Hot extrusion of a Ti-Al-Nb-Mn alloy

This paper reports on forward extrusion of a gamma-TiAl alloy (Ti-49.5 Al l-2.5 Nb-1.1 Mn) that was investigated, with special reference to the role of preheat temperature, ram velocity, and can material. Cylindrical billets were sealed in evacuated cans, soaked in extrusion temperatures ranging from 1050 to 1350 degrees C for 2 hr and then extruded through streamlined dies held at 260 degrees C. Microstructural features of the extruded billets which evolved under steady-state conditions were characterized. In conjunction with these observations, a coupled (thermal-deformation) finite-element analysis procedure was used to predict the local distributions of strain, strain rate, temperature, and stress present during extrusion. The microstructures of the extruded products are compared with those obtained in samples subjected to isothermal constant-strain-rate compression tests