The hot extrusion reaction synthesis of nickel aluminide alloys

Elemental powder compacts of Ni–13.3 wt.% Al, the composition that corresponds to stoichiometric Ni3Al, have been processed by hot extrusion reaction synthesis (HERS) to form a dense rod. A narrow processing window has been determined for the experimental scale rig used. The success of the processing route has been shown to be highly dependent on the initial billet temperature, the heating time of the billet, and the extrusion speed. HERS has been successful at relatively low processing temperatures (less than 600 °C) and offers a highly economical method of producing aluminide extrusions. The extruded microstructure consisted of a mixture of ordered gamma prime precipitates in a Ni-rich matrix and grains of twinned martensite. Both a {200} texture and a weaker {111} texture were observed along the extrusion direction. The Vickers hardness of the extruded material was 340 kgf /mm2. The 0.2% compressive yield stress at room temperature at a constant strain rate of 10−3 s−1 was 600 MPa.