Effects of Heat Treatment on Mechanical Properties of VAR-Cast Ti-6 Al-4 V Alloy

Production of casting titanium alloys has been increased due to a significantly high competitive price rather than processed products (e.g. forging, extrusion and rolling). Therefore, advanced casting skills have been developed to manufacture titanium alloys with high quality. However, as-cast titanium alloys have a limit to improve their properties because of lower mechanical properties than forged alloys. In this study, Ti-6Al-4V alloy was fabricated by vacuum arc re-melting (VAR); it is a commercial casting’s method. Heat treatment is useful method for improving mechanical properties of the casting parts through microstructure’s evolution. The main aim of this work is to study relationship between heat treatment, microstructure and mechanical properties have been investigated. Solution treatment was performed at 950°C for 0.5h followed by water quenching. After that, the samples were aged at 450, 550 and 650°C. Hardness and tensile tests (at RT and high temperature) were conducted. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure as well. The hardness slightly increased with increasing aging time. In addition, tensile properties at high temperature (400°C) by aging treatment were improved.