Formation of (α + β) Microduplex Structure in a Ti-15V-3Cr-3Sn-3AI Alloy

Abstract

The cold rolling effect of β single-phase on a precipitation behavior and the mechanical properties were studied using a Ti-15V-3Cr-3Sn-3AI metastable β alloy. The β single-phase material was prepared by heating the alloys above the β transus temperature followed by quenching in water, and subsequent aging at the (α + β) two-phase temperature after cold rolling. Cold rolling of the β single-phase had a considerable effect on the resulting (α + β) structures. Without cold rolling, preferential a precipitation occurred at the β grain boundaries, and then lath-shaped α precipitated in the β grains. When the amount of cold rolling was less than 50%, preferential precipitation of α occurred at dislocations introduced into the β grain by cold rolling, as well as the β grain boundaries. On the other hand, with an increase in the amount of cold rolling, a precipitation occurred predominantly at β subgrain boundary nodes which were formed through recovery of the deformed β single-phase during heating to the aging temperature or in the early stage of aging. In heavily cold rolled specimens, an (α + β) microduplex structure, which consisted of very fine α subgrains and a particles, was obtained. Mechanical properties, such as tensile strength and elongation, were improved by the formation of the (α + β) microduplex structure. © 1991, The Iron and Steel Institute of Japan. All rights reserved.