Dependency of microstructure parameters and microhardness on the temperature gradient for directionally solidified Ti–49Al alloy

Abstract

Intermetallics Ti–49Al (at.%) alloy was directionally solidified with different temperature gradients ( G) ranged from 2.8 K mm −1 to 12.5 K mm −1 at a constant growth rate ( V = 10 μm s −1) by using a Bridgman-type directional solidification furnace. The microstructure of the directionally solidified specimen is constituted of α 2(Ti 3Al) and γ(TiAl) lamellar structures. The values of the primary dendritic spacing ( λ), interlamellar spacing ( λ L) and microhardness ( HV) were measured. Dependencies of λ, λ L and HV on G were determined by using the linear regressing analysis. According to these results, the values of λ and λ L decrease with the increase of G, and the values of HV increase with the increase of G and with the decrease of λ and λ L. In addition, these results were compared with the previous similar experimental results of TiAl-based alloys.