Dependency of microhardness on solidification processing parameters and microstructure characteristics in the directionally solidified Ti-46Al-0.5W-0.5Si alloy

TiAl-based alloy (Ti-46Al-0.5W-0.5Si at.%) was directionally solidified at a constant temperature gradient (G = 20 K/mm) in a wide range of growth rates (2-100 μm/s) by using a Bridgman type directional solidification furnace. The dendritic spacing (λ), lamellar spacing (λL) and microhardness (HV) were measured. The value of HV increases with the increasing growth rate (V) and decreases with the increasing dendritic spacing and interlamellar spacing. The dependence of HV on V, λ and λL was determined by linear regression analysis. The relationships between the V and HV, and λ and HV, and λL and HV were given as HV = 794.7 V0.15, HV = 398.1λ−0.31 and HV=491.5+53.4λL−0.5, respectively. The fitted exponent values obtained in this work were compared with the previous similar experimental results.