Effects of Heat Treatment on Microstructure and Corrosion Behavior of SiCp/Al-6wt%Mg Composites

The present work investigated the influence of heat treatment (T1, T4, T6 and annealing) on the microstructure related to the interfacial reaction and corrosion behavior of SiCp/Al-6wt%Mg composites prepared by a pressureless infiltration technique. The results show the occurrence of the precipitates of Si, MgA12O4 and Mg2Si as a result of the interfacial reaction between the SiC particle and the matrix of the composites during heat treatment. The precipitates contents (f) of the composites correlate with T1, T4, T6 and annealing heat treatment, following the order of fT1 < fT4 < fT6 < fannealing. The precipitates near SiC particles are responsible to pitting corrosion as a degradation mechanism of the composites. The heat treatments carried out on the composites present a significant influence on the corrosion rate (jcorr). The correlation between jcorr and heat treatment shows the characteristic of jcorr-ann > jcorr-T6 > jcorr-T4 > jcorr-T1, which may be attributed to the interfacial reaction precipitates of the composites during heat treatment.