Effect of growth rate on microstructure parameters and microhardness in directionally solidified Ti–49Al alloy

Intermetallics Ti–49Al (at.%) alloy was directionally solidified with different growth rates (V = 5 μm/s–30 μm/s) at a constant temperature gradient (G = 12.1 K/mm) by using a Bridgman type directional solidification furnace. The primary dendritic spacing (λ), interlamellar spacing (λL), and microhardness (HV) were measured. Effect of V on HV, λ and λL was experimental investigated. The dependencies of λ, λL and HV on the growth rate were determined by using linear regressing analysis. According to the result, the values of λ and λL decrease with the increasing of V, and the values of HV increase with the increasing of V and with the decreasing of λ and λL. The results were compared with previous similar experimental results for TiAl-based alloys.

► The α phase is the primary solidification phase in DS samples.
► The values of λ and λL decrease with the increasing of V.
► The values of HV increase with the increasing of V.
► The values of HV decrease with the increasing of λ and λL.