TRANSFORMATION BEHAVIOUR OF THE Al - 65% Ni ALLOY

Abstract

The martensitic transformation and the precipitation behaviour of quenched Ni65Al35 alloys were studied by structural and thermal analytical techniques. It is shown that the thermally induced martensite phase is not thermoelastic at this composition, but thermoelastic martensite may be created hy the introduction of thermal or mechanical stress. The Ni5Al3 precipitate fJhAse developed from the martensite during annealing above 600 K is suggested to be metastable, in contrast to the generally accepted view. The presence of NbAl type ordering in the martensite phase of slowly cooled samples is reported and correlated with the greater stability and irreversibility of the martensite.