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

Abstract

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 ( λ L ) and microhardness ( H V ) were measured. The value of H V increases with the increasing growth rate ( V) and decreases with the increasing dendritic spacing and interlamellar spacing. The dependence of H V on V, λ and λ L was determined by linear regression analysis. The relationships between the V and H V , and λ and H V , and λ L and H V were given as H V = 794.7 V 0.15, H V = 398.1 λ −0.31 and H V = 491.5 + 53.4 λ L − 0.5 , respectively. The fitted exponent values obtained in this work were compared with the previous similar experimental results.