Ageing behavior in the Cu–10 wt.%Al and Cu–10 wt.%Al–4 wt.%Ag alloys

In this work the ageing behavior in the Cu–10 wt.%Al and Cu–10 wt.%Al–4 wt.%Ag alloys was studied using microhardness measurements, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and in situ high temperature X-ray diffractometry (XRD). The results indicated that the presence of Ag disturbs the (α + γ1) pearlitic formation in the Cu–10%Al, stabilize the martensitic phase and causes the reaction of the consumption of α phase to be the dominant process on ageing at the temperature and time ranges considered. This is due the dissolution of Cu atoms in the martensitic matrix which decreases the Al relative fraction, thus decreasing the ordering degree of the β′→β′1 ordered martensite and making the consumption of α phase the dominant process. This process is intensified by the presence of Ag precipitates that will interfere in the Al diffusion process.