日本金属学会誌

J. Japan Inst. Metals, Vol. 50, No. 6 (1986),
pp. 555-562

The Effect of Cold Rolling and Heat Treatment Conditions on Microstructures and Mechanical Properties of Ti-15V-3Al-3Sn-3Cr Alloy

Minoru Okada1 and Tomio Nishikawa1

1Central Research Laboratories, Sumitomo Metal Ind. Ltd., Amagasaki

Abstract:

Cold rolling of an alpha-beta titanium alloy is very difficult, because alpha phase has the close packed hexagonal crystal structure. A Ti-15V-3Al-3Sn-3Cr alloy has been developed as a cold formable and age-hardenable, metastable beta titanium alloy. The effect of cold rolling conditions on microstructures and mechanical properties of this alloy has not been reported in detail yet.
In this report, the changes in mechanical properties with cold rolling up to 90% were examined on samples as-rolled and heat-treated. The results show that the 0.2% proof stress and the tensile strength after cold rolling increase with cold rolling reductions. The tensile strength becomes constant at 700 MPa after the beta solution treatment and at 1400 MPa after 723 K--86.4 ks aging despite of different cold rolling reductions.
The texture of beta phase shows (100)[011] type after 90% cold rolling and (111)[112] type after the beta solution treatment. After beta solution treatment no anisotropy of the 0.2% proof stress is observed because of the inclination of the change in texture to uniformity.
Microstructures and mechanical properties of directly aged samples after cold rolling were also examined. Very fine particles of alpha phase precipitate in the directly aged samples. The 0.2% proof stress and the tensile strength increase with cold rolling reductions in the directly aged samples at 813 K for 28.8 ks. On the other hand, the samples directly aged at 723 K for 86.4 ks show no macroscopic ductilities, and the fracture surfaces are strongly faceted, like the samples aged at 573 K for 360 ks reported before.


(Received 1985/10/14)

Keywords:

Ti-15V-3Al-3Sn-3Cr, cold rolling, beta titanium alloy, microstructure, texture, mechanical properties, alpha phase


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