Microstructure evolution and properties of powder metallurgy Ti43Al9V0.3Y alloy sheets at different rolling temperatures

Abstract

TiAl alloy is a new type of lightweight high temperature structural material with excellent properties. Its room temperature brittleness can be improved by refining the microstructure and adjusting the composition. In this study, the pre-alloyed powder was sintered and densified by hot isostatic pressing, and TiAl alloy sheets were prepared using hot pack rolling. The present work establishes a fundamental understanding of the microstructure and properties during hot rolling. An ultrahigh ductility TiAl alloy was prepared by a combination of introduction of twins, purifying matrix and high sphericity grains. The room temperature elongation of the TiAl sheet is 3.0% and the elongation reaches 65% at 700 °C. The high uniform malleability might be due to several reasons: (i) Some twins are formed during the rolling deformation, in the process of dislocation slip, twins can adjust the crystal orientation to facilitate the continued dislocation slip. In this way, twinning slightly improves the room temperature plasticity of TiAl alloys; (ii) Y purifies matrix of the TiAl alloy; (iii) the grain has the high sphericity, and the spherical grain could minimize the stress concentration.