Effect of Ageing on the Martensitic Transformation in a Monocrystalline Cu-Al-Ni Shape Memory Alloy

In this work we have studied the effect of post quench ageing on the martensitic transformation in a monocrystalline Cu-13,7Al-5Ni (wt.%) shape memory alloy. Internal friction and modulus change have been measured by an inverted torsion pendulum operating at 1 Hz for different ageing times. The results show a shift of the heating and cooling internal friction peaks towards high temperatures with the increase of the ageing time at 473 K. On the other hand, the quenched sample shows only one sharp peak on heating and cooling runs with low hysteresis transformation. Nevertheless, two separated internal friction peaks appears on heating as ageing time increases. The results can be attributed to a change in the thermally formed martensite from β1' in the quenched sample to a mixture of β1' and γ1' in the aged sample