Effect of (Pr + Ce) addition and T6 heat treatment on microhardness and corrosion of AlSi5Cu1Mg alloy

Abstract

Abstract The effects of T6 heat treatment and 0.6 wt% (Pr + Ce) addition on microstructure, microhardness, and corrosion of AlSi5Cu1Mg alloy were investigated. Optical microscopy and scanning electron microscopy revealed that the T6 heat treatment and the addition of 0.6 wt% (Pr + Ce) effectively refined the α-Al and eutectic Si phases, which were uniformly distributed with Al2Cu phase in the alloy. Microhardness, weight loss, hydrogen evolution, Tafel polarization, and EIS tests showed that the combination of T6 heat treatment and 0.6 wt% (Pr + Ce) addition resulted in the best corrosion resistance and microhardness of the alloy. The microhardness of the AlSi5Cu1Mg+0.6 wt% (Pr + Ce)/T6 (115 HV) was 27.8% higher than that of the matrix (90 HV). At the same time, the corrosion current density of the alloy also reached the minimum value (38.4 μA cm−2). The T6 heat treatment and the addition of (Pr + Ce) can significantly decrease the average grain size, change the redistribution of the precipitated Al2Cu phase, refine the Si phase, and increase the pitting formation position, thus reducing the sensitivity of exfoliation corrosion.