Correlation of Alpha Phase and Its Texture Stability in Heat-Treated Ti-6.5%Al-4.4%V-0.15%Fe Alloy

In the present work, microstructure, texture, and mechanical properties were investigated for the heat-treated two-phase ( α + β ) titanium alloy samples. Ti-6.5%Al-4.4%V-0.15%Fe alloy samples were heated to three different temperatures (850, 930, and 1066 °C) followed by oil quenching (OQ), air cooling (AC), and furnace cooling (FC), respectively. Primary alpha ( α P ) and secondary alpha ( α S ) were dominant in the microstructure, when heat-treated below β T (beta-transus) temperature, i.e., 850 and 930 °C. Widmanstatten α ( α WS ) and basket-weave α ( α BW ) were dominant features in the microstructure of the samples heat-treated above the β T , i.e., 1066 °C. Formation of the martensite ( α ′) was observed in all three cases of the OQ samples. Differences in the volume fraction of the α P and α S were observed in the microstructure due to differences in the heating temperature and cooling rate. Texture developments after heat treatment were measured through the electron back-scatter diffraction (EBSD) technique. Variation in the texture intensity values was observed in the samples heat-treated below the β T which shows the dependence of the texture on the volume fraction of α P and α S . Similarly, formation of the big α colonies causes the changes in the texture when heat-treated above the β T . Grain partitioning of α P and α S in 850 and 930 °C-OQ samples shows a similar type of the texture for both the phases, difference being in the intensity of the texture fibers. Martensite ( α ′) formation during OQ increased the microhardness, whereas coarsening of grains during FC decreased the microhardness of the samples. There was ~ 23% variation in the modulus of elasticity ( E ), which depended on the heating temperature and cooling rate.