The microstructure parameters and microhardness of directionally solidified Ti–43Al–3Si alloy

TiAl-based alloy (Ti–43Al–3Si at.%) was directionally solidified at a constant temperature gradient (G = 20 K/mm) in a wide range of growth rates (5–60 μm/s) by using a Bridgman type directional solidification furnace. The cellular spacing (λ), lamellar spacing (λL), volume fraction of Ti5Si3 phases (fV) and microhardness (HV) were measured. The values of λ, λL and fV decrease with increasing growth rate (V). The value of HV increases with the increasing values of V and λL−0.5, and decreases with the increasing values of λ, and fV. The dependence of HV on V, λ, λL−0.5 and fV was determined by linear regression analysis. The fitted exponent values obtained in this work were compared with the previous experimental results for similar alloy systems.

Research highlights▶ In this paper, the evolution of microstructure characteristics for Ti–43Al–3Si(at.%) alloy during directional solidification was investigated. ▶ The values of cellular spacing (λ), interlamellar spacing (λL) and volume fraction of Ti5Si3 phases (fV) decrease with increasing growth rate (V). ▶ The value of microhardness increases with the increasing values of V and λL−0.5, and decreases with the increasing values of λ, and fV. ▶ These results will give a reference for the lamellar orientation control of TiAl-based alloys by directional solidification and Ti–43Al–3Si(at.%) seed materials.