Formation of (.ALPHA.+.BETA.) Microduplex Structure in a Ti-15V-3Cr-3Sn-3Al Alloy.

Abstract

The cold rolling effect of p single-phase on oe precipitation behavior and the mechanical properties were studied using a Ti-1 5V-3Cr-3Sn-3A1 metastable p alloy. The p single-phase material was prepared by heating the alloys above the fi transus temperature followed by quenching in water, and subsequent aging at the (ce + p) two-phase temperature after cold rolling. Cold rolling of the p single-phase had a considerable effect on the resulting (c(+fi) structures. Without cold rolling, preferential oe precipitation occurred at the fi grain boundaries, and then lath-shaped a: precipitated in the p grains. When the amount of cold rolling was less than 500/, preferential precipitation of c( occurred at dislocations introduced into the P grain by cold rol]ing, as we]1 as the p grain boundaries. On the other hand, with an increase in the amount of cold rollin~, c( precipitation occurred predominantly at P subgrain boundary nodes which were formed through recovery of the deformed p single-phase during heating to the aging temperature or in the early stage of aging, In heavily cold rolled specimens, an (oc+fi) microduplex structure, which consisted of very fine p subgrains and ce particles, was obtained. Mechanical properties, such as tensile strength and elongation, were improved by the formation of the (ce+p) microduplex structure.