High tensile elongation of a directionally solidified NiAl multiphase alloy at high temperatures

The ductility of a directionally solidified Ni-30Al-5Mo-0.5Hf (at.%) alloy was examined in various experimental conditions of temperatures and strain rates. Tensile tests revealed that the present alloy exhibited tensile elongation from room temperature to high temperature, in particular, the large elongations, 140-160%, were observed at high temperatures, depending on the temperature and strain rate. The value of strain rate sensitivity index, m, of 0.27 and the apparent activation energy of 413 kJ/mol were measured. Based on the observed mechanical behavior and microstructures, the mechanism responsible for this large elongation operative at high temperatures was suggested.