US 2596489 A
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Patented May 13, 1952 UNITED STATES PATENT OFFICE TITANIUM-BASE ALLOYS ware No Drawing. Application March 2, 1951, Serial No. 213,690
Claims. (Cl. 75-134) 1 This invention relates to titanium-base alloys, and particularly to ternary alloys of titanium and aluminum with boron.
The use of titanium as a structural material is at a given strength level, the quantity of each which can be tolerated depends to a considerable extent upon the quantity of the others. The limiting factor is usually ductility, and the relimited by its relatively low strength and high 5 quirement as to ductility varies with the intended cost, and it becomes desirable to alloy titanium use of the alloy. Further, increasing the with such other metals as will increase the amounts of the substitutional metallic alloying strength to acceptable levels and preferably at ingredients tends to decrease the tolerance for the the same time effect some reduction in the total interstitital components, particularly embrittling material cost. Aluminum is a metal well suited nitrogen. An alloy of high purity titanium with to the attainment of these objectives, being low in 5% aluminum will tolerate as much as 0.25 weight, relatively low cost, and having amaterial nitrogen, but the addition of one or two percent strengthening effect on titanium. However, the of another metal materially reduces nitrogen amount of aluminum alone that can be added to tolerance. titanium is limited by its adverse effect on duc- The alloys of this invention may be prepared tility. Binary alloys of titanium with more than by melt-casting i an atmosphere of argon, 1 about 5% 0f aluminum are tOO brittle for most ing at a, uitable temperature, say 980 (1., and stru tu al us s; a d suc a y alloys a annealing under conditions which will effect res less n b u aluminum do not crystallization, but not substantial grain growth possess sufficient strength to be of general utility. or re solution of carbides A typical but by no A further strenethemng 1S hlgmy means universal annealing treatment comprises The present invention comprises the discovery Soaking at a temperature f about 0 f r that the addition to titanium-aluminum alloys of about 1 hours The rate f cooling ft 9 to about; 05% of borcfn effecls marked nealing is not material, since in these alloys the improvement in the properties of t1tan1um-alutitanium is an in the alpha phase except for minum alloys of a given aluminum contentzsay minor amounts which may be combined as titato alloys Show a i combma' nium carbide. The properties of selected alloys tion, 9 extraordmary Strength Wlth adequate of titanium of requisite purity with aluminum ductlhty and tin, as annealed for 3%.; hours at 850 0., un-
The metal used as a base for the alloys of the less otherwise noted are as follows.
present invention may contain the interstitial The properties of g alloy of subsantiauy pure contaminants carbon" oxygen. and/Or titanium with 5% aluminum, as annealed for 3 up to at least the total quantity to be found in hours at are as follows. good quality commercial titanium. Carbon, for example, has been found to be beneficial when Proportional Limit, 1 43,000 present in amounts between 0.02% and 0.3%, the 0 ofi et yield Strength i 51000 latter being about the maximum amount which is 0 Ofiset Yield strength i 09 soluble in alpha titanium. An excess of carbon t t Strength 79 00 tends to form embrittling carbides. For a typip t Ehmgation, in 1 inch 13 cal alloy, a carbon content of 0.1% to 0.2% is Minimum Bend Radius desirable, but the optimum amount varies with other factors. Nitrogen is a potent hardener of The properties of selected alloys embodying the titaniumbut tends to cause embrittlement. The present invention, as annealed for 3 hours at effect of the three contaminants being additive 850 C., are as follows:
Composition Tensile Properties-p. s. 1.
(Balance Titanium) Propor- 0 2% Elongn B $35??? n 5 1.0 378 117,000 124. 000 135, 000 7 Brittle thickness, to which the specimen can be bent to an angle of 75 without fracture.
It will be seen that the addition of as little as 0.1% of boron effects a substantial increase in strength as compared with the strength of an otherwise identical alloy without boron, and that ductility is actually slightly increased rather than diminished. Increasing the boron content to 0.5% produces a further increase in strength with an almost negligible efiect on ductility. At a boron content of 1 the strength level is about double that of the titanium-5% aluminum base, and enough ductility remains for a wide variety of uses, about the only use excluded being sheet and other forms which are stretched in fabrica tion.
'The alloys are characterized by a fine grain structure, average grain size being from 0.017
mm. to 0.022 mm., and by the presence in a matrix of alpha titanium of dispersed particles of a second phase, believed to be titanium boride. The solubility of boron in the titanium-5 aluminum base is thus less than 0.1 and there is experimental evidence that its solubility in beta titanium is not materially different. The presence of the insoluble second phase particles is, as in other related alloys, associated with fine grain structure and a spread of several thousand p. s. i. between yield strength and ultimate strength, with the enhanced utility resulting therefrom.
The alloys having the properties tabulated above were made by the use of amorphous boron. While crystalline boron may be used, it appears to be more difilcult to melt, and incomplete melting may yield inconsistent results.
What is claimed is:
1. An alloy consisting essentially of from 3.5% to 5% aluminum, from 0.1% to 1% boron, balance titanium. I 2. An alloy consisting essentially of from 3.5% to 5% aluminum, from 0.1% to 1% boron, from 0.02% to 0.3% carbon, balance titanium,
3. An alloy consisting essentially of from 3.5% to 5% aluminum, from 0.1% to 0.5% boron, balance titanium.
4. An alloy consisting essentially of about 5% aluminum, from 0.1% to 1% boron, balance titanium. t Y
5. An alloy consisting essentially of about 5% aluminum, from 0.1% to 0.5% boron, balance titanium.
ROBERT I. J AFFEE. HORACE R. OGDEN. DANIEL J. MAYKUTI-I.
No references cited.