US2920957A - Alloys of titanium-group metals - Google Patents

Description

Jan. 12, 1960 w. w. GULLl-:T'r 2,920,957

ALLOYS OF TITANIUM-GROUP METALS Filed June 20, 1957 5 Sheets-Sheet 1 Jan. l2, 1960 ALLOYS OF TITANIUM-GROUP METALS Filed June 20, 1957 3 Sheets-Sheet 2 Jan. 12, 1960 w. w. GULLETT ALLOYS OF TITANIUM-GROUP METALS Filed June 20, 1957 United States PatentY ALrjoYs oF 'rlrANruMonoUP METALS William W. Gullett, College Park, Md., ass'ignor to Chicago Development Corporation, Riverdale, Md., a

corporation of Delaware Application June 20, 1957, Serial No. 666,841 7 Claims. (Cl. 75-175.5)

The present invention relates to titanium alloys and zirconium alloys, and is concerned with the provision of titanium alloys and zirconium alloys of high strength and good ductility which alloys contain relatively ksmall contents, only, of beta stabilizing elements.

lt has been known to make titanium alloys having high strength and reasonable ductility by the addition to titanium of beta stabilizing elements such as vanadium and Amanganese together with at least one alpha stabilizer such as oxygen or aluminum. By suitable heat treatment, such alloys are obtained with desired proportions of alpha and beta phases. The importance of the two phases is not only to provide a dual structure, but more importantly to reduce the oxygen contentof the beta phase by providing an oxygen sink of alpha phase, in which latter oxygen is much more soluble than it is in the beta phase. This reduction in oxygen content reduces brittleness in the beta phase. Y

Heretofore, in order to obtain alloys in which the beta phase is sulciently stabilized to provide a major proportion of beta after annealing at, say, 800 C. and 4furnace cooling, it has been necessary to add considerable amounts of the beta stabilizing elements. Examples of such 'commercial titanium alloys are: 15 V, 2% Al; 6% Al-4% V; 8% manganese; 4% manganese-4% aluminum'.

I have discovered that the employmnet of relatively large amounts of the beta stabilizing elements-heretofore necessary-has been rendered essential because the titanium (or, zirconium) base of the aloy as conventionally made has contained a relatively large amount of oxygen in interstitial solid solution. That is `to say, I have discovered that a titanium alloy ,containing only a very minute amount of oxygen requires very much less of the beta stabilizer than conventionally thought necessary in order to confer thereto the desired hardness and strength properties. A

My invention, therefore, consists in reducing the .oxygen content of the titanium alloys to such an extent that lthe beta phase can be substantially stabilized with a much lower percentage of the beta stabilizing elements than heretofore known or used. As beta stabilizing agents, I may use vanadium, iron, chromium, manganese or molybdenum. Y

The degree of strengthening which I obtain in the beta phase before separation of alpha phase is much greater than has heretofore been obtained. One embodiment of my invention, therefore, consists in providing stable alloys entirely or substantially all beta phase, strengthened almost entirely by solution hardening of the beta phase without loss of ductility by heat treatment which is characteristic ofthe beta phase alloys of the prior art.

It must be pointed out for the full understanding of my invention that the critical compositions of the alloys of my invention .especially as vregards oxygen content referto the fully fabricated alloy and to the specic portion of the alloy being tested. I am familiar with the practice of making alloys from pure iodidey titanium which may have oxygen contents within the limits yof ICC my invention. Such alloys in the fully fabricated form have not, in the known art, been within the composition range of my invention. This situation Vclearly prevails even though the investigators have not reported it and have therefore, in certain instances, given the incorrect impression that the alloys which they prepared and fabricated from iodide titanium had oxygen contents in the range of the base titanium used. The literature is replete with references showing that such an assumption is invalid. I shall here refer to only a few.

Second Progress Report on Research and Development on Titanium Alloys, Battelle Memorial Institute, October 31, 1949, Contract No. 33(038)373,6, Wright Patterson Air Force Base, Dayton, Ohio, p. 116. melted iodide titanium analyzed .041 oxygen.

Summary Report on Diffusion of Hydrogen, Nitrogen,

and Oxygen in Titanium, Columbia University, Report W.A.L. 401/149-112,y dated `luly 13, 1953, to Watertown Arsenal Laboratory. Shows that iodide titanium used contained .011% Ioxygen but that oxygen was taken up very rapidly so that alloys fabricated by hot rolling would have oxygen contents beyond the limits of the present invention.

An illustration of the difference between the alloys of my invention and those of the prior art may be seen from the paper Effect of Alpha Solutes on the Heat Treatment Response of Ti-Mn Alloys by Ogden, F. C. Holden and R. I. laffee, Trans. AIME., January 1955, p. 105 The alloys reported on by these investigators were made from iodide titanium but were forged at 875 C, and swaged at 750. Such a procedure raises :the oxygen contentbeyond the limit of my invention as shown by the hardness data in Figure 12 of the paper. The hardness on `:furnace cooling the alloys isv only about 200 Vickers at 3% manganese as compared to 412 for a 3% manganese alloy of my invention heat treated in the same manner. Clearly, a `conventional hot working procedure produces fabricated alloys outside the composition limits of my invention even if .highly pure iodide titanium is used as initial material.

It :is very tedious and time consuming to fabricate hard strong alloys by cold work and repeated vacuum annealing. I have found that titanium carbide coatings permit hot working without oxygen absorption beyond the limits of my invention. This `method is highly useful in the commercial application of my invention and is illustrated in Example IX hereinbelow.

Even when hot working was not employed, alloys of the prior art fabricated from iodide titanium have not been within the composition limits of my invention; for example, Finlay and Snyder in their article on Effects of Three Interstitial Solutes, Trans. A.I.M.E., 188, p. 277 (1950).. The graphs of this report indicate values for alloys down to zero oxygen; however, these investigators analyzed only one alloy and in this found .03% oxygen above the reported values.

It may, therefore, bev concluded that all the alloys reported by these investigators were outside the limits of the present invention, a conclusion fully supported by the extrapolated hardness of the base titanium of more than Vickers, although the hardness of the base iodide titanium used is given as Vickers 60-70.

The unusual and unexpected results owing from drastically reducing the content of oxygen in the titanium and zirconium alloys n accordance with my invention will be illustrated in `the case of titanium-vanadium. By reducing the oxygen content, in the fabricated material, to about .01%, I make titaniumvanadium alloys up to at least 4% vanadium which are stable substantially beta alloys even when slowly cooled from 900 C. Figure l shows the hardness curve of these very low oxygen astres? Shows that 3 titanium-vanadium alloys of my invention, 'the numerals representing Vickers hardness values.

I nd that a very smallcontent of oxygen- 0.01- 0.03%-increases hardness probably by producing a dispersion of sub-microscopic alpha particles; however, an

abscissae vincrease into the range of oxygen content of alloys of 'the prior art, that is .O4-.15% oxygen, `greatly lowers hardness and strength. Figure 2 shows 'a series of curves ble result flowing from drastically reducing 'the oxygen Y Yield Strength Elong. Percent in 2" Percent V l 125, ooo 14o, ooo 17o, ono 185, ooo

Manganese and molybdenum alloys follow the pattern of the vanadium alloys discussed in detail. The hardness curves for titanium alloys of manganese and of molybdenum are shown in Figure 3 and Figure 4, respectively, the oxygen contents in both instances being about 0.01% in the fabricated material. Ductility is slightly less for the same strength for manganese and molybdenum alloys than for the vanadium alloy.

My invention is also applicable to zirconium alloys in the same way as for titanium. Figure shows the hardness curves for a zirconium-vanadium alloy containing about 0.01% oxygen in the fabricated form. 1

My invention has particular applicability to titanium (and, zirconium)-iron alloys, sincerthe eifect of iron on the hardness and strength of titanium (and, zirconium) is very great at the low oxygen levels referred to above. This has not, to my knowledge, been known before my invention. In Figure 6, I have'plotted the yield strength and elongation of titanium-iron alloys asdeterrnined on alloys containing .06% oxygen and for alloys within the composition range of my invention, viz. .02% oxygen, all after cold reduction of 50% and annealing at 700 C.

The data which I have determined for .06% oxygen is substantially in accord with that given in McQuillan and McQuillan, Titanium, p. 345. It is stated in that text that the titanium used to make the alloys was ofrhigh purity, however, the melting and fabricating must have introduced about .06% oxygen, since the hardness of the metal without iron is given as Brinell 100, and furthermore, the hardness at 0.5% iron was about 140 which is. in good agreement with a hardness of about 150 obtained by McKinley on adding 0.5 iron to titanium containing .06% oxygen, as set forth in an article on Elect of Impurities on the Hardness of Titanium by T. D. McKinley, Journal Electrochemical Society, October 1956, p. 563.

It is significant that in studying the beta stabilizing elements, iron, chromium, vanadium, molybdenum and manganese, McKinley did not report the increase in hardening effect due tovbeta stabilizing elements when oxygen is lowered below .06%, which is the essence of the present invention.

In Figure 6, I have plotted the yield strength and elongation for fabricated low iron alloys because these are the most important engineering parameters. It will be noted that with less than .5% iron and .02% oxygen, a yield strength can be obtained as high as with 15% iron and .06% oxygen. Further, the ductility of the low oxygen alloy is much higher at equal yield strength.

In the case of zirconium alloys, the great strengthening effect of iron is of great importance. Zirconium with .02% oxygen and .3% iron has U.T.S. 180,000 lbs., Y.S. 16S-,000 lbs., elongation in 2" 20, after 50% cold reduction and annealing at 700 C. A Y

The alloys of my invention are thermally stable in the sense that Ythey may be reheated and furnace cooled from 70D-800 C. without change. The fabricated `alloys with less than .01% oxygen are not significantly hardened by quenching from 900 C., but those with .03% oxygen are hardened by as much as points Brinell by such treatment. The properties are ,restored by annealing at 700-800 C. By long heating at 600 C., the furnace cooled alloys of my invention are not changed in hardness.

vrrrhe behavior of fabricated alloys made in accordance with my invention when the content of alloying element is substantially increased is shown in Figure 8. In this -gu're, I have plotted yield strength and elongation as a function of alloy content for two series of alloys containing Fe, Mn 'and V respectively. One seriesfshown by solid lines numbered 1, 2 and 3, consists of conventional alloys of titanium with iron, manganese and vanadium, respectively, and containing .09% oxygen. The other series, shown in dotted lines numbers 4, S and 6, shows alloys of titanium with iron, manganese and vanadium, respectively, made in accordance with the present invention and containing .02% oxygen. The elongation curve, solid line numbered 7, 'represents the average elongation of the series of conventional alloys identilied by lines 1, 2 and 3, while the elongation curve, solid line numbered 8, 'represents the averageelongation of the series of lowoxygen alloys identified by lines 4, 5 and 6.

It will be seen that the maximum yield strength of alloys according to my invention is reached below 5% alloy content, and since ductility falls rapidly with increasing alloy content, the alloys showing desired strength at the lowest alloy content are generally most favorable.

Increasing oxygen in the alloys of my invention causes them to approach theYP-alloy content relationship shown in Figure 8 for conventional alloys. Within an oxygen content of more than .03%, the properties of the alloys are not significantly different from conventional alloys and this oxygen content is therefore regarded as the upper limit of my invention.

The maxima in the yield strength curves of the alloys of my invention as shown by the heavy lines of Figure 8 arise from a dispersion of a very small amount of alpha phase; with increasing content of beta stabilizers, the strengthening becomes that of solution only.

It will be understood that the analyses of the alloys to which I refer in this application are for the fabricated alloy'and are for the average of a number of samples with armaximum variation of .005% oxygen. The elements present other than the specified oxygen and beta stabilizing elements are, in every case, less than .005%.

I have illustrated my invention with alloys containing a single beta stabilizing element. My invention encompasses alloys with two or more of the illustrated elements. In general, the effect of two or more alloying elements is additive so far as strengthening and the effect on ductility is concerned.

I have found, for example, that an alloy of 4% vanadium and 2% manganese vwith .01% oxygen provides a. yield strength at 6% total alloy of 275,000 lbs. per square inch and an elongation of 18%. Such an alloy is but little alected by heat treatment since it is fully beta stabilized. The same alloy .containing .07% Oxyelongation in 2` of v9%.

Example -I i I made an alloy of titanium With 3% vanadium and 3% oxygen and the usual' impurities in' commercial titanium and vanadium. 'I comminuted theresulting brittlealloy to pieces having ka largestdimensionof`0l25 inch and smaller, and electro-refined it ,as follows: I placed the comminuted alloy in an annularaforainiiious steel basket and used thisv basket "and contents as an A6 I used this comminuted material as an anode exactly as in Example I, except that the bath contained '8% soluble zirconium chloride and `2% sodium.

The material adherent the cathode was a 3% vanadiumzirconium alloy containing 0.005% oxygen. This product was pressed into a consumable electrode, and was melted in an arc furance with .a water-cooled copper hearth at 1 micron argon pressure. The resulting ingot was cold worked with vacuum annealing into bars. The resulting bars contained 0.025 oxygen and 2.9% vanadium. These bars had the following properties:

anode in an electrolytic cell having a cylindrical cathode s in the center of the annular anode basket. The Acell was Vickers Hardness :HDsL/s-s-l,1 YS- gione-,t provided with an argon atmosphere with means for q lbe/gin.

separating the cathode and adhering material-I from the 1D v salt bath which latter was molten NaCl having dissolved 200 140,000 120,000 55 therein 4.5% titanium as soluble chloride and 1% dissolved sodium. I passed a directl current through the cell kat l amperes per lb. of comminuted' `anode mate- ExampleIV rial and. 600 amperesper square inch o n ,the cathode. 20 In this example I proceeded as in Example H except A'Pfactlcauy 0XYgen'ffee tltamum'vanadlum @Hoy 9011,' that instead of .5% electrolytic manganese I added taining about 3% vanadium `was formed, `attached to 10% puremolybdenum the cathode at the rate of' about 75 gram per ampere The resulti v A f n bars had the followin ro 110111'. The oxygen content of the alloy was only 0.005% 5 g g p pemes OXYECIL 1 Urns., Y.s., niong.,

v i Example V U,T.s.,` Ys., El 1 Vickers Hardness mst/seem msi/Sein'. Pg-1t In this'exampleLI made three series of alloys by vacu- 1n 2 Q um melting highly pure titanium and vanadium, and i v Y 0i after fabricating by cold rolling and annealing in vacu- .330 17,5, 000 160,000 '21 um at 800 C., I obtained the following properties and analysis:

l .02% Oxygen .03% Oxygen .07% Oxygen PercentV e U.T.S.1 Y.s.1 E 1 U.T.s, Y.s. E U.T.s. Y.s. E

125 90 30 70 55 28 55 45 20 140 120 25 89 70 V23 75 00 18 170 155 20 125 100 17 90 70 15 185 170 y 20 145 r130 17 95 77 e 220 210 20 100 180 15 100 s2 0 l. UA.T.S.-1nlbs./sq. in. Y.S.-lbs./sq. in. for .1% oiset. E-Elongation, percent; in 2.

Example II These data are illustrated graphically in Figure 7 f Y Y.S. Elong., Vickers Hardness U.T.S., (1% 01T- Percen 1bs./sq.in. set in 2 1bs./sq.in.

Example III In this example, I took a commercial zirconium alloy containing 3% vanadium and the customary amount of oxygen in solid solution, and comminuted it by milling.

which shows the sharp change in relationship of yield strength and percent V in passing from the low oxygen contents of the present invention to the higher oxygen contents of the known art, e.g., .07% oxygen.

Example Vl In this example, I proceeded exactly as in Example I,` exceptV that I substituted chromium for vanadium in each and every operation. 'I'he result was 'a pure titanium-chromiumvalloy containing 1% Cr and, when fabricated, .02% oxygen.

The properties of the sheet alloy were:

. 7. The resulting alloy was found to'contain U.T.S. Y.S. (.l% Elong. lbs/sq. in. onset), in 2,

lbs/sq. in. l percent 16s, 000 155, 000 I 22 Example VIII I proceeded as in Example I, except that I used as anode material comminuted zirconium alloy containing 2% manganese and 2% vanadium and 3% oxygen.4 YThe electrolyte was initially that of Example I. I carried out4 a preliminary electrolysis until the alloy being dcposited on the cathode analyzed 46% Ti, 46% Zr, 4% V and 2% Mn. This alloy was melted in vacuum to produce an alloy containing equal parts of titanium and zirconium with 4% V, 2% Mn and .01% O2. This alloy was fabricated without oxygen absorption `or other contamination and had the following properties when annealed in vacuum at 800 C.:

U.T.S., Y.P., Elong., p.s.i. p.s.i. percent Example IX In this example, I took needle-likeV crystal intergrowths containing 0.3% iron produced by electroreiining an iron-titanium alloy-containing 5% iron according to ExampleV I at a temperature of 1025 C. I melted'theseV crystal intergrowths in an argon atmosphere at a pressure of microns. The resulting ingot was coated with graphite and made a cathode in the refining bath of Example I, whereby to produce a continuous adherent coating of TiC thereon. I hot-rolled the ingot at ,850 C. and scalped on? .004 inch of surface. Analyses of the resulting fabricated 'alloy showed .025%

oxygen, .3% iron, .0002 nitrogen and no other detectable impurities. r I

This alloy had the following properties after vacuum annealing at 900 C. and furnace cooling: Y

U.'l.S.I Y.S. (.l%

p.s.i. onset), Elongation p.s.i.

stabilizing agent and about 100,000 lbs. sq. in. greater at 10% beta stabilizing agent, with intermediate 1ncreases at intermediate amounts of beta stabilizing agent, thanthatof an,alloy vof the `same metal composition but containing .0S-.2.0%y oxygen.,y p n,

2. fabricated titanium-vanadium alloy which is ssentially a uniform solid solution on slow cooling from the beta range, said alloy consisting essentially of from' about 1 to about 5% vanadium and from about 0.01 to not more than 0.03% oxygen in interstitial solid solution, balance substantially all titanium said alloy having a yieldl strength (.l% oifset), when slow-cooled from the' beta range, of about 50,000 p.s.i. greater at 1% alloy` metaland about 100,000 p.s.i. greater at 5% alloy metal, with [intermediate increases at intermediate amounts of alloy` metal, than that of an 'alloy of the same metal composition but containing .0S-.20% oxygen;

3. A fabricated titanium-manganese alloy which is essentially auniform solid solution on slow cooling from the beta range, said' alloy consisting essentially of from about 1 to about 5% manganese and from'about 0.01 to not more than 0.03% oxygen in interstitial solid solution, balance substantially all titanium said alloy having a yield strength (.l% offset), when slow-cooled from thebeta range, of about 50,000 p.s.i. greater at 1% alloy metal and about 100,000 p.s.i. greater at 5% alloy metal, with intermediate increases at intermediate amounts of alloy metal, than that of an alloy of the same metal composition but containing .0S-.20% oxygen.

4. A fabricated titanium-iron alloy'which is essentially a uniform solid solution on slow cooling from the beta range, said alloy consisting essentially of from about 0.1 to about 1.0% iron and from about 0.01 to not more than 0.03% oxygen in interstitial solid solution, balance substantially all titanium.

5. A fabricated zirconium-iron alloy which is essentially a uniform solid solution on slow cooling from the beta range, said alloy containing from about 0.1 to about 1.0% iron and from about 0.01 to not more than 0.03% oxygen in interstitial solid solution, balance substantially all zirconium.

6. A fabricated alloy as defined in claim l, in which Y the beta stabilizing element is molybdenum in an amount within the range 1 to 10%.

7. A fabricated alloy'as deiined in claim 1 having a total alloy content of beta stabilizing element of from 1 to 6% made up of vanadium and manganese in a proportion of at least 2 to 1.

References Cited in the tile of this patent UNITED STATES PATENTS Re. 24,013 Jaifee'et al. May 31, 1955 2,596,485 Jatfee et al. May 13, 1952 2,622,023 Frazier Dec. 16, 1952 2,754,203 Vordahl'` July l0, 1956 2,754,204 Jaffee et al. July l0, 1956 2,754,205 Jaee et al. July 10, 1956 OTHER REFERENCES Transactions of ASM (Adenstedt et aL), vol. 44, pp. 990-1003, 1952. (Pages 990 and 991 relied on.)

Metal Treatment and Drop Forging (Allen), pp. 24S-252, June 1953. (Page245 relied on.)

ASM 1952 Preprint, No. 35, pp. 1-7, March 1953.

A UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIN 11a-tent Ne, 2,92%957 January i2, 1960 William W; euilett It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8. line 38, elaim'5,. strikey "containing" iand insert instead ,fm consisting essentially o" esigned and ,sealed this 7th day of June i960.

(SEAL) Attest: n

KARL AXLINE ROBERT C. WATSON Attesting OHcer Commissioner of Patents

Claims (1)

1. A FABRICATED ALLOY, WHICH IS ESSENTIALLY A UNIFORM SOLID SOLUTION ON SLOW COOLING FROM THE BETA RANGE, CONSISTING ESSENTIALLY OF A METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM AND ZIRCONIUM WITH FROM 1 TO 10% OF AT LEAST ONE BETA STABILIZING ELEMENT AND FROM 0.01 TO NOT MORE THAN 0.03% OF OXYGEN SAID ALLOY HAVING A YIELD STRENGTH (.1% OFFSET), WHEN SLOW-COOLED FROM THE BETA RANGE, OF ABOUT 50,000./SQ. IN. GREATER AT 1% BETA STABILIZING AGENT AND ABOUT 100,000 LBS. SQ. IN. GREATER AT 10% BETA STABILIZING AGENT, WITH INTERMEDIATE INCREASES AT INTERMEDIATE AMOUNTS OF BETA STABILIZING AGENT, THAN THAT OF AN ALLOY OF THE SAME METAL COMPOSITION BUT CONTAINING .05-20% OXYGEN.

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