Microstructures and mechanical properties of a γ-TiAl alloy modified by Gd additions

Abstract

The microstructural evolutions and room-temperature tensile properties of Ti-45Al-2.5Nb-1.5Mo-(0-0.2)Gd were investigated in details. Experimental result revealed that there were precipitated particles, involving Gd2TiO5 and GdAl3, distributing within the microstructure of the Gd-containing TiAl alloys, and the increase in the Gd addition resulted in the aggregation of Gd-containing particles, forming a network structure along grain boundary and colony boundary. The addition of Gd also had a significant refining effect on the average inter-lamellar spacing. The ultimate/yield strength and elongation increased first and then decreased with the content of Gd. Gd addition did not change the mixed fracture mode of crack propagation along and across the lamellae. In the plastic deformation process of Gd-containing sample, except for dislocation gliding, twinning-controlled deformation mode occurred, contributing to the improvement of mechanical properties. Moreover, dislocations could directly cut through the small-size Gd-containing particle, while some dislocations would continue to slip via bypassing the large-size Gd-containing particle.