US2949357A - High purity titanium-manganese alloy - Google Patents

Description

Aug- 16, 1960 L. D. REsNlcK 2,949,357

HIGH PURITY TITANIUM-MANGANESE ALLOY Filed Jan. 16, 1958 2 Sheets-Sheet l FIG IIO

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sa 3 O ('0.08 NOEL-I CIBHONSIO 8 'SIEIOI BONSHBsIdICI HBBWN HdCI 47 97M INVNTOR HIGH PURITY TITANIUM-MANGANESE ALLOY Leroy D. Resnick, Silver Spring, Md., assignor to Chicago Development Corporation, Riverdale, Md., a corporation of Delaware Filed Jan. 16, 1958, Ser. N0. 709,275

1 Claim. (Cl, 75`175.5)

This invention relates to titanium-manganese alloys. It relates particularly to thermally stable alloys of titanium and manganese containing about 8% manganese. By thermally stable alloys I mean to describe alloys which have the same hardness when cast as when quenched or slow cooled from 850 C. By the same hardness l mean to dei-lne a range of less than 20 numbers DPH.

Such alloys can be made in various ways known in the art, but I prefer to make them by providing an anode of titanium and manganese in an electrolytic cell having an electrolyte of sodium chloride and dissolved therein manganese chloride, lower chlorides of titanium, and metallic sodium, and passing a current from said anode to an inert cathode to deposit thereon, coarse crystals of pure manganese titanium alloy. These crystals are melted in a vacuum arc furnace.

The alloys of my invention may be fabricated by any of the usual procedures including casting, forging, rolling, and welding, provided oxygen and nitrogen are rigorously excluded. The cast alloys have the same hardness and elongation as the hot rolled alloys so that Weldments may be made with the same properties as the base material. The prevention of oxygen and nitrogen absorption may be conveniently accomplished by the method set forth in the copending application of F. X. McCawley, Serial No. 694,504, led November 5, 1957, now Patent No. 2,865,797, granted December 23, 1958.

The alloys of my invention are characterized by thermal stability as defined above and by much greater strength and ductility 'for a given percentage of manganese than the alloys of the known art.

The greatly improved properties of the alloys of my invention are, in my opinion, due to their critically low oxygen content. I have found that this cannot be established by the usual procedure for oxygen analysis, namely vacuum fusion. I have found that the only reliable procedure for defining the quality of alloys of my invention is the measurement of electrode potential as disclosed in the copending application of W. W. Gullett, Serial No. 655,834, led April 29, 1957, now abandoned. In Figure l, I have made a graph showing the relationship of electrode potential of a series of titanium-manganese alloys containing l-12% manganese, to hardening on quenching from 850 C. It will be clear that thermal instability as thus dened is 4directly related to the electrode potential of the alloys. It is my opinion that the electrode potential is the most accurate measure available of the oxygen content, and I have found that those procedures and precautions which lower oxygen content of the alloy also lower electrode potential. My invention may then be defined as making and' fabricating alloys of titanium with about 8% manganese, having an electrode potential against pure Ti of 50-80 mv. at 1000 C., in an electrolyte of sodium chloride having dissolved therein 4.5% titanium as lower chloride and 1% metallic sodium, whereby to obtain thermally stable alloys as defined above, having a DPH number and an elongation within the bands shown in Figure 2.

The properties included in these bands encompass cast ite States Patent ice and hot rolled `alloys in the as cast, as hot rolled, annealed, and quenched condition.

I have found that the thermally stable alloys of my invention have a single structural constituent as determined by metallographic examination. I have also found that the constituent is shown by X-ray spectrometry to have a cubic structure corresponding to beta titanium with manganese in solid solution.

For the denition of the alloys of my invention, I have, however, chosen the mechanical properties of commercial importance, namely DPH number and elongation. The other mechanical properties are related to these. The yield strength is substantially parallel to the DPH number, and the difference between yield strength and UTS is parallel to the elongation.

Example I I make crystal intergrowths of manganese and titanium by using an anode material of comminuted crude titanium mixed with 10% standard ferromanganese in an electrolytic cell bath composed of sodium chloride having dissolved therein 3.3% Ti as lower chlorides, average valence 2.30, manganese as chloride 0.24%, sodium 1.1%. I provide an inert cathode and pass a direct current at a cathode current density of from 800 to 1000 amperes per sq. ft. Crystal intergrowths are deposited adherent to the cathode which, when cooled in an inert atmosphere and Washed to remove salt, analyze 91.45% Ti, 8.5% Mn, with not more than .05% other elements.

The oxygen content of these intergrowths, as estimated from an electrode potential of 60 mv. against pure titanium in the electrolyte hereinbefore described, is .015%. I melt these crystal intergrowths in a vacuum arc furnace and obtain an ingot having 8.0% Mn and the following properties:

As Cast Annealed, Queuched,

DPH Number l 396 384 382 Elougatlon (Percent in 1 inch) 9. 5 9. 8 0. 5 Yield Strength (11.5.1.) 205, 000 202, 000 201,000 UTS (p.s.1.) 210,000 206,000 207,000

I now enclose this ingot in a tight iron sheath and roll it at G-900 C. to a bar 5A in diameter. I turn off the sheath and l" of the bar to remove contamination with iron. This bar then had the following properties:

As Rolled Annealed, Queuched,

DPH Number 400 393 401 Elongation (Percent ln 1 inch) 9. 2 9. G 0. 3 Yield Strength (psi.) 208,000 203, 000 206, 000 UTS (p.s.i.) 213,000 209,000 210,000

Example II As Cast Annealed, Quenched,

DPH Number 361 352 379 Elongatlon (Percent in 1 lnch). 8. 7 9.3 8. 5 Yield Strength (psi.) 191, 000 184, 000 186, 000 UTS (psi.) 198, 000 191, 000 194, 000

What is claimed is:

An alloy of titanium, manganese and oxygen with substantially no other constituents, the content of manganese being about 8% by weight, and the content of oxygen corresponding to an electrode potential measured against pure titanium of 50-8()` mv. at 1000 C. in an electrolyte of sodium chloride having dissolved therein from 1.0 to 6.0% titanium as lower chloride with an average valence of from 2.0 to 2.6, metallic sodium from 0.1 to 2% and from 0.1 to 2.0% manganese as lower chloride, said alloy, when examined metallographically, having a single structural constituent which constituent has a cubic structure corresponding to beta titanium with manganese in solid solution, said alloy having 'die same hardness within 30 numbers DPH when cast, quenched from 850 C. and furnace-cooled from 850 C.

4 l l References Cited in the tile of this patent UNITED STATES PATENTS Vordahl Mar. 15, 1955 Vordahl Oct. 21, 1958 OTHER REFERENCES Equilibrium Diagrams of Titanium Alloy Systems, Metallurgical Advisory Committee on Titanium, Information Bulletin No. T4. Compiled by the Metallurgical Staff of New York University, March 1952. Pages 31- 34.

General Physical Metallurgy of Titanium Reviewed, Iafee, Journal of Metals', Volume 7, 1955. Pages 247- 252.

Heat Treatment, Structure, and Mechanical Properties of Ti-Mn Alloys, Holden et al., Journal of Metals, Volume 6, 1954. Pages 169-184.

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