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 e xhibited higher creep rates due to the development of a strong [110] t exture 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 lowe r than those in their case counterparts. Improved creep resistance of MA NiAl is postulated to result from the presence of dispersoids and i nterstitial atoms and, to a limited extent, from its fine grain size. Taking into consideration the temperature and stress ranges in the pre sent study, the measured values of the stress exponent and the activat ion energies for creep, and the occurrence of the threshold stress bel ow which creep does not occur, one can conclude that creep in the MA N iAl materials is controlled by climb of dislocations over dispersoid.