US2843921A

US2843921A - High-strength high-density tungsten base alloys

Info

Publication number: US2843921A
Application number: US594039A
Authority: US
Inventors: Ang Choh-Yi
Original assignee: PR Mallory and Co Inc
Current assignee: Duracell Inc USA
Priority date: 1956-06-26
Filing date: 1956-06-26
Publication date: 1958-07-22
Anticipated expiration: 1975-07-22

Description

July 22, 1958 v CHQH-Yl ANG 2,843,921.

HIGH-STRENGTH HIGH-DENSITY wuncsmu BASE ALLOYS Filed June 26, 1956 -e Sheets-Sheet 2 1 Q 6 mi a 4 6 8 (0 12 14. 1e 18' 29 22 24 26 I .'/p 'f ['uj INVENTOR ATTORNEY July 22, 1958 CHOH-Yl ANG HIGH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Filed June 26.-1956 6 Sheets- She et s @SQEEQ s gm INVENTOR (HQH-Yf AN' ATTO R N E July 22, 1958 CHOH-Yl ANG HIGH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Filed June 26, 1956 6 Sheets-Sheet 4 FIG. 4.

FIG

INVENTOR 'CHOH-YI ANG ATTORNEY July 22, 1958 CHOH-Yl ANG HICH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Filed June 26, 1956 6 Sheets-Sheet 5 FIG. 6.

FIG. 7.

INVENTOR CHOH-Yl ANG ATTORNEY July 22, 1958 CHOH-Yl ANG 2,843,921 v HIGH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Filed June 26, 1956 6 Sheets-Sheet 6 INVENTOR C HOH-YJ ANG ATTORN EY tungsten base alloys.

United States atent ice HIGH-STRENGTH HIGH=DENSITY TUNGSTEN BASE ALLOYS Y f Choh-Yi Ang, Indianapolis, Ind., assignor lory & Co., Inc., Indianapolis, Ind.,.a corporation of Delaware Application June 26, 1956, Serial No. 594,039

Claims. (11. 29-182 This invention relates to high-density tungsten base alloys, and, more particularly, to tungsten base alloys having improved physical properties, such as. greatly in- I creasedultimate tensile strength, which could not be obtained with prior-alloys of the same general type.

Heretofore,tungsten base alloys, esp'eciallyagroup of' these alloys in which small percentages of nickel and copper were'alloyed-with the tungsten base, have been used-commercially on a substantial scale for applications where their high density and other physical chaarc'ter-' istics' have been found to be desirable, for example, for radiation shielding, weight balancing, mwrser gyroscopes and gyrocompasses, balance crankshafts of aeromotors, boring bars, tool shanks, and the like, Although these prior tungsten nickel-copper alloys possessed valuable properties in addition to their high densit-ies such as the possibility of machining them to final dimensions without grinding orother expensive operations, they had the disadvantage of relatively low strength. Thus,'one' of the strongest known tungsten-nickelcopper alloys was reported to have a tensile strength of only 112,000 p. s. i. This circumstance has limited the use, of these alloys for certain applications,- particularly "as'rotors ofgytoscopes and gyrocompasses, where the present trend of development is toward increased rotational speeds requiring higher tensile strength of the structural materials used.

to P. R. Mal

Fig. 2 is a similar graph indicating the composition limits of another group of tungsten base alloys of the vention; a v a Fig. 3 is a graph showing the eifect of 'sinteringtirne on the physical properties of the alloys embodying the" invention; 7 p g Figs. 4 to 8 are phc'ytomicrographs of the microstr-ue:

ture of an alloy of the inventionmade with diiferent sintering times; and

Fig. 9 is a similar photomicrograph of the microstructure of a conventional high-density tungsten base alloy. Broadly stated, the present invention is based on the discovery that high-density alloys of heretofore unobtainable strength and other characteristics maybe 'obtained by alloying tungsten with minor proportions of copper, nickel and molybdenum, or of copper,""nickelj molyb l The alloys within the contemplation denum and iron. v of the invention contain at least 65% by Weight of tungsten and various amounts of nickel, copper, jniolybd'enu'm' and iron in controlled and correlated proportions minor constituents, the function of which is to form aj strong alloy matrix surrounding the tungsten or'tung It is an object of the present invention to improve It is another object of the present invention to provide improved high-density tungsten base alloys characterized with conventional tungsten base alloys.

v It is a further object of the invention to provide highdensity tungsten base alloys containing, in addition to the usual alloying metals of nickel and copper, also other metals in critically controlled proportions and which will yield ultimate tensile strengths from 10% to more than 50% greater than thoseof the heretofore reported tungsten-nickel copper materials or of their modifiedalloys.

, t It is also within the contemplation ofth e invention to a provide a'novel methodtor the commercial production of high-density tungsten base alloys of high strength.

by tensile strengths greatly'exceeding those obtainable 7 The invention also contemplates a novel and improved I group of high-density tungsten. base alloys which, as to V thecost of the initial materials and production, are not more expensive than present tungsten base alloys for similar applications, which are characterized by ultimate tensile strengths which were hereto unobtainablep-in the present tungsten base alloys, and'which may be readily manufactured and sold on-a practicaland-commercial scale at a low cost. I

Other and further objects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

. Fig. 1 is a graph indicating the composition limits of a group of. tungsten base alloys embodiyng the invention;

sten and molybdenum grains, imparting to the alloy 'as. a whole under controlled conditions ultimate tensile strengths much greater than those of the conventional high-density tungsten alloys to as high as that of well annealed pure tungsten. I I have found that withspecificj powder characteristics and under controlled sintering conditions the mechanical properties of the sintered alloys of the invention may be varied with-inwide'limits; thus,

. ultimate tensile strengths from 100,000 ps i to greater than 160,000 p. s. i, and ductilities fromfa fraction'of 1% to greater than 9% in one inch may be readily obtained.

For the purposes of the present description-[the 'term high-densityv alloy is intended to mean alloys which have theoretical densities not less than 13.5 gm./ cc.

sintered densities at least 9 3% of the theoreticahthatis, approximately 12.6 gm./cc.

I am aware of the fact that itwas already ,previously attempted to form alloys containing molybdenumin ,addi-' .tion to tungsten, nickel and copper. However, these; prior alloys have been eithermolybdenurn-basejalloys' containing tungsten, nickel and copper only as minor constituents, or have employed molybdenum" merely to replace some or most of the tungsten, thereby to obtain alloys of lower density. In contrast to this, in accord m with. t e P Q P f t eme ent nve n t e 1' molybdenum is not added as a density diluting a e t; but is adjusted in critically controlled amounts Wilhlf J spect to the nickel and copper contents. 6 As a resulty the alloys of the invention, when given a proper length l of additional sintering time at temperature aft-eradequate the inventions under certain conditions Will yield ultimate tensile strengths approaching or egual'tothat oi well-annealed pure tungsten.

In the case of the second series of the tungsten base alloys ofthe invention comprising nickehcopph'rdolybdenum and iron, further novel'and uniqueresults are; obtained. Thus, in the presence of molybdenum, the addition of iron in calculated amounts with respect to"; the nickeland copper contents also functiions as a matrix- 3 a strengthening agent. The addition of iron in- Iirnited but j 2,843,921 P te te my 9 .5 a t sufficient quantities not only improves under given conditions the ductility of the alloys without jeopardizing their high tensile strengths, but also raises the degree of response of these alloys to sintering treatments so that additional desirable mechanical properties may be obtained.

The alloys of the invention may be made by powder metallurgical methods. The uniformly and intimately. mixed, preferably partially or totally pre-alloyed, powders of the desired constituents, having a suitable average particle size (as measured with a Fisher sub sieve sizer) not greater than 8 microns, preferably between 2 and 6 microns, with a normal particle size distribution, wit'n or without a binder, are formed under pressure into coherent bodies and subsequently sintered in a protective or reducing atmosphere at suitable temperatures. The sintering temperatures must not be lower than the liquidus temperature of the theoretical binary Ni-Cu phase and the sintering time must not be shorter than that required at the selected temperature to produce a sintered density at least 93% of the theoretical. As a function of the average particle size of the prepared powder and the sintering temperature, for a given composition, the sintering time after the minimum densification period may be varied to obtain desired mechanical properties of the sintered alloy.

In making the alloys of the invention, rather than starting out from powders of the elementary metals, it is generally preferred to mix the oxides or other readily reducible compounds of the constituent metals in powder 3 form, co-reducing the mixture of metal compounds, for example, by heating under reducing conditions, to a mixture or. partial alloy of the elementary metals, and further treating the reduced metal or partially alloyed powder by powder metallurgical procedures.

The invention will now be more fully described with particular reference to the accompanying drawings.

COMPOSITION LIMITS Grn;/ cc. Tungsten 19.32 Nickel 8.9 Copper 8.92 Molybdenum 10.2 Iron 7.87

The invention contemplates alloys within the following ranges, it being noted that throughout the description all percentages are intended to mean percentages by weight (w/o):

(1) W At least 65%.

(2) Ni+Cu+Md+Fe Not over 35%.

(3) Ni-l-Cu 4% to 25%.

(4) Ni-l-Cu ratio 0.5'to 2.5.

(5) Mo 0.4(Ni+Cu)% to'1.5

(Ni+Cu)%.

(6) Fe. 0 to 1.5(Ni.+Cu)% but not over 10%.

For clearer understanding of these alloy ranges, reference may be had to Figs. 1 and 2 of'the drawing,of which Fig. 1 illustrates the compositionranges of the first series of alloys composed of W-Ni-Cu*Mo and Fig." 2 illustrates the composition ranges of thesecond series" of alloys composed of W-Ni-Cu-Mo-Fe.

It will 'be noted that by equating Fe with zero, Fig. 2 becomes identical with Fig. 1.

Considering first Fig. l, the application of this graph to determine the ranges covered by the first series of alloys is self-evident. As to the second series of alloys shown in Fig. 2, all of the alloys contemplated by the present invention are represented by the area QRHJK,

i with the aid of the smaller enclosure in the upper left corner. Here, a little extrapolation is required to identify a particular alloy composition. According to condition (6'),i the Fe content may approach 0%, therefore, the Ni+Cu+Mo contents (W the balance) may be first plotted in the area QRHJK, and then the Fe content is located in the upper left enclosure by graphic extrapolation from the plotted point within QRHJK. The method of graphic extrapolation is quite simple and becomes readily understandable from the following:

1. Area A (QRSN) The maximum Fe contents in the compositions enclosed by this area may vary from 6% to 10%, depending on its location in the area in terms of Ni+Cu and Mo contents. For example, partial composition a, (5.7% Ni-l-Cu), 6% Mo, balance W) or a (5.7% (Ni+Cu), 4% Mo, balance W) may represent a large number of alloys containing Fe from 0% to 8.5%. this is shown by drawing a line from either a or a perpendicular to the abscissa (or parallel to line SN), until it intersects line RS. From this point of intersection, another line is drawn parallel to SM until it meets the left boundary line of the upper left enclosure. This terminal point is 8.5% Fe; therefore, alloys containing 0% to 8.5%Fe plus Ni, Cu, Mo and W in amounts indicated by al and a are all within contemplation of the invention.

2. Area B (NSM) All compositions may contain 0% to 10% Fe.

partial Ni-Cu-Mo composition,-for example b perpendicular to the abscissa, to line SM. The continuationof' SM terminates at 10% Fe maximum.

3. Area C (MSTL) All compositions may contain 0% to 10% Fe. The method of graphic extrapolation is self-evident, as shown by the example given in Fig. 2, i. e., 0 alloy.

4. Area 'D (LTHJKL) Graphic extrapolation is the same as for area C. However, the alloys in area D may have their maximum Fe contents varying from 10% to 0% as a function of their Mo and Ni+Cu contents. For example, d with 11% Mo and 16.5% (Ni+Cu) may contain up to 7.5% Fe, whereas d with the same amount of Mo but- 22% for Ni+Cu can contain no more than 2% Fe.

CONSIDERATIONS RELATING TO COMPOSITION RATIOS AND LIMITS Ina tungsten"all'oy of the type contemplated by the invention, Ni and Cu are essential to give a liquid phase" Graphically, i

Graphically, this may be presented by a line drawn from any W or W and Mo are diflicult to achieve.

sintering temperature under these conditions will result in'all kinds of trouble, such as warting, blistering, or

at commercially feasible sintering temperatures and to promote the solution and precipitation of the refractory elements, W or W and Mo. When Ni-i-Cu is less than 4%, the powder compact has difliculty in attaining high sintered density to deficiency in liquid phase.

The pow-z der is also difficult to press, resulting in pressure cracks.

Ni-l-Cu greater than 25% will cause-the presence of too much liquid phase during sintering, which makes.

sintering very diflicult to control. Experimental investigation has indicated that unless 'the other components 1 (M0, lie and W) -were present in certain specific amounts, Ni+Cn contents higher than 25% resulted 1n weaker alloys. I- ,7 7 A Ni/Cu ratios -are-important because: (a) when,Ni

is more. than 2.5. times. Cu, the sintering temperature willhave to be very high'to effect the solution and precipitation of W or W and Mo; (b) when Cu is more than twice the Ni (or Ni/ Cu is less than the formation temperature of the liquid phase is low, and at low sintering temperatures (for examp1e,'in the range of 1100 to 1300 C.), the solution and precipitationof Using a higher shape distortion. I V

3'. M0 an'id Fe contents These two elements do not contribute much to the formation'of a liquid phase, although Mo-Ni does have a"eutectic"composition which melts at 1300 C.

There are no .Mo-Ni-Fe, W-Mo-Ni-Cu, or Mo-Ni-Cu constitutional diagrams available in the literature, but 'we may think in terms of Mo-Ni and Mo-Fe and Fe-Ni systems... JA Mo'content'. exceeding the maximum of 1.5

times Ni+Cu (or more than 2 times Ni if maximum Niis present in Ni.-|-Cu), puts the binary Mo-Ni in a high melting phase where diffusion rates of; all elements concerned are slow. This is strongly indicated by experimental evidence. I A a 1 The addition of Fe to the Ni-Cu system will strengthen the alloy phaseto a certain extent. Since in the second .6 essentially comprising Ni and Cu. If Fe plays arole of precipitation hardening, the long time sintering may develop some phenomena equivalent to high temperature over-aging, which resultsina softer alloy. p l

The addition of Fe to W-Ni-Cu-Mo in limitedamounts not only improves ductility without reducing the strength, but also makes the control .of the sintering. operation. This is probably due to thecontroliof less diflicult. I I particle size of'the powderduring powder preparation. In the presence of the oxides of Fe and M0, the co-reduction of the mixture of all oxides can be easily controlled to give an average particle in thepreferred range of 2 I to 6 microns. Too small a partic'lesize is not onlyhard to' handle, but also makes it difficult to arrest the sin te'red alloy in the correct conditions which give high strength properties. In other words, due 'to so 'largea total active surface area, the action of'solution andpre: cipitation takes, placeso Irapidly'that strengthening .phe:

nomena occur as soon as .the compact densifies,and dist-f appearvery soon after densification. Excessively. large particle size, on the other hand, makes it difficult to densify the compact. When a very long sintering is used to achieve densification, the alloy is already in the soft" state ACTUAL POWDER PREPARATION In making the alloys of the invention by powder metallurgical procedures, it is preferred to start out from oxidesof the component metals, rather than from powders of the elementary; metals. ides is usedto prepare the pre-alloyed powders, the

Co-reduction of these 0x- I average particle size of which should not exceed 8 microns and preferably should be between 2 and 6,microns.

' Oxides of W, Ni, Cu',"Mo' and Fe are thoroughly blended I together and then reduced at 900 to 1100 C. in dry cracked ammonia or hydrogen atmosphere.

sizeof the ,resulting'powder is controlled by varying re- Particle j duction time and temperature and bed thickness.

The average particle size of typical oxide materials suitable for the purposes of the present invention will appear from the following:

series of-alloys, Fe is added onlywhenf'Moljis; present in order to have high strength properties, the Mo-Fe system then plays a part which may be important. If the Mo content is greater'than the Fe content, the binary phases are epsilon and delta, which inherit morev properties from Mo than from Fe., When the Fe ismorethan the M0, the ductility of the alpha phase (high Fe) shows up" until too much Fe is added, then the alloyfloses strength. -Theretore, maximum Fe is specified as the same as maximum M0 (1.5 times Ni-l-Cu), but not more than 10%. Experiment showed that too much Fe did Molybdic oxide l w Very fine, difficult to measure. "Blue tuugstic oxide 11-17 microns.

I Magnetite 2.3 microns Nickel oxide Approximately 3 microns.

Cuprous oxide Approximately 3 microns.

In general, pre alloyed powders having the desired average particle size within 2 to 6 microns were obtained by loading the thoroughly blended oxide materials having the above characteristics in stainless steel trays with I a bed thickness of about 5 and co-reducing them at weaken the alloy, although the ductility was improved.

Furthermore, the density limits imposed by practical considerations also restrict the amounts of Fe addition due to the fact that Fe is a light element having a density of only 7.87 'gm./cc. a

I )Fromthe foregoing considerations, it appears that'vboth Mo and Fe play important roles in strengthening W-Ni- Cu alloys. Their function the following: a. They strengthen the matrix by going into solid solutions.

b. They, when in the form of very minute (submicroscopic) precipitates in the matrix, strengthen the alloy. 0. They slow down the rate of precipitation of'W from the matrix when the latter is already in'solution,

thus strengthening the alloy.

- 'This explanation ofthe strengthening phenomena also clarifies why the properties of the alloys of the invention drop to.those of conventional W-Cu-Ni alloys after excessively, long sintering. Unduly long sintering precipitates out W or high W and high Mo phases, accompanied, of course, by grain growth, leavingthe matrix 900 10009 C. for a time, at heat, of one-half to threequarters of an hour infdry cracked ammonia atmosphere.

vIn a heat zone of approximately 2" x 8" x 24" with a load of not morethan 4 kilos of material, the gas flow was about 340 cubic feet per hour. If the particle sizes 6010f the oxides were different from the ones listed in the consists of anyone or all of PRESSING POWDERS Pressing of the co-reduced and at least partiallyIprealloyed powders having an averageparticle size not ex-" ceeding 8 microns and preferably withinthe range of 2 to 6 microns, maybe carried out withor without ad axi- ' d. Thus,

is require APPLICATIONS f their extremely high strength, they are especial- The alloys of the invention are suitable for all applications where a high-density material having high strength and good machining properties in view 0 ly advantageous as gyroscope rotors, as they can be spun at rotational speeds exceeding by as much as 50% to 100% the highest rotational speeds that were heretofore obtainable with conventional high density materials with 75 out developing a permanent set beyond the tolerable tn 75 Pg G S r m t 50050005005000000558220808850505001500000608980 u 0 a r n s e e 4 6523253322585251009302710034482526744352010121 r c 0000 m fiwom m mmm O .1 C 0 f 8 m wm mmemm P e P h 1 0 00 00 00 0000 0 0 0 0000 0000 00 F m mm m mm d n s1 mmmmmmmmmmmwmmmmmmwwmmmmmmmmmmmmmmmmmmmmmmmwmmm Mmd f T 0 P.m e e S S C H td T 32 55 334433 5443335244442545543423344 4 6435 P gv. e n U mis W w 6 WM M m m mmmmmmm m mmwnflflmmmnmnmmmmmmmmmmmmmm S a 111 S e .1 M e a e U S M N H am a W t T O n n e X h u 4 70 i t Y S G 0 63 I u a cm a D mWWW mmwW mmmmmmmmmmmmmmmmmwwwmmwmmmmwwwwmmmmw N S W n 0 1m W. c w LLLIYLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL. 0 e H m 3. y T m mama w mm mm% C 6. a 1 +m w M Mal r. m t mmd 6 We %%HMB%%%M%%%%HMMH%%QWM%%Uwmwnwflmwm%fimfim%wfinflfiflw% is O t m fifi s am 77llmllzeeeetaeesaaaaaassassin4IaIt4IiIiIliaaaaaeeae ND C f W O p O m d C t n Qmpnm 1l111111111111111111111111.111111111111111111111 Oa HIf m n. 57 V r r. t V 0 e 0 U e 23 P a C t. .1 I m 0 am .m W E u "080 n 40 7 250 "74. "20 n" 555" 800 1 e e S p L C .16 0 .512 .11 15 I W .m gm h. s a e I00 0 I Iaaeo Ioeo I10 I0 0 I I I000 I m nam m rm m 1 I II I I I I I I .1 r. .1 m wmmwm m mmom T N I II I I I II I I I 6 S u 6 w PM 0 0 w k MW wm%%%o a% WWmmwmwmmwflmflwmwfl%w%mwmww%%fifiwfimfifiwfi h M a e w tm m n m O O O O O U O U 0 O 0 O 0 0 0 0 LLLQQQLQLLLQQQQLQLQQQQQQQQQQQQQ l v T m mmmm mfmm m 4 pt 0 S 6.1 O C. 5 0 5 O in M fl%fl%wfiwmmmmmmmm%nw wmmwwmmmmfimmmmmmw.dwm mmwmmw 1 1 2 N LLLQQLLL f.. 6 n nu LIe l wm a nhz b t 56378 8 C. I u 0 5 3 e 6 S H u m u 0 O C m l tm ndas n C dm u mm TW 75557774 b e e 0 t v. aee e h0. 4 @m m p mm nm We a N Hm mmsm m mm mmmmm mm awmmawanwmmw l e w.m w md a a T m mm amwaawamwannvfifi wmmwmwmwwm I S .1 p .fib nmmw WP 7 d cw i m nd .15 m n IIII .w w oo mBe. 1t e h I. as r o d 0m .m p rivet T%%ue H4 m 2 1 wm wy G wm w :p mawwnw h Wd Ortmmfl 411111 am m nw mmrmmmdt m .1 S I hdJ T B 4 U a mim s m mb ndw .w m S oWOmmheumm u d 4etmh,m 5 n .1 p e m W H e a m i m Tse a mwa Emai 3 E 1 C n mmm m e cvmw m wwn .y h m I nm 0 mmanm w smwmwa mo O S qf e. Ybm som my m msm. g a n mwm s d d mnn t .wIam eD D pg e ufia mrscsnc k nm dn mmwmmm mma mno m Prtsc mpfbmaafi mixture of abinder, such as glyptal. Conventional equip- 1 Contents of the minor elements were determined by chemical analyses.

sintering temperature of The sintered densities of the specimens used obtained, and can be readily determined in each case by 65 making a few test bars under different sintering conditions.

Fig. 3 is a graph illustrating some typical variations in ultimate tensile strength and percent elongation in one inch on standard specimens of four compositions as a function of sintering time at a 1440 C. for the determination of mechanical properties plotted in the graph were all greater than 97% of the theoretical. The four compositions were the following mum. For such applications, the alloylisted under 6-'A-2 inTable I'has been found to be particularly useful; The composition of this alloy is: v

Table II is a comparison of the average properties of alloy 6-A-2 of the invention and those of one of the best conventional heavy alloys sold on the market, composed of 90% W, 6% Ni and 4% Cu:

TABLE II Density, gm./cc Hardness, Rc Endurance limit, p. s. i. Electrical conductivity, percent I. A. O. S. Thermal conductivity, caL/ cm. /cm./sec./ O. Coefiicient of expansion (25 900 0.) in./in., C. Modulus of rupture, p. s. L.-. Ultimate compressive strength, p. s. i. Compressive yield strength,

p. s. Ultimate tensile strength,

p. s. 1. Tensile yield strength, p. s. i- Percent elongation in one inch.

Proportional limit, p. s. i 00.- 62,000.

.Modulus of elasticity, p. s. i.-- 40,000,000 44,000,000.

High temperature tensile {70,000 (300 0.).... 98,000 (300 0.).

strength, p. s. 1. 55,000 (450 (1)....

84,000 500 0. Temperature limit for good 450.

oxidation resistance, 0.

From the foregoing table, the superiority of the alloy of the invention is clearly'apparent.

MICROSTRUCTU RE Figs. 4 to 8 are micrographs for alloy 17D, shown in Table I, sintered at 1400 C. for 4, 8, 15, 30 and 60 minutes, respectively. All of these micrographs have been taken at a magnification of 500 diameters, using K Fe(CN) as the etchant.

Fig. 9 is a micrograph taken at the same magnification and made by using the same etchant, of one of the best conventional heavy alloys (90% W, 6% Ni, 4% Cu), sintered under conditions (16 minutes at 1400 C.), which were found to be the most satisfactory for an alloy of this type.

The most significant changes that can be observed in Figs. 4 to 8 are the change in grain size with sintering time. However, unlike the conventional W-Ni-Cu alloys exemplified by Fig. 9, the properties of which do not appreciably change as a function of grain size, the alloys of the invention exhibit a high degree of correlation between properties and sintering time, therefore, grain size. (See the graph shown in Fig. 3.) In the microstructure of the alloys of the invention, the visible grains are W, Mo, and high W and high Mo phases. The material between grains is the matrix, which is believed to be 'Ni-Cu base containing W, Mo, and Fe at short sintering (small grain size), and Ni-Cu base containing mostly Fe and very small amounts of W and M at long time sintering (large grain size).

Although the present invention has been disclosed in connection with preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the invention. I consider all of these variations andmodifications to be within the true spirit andscope of the present defined by the appended claims.

I 1. A sintered high-density alloy prepared by j-pre'ssing and sintering particlesof theconstituents having'an average size between 2 and 6 microns, said alloy consisting essentially of at least 65% by weight of tungsten, with nickel and copper in such amounts that their combined weight constitutes 4% to 25% of the weight of the composition and their weight ratio is between 0.5 and 2.5, and molybdenum in an amount from 0.4 to 1.5 times the combined weight of the nickel and copper.

2. A sintered high-density alloy prepared by pressing and sintering particles of the constituents having an average particle size less than 8 microns, said alloy consisting essentially of at least 65% by weight of tungsten, with invention, as disclosed in the foregoingdescription and nickel and copper in such amounts that their combined weight constitutes 4% to 25% of the weight of the composition and their weight ratio is between 0.5 and 2.5, molybdenum in an amount from 0.4 to 1.5 times,

the combined weight of the nickel and copper, and iron in an amount up to 1.5 times the combined weight of the nickel and copper but not exceeding 10% by weight of the composition. I

3. A high-density high-strength sintered alloy compact prepared by pressing and sintering of at least partially prealloyed particles of the constituent metals initially having an average particle size not in excess of 8 microns, said compact being essentially composed of at least 65% by weight of tungsten, with nickel and copper in such amounts that their combined weight constitutes 4% to 25% of the weight of the compact and their weight ratio is between 0.5 and 2.5, and molybdenum in an amount from 0.4 to 1.5 times the combined weight of the nickel and copper, said compact being characterized by a sintered density at least 93% of a theoretical density of not less than 13.5 gm./cc. and an ultimate tensile strength substantially higher than 112,000 p. s. i.

4. A high-density high-strength sintered alloy compact prepared by pressing and sintering of partially prealloyed particles of the constituent metals initially having an average particle size between 2 and 6 microns, said compact being essentially composed of at least 65% by weight of tungsten, with nickel and copper in such amounts that their combined weight constitutes 4% to 25 of the weight of the compact and their weight ratio I is between 0.5 and 2.5, molybdenum in an amount from 0.4 to 1.5 times the combined weight of the nickel and copper, and iron in an amount up to 1.5 times the combined Weight of the nickel and copper but not exceeding 10% by weight of the alloy, said compact being characterized by a sintered density at least 93% of a theoretical density of not less than 13.5 gm./ cc. and an ultimate tensile strength substantially higher than 112,000 p. s. i.

5. A sintered high-density high-strength tungsten base alloy particularly suitable for high speed rotor applications prepared by pressing and sintering of partially prealloyed particles of the constituent metals initially having an average particle size not in excess of 8 microns, said alloy being essentially composed of about 88.5%

to 90.5% tungsten, about 2.75% to about 3.25% nickel,

about 2.75% to about 3.25% copper, about 2.75% to about 3.25% molybdenum, and about 1.25% to about 1.75% iron constituting the balance, said alloy being characterized by a sintered density at least 93% of a,

theoretical density of not less than 13.5 gm./cc. and

an ultimate tensile strength substantially higher than 112,000 p. s. i.

(References on following page) 11 References Cited in the file of this patent 2,491,866 UNITED STATES PATENTS 25201555 1,229,960 Humphries June 12, 1917 1,453,057 Williams Apr. 24, 1923 5 517 442 1,829,635 Davey Oct. 27, 1931 74 ,212 2,206,537 Price July 2, 1940 12 Kurtz et a1. Dec. 20, 1949' Lenz Dec. 9, 1952 FOREIGN PATENTS Great Britain Jan. 30, 1940 Great Britain Mar. 14, 1956

Claims

1. A SINTERED HIGH-DENSITY ALLOY PREPARED BY PRESSING AND SINTERING PARTICLES OF THE CONSTITUENTS HAVING AN AVERAGE SIZE BETWEEN 2 AND 6 MICRONS, SAID ALLOY CONSISTING ESSENTIALLY OF AT LEAST 65% BY WEIGHT OPF TUNGSTEM WITH NICKEL AND COPPER IN SUCH AMOUNTS THAT THEIR COMBINED WEIGHT CONSTITUTES 4% TO 25% OF THE WEIGHT OF THE COMPOSITION AND THEIR WEIGHT RATIO IS BETWEEN 0.5 AND 2.5, AND MOLYBDENUM IN AN AMOUNT FROM 0.4 TO 1.5 TIMES AND COMBINED WEIGHT OF THE NICKEL AND COPPER.