Considerable work has been performed on N iAI over the past three decades, with rapid growth in research on this intermetallic occurring in the past few years because of recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still debated. This is due in part to the incomplete characterisation of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure, and the apparent difficulty in accurately measuring composition have made direct comparison between individual studies sometimes tenuous. The purpose of this review is to summarise all available mechanical and pertinent physical properties of NiAI, stressing the most recent investigations, in an attempt to understand the behaviour of NiAI and its alloys over a broad temperature range.1MR/247

Considerable work has been performed on N iAI over the past three decades, with rapid growth in research on this intermetallic occurring in the past few years because of recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still debated. This is due in part to the incomplete characterisation of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure, and the apparent difficulty in accurately measuring composition have made direct comparison between individual studies sometimes tenuous. The purpose of this review is to summarise all available mechanical and pertinent physical properties of NiAI, stressing the most recent investigations, in an attempt to understand the behaviour of NiAI and its alloys over a broad temperature range.1MR/247

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Tensile testing of cast and extruded binary NiAl was performed from 300 to 900 K at strain rates of 1.4 × 10−4 to 1.4 × 10−1 × s−1. The brittle-to-ductile transition temperature (BDTT) was dependent on strain rate, with a three order of magnitude increase in strain rate resulting in approximately a 200 K increase in transition temperature. Regardless of strain rate, at temperatures just above the BDTT the fracture strength increased significantly and the fracture morphology changed from mostly intergranular to predominantly transgranular. It was also determined that the mechanism responsible for the brittle-to-ductile transition in NiAl had an apparent activation energy of approximately 118 kJ/mol. These results support the argument that the mechanism for the brittle-to-ductile transition in NiAl is associated with the onset of a thermally activated deformation process. This process is probably dislocation climb controlled by short circuit diffusion.

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