US 5,472,526 AGranted

Method for heat treating Ti/Al-base alloys

AssigneeGeneral Electric Company

InventorMichael F. X. Gigliotti, Jr.

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Abstract

A method of heat treating Ti/Al-base alloys to improve tensile ductility and reduce the likelihood of in-service embrittlement is disclosed. The method comprises: selecting a Ti/Al-base alloy that contains a mixture of .alpha. and .alpha.2 phases, heat treating the alloy so as to form a controlled amount of .alpha.2 particles, and then cooling the alloy so as to primarily promote the growth of additional .alpha.2 on the previously formed particles, rather than the nucleation of new .alpha.2 particles. This method may be used with Ti/Al-base alloys that also comprise Sn, Ga and In as alloy constituents, and is believed to be useful for a number of Ti/Al-base engineering alloys. Alloys made by this method have been observed to maintain significant tensile ductility, even after aging at elevated temperatures under load (e.g. creep conditions).

Claims14

Dependent claims

A method of heat treating a Ti/Al-base alloy, comprising the steps of:

selecting a Ti/Al-base alloy having an Al concentration such that the alloy comprises a mixture of .alpha. and .alpha.2 phases under equilibrium conditions at room temperature, wherein the .alpha.2 phase occupies at least 25 volume percent of the alloy at room temperature;
heat treating the alloy at a temperature which is above .alpha./.alpha.2 solvus temperature of the alloy for a time sufficient to dissolve substantially all of the .alpha.2 phase;
forming a plurality of .alpha.2 particles within the alloy by cooling the alloy to a temperature which is in the range of about 1.degree.-200.degree. C. less than the .alpha./.alpha.2 solvus temperature of the alloy;
cooling the alloy slowly to a temperature of about 650.degree. C. or less, wherein the rate of cooling is sufficiently slow to permit the formation of an additional quantity of the .alpha.2 phase consistent with the phase equilibria relationships of the alloy and to permit substantially all of the additional quantity of .alpha.2 to be formed on the existing .alpha.2 particles.

1 more element

Dependencies are inferred from the claim text.