Temperature distribution for controlled-dwell extrusion of γ-TiAl

Abstract

Ti-47Al-2Cr-2Nb-0.15B alloy (atom fraction) was extruded at temperatures (T_α) of 1 250 and 1 330 °C, respectively. The method of adding a thermal insulating layer was used to overcome the problem associated with the flow stress mismatch between the can and the billet during extrusion. Effects of two kinds of insulations, ZrO₂ powders and silica fibers, on the quality of extrude bar along the radial direction were studied, and the process parameters were optimized by combining with finite element method (FEM). Tensile properties of the extruded alloy at room and elevated temperature were tested. The results show that the silica fibers has better thermal insulating property than ZrO₂ powders. The temperature distribution in radial is more homogeneous using silica fibers. The alloy has a good balance of yield strength and room temperature ductility and the values are 680 MPa and 3.5%, respectively.

Keywords

TiAl alloy / controlled-dwell extrusion / can / temperature gradient