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

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 mu m s(-1)) by using a Bridgman-type directional solidification furnace. The microstructure of the directionally solidified specimen is constituted of alpha(2)(Ti3Al) and gamma(TiAl) lamellar structures. The values of the primary dendritic spacing (lambda), interlamellar spacing (lambda(L)) and microhardness (HV) were measured. Dependencies of lambda, lambda(L) and HV on G were determined by using the linear regressing analysis. According to these results, the values of lambda and lambda(L) decrease with the increase of G, and the values of HV increase with the increase of G and with the decrease of lambda and lambda(L). In addition, these results were compared with the previous similar experimental results of TiAl-based alloys. (C) 2011 Elsevier B.V. All rights reserved.