Kinetics of martensite decomposition in a Gd-modified Cu-Al alloy

In this study, the kinetics of martensite decomposition and the microstructural evolution of the Cu79.7Al19.2Gd1.1 alloy were evaluated based on microhardness measurements as a function of the aging time and quenching temperature, as well as differential scanning calorimetry, scanning electron microscopy, and X-ray diffractometry. The results indicated that the α2-(Cu4Al) phase was more rapidly disordered than the β1′-(Cu3Al) phase in the Cu81.1Al18.9 alloy. The addition of Gd to the Cu81.1Al18.9 alloy seems to increase the α phase precipitation and the martensite phase decomposition rates. A new thermal event was observed in the Cu79.7Al19.2Gd1.1 alloy after aging at 150 °C for 14400min (10 days). Changes in the phase transition mechanism also occurred during aging from 350 °C for the Cu81.1Al18.9 alloy and from 300 °C for the Cu79.7Al19.2Gd1.1 alloy.