Elevated temperature deformation behaviour of multi-phase Ni-20 at% Al-30 at% Fe and its constituent phases

The mechanical behaviour of the multi-phase (beta' + gamma/gamma') alloy Ni-20 at % Al-30 at % Fe and alloys similar to its constituent beta' and gamma/gamma' phases, Ni-30 at % Al-20 at % Fe and Ni-12 at % Al-40 at % Fe, respectively, were investigated. When tested in tension at 300 K, the alloys exhibited approximate to 20%, 2% and 28% elongation, respectively. At elevated test temperatures (700, 900 and 1100 K), the multi-phase alloy exhibited increased ductility, reaching an elongation in excess of 70% at 1 100 K without necking or fracture. Similarly, the beta' alloy demonstrated increased ductility with increasing test temperatures. In contrast, the gamma/gamma' alloy showed greatly reduced ductility with increasing temperature and was quite brittle both at 900 and 1100 K. Thus, whilst at room temperature the gamma/gamma' phase improved the ductility of the beta' + gamma/gamma' aggregate, at elevated temperatures the beta' phase alleviated the brittleness of the gamma/gamma' phase, thereby preventing any embrittlement of the multi-phase alloy over the temperature range 300-1100 K. Also, whilst the beta' phase improved the room-temperature strength of the multi-phase alloy, at elevated temperatures where the beta' phase is known to be weak, the gamma/gamma' phase improved the strength of the multi-phase alloy up to 900 K, beyond which the strength deteriorated due to disordering and lack of anomalous strengthening in the gamma/gamma' component.