Creep in mechanically alloyed NiAl

The creep behaviour of mechanically alloyed (MA) NiAl, consolidated by a hot extrusion or hot pressing, was examined. Hot extruded MA NiAl exhibited higher creep rates due to the development of a strong 〈110〉 texture along the extrusion direction, the presence of somewhat coarser oxides and the lower level of interstitial atoms. In general, minimum creep rates in Ma NiAl were on average three orders of magnitude lower than those in their case counterparts. Improved creep resistance of MA NiAl is postulated to result from the presence of dispersoids and interstitial atoms and, to a limited extent, from its fine grain size. Taking into consideration the temperature and stress ranges in the present study, the measured values of the stress exponent and the activation energies for creep, and the occurrence of the threshold stress below which creep does not occur, one can conclude that creep in the MA NiAl materials is controlled by climb of dislocations over dispersoid.