Ultra-Fine Grain Refinement and Tensile Properties of Titanium Alloys Obtained through Protium Treatment
Jun NAKAHIGASHI and Hirofumi YOSHIMURA
Abstract:One of the few methods available for creating fine grains is protium treatment, which easily produces a fine-grain size of 1 to 3m in +Ti-6Al-4V alloys. However the minimum grain size obtainable by this treatment is not yet known. The purpose of present investigation is to obtain submicron grain size through improvement of the protium treatment conditions by varing the protium absorption content and lowering the protium desorption temperature. The experimental results obtained are as follows. The grain size of titanium alloy becomes ultra-fine grain (grain size : 0.3`0.5 m) through a process in which 0.5mass% of protium is absorbed and the protium desorption temperature is lowered from 973K to 873K. The phase percentage in the phase matrix tends to increase as a result of the protium treatment. The yield strength of ultra-fine grained materials is improved by protium treatment in accordance with the Hall-Petch's law. Such materials show high elongation for high strength. Key Words:Titanium alloy, Protium treatment, Fine grains, Tensile properties, Uniform elongation, Microstructure