Effect of Heat Treatment on the Microstructure and Property of TiAl Alloys Prepared by Gas Atomization Powders

Powder metallurgical TiAl alloy was fabricated by gas atomization powders, and the effect of heat treatment temperature on the microstructure evolution and room tensile properties of PM TiAl alloy was investigated. The uniform fine duplex microstructure was formed in PM TiAl based alloy after being heat treated at 1250/2h followed by furnace cooling (FC)+ 900/6h (FC). When the first step heat treatment temperature was improved to 1360/1h, the near lamellar microstructure was achieved. The ductility of the alloy after heat treatment improved markedly to 1.2% and 0.6%, but the tensile strength decreased to 570MPa and 600MPa compared to 655MPa of as-HIP TiAl alloy. Post heat treatment at the higher temperature in the alpha plus gamma field would regenerate thermally induced porosity (TIP).

The Effect of Isothermal Forging Parameters on the Microstructure and Properties of Ti-5Al-5Mo-5V-1Cr-1Fe Titanium Alloy

In this paper the effect of isothermal forging process parameters on the microstructure and the mechanical properties of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was researched. The results of the tests indicate that, in the temperature range of 755~905 °C and the deformation degree range of 20~60 %, with the increase of deforming temperature, the volume of primary α-phases decrease, but the globularization extent of the α-phases increases and partial secondary α-phases transform into equiaxed shape. At the temperature of 860 °C, the alloy exhibits excellent strength and plasticity, as the uniform and fine duplex microstructure formed after isothermal forging. When the deformation degree increased from 20% to 60%, primary and secondary α-phases were gradually broken and the recrystallization energy was continually accumulated, which ceaselessly strengthened the properties of the alloy. With the increase of forging times, the globularization extent of decreases, leaving the chain of α-phases, which damages the strength and plasticity of the alloy.