Internal friction behaviour during martensitic transformation in shape memory alloys processed by powder metallurgy

Powder metallurgy is a very powerful method to obtain polycrystalline Cu–Al–Ni shape memory alloys with enhanced thermo-mechanical properties. Nevertheless, it is shown that the powder metallurgy process can still be improved by the mechanical alloying of a mixture of powders showing different compositions before the compacting stage. This method gives better results than the ones achieved by just compacting the mixture of powders, due to the improvement of composition homogenisation produced by mechanical alloying. Moreover, the alloy obtained in this way shows accurate martensitic transformation temperatures, hysteresis and width, as it is inferred from the internal friction study, which is carried out on the different specimens.