Hot deformation behavior of TiAl alloys prepared by blended elemental powders

A nearly full dense Ti-45Al-7Nb-0.4W (at.%) alloy billet with dimension of 120 mm in diameter and 50 mm in height was fabricated by reactive sintering of blended elemental powders. The high temperature deformation behavior was investigated by isothermal compressive tests, performed at temperature in 1000-1200 degrees C with strain rates from 1 x 10(-3) s(-1) to 1 x 10(-1) s(-1). Results indicate that the dependence of flow stress on temperature and strain rate is well fit for a hyperbolic-sine relationship using the Zener-Hollomon parameter. The measured apparent activation energy Q and stress exponent are determined as 420 kJ mol(-1) and 3.7, respectively. High oxygen content, high Nb content and fine grain size are main reasons for the high activation energy and high strength of PM TiAl alloy. An appropriate set of deformation processing parameters of 1200 degrees C and 1 x 10(-3) s(-1) are recommended for the present TiAl alloy. (C) 2010 Elsevier Ltd. All rights reserved.