 from which a wire of the same material to the outside of 

the furnace was made. The entire assembly was placed in a tube, evacuated to 

2.0 x torr, and heated by a resistance furnace at about 5" C per minute. 

The emf (millivoltage) across the Chromel-Alumel thermocouple in the specimen 

was used to determine the temperature and the emf across the Alumel wires to 

detect any temperature arrests. 

rate were used to determine solidus and liquidus temperatures during differential thermal analysis. In the time-temperature method, the specimens were 

wrapped in a piece of tantalum foil, a tungsten-tungsten 26-percent rhenium 

thermocouple was spotwelded to the outside of the foil, and the whole assembly 

was then thermally cycled, using as uniform a heating and cooling rate in an 

induction furnace as possible. The endothermic reaction that occurs when 

metals go from the solid to the liquid state causes a decrease in the apparent 

rate of heating, and therefore may be taken as the solidus temperature. A 

vacuum of torr or less was employed in the induction furnace. 

The changes in apparent heating or cooling 

Results from the solidus and liquidus determinations are listed in 

table 4, and a number of these are illustrated graphically in figure 2. These 

data indicated the presence of eight isotherms at 1,290°, 1,300°, 1,270°, 

1,180°, 1,070°, 890°, 700°, and 775" C. Maxima in the liquidus were noted 

at 1,550" and 980" C, where the compounds Ni,Gd and NiGd melted congruently, 

respectively. Minima in the liquidus were observed at 1,290", 890", and 

700" C where eutectic reactions occurred. Peritectic reactions occurred at 

the remaining isotherms. 

Heat Treatments and Metallography 

An extensive amount of metallographic work was conducted for the following reasons on this system: first, to check the homogeneity and to determine 

structures in as-cast alloys; second, to determine the effect of annealing on 

obtaining homogenized structures and to determine the phases present; and 

third, to determine the effectiveness of each heat treatment by observing 

phases present. 

5References to trade or brand names are made only for identification and 

mention of them does not imply endorsement by the Bureau of Mines. 
8 4 

TABLE 4. - Liquidus and solidus data 

Composition, 

wt pct Gd 

0 

5 

10 

15 

20 

25 

30 

35 

37.5 

40 

43.3 

45 

47.1 

50 

55 

60 

65 

70 

75 

80 

85 

90 

95 

1No determinal 

2Not detected. 

Optical 1 

Liquidus, C 

1,455 

1,460 

1,330 

1,375 

1,370 

1,410 

1,415 

1,540 

1,550 

1,475 

1,155 

1,155 

1,075 

1,045 

960 

955 

) 

) 

(2 

(2 iz j (2) 

.on. 

ithod 

Solidus, " C 

1,455 

1,380 

1,255 

1,250 

1,260 

1,265 

1,380 

1,310 

1,155 

1,290 

) 

(I) 

1,090 

1,090 

(" ) 

(2 

(" 

(2 

(" 

(2) 

1,035 

1,045 

Thermal snalysis, 

solidus, " C 

) 

1,290 

1,290 

1,300 

1,290 

1,290 

1,283, 1,500 

1,260 

1,274 

1,263, 1,174 

1,245, 1,163 

1,263, 1,172 

1,080, 1,195 

1,080, 1,190 

900, 1,080 

890 

890 

8 94 

6 75 

697 

775 

768 

(I ) 

Specimens to be heat treated and cooled rapidly prior to examination by 

metallographic techniques were wrapped in molybdenum or tantalum foil and 

sealed in quartz ampules which were evacuated and partially backfilled with 

helium. The specimens were wrapped in the foil to prevent any reaction 

between the ampules and the specimen. The specimens were heat treated at 

650" to 1,340" C from % to 148 hours. 

were transferred from the furnace to water and fractured as rapidly as 

possible. 

The ampules containing the specimen 

The heat-treated specimens were mounted in Bakelite and polished. Water 

was used as a coolant and lubricant in all but the last two polishing steps 

where diamond abrasive and kerosine were used. Three types of etchants were 

employed: 10 percent by weight chromic acid in water, 10 percent by weight 

oxalic acid in water, and nital etchants (1 to 5 percent by volume of HNO, in 

ethyl alcohol). The chromic and oxalic acid solutions were uszd to etch the 

specimens by electrolytic methods, using about 3 volts dc. 

tions were used on alloys containing 1- to 26-percent gadolinium, and oxalic 

acid on alloys containing about 43 to 47 percent gadolinium. Nital was used 

on all the other alloys by swabbing the solution on the polished specimen and 

rinsing with absolute alcohol. 

Chromic acid solu- 
FIGURE 3. - Structure of the Intermetal I ic Compound Ni 15Gd2 , 

(X 500); Nital Etch. 

Phases Observed 

Seven compounds were observed in the nickel-gadolinium alloy system. Five 

of these, Ni,,Gdz, Ni,Gd2, NhGd, NiaGd, and NiGd3, melted incongruently as 

peritectic reactions at 1,300°, 1,270", 1,180", 1,070", and 775" C, respectively. The two compounds, Ni,Gd and NiGd, melted congruently at about 1,550" 

and 980" C, respectively. With the exception of Ni5Gd, all of the phases were 

observed to be intermetallic compounds of constant stoichiometric composition. 

A slight solid solubility of Nil,Gd, in Ni,Gd was noted. 

Metallographic data observed after heat treatment are plotted in figure 2. 

Considerably more metallographic data were obtained in the course of the 

investigation, but for clarity these were left off the diagram. One of the 

phases, Nil,Gd2, observed in an alloy containing 26.4-wt pct gadolinium, is 

clearly illustrated in the photomicrograph illustrated in figure 3. This 

single-phase alloy was heated to 1,280' C for 1 hour and furnace-cooled. 

X-Ray Diffraction Data 

Extensive X-ray diffraction studies were made in this investigation to 

confirm the results observed during metallographic studies and to identify the 

phases present. The crystal structure of intermetallic compounds was also 

determined. Samples of alloys of 24 different compositions were studied. 

Most of these alloys were first studied using the same specimen and surface 

that was examined metallographically. The specimens were mounted in the 

rotating sample holder of a diffractometer. A molybdenum target X-ray tube 

was used with a zirconium filter and a krypton-filled Geiger tube. Those 

samples which were brittle enough to pulverize were reanalyzed as powders 
10 

in the diffractometer to produce more nearly random orientation of crystallites. In those cases where even greater resolution seemed necessary, the 

samples were reanalyzed in a 114.6 m-diameter powder camera with manganesefiltered iron radiation. 

The seven intermediate phases, Ni Gd,, Ni,Gd, Ni7Gd2, Ni Gd, Ni,Gd, 

NiGd, and NiGd,, that were identified 9; metallography, were also identified 

by X-ray diffraction. These seven compounds are discussed individually as 

follows: V 

1. NiIBGd, was determined to crystallize in the hexagonal system, 

a 

oiserved atomic ratios and the lattice parameters of this compound were unlike 

those reported by Novy, Kleber, and Vickery (17) for the compound occurring in 

this composition range. They reported NiI5Gd2, hexagonal, a. = 8.18 A, and 

co = 8.98 A. 

by Beaudry and Daane e) in this composition range for nickel-yttrium alloys. 

They reported Nil,Yz, hexagonal, a. = 8.34 A, co = 8.08 A. 

parameters agreed very closely to those observed in this investigation, but 

metallographic studies did not confirm the same composition. 

= 8.336 A, co = 8.054 A. The X-ray pattern is tabulated in table 5. The 

The atomic ratio of the compound also differed from that reported 

These lattice 

2. 

co = 3.964 A. 

and Klemm (8) who reported a. = 4.91 A and co = 3.99 A, and Nassau, Cherry, 

and Wallace (16) who reported a. = 4.90 A and co = 3.96 A. The latter authors 

state that Ni,Gd has the Cu,Ca-type (also known as Zn,Ca) structure along with 

18 other compounds of the formula-type A B where A represents the element 

alloyed to the rare earth B. The systematlc extinctions observed for Ni,Gd 

in this investigation can be attributed to space group P6/mmm, which is the 

space group of CusCa. 

tion is listed in table 6. 

Ni,Gd was found to have a hexagonal unit cell with a. = 4.902 A and 

This is substantially in agreement with the findings of Endter 

5.: 

The X-ray pattern observed for Ni,Gd in this investiga4. Ni,Gd was determined to crystallize in the hexagonal system with 

Since the 

a. = 4.982 A and co = 16.31 A. 

hexagonal with similar parameters and the space group P6,/mmc. 

systematic extinctions observed for Ni3Gd agree with those of that space 

group, it seems probable that Ni,Gd is isostructural with Ni,Ce. 

data noted are listed in table 8. 

Cromer and Olsen (6) reported that Ni,Ce is 

The X-ray 

3. Ni Gd, was observed to have a hexagonal unit cell with a. = 4.960 A 

and co = 2.222 A. 

space group P63/mmc, which has been reported by Cromer and Larson (5) to be 

the probable space group of the analogous compound Ce,Ni,. The similarity of 

these two unit cells makes it seem very probable that Ni,Gd, is isostructural 

with Ni,Ce,. This structure consists of double layers of the Ni,Ce structure 

(Cu,-Ca-type) alternating with double layers of the Ni,Ce structure (MgCu, - 

type). The X-ray data observed in the Bureau analysis of this compound are 

tabulated in table 7. 

The systematic extinctions appear to be consistent with the 
d (observed), 

ang s t r oms 

3.504 

3.286 

2.987 

2.687 

2.586 

2.510 

2.407 

2.257 

2.155 

2.086 

2.065 

2.014 

1.914 

1.852 

1.811 

1.760 

1.620 

1.546 

1.469 

1.450 

1.410 

1.389 

1.313 

1.278 

1.216 

1.203 

1.172 

1 154 

1.129 

1.111 

1.0939 

1.075 

1.042 

1.033 

1.022 

- 

- 

- 

- 

1.010 

1Crystal system: 

TABLE 5. - Ni,,Gdz X-ray diffraction datal 

d (calculated), 

angs trms 

3.515 

2.393 

2.895 

2.687 

2.684 

2.585 

2.516 

2.406 

2.259 

2.257 

2.154 

2.084 

2.065 

2.013 

1.914 

1.851 

1.813 

1.761 

1.620 

1.544 

1.467 

1.448 

1.410 

1.389 

1.313 

1.279 

1.278 

1.216 

1.203 

1.172 

1.155 

1.129 

1.111 

1.096 

1.091 

1.075 

1.042 

1.033 

1.022 

1.021 

1.010 

hexagonal. 

Relative (observed) 

int ens ity 

1 

6 

30 

5 

- 

7 

3 

32 

4 

28 

50 

100 

39 

15 

19 

2 

6 

8 

9 

11 

18 

8 

8 

10 

8 

5 

10 

13 

3 

1 

2 

1 

1 

12 

8 

9 

- 

- 

- 

- 

3 

11 

hkl 

planes 

102 

201 

112 

202 

003 

211 

103 

300 

212 

113 

203 

220 

302 

0 04 

2 13 

222 

114 

401 

2 14 

3 04 

412 

2 24 

323 

330 

322 

324 

116 

423 

600 

306 

325 

4 24 

522 

207 

611 

505 

44 0 

44 1 

434 

416 

5 15 

- 

Lattice constants: a. = 8.336 A, co = 8.054 A. 
12 

TABLE 6. - Ni,Gd X-ray diffraction datal 

d (observed) , angstroms 

3.969 

2.895 

2.451 

2.125 

2.086 

1.981 

1.874 

1.543 

1.490 

1.450 

1.417 

1.334 

1.261 

1.227 

1.163 

1.153 

1.130 

1.063 

1.043 

1.020 

.991 

1CrystaI system: 

d (calculated) , Relative (observed) 

ang s tr oms intensity 

3.963 

2.899 

2.454 

2.125 

2.086 

1,982 

1.873 

1.542 

1.489 

1.450 

1.417 

1.334 

1.262 

1.227 

1.153 

1.130 

1.063 

1.043 

1.020 

* 1.163 

hexagonal. 

8 

45 

20 

30 

100 

40 

10 

13 

13 

30 

6 

27 

6 

11 

24 

10 

7 

3 

18 

6 

5 

Space group: P6/mmm. 

Lattice constants: a. = 4.902 A, co = 3.964 A. 

hkl 

planes 

00 1 

10 1 

110 

200 

111 

002 

201 

112 

211 

202 

300 

30 1 

103 

220 

113 

302 - 313 

400 

222 

213 

004 

5. Ni,Gd was determined to be a.cubic MgCu,, Laves-type phase, with a 

Fd3m space group and a. = 7.223 A. The X-ray diffraction data are presented 

in table 9. Novy, Kleber, and Vickery (17) reported a parameter measurement 

of a. = 7.27 A. 

where A represents the elements alloyed to rare earth B, are reported in the 

literature to have the MgCu,-type structure. 

Many other compounds of the stoichiometric ratio of %B, 

6. NiGd: When a sample of NiGd was broken up to prepare a powder sample, one of the pieces was found to be a single crystal. This crystal was 

studied on a Buerger Precession camera and was found to be orthorhombic with 

a. = 3.765 A, bo = 10.30 A, and co = 4.24 A. The X-ray data observed are in 

table 10. 

and C,cm. 

Rosenzweig (9) for the analogous compound Nice which is orthorhomic 

%Ce has the ThI (also known as CrB) type of structure. 

NiGd has this structure, but further work will be necessary to prove this 

definitely. The sample studied in this investigation definitely does not 

have the FeB structure reported €or NiGd by Baenziger and Moriarty (I). 

The systematic extinctions were those of space groups Cmcm, Cmc2,, 

This unit cell closely resembles that reported by Finney and 

= 3.88 A, bo = 10.46 A, and co = 4.37 A, space group Cmcm. They show that 

It seems likely that 
d (observed) , ang s tr oms 

4.280 

4.025 

3.027 

2.740 

2.697 

2.478 

2.143 

- 

2.108 

- 

2.012 

1.963 

- 

1.918 

1.787 

1.732 

1.565 

1.542 

1.514 

1.473 

1.432 

1.419 

1.348 

1.295 

1.240 

1.210 

1.183 

1.129 

1.117 

1.105 

1.090 

1.073 

1.057 

1.009 

- 

- 

lCrystal system: 

TABLE 7. - Ni7Gd2 X-ray diffraction datal 

d (calculated) , angs troms 

4.295 

4.036 

3.028 

2.695 

2.470 

2.147 

2.140 

2.115 

2.113 

2.109 

2.018 

1.963 

1.959 

1.918 

1.730 

1.565 

1.539 

1.514 

1.471 

1.470 

1.432 

1.419 

1.346 

1.294 

1.240 

1.211 

1.184 

1.183 

1.127 

1.114 

1.104 

1.089 

1.074 

1.057 

1.009 

- 

hexagonal. 

Relative (observed) 

intensity 

3 

5 

4 

15 

20 

40 

40 

- 

100 

- 

25 

15 

3 

3 

10 

2 

2 

2 

10 

15 

10 

18 

4 

18 

3 

5 

5 

3 

5 

5 

5 

5 

- 

- 

10 

- 

Space group : P63 /mc. 

Lattice constants: a. = 4.960 A, co = 2.422 A. 

13 

hkl 

planes 

100 

006 

008 

107 

110 

200 

20 1 

202 

116 

0012 

205 

118 

0014 

2 15 

0016 

2 12 

300 

1, 1, 14 

0018 

308 

220 

0020 

2, 1, 14 

226 

317 

1, 0, 21 

2, 2, 10 

- 

1, 0, 10 

1, 0, 11 

- 

1, 1, 12 

2, 0, 12 

319 

400 

4 04 

0024 
14 

TABLE 8. - Ni3Gd X-ray diffraction datal 

d (observed), 

angs tr oms 

4.280 

4.110 

2.775 

2.715 

2.617 

2.491 

2.168 

2.135 

2.110 

2.041 

- 

2.015 

1.978 

1.840 

1.628 

- 

- 

1.485 

1.442 

1.419 

1.367 

1.359 

1.350 

1.319 

1.246 

1.240 

1.133 

1.098 

1.080 

1.064 

1.056 

,991 

- 

1Crystal system: 

d (calculated), 

angstroms 

4.315 

4.076 

2.718 

2.606 

2.491 

2.158 

2.139 

2.126 

2.050 

2.038 

2.006 

1.980 

1.843 

1.837 

1.631 

1.483 

1.482 

1.438 

1.417 

1.364 

1.359 

1.354 

1.314 

1.246 

1.242 

1.132 

1.098 

1.079 

1.064 

1.054 

,990 

- 

- 

hexagonal. 

Relative (observed) 

intensity 

5 

7 

10 

65 

3 

80 

30 

100 

80 

40 

40 

33 

15 

14 

15 

22 

20 

10 

40 

20 

6 

13 

10 

5 

5 

10 

5 

12 

- 

- 

- 

- 

Space group : 

Lattice constants: 

P6, /mc . 

a. = 4.982 A, c0 = 16.31 A. 

hkl 

planes 

100 

0 04 

006 

105 

110 

200 

20 1 

114 

107 

008 

203 

115 

108 

116 

2 10 

0011 

208 

300 

302 

0012 

3 04 

305 

220 

221 

226 

227 

400 

317 

1, 0, 15 

320 

- 

0, 0, 10 

1, 1, 10 
c 

t 

d (observed), 

angstroms 

4.200 

2.560 

2.180 

2.090 

1.660 

1.480 

1.390 

1.279 

1.143 

1.102 

1.089 

- 

,9655 

.9406 

.9020 

.8503 

.8337 

.7934 

,7706 

.7566 

.7373 

- 

- 

TABLE 9. - Ni,Gd X-ray diffraction datal 

d (calculated), 

ang s tr oms 

4.170 

2.560 

2.180 

2.090 

1.660 

1.480 

1.390 

1.277 

1.142 

1.101 

1.089 

- 

.9652 

.9404 

.9029 

.85 12 

.8340 

.7928 

.7700 

.7572 

,7372 

- 

- 

- 

Relative (observed) 

in t en s it y 

10 

80 

100 

30 

5 

40 

45 

45 

15 

19 

10 

13 

22 

3 

5 

11 

2 

2 

5 

9 

- 

- 

- 

- 

15 

kh 1 

planes 

111 

2 20 

311 

222 

331 

422 

511 

333 

44 0 

620 

533 

622 

64 2 

731 

800 

822 

660 

75 1 

555 

911 

75 3 

6 64 

93 1 

844 

1Crystal system: cubic. 

Space group: Fd3m. 

Lattice constant: a. = 7.223 A. 

7. NiGd,'s unit cell is unknown, for repeated attempts to index the 

pattern were unsuccessful. There is also some uncertainty about a few diffraction lines in the pattern since some of them may be caused by the presence 

of small amounts of other phases. However, there are enough lines which 

cannot be attributed to any other compound so that there can be little doubt 

that such a compound exists. The X-ray data observed are tabulated in 

table 11. 
16 

TABLE 10. - NiGd X-ray diffraction datal 

d (observed), 

ang s troms 

3.317 

3.251 

3.115 

3.092 

2.704 

2.635 

2.561 

2.193 

2.176 

2.114 

1.875 

1.655 

1.626 

1.592 

1.517 

1.469 

1.421 

1.368 

1.307 

1.267 

1.231 

1.213 

1.148 

1.112 

1.098 

1.089 

1.055 

1.027 

.999 

- 

- 

- 

lcrystal system: 

d (calculated), 

angstroms 

3.273 

- 

- 

2.706 

- 

2.575 

2.201 

2.172 

2.120 

1.869 

1.660 

1.623 

1.625 

1.591 

1.512 

1.425 

1.369 

1.311 

1.264 

1.232 

1.231 

1.212 

1.150 

1.106 

1.101 

- 

- 

1.060 

1.030 

1.025 

1.001 

orthorhombic. 

Relative (observed) 

intensity 

5 

25 

d 

5 

75 

5 

100 

40 

45 

50 

5 

15 

30 

15 

5 

‘5 

5 

15 

10 

d 

15 

5 

10 

4 

25 

d 

5 

5 

- 

- 

Space group: probably Cmcm. 

Lattice constants: a. = 3.765 A, bo = 10.30 A, co = 4.24 A. 

hkl 

planes 

- 

021 

- 

- 

111 

040 

04 1 

311 

002 

200 

15 1 

221 

132 

061 

24 0 

24 1 

170 

113 

260 

081 

24 2 

261 

172 

15 3 

223 

004 

0, 10, 0 

332 

0, 10, 1 

- 

- 

- 
d (observed) , 

ang s t r oms 

3.344 

3.238 

3.139 

3.023 

2.885 

2.865 

2.816 

2.750 

2.696 

2.635 

2.594 

2.561 

2.462 

2.404 

2.349 

2.265 

2.164 

2.104 

1.978 

1.854 

17 

TABLE 11. - NiGd3 X-ray diffraction data 

Re la t ive (ob served) 

in t ens i ty 

10 

10 

10 

13 

100 

27 

37 

9 

30 

5 

45 

21 

8 

16 

9 

22 

13 

9 

- 

20 

d (observed) , I Relative (observed) 

ang s t r oms in t ens it y 

8 - --- 

L. /Y8 

1.741 

1.706 

1.661 

1.626 

1.610 

1.553 

1.542 

1.519 

1.481 

1.436 

1.393 

1.370 

1.344 

1.323 

1.298 

1.291 

- 

- 

- 

5 

15 

21 

12 

37 

36 

40 

35 

20 

15 

21 

20 

7 

6 

12 

10 

- 

- 

- 

DISCUSSION OF RESULTS 

The identification of all of the intermetallic compounds was difficult 

when as-cast alloys were used for metallographic studies. Cored structures 

masked the presence of several of the compounds, notably in the composition 

range where Ni,Gdz, Ni Gd, and Ni,Gd occurred. 

were made homogeneous %y annealing treatments before analyses by thermal, 

metallographic, or X-ray diffraction techniques. 

For this reason all the alloys 

Metallographic and thermal analysis data, indicating the presence of a 

solidus boundary, correlated well, usually with a variation of less than 

10" C. Metallographic data were used to substantiate the temperature and the 

composition extent of all peritectic and eutectic isotherms as indicated by 

thermal analyses. Whenever a confliction of thermal analyses and metallographic data was observed, the latter was used to determine the extent of the 

isotherm. The structures resulting from heating several alloy compositions to 

temperatures slightly exceeding their respective solidus isotherms are illustrated in figures 4 through 9. A sample containing 10 percent gadolinium 

heated to 20" C above the eutectic isotherm occurring at 1,290" C is illustrated in figure 4. A eutectic structure and nickel are depicted in this 

illustration. The structure of four heat-treated specimens, which helped 

place the location of the peritectic isotherms where Ni15Gd2, Ni,Gd2, Ni3Gd, 

and Ni,Gd melt incongruently, are illustrated in figures 5, 6, 7, and 8, 

respectively. The eutectic structure resulting from heating a Ni-70 percent 

Gd alloy 10" C above the eutectic isotherm occurring at 890" C is illustrated 

in figure 9. 
18 

FIGURE 4. Dendritic Structure 

Observed in an Ni10 wt pctGdAlloy 

(X 500); Chromic 

Acid Etch. 

FIGURE 5. - Cored Structure in 

Ni-26.4 wt pct Gd 

Specimen Developed After Heat 

Treatment at 1,310' 

C (X 500); Chromic 

Acid Etch. 
19 

FIGURE 6. - Structure of an Ni-37.5 

wt pct Gd Alloy Held 

at 10°C Above the Peritectic Isotherm Occurring at 1,270°C(X 500); 

Nital Etch. 

FIGURE 7. -Cored Structure in an 

Ni-45 wt pct Gd Alloy 

After Heat Treatment 

at 10" C Above the 

Peritectic Isotherm 

Occurring at 1,180"C 

(X 500); Nital Etch. 
20 

FIGURE 8. - Cored Structure Observed After Holding 

at 10" C Above the 

Peritectic Isotherm 

at 1,070" C, Where 

Ni2Gd Melted Incongruentl y (X500);Nital 

Etch. 

FIGURE 9.- Eutectic Structure Observed in an Ni-70 wt 

pct Gd Specimen Held 

at 10°C Above the 

890°C lsotherrn(X500); 

Nital Etch. 
21 

FIGURE 10. -Duplex Structure Consisting of Ni5Gd and 

Ni7GdzObserved in an 

Annealed Ni-39 wt pct 

Gd Specimen (X 500); 

Nital Etch. 

FIGURE 11. - NiGd and NiGd3 

Phases Observed 

in an Ni-80 wt pct 

Gd Alloy (X 500); 

Nital Etch. 
22 

The solid solubility of the phases in each other were determined metallographically. No solid solubility of the phases in each other was observed 

except for a small solubility of Ni,,Gd, in Ni,Gd. All of the intermetallic 

phases, except Ni5Gd, were of constant stoichiometric composition. 

The effect of nickel on the gadolinium transformation occurring at 

1,264" C was not investigated. 

was observed to occur at temperatures much below the transformation. This 

factor plus the very limited solid solubility of NiGd, in gadolinium indicated 

that very little change would be expected in the transformation of gadolinium 

on alloying with nickel. 

An extensive solid plus liquid phase region 

Two of the compounds, Ni4Gd and Ni,Gd,, reported by Novy, Kleber, and 

Vickery (E), were not observed in this investigation. A structure containing 

the phases Ni,Gd and Ni,Gd, is illustrated in figure 10. 

composition was isotypic with the compound Ni4Gd containing 39-wt pct gadolinium, was annealed at 1,100" C for 2 days. A specimen containing almost equal 

parts of NiGd and NiGd3, observed in an alloy containing 80-wt pct gadolinium 

after annealing at 690" C, is illustrated in figure 11. This alloy composition would be isotypic with Ni,Gd,. 

This alloy, whose 

CONCLUSIONS 

The nickel-gadolinium phase diagram illustrated in figures 1 and 2 was 

believed accurate within 10" C in temperature and 2 percent in composition. 

The alloy system contains three eutectics and seven compounds. The eutectics 

occur at 13, 67, and 85 percent gadolinium, and they melt at 1,290°, 890°, and 

700" C, respectively. 

Ni3Gd, Ni2Gd, NiGd, and NiGd, ; the first four crystallize in the hexagonal 

system. 

the orthorhombic system, and the crystal system of NiGd, was not identified. 

The five observed phases, Ni,,Gd,, Ni Gd,, Ni Gd, Ni2Gd, and NiGd,, melt 

peritectically at 1,300", 1,270", 1, 180°, l,O?Oo, and 775" C, respectively. 

Ni,Gd and NiGd melt congruently at 1,550" and 980" C, respectively. 

little solid solubility of the phases in each other was observed except for 

a slight solubility of Ni,,Gd, in Ni,Gd. 

formation temperature of gadolinium was not investigated. 

The compounds observed are Ni, Gd,, Ni,Gd, Ni7Gd2, 

Ni,Gd is a Laves phase with a cubic structure. NiGd crystallizes in 

Very 

The effect of nickel on the trans- 
23 

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Intermetallic Phases. The Crystal Structures of DyGa and GdPt and 

Their Related Compounds. Acta Cryst., v. 14, 1961, p. 946. 

2. Beaudry, B., and A. H. Daane. Yttrium-Nickel System. Trans. AIME, 

v. 218 Met. SOC., 1960, pp. 854-859. 

3. Copeland, M., and H. Kato. Gadolinium Alloys of Iron, Chromium, Nickel, 

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C. Lundin, Gordon and Breach Science Publishers, N.Y., 1962, 

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4. Copeland, M. I., M. Krug, C. E. Armantrout, and H. Kato. Iron-Gadolinium 

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V. 12, 1959, pp. 855-858. 

6. Cromer, D. T., and C. E. Olsen. The Crystal Structures of PuNi, and 

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Chem. (Journal Zor Inorganic and General Chemistry), v. 252, 1943, 

pp. 64-66. 

9. Finney, J. J., and A. Rosenzweig. The Structure of CeNi. Acta Cryst., 

v. 14, 1961, p. 69. 

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LOS Alamos, N. Mex., undated, 71 pp. 

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New York, 1958, pp. 525-533, 541-546, 677-684. 

12. Howes, R. B. The Rare Earths. Metals Prog., v. 75, No. 6, June 1959, 

pp. 108-112. 

13. Hughes, D. J., and J. A. Harvey. Neutron Cross Sections. Brookhaven 

National Laboratory, Upton, N.Y., BNL 325, July 1, 1955, pp. 8, 18. 

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Between Lanthanous and Transition Metals of the First Long Periods. 

J. Phys. Chem. Solids, v. 16, 1960, pp. 123-130. 

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System. Trans. AIME, v. 221 (Met. SOC.), 1961, pp. 585-588. t 

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With Ca,Ca Structure. Acta Cryst., v. 12, 1959, pp. 662-665. 

INT..BU.OF MINES.~GH. .?A. 7544