Research on the tensile properties and the crack mechanism of β type γ-TiAl bar

Abstract:

Ti-44Al-3Ta-0.3(Cr,W) (at%) bars were prepared by the hot canned extrusion. The as-extruded (AE)and heat-treatment structure（HT）microstructure, the tensile properties and fracture morphology of the bars were investigated by SEM、XRD、TEM . The results show that the yield strength of the two kinds of microstructure decreases with the increase of the tensile temperature, and the peak stress value increases with the increase of the temperature from room temperature to 600℃. The ultimate strain value of the extrusion microstructure is slightly higher than that of the heat treatment. The brittle-toughness transition (BDT) temperature of the alloy is around 800℃. The room temperature fracture of the extruded microstructure is mainly controlled by the mixed fracture modes of inter-lamellar and tans-lamellar fracture, and there are secondary cracks on the fracture surface. The tensile temperature has affected the size, the lamellar thickness, twin and phase transformation in the two kinds of the microstructure.

Key words:TiAl alloy; Tensile property; Microstructure; Twin