A COMPARATIVE-STUDY OF MICROSTRUCTURE, MECHANICAL AND FRACTURE PROPERTIES OF NI3AL-BASED INTERMETALLICS PRODUCED BY POWDER-METALLURGY AND STANDARD MELTING AND CASTING PROCESSES

A comparative study of the microstructure, mechanical properties and f ractography of Ni3Al macro- and microalloyed intermetallics produced b y powder metallurgy (PM) and standard vacuum melting and casting proce sses has been carried out. Non-porous PM compacts were obtained by vac uum hot pressing of powders produced either by gas atomization or by a rotating electrode process. All materials showed a positive temperatu re dependence of the compression yield strength. The maximum strength was attained between 600 and 700 degrees C, then the decrease occurs. With increase in temperature the ductility of all materials slightly d ecreased to a minimum and then abruptly increased. Values of mechanica l properties of PM compacts were higher than those of as-cast material . There is a correlation between the fracture morphology and the ducti lity of Ni3Al, i.e. the higher ductility corresponds to transgranular fracture, while the minimum ductility is a consequence of intergranula r fracture.