Consolidation of a gamma TiAl–Mn–Mo alloy by elemental powder metallurgy

An intermetallic compound based on gamma TiAl–Mn–Mo was consolidated from elemental powders. The process route consisted of powder blending, compacting and final consolidation by hot extrusion or hot forging. Good tensile properties were obtained by the heat treatment given to generate either duplex microstructure or fully lamellar microstructure. In hot forged samples, porosity control was of critical importance. Kirkendall pores in this material were attributed to the formation of transient phases such as TiAl3 and two preventive methods, heating rate control and extended soaking treatment, were suggested and experimentally verified. Beta phase was found in the regions rich with Mo and could be removed by controlling the heat treatment schedule. Microstructural evolution during heat treatment of elemental powder metallurgy (EPM) TiAl alloys was studied by X-ray diffraction, optical microscopy and micro-hardness measurement and was explained in terms of a phase diagram. Overall this work proposes EPM as a viable method for economic production of gamma TiAl alloys.