Abstract:Effect of thermal stabilization on the microstructure and mechanical property of directionally solidified Ti−46Al−0.5W−0.5Si (mole fraction, %) alloy was investigated. The specimens were thermal stabilized for different time (t) and directionally solidified at a constant growth rate of 30 μm/s and temperature gradient of 20 K/mm. Dependencies of the primary dendritic spacing (λ₁), secondary dendritic spacing (λ₂), interlamellar spacing (λ_L) and microhardness (HV) on holding time were determined. The values of the λ₁, λ₂ and λ_L increase with the increase of t, and the value of HV decreases with the increase of t. The increase of t is helpful to obtain a good directional solidification structure. However, it reduces the mechanical property of the directionally solidified TiAl alloy. The optimized value of t is about 30 min.

Key words: intermetallics; TiAl-based alloy; crystal growth; microstructure evolution; mechanical properties