Experimental study of the effects of heat treatment on microstructure and grain size of a gamma TiAl alloy

The article presents the results of the X-ray diffraction, optical microscopy, scanning electron microscopy (SEM) conducted on a Ti-46Al-1.9Cr-3Nb alloy before and after different heat treatments. X-ray diffraction and microscopy data prove that the as-received state of the alloy with a duplex microstructure consists of the grains of the gamma, alpha(2) and B2 phases. Heat treatment of the alloy at 1450 degreesC followed by furnace cooling at different rates, air cooling and water quenching has led to the formation of a fully lamellar microstructure which consists of gamma lamellae mostly and of small volume fraction of alpha(2) lamellae. The grain size of the lamellar structure has been found to fall into the hundreds of micrometer range and to refine with increasing cooling rate and decreasing holding time. (C) 2003 Elsevier Science Ltd. All rights reserved.