Atomization die and method for atomizing molten material

The die comprises at least one set of opposed linearly configurated die elements spaced in substantially parallel relationship to define a longitudinally configurated die space therebetween dimensioned to pass therethrough a sheet of the molten material, the die elements defining a nozzle assembly characterized by oppositely disposed orifice-bearing surfaces. Each of the linear die elements has a gas pressure manifold for receiving atomizing gas under superatmospheric pressure, each of the oppositely disposed nozzle-defining surfaces having at least one array of orifices extending therealong and embracing each side of the longitudinally configurated die space defined by the oppositely disposed linear die elements. Conduits are provided for communicating the orifices with the gas manifold, the array of orifices in each of the die elements being convergently directed towards the other through an included angle of, for example, 40.degree. for directing atomizing gas against a predetermined focal region on a sheet of molten material passing through the longitudinal die space, each of the orifice conduits connected to resonating cavities for generating ultrasonic, high frequency shock waves for one-step disintegration of the sheet of molten material at said focal region into fine atomized particles which later solidify. The uses include the production of dry powders and liquid dynamically densified shapes, such as ingots, forging and rolling preforms and highly dense compacts.

This invention relates to an atomization die and to a method of atomizing 
molten material which is solid or which hardens at room temperature in 
order to form atomized particles of controlled particle size when 
subjected to a high rate of solidification by the nature of the 
atomization process. 
STATE OF THE ART 
Following World War II, powder metallurgy (P/M) has increasingly become an 
important adjunct to the conventional production of metal parts, 
particularly in the production of complex alloy parts difficult to produce 
by conventional methods, such as by melting, casting, and hot and cold 
working. 
A case in point is the latest generation of superalloys for use in jet 
aircraft. These alloys, when cast into ingots, are generally very 
difficult or impossible to hot work due to the presence of coarse 
segregates, coarse dendrites, and coarse grain size. 
As part of P/M technology, one method has been to produce powders of 
complex alloys by atomization, wherein each particle is in effect a micro 
casting having a very fine metallurgical structure due to the rapid 
cooling of finely atomized molten material. Thus, each atomized rapidly 
solidified particle in the solid state is substantially a uniform 
relatively unsegregated representation of the original melt, such that a 
sintered or other consolidated part produced from the atomized powder has 
a substantially uniform chemical composition and overall a substantially 
uniform metallurgical structure as compared to conventionally produced 
castings. 
Methods for producing atomized powders and shapes therefrom are well known 
in the art. In this connection, reference is made to U.S. Pat. No. 
4,066,117 which relates to the spray casting of gas atomized molten metal 
to produce high density ingots. In this patent, a detailed method is 
disclosed for atomizing molten metal for spray casting, such as heat 
resistant nickel-base alloys, in which an atomizing apparatus is described 
comprising an array of high pressure gas jets concentrically disposed 
relative to a central flow of a molten metal stream substantially 
cylindrical in shape, the jets being focused downwardly at a predetermined 
small segment of the molten stream in order to cause it to shatter into 
minute molten particles prior to casting of the particles into a receiving 
mold. 
In U.S. Pat. No. 2,997,245, a method and die are disclosed for the 
production of atomized particles using high frequency shock waves. It is 
pointed out in the patent that one of the objects is to produce atomized 
particles having a narrow particle size range as opposed to prior 
atomization methods which produced disparate particle sizes. As an 
example, the patent mentions a particle size range of 0.5 to 2 microns. In 
its broad aspects, the method described in U.S. Pat. No. 2,997,245 
comprises generating a sequence of wave fronts, each of the wave fronts 
being initially on generation composed of compressional waves in the form 
of shock waves which remain in that form. The thus-produced shock wave 
fronts are then caused to impinge in sequence onto a small volume of a 
molten cylindrical stream of material from all sides, the shock wave 
fronts being composed of compressional waves having an ultrasonic 
frequency and also advancing at supersonic velocity adapted to produce 
alternately compressive and expansive forces in the small volume of the 
molten stream to cause disintegration thereof into fine particles. 
This method is advantageous in that the particle size can be controlled by 
controlling the frequency of the shock wave; the higher the frequency, the 
smaller the particles. Also, the higher the amplitude of the shock waves, 
the smaller the particles produced. However, a disadvantage with a 
cylindrical die having nozzles disposed peripherally therearound is the 
limitation in the size of the stream that can be completely disintegrated 
into small particles. If the diameter of the stream is too large, for 
example, exceeds substantially 5 mm in diameter, only the outer rim of the 
stream tends to be disintegrated while the center core of the stream 
passes on through the disintegrating zone virtually untouched. 
Articles have been written on the theory of atomization of metals, 
reference being made to the following: "The Disintegration of Liquid Lead 
Streams by Nitrogen Jets" by J. Bruce See et al, Metallurgical 
Transactions Volume 4, November 1973 (pp. 2669 to 2673) and "Atomization 
of Specialty Alloy Powders" by Alan Lawley, Journal of Metals, January 
1981 (pp. 13 to 18). 
The foregoing articles discuss in some detail the breakup of a liquid metal 
stream when gas atomized using conventional procedures. According to the 
articles, the overall process of gas atomization consists of three stages: 
(I) primary breakup of the liquid stream, (II) the secondary 
disintegration of the droplets into fine particles while they are still 
molten, and (III) the solidification of the particles. It is generally 
believed that a sinuous wave is initiated which rapidly increases in 
amplitude, the wave then detaching itself from the bulk liquid of the 
stream to produce ligaments and flakes or platelets which subsequently 
break down during secondary disintegration. A model as applied to a sheet 
of liquid metal is referred to based on work by Dombrowski and Johns 
(Chem. Eng. Sci. 18 (1963) pp. 203-214), in which the sheet undergoes (1) 
sinuous wave formation, (2) ligament formation, and (3) finally ligament 
breakdown into droplets. 
The three-stage formation of atomized particles is characteristic of 
straightforward gas atomization at normal gas velocities (0.5 Mach, for 
example). This technique does not assure close particle size control. With 
ultrasonic gas atomization, at gas velocities of 2 to 2.5 Mach, the 
extremely high velocity impact of the pulsed gas leads to extreme rigidity 
of the liquid stream which nevertheless still has very low shear 
resistance. The high energy, high rate gas impact results in single step 
disintegration of the liquid stream as seen in high velocity movies. 
Further, the liquid droplets are accelerated at very high velocity in the 
resultant gas atmosphere. The combination of fine liquid droplets in a 
narrow size range, plus the high velocity of the droplets, leads to rapid 
solidification or quenching, which is a major advantage of this process. 
As stated earlier, a limitation in the atomization of metals has been the 
dimensional limitations of cylindrically configurated atomizing dies. It 
would be desirable to provide an improved atomization die and method 
capable of providing high production atomization rates of powder material, 
e.g., metal powder. 
OBJECTS OF THE INVENTION 
An object of the invention is to provide an improved method for atomizing 
liquid streams of material which exist in the solid state at room 
temperature. 
Another object is to provide an improved die assembly for atomizing molten 
materials, said die assembly being characterized by a linearly 
configurated space or opening through which a ribbon of molten material is 
fed for the gas atomization thereof.

STATEMENT OF THE INVENTION 
One embodiment of the invention resides in a linearly configurated 
atomization die assembly, particularly suited for but not limited to the 
ultrasonic gas atomizing of molten material which normally exists in the 
solid state at room temperature, the die comprising at least one set of 
opposed linearly configurated die elements spaced in substantially 
parallel relationship to define a longitudinally configurated die space or 
gap therebetween dimensioned to pass therethrough a sheet of molten 
material, the die elements defining a nozzle assembly characterized by 
oppositely disposed orifice-bearing surfaces disposed along the die, one 
on each of the die elements. The die elements are preferably adjustably 
mounted to provide lateral adjustment as well as angular adjustment about 
a pivot. Each of the linear die elements has a chamber for receiving 
atomizing gas under superatmospheric pressure. The oppositely disposed 
orifice-bearing surfaces forming the nozzle assembly have a linear array 
of orifices extending therealong and embracing each side of the 
rectangular die space. Conduit means are provided for communicating the 
orifices with the gas chamber, the linear array of orifices on each die 
element being convergently directed towards the other for preferably 
directing an ultrasonic atomizing gas against a predetermined focal region 
of a sheet of molten material passing through the die space or gap between 
said array or sets of orifices, each of the orifice conduits having 
resonating cavities cooperably associated therewith for generating 
ultrasonic high frequency shock waves for disintegrating the sheet of 
molten material at the focal region into fine particles. 
Another embodiment of the invention comprises a method of atomizing molten 
material which exists as a solid at room temperature, which method 
includes the steps of providing a free flowing stream of molten material 
in the form of a sheet, and then passing the free flowing sheet of molten 
material through a rectangular die space of sufficient opening to 
accommodate the molten material for atomization thereof, the rectangular 
die space having a linear array of gas flow orifices on each side thereof 
spanning the width of the sheet and directed towards the sheet of molten 
material, each of the linear arrays of orifices converging relative to the 
other towards a predetermined focal region of atomization of said molten 
sheet. The atomization of the molten stream is effected by feeding gas 
under superatmospheric pressure to the orifices, and through at supersonic 
velocity in the form of high frequency shock waves, thereby disintegrating 
the sheet of molten material at the focal region so as to produce atomized 
particles of controlled particle size and narrow size range. 
An advantage of the invention is that the linear die enables production 
rates far beyond those obtainable with cylindrical gas-atomizing dies. For 
example, assuming that a cylindrical die can atomize a cylindrical stream 
of diameter of not more than about 5 mm, the cross section of the stream 
would have an area of about 19 to 20 mm.sup.2. On the other hand, a sheet 
of metal having a thickness of about 2 mm and a width of about 40 mm would 
have a cross sectional area of about 80 mm.sup.2, or four times that of a 
cylindrical stream. Thus, assuming everything equal, including the linear 
rate of flow of the molten material, the linear die described above would 
be capable of increasing the production rate upwards of four times that of 
the circular die. A wider sheet or a larger thickness may increase the 
atomization rate even more. 
Other advantages of the invention are that the die assembly, unlike the 
cylindrical die, may comprise two die elements capable of being adjustably 
set either laterally and/or at a predetermined angle relative to each 
other (note FIG. 3) to control atomization efficiency, back pressure 
(upward against the pouring system), and the lateral spacing between the 
two linear die elements or segments (which controls the distance of gas 
travel from the orifice exit to the point of contact with the molten sheet 
of poured material). Such control will regulate the gas flow to avoid 
turbulent flow. 
Referring to FIG. 1, a die assembly is shown designated generally by the 
numeral 10 comprising linear die elements 11A, 11B disposed substantially 
parallel to each other, the two die elements being fixed in their relative 
position via a cross member or members 12. The two linear die elements or 
segments can be water- or gas-cooled if desired, die element 11A having 
water inlet and outlet ducts 13 and 13A and die element 11B similarly 
having water inlet and outlet ducts 14 and 14A. 
Each of the die elements has gas duct manifolds, such as duct 15A, 15B, 
15C, etc., shown for linear die elements 11B and 11A. The gas, e.g., 
argon, is fed under superatmospheric pressure and issues from linearly 
disposed orifices 16 at supersonic velocity as shock waves, the issuing 
gas jets 17 being focused as shown to impact a small volume of the sheet 
of molten metal passing between the two die elements (FIG. 3). In the 
alternative, the gas may enter through the opposite ends of the linear die 
elements. 
The inner details of one embodiment of the die assembly are shown in FIG. 2 
which is an enlarged cross section taken along line 2--2 of FIG. 1. Thus, 
referring to FIG. 2, die elements 11A, 11B are shown made up of part 
segments welded together. In die element 11A, the welded segments include 
18A, 19A, and 20A, while in element 11B, the corresponding welded segments 
are 18B, 19B, and 20B. 
The welded segments define in each of the die elements water jackets 21A 
and 21B (if used), respectively, and gas manifolds or ducts 22A and 22B, 
the water jackets communicating with water inlets 23A and 23B, the water 
outlets being more clearly shown in FIG. 1. Likewise, the gas manifolds 
communicate with gas inlet ducts 24A and 24B, the gas passing through 
conduits 25A and 25B and out through orifices 26A, 26B, the orifices being 
directed convergently, one towards the other, and focused to a 
predetermined small volume on a sheet of liquid metal passing vertically 
between the two die elements (FIG. 3). As shown in FIG. 2, each of the 
orifice channels makes an angle of about 22.5.degree. with center line 27 
of the sheet of metal 28, the included angle being about 45.degree.. The 
metal passes through ceramic (metallic, graphite, etc.) tube 28A. 
The gas under superatmospheric pressure passes through chamber exit ducts 
29A and 29B, respectively, of die elements 11A, 11B, the chamber exit 
ducts communicating with orifice channels 25A, 25B, respectively, such as 
to provide a pair of resonating cavities 30A, 30B in die element 11A and 
resonating cavities 31A, 31B in die element 11B. 
When compressed gas under superatmospheric pressure (e.g., argon, helium, 
nitrogen, etc.) is supplied through gas inlets 24A, 24B and caused to flow 
out through chamber exits 29A, 29B and the gas is caused to reflect off 
resonating cavities 30A, 30B and 31A, 31B, non-stationary shock waves are 
generated as described in U.S. Pat. No. 2,997,245, the disclosure of which 
patent is incorporated herein by reference. The shock waves have a 
moveable wave front, supersonic speed, and ultrasonic frequency as they 
exit from orifices 26A, 26B. 
The shock waves are generated in a series of steps. First, the gas escapes 
from the gas nozzles at supersonic speed; primary and secondary shock 
waves are generated by virtue of resonating cavities 30A, 30B, 31A, and 
31B (Hartman reflecting chambers), with characteristic frequencies of 
about 20,000 to 30,000 cycles/second and at about 100,000 cps. The first 
shock wave is due to reflections from cavities 30A and 30B, the second 
reflections occurring at cavities 31A and 31B. The secondary shock wave is 
the stronger shock wave and has a frequency of about 100,000 cps. 
The gas passes through conduits 25A, 25B and out through orifices 26A, 26B, 
in a pulsating manner, the shock wave front being of such velocity and 
intensity as to shatter the metal stream and convert it to atomized 
particles in one step. The gas exits out of the orifices at speeds of up 
to 2 to 2.5 Mach. The frequency ranges from about 20,000 to 30,000 
cycles/second and about 100,000 cycles/second. 
Typically, gas exit ducts 29A, 29B and conduits 25A, 25B will have the same 
cross-sectional dimensions, for example, about 0.8 mm. 
The die elements may be separately supported and adapted to be set at a 
desired angle relative to the sheet of metal flowing between them as shown 
in FIG. 3 which depicts in cross section a trough or funnel 32 having a 
slotted opening 33 at the bottom through which a stream of molten metal 34 
flows between die elements 35, 36 with orifices 37, 38 convergently 
focused to a small volume 39 of the sheet of molten metal to shatter it 
into atomized particles 40. 
It is desirable to maintain a constant head 32A (FIGS. 3 and 6) in funnel 
32 to assure a continuous and a uniform flow rate of the molten material 
during atomization. The constant head is maintained by feeding molten 
metal into the funnel from a crucible or from a tundish. In a preferred 
embodiment, the die elements are axially mounted at fixed pivots 41, 42 to 
enable angular adjustment of one die element relative to the other 
according to the angle of impingement to be achieved. In addition, the 
dies may be laterally displaced relative to each other along slots 41A, 
42A, respectively, via bolts not shown. In this connection, the die 
assembly of the invention is particularly advantageous as compared to the 
non-adjustable unitary cylindrical die of the type disclosed in U.S. Pat. 
No. 2,997,245. 
Another advantage of the die assembly is that the orifices can be linearly 
staggered in several rows along a bevelled face of the die element to 
provide maximum packing density as shown in FIG. 4, with each row having a 
slightly different angle of attack or impingement (note 39 of FIG. 3). 
Thus, referring to FIG. 4, a die element 43 is depicted schematically as 
viewed from its underside, the die element showing a water jacket 44 which 
is fed by water inlet duct 45, the outlet duct being out of view. The die 
element has a gas manifold 46 which is fed by gas under superatmospheric 
pressure via gas inlet or duct 47 (which can be introduced in several 
ways, e.g., by gas inlets at the opposite ends of the die or at several 
inlets like duct 47 spaced along the linear die element), the gas manifold 
having a series of gas exit conduits 48 and 49 with resonating cavities of 
the type shown in FIG. 2. Each of the gas conduits 48, 49 connects the gas 
manifold to the orifices depicted by numeral 50, which are staggered 
linearly along bevel face 51 of the die element. By staggering the 
orifices on each bevel face, a judicious spreading of the gas stream 
exiting from the orifices can be obtained to encompass a predetermined 
small volume of the sheet of molten metal flowing between the die elements 
shown in FIG. 3. One, two, three or more such arranged rows can be 
prepared. 
Another advantage of the linear die assembly provided by the invention is 
that since the die element can take on a rectangular shape, several die 
elements can be arranged in tandem fashion as shown in the schematic of 
FIG. 5, wherein die elements 52, 52A, and 52B are arranged in tandem in 
opposed relationship to corresponding die elements 53, 53A, and 53B, such 
that substantially wider sheets or interrupted segments of sheets of 
molten metal or other material can be atomized at high production rates. 
As shown in FIG. 5, the die elements are arranged to provide a correctly 
distributed flow of atomizing gas 54 which is focused to impinge on a 
predetermined small volume of a sheet of molten metal (not shown). 
As stated earlier, the linear die assembly of the invention overcomes 
certain inherent disadvantages of unitary cylindrical dies in that a broad 
range of production rates can be obtained, depending upon the thickness of 
the molten stream and its width. Other advantages of the invention include 
(1) the preferred feature of varying the angle of impingement to change 
the included angle of impact depending upon the results to be achieved, 
and (2) of varying the distance of the jet nozzle outlet to the liquid 
sheet surface for greater size control of the atomized particle and to 
assure laminar flow rather than turbulent flow. 
The thickness of the sheet will generally be in excess of 1 mm and range up 
to as high as 5 mm or more with the width of sheet of molten material 
being at least 5 times the thickness of the ribbon and generally over 10 
times. Thus, assuming a thickness of about 3 mm and width of 40 mm, the 
cross section of the ribbon will be 120 mm.sup.2. A cylindrical stream of 
molten metal of 5 mm in diameter has a cross sectional area of only 
approximately 20 mm.sup.2. Assuming the same linear flow rate of molten 
material through the die aperture, the sheet of molten material of the 
aforementioned dimension would have a production rate of over 6 times that 
obtained with a cylindrical die. With a ribbon width of 50 mm and a 
thickness of 5 mm, a still higher cross sectional area of 250 mm.sup.2 can 
be atomized. 
The term molten material used in the context of this invention includes 
metals (e.g., alloys) and non-metals (certain glasses, polymers and 
ceramics) which exist in the solid state at room temperature. 
Examples of atomizing metals or alloys are as follows: 
A melt of 10 lbs. (4,540 grams) of a stainless steel composition (for 
example, type 316 stainless steel) is melted and adjusted to a temperature 
of 1600.degree. C. to 1650.degree. C. The melt is poured into a preheated 
tundish with a suitable nozzle (e.g., 20 mm.sup.2 cross sectional area), 
which in turn is used to feed a pouring funnel of the type shown in FIGS. 
3, 6, and 7, the exit rectangular tube of the funnel being disposed 
between the two linear die elements as shown. As the metal exits the 
pouring tube, high pressure argon gas is activated at, for example, 1200 
psig. Atomization is accomplished at a rate of 1000 to 2000 lbs. per hour, 
achieving quench rates of 10.sup.5 degrees C./sec. In a second case, a 
copper-base alloy of the composition Cu-5Ni-2.5Ti is similarly atomized 
using a pouring temperature of about 1200.degree. C. In a third case, an 
aluminum alloy of the composition Al-4.2%Cu-1.6%Mg-0.5%Mn-3%Li is 
preheated to a temperature of 800.degree. C. and atomized through the 
linear ultrasonic gas atomization die to produce minus 250 microns powders 
at quench rates of 10.sup.5 degrees C./sec. 
Examples of atomizing a non-metal material are as follows: 
A 20 lb. melt (9,040 grams) of a borosilicate glass is melted and adjusted 
to a temperature which will result in a viscosity of about 100 poises to 
assure easy flow of the fluid glass. The glass is poured into a preheated 
tundish which in turn flows into the funnel delivery system as described 
hereinabove to provide a sheet of glass 2 mm thick and 25 mm wide. As the 
sheet of glass flows from the funnel into the gap between the two linear 
die halves, nitrogen gas, which is delivered to the atomizing dies at 1000 
psig, exits the rows of orifices, ultrasonically pulsed, to atomize the 
glass into fine droplets which harden in the nitrogen atmosphere into fine 
uniform spheres. In a second instance, vanadium pentoxide (V.sub.2 
O.sub.5) is melted, heated to a temperature of 850.degree. C. and is 
atomized using a pulsed air stream to provide a glassy product. 
Because the invention enables the production of molten atomized metal 
particles having a narrow particle size range, (solidification takes place 
in a rapid, predictable time), the invention is particularly applicable to 
the spray casting of metal ingots (reconstitution of ingots), the 
production of forging and extrusion preforms, and dense compacts. An 
example of spray casting is illustrated in the schematic of FIG. 7 which 
shows a funnel 55 of metal 56 maintained at a substantially constant head 
57 to provide a uniform flow of a sheet 57A of molten metal passing 
between linear die elements 58, 59, the molten sheet being atomized by a 
supersonic flow of gas 60, 61 in the form of high frequency shock waves to 
form molten atomized particles which are directed to the interior of mold 
63, for example, a water cooled copper mold with water jacket 65, the mold 
having a plate 66 which is movable supported as shown by worm 64 to enable 
vertical movement of the plate during the filling of the mold. The mold 
has a slight draft to assure downward movement of the plate as the ingot 
is being formed. 
The production of a narrow range of atomized particles which are propelled 
at a very high velocity is critical to the successful spray casting of 
metal ingots, forging preforms and compacts. Further, it has been shown 
that the ultrasonic gas atomization process is a single step process 
wherein the liquid metal stream is fully atomized at the point of impact 
of the pulsed gas stream, which is very near the orifice or near points 60 
and 61 in FIG. 7. This means that the atomization and particle flight 
patterns are well defined. 
Based primarily on the liquid atomized droplet size and its velocity in the 
surrounding atmosphere (argon, nitrogen, helium, for example), one is able 
to determine the start and end of solidification. By maintaining the 
preferred distance from the point of atomization to the point of impact of 
the atomized droplets, one can assure that the great majority of the 
droplets will be 10% to 90% solidified at the point of impact in the mold. 
The partially solidified droplets, delivered at very high velocity, are 
thus splat quenched (flattened out into thin discs from less than 1 to 
about 10 microns thick) against the mold surface or the previously laid 
down deposit resulting from spray casting, which preferably is called 
Liquid Dynamic Compaction. In splat quenching, the solidification rates 
will be near 10.sup.2 .degree.C./sec. and vary from 10.sup.2 to 10.sup.5 
.degree.C./sec. Secondary cooling, in the solid state, will be less, but 
the minimization of segregation, the production of a fine secondary 
dendrite arm spacing and a very fine grain size will depend on the 
solidification rate. 
Since no copious continuous liquid phase can exist as in large castings, 
solidification is local, uniform and essentially free of porosity. 
Densities may be in excess of 99% and seldom less than 97%. The resultant 
reconstituted ingots, preforms and compacts have excellent hot working, 
and even cold working, characteristics as a result of the fine grained, 
relatively unsegregated, fine phase distribution. Structures and 
properties are often of such merit as to permit use of the spray cast 
product in the as-deposited condition. 
As illustrative of the invention, the following examples are given: 
EXAMPLE 1 
In producing a spray-cast ingot, an austenitic stainless steel, type 316 
containing 0.3% Ti and 0.05% C, is melted and preheated to 1600.degree. C. 
The steel is poured into a tundish which in turn meters the flow of the 
alloy into the pouring and delivery funnel which permits the flow of a 
liquid sheet of alloy of dimensions 2 mm thick and 40 mm wide. Argon gas 
is delivered to the gas distribution manifold of the two aligned linear 
ultrasonic gas atomization dies at 1000 psig. The gas passes through the 
two Hartman reflection chambers in each die and exits as pulsed gas jets 
at Mach 2 to 2.5, with a primary frequency of about 100,000 cps and a 
secondary frequency between about 20,000 to 30,000 cps. The ultrasonically 
pulsed gas streams strike the liquid steel sheet and instantaneously 
atomize the liquid steel into droplets which are usually finer than 250 
microns and are propelled at very high velocity in a narrow spray. The two 
halves of the linear dies are set to provide an included angle of about 
45.degree. or about 221/2.degree. between the gas jet and the plane of 
the metallic sheet. The die length is about 10% longer than the liquid 
steel sheet and the distance between the two parallel die halves is 10 mm. 
The narrow spray will travel about 30 cm before it strikes the bottom of 
the ingot mold shown in FIG. 7. This allows for 10 to 90% solidification 
during flight and before splatting against the metallic substrate of the 
ingot mold, which is constructed of high conductivity copper (which may be 
water cooled if the ingot or compact is large). The copper mold acts as a 
high quench rate substrate to achieve high solidification and high 
secondary quench rates. The ingot mold is installed such that it has two 
dimensional translation, horizontally to permit ingot build-up uniformly, 
and an up and down motion to permit the ingot to grow in length by 
lowering the mold bottom to maintain the distance of flight of the 
partially solidified droplets to a constant distance from point of 
atomization to the plane of impact and form the ingot by liquid dynamic 
compaction. The resultant ingot (or compact) of about 25 cm diameter by 
100 cm long with a high density, e.g., 99% or more, may be hot extruded 
into rod, bar or tubing achieving an average grain size of about 10 
microns or less and is characterized by improved strength and ductility. 
EXAMPLE 2 
A superalloy designated as IN-100 is particularly suited for the method of 
the invention. This alloy which nominally contains 0.15% C, 10% Cr, 15% 
Co, 3% Mo, 4.7% Ti, 5.5% Al, 0.014% B, 0.06% Zr, 1% V, and the balance 
nickel is designed for casting purposes only. The cast alloy is normally 
coarse grained (4000 microns), has a segregated structure and is not 
forgeable. The alloy, which is supplied as vacuum melted stock, is melted, 
preheated to about 1550.degree. C. and is atomized under similar 
conditions as in Example 1. Instead of producing an ingot or compact, the 
atomized partially solidified droplets are delivered into a copper forging 
preform in the shape of a small disc (or a jet engine bucket). The preform 
may have one surface which essentially reproduces one of the desired 
surfaces and shapes. The partially solidified atomized droplets, propelled 
at very high velocity, form a dense structure of about 99% or more density 
with ultra fine dendrite arm spacing and grain size, with minimum size of 
intermetallic phases. The as deposited structure is readily hot workable 
and produces a product with average grain size finer than 10 microns 
routinely and even less than 5 microns through careful control of 
processing variables. This structure generally has superplastic 
properties. Resultant properties at 20.degree. C. show superior strength 
with elongation values of about 20% compared to values of less than 5% for 
conventional ingots or castings made under precision casting conditions. 
Although the present invention has been described in conjunction with 
preferred embodiments, it is to be understood that modifications and 
variations thereto may be resorted to without departing from the spirit 
and scope of the invention as those skilled in the art will readily 
understand. Such modifications and variations are considered to be within 
the purview and scope of the invention and the appended claims.