Microstructural characterisation and mechanical properties of the cast Gd-containing Mg−8Mg2Si in situ composites

Abstract

Cast Mg–8 wt% Mg2Si in situ composites containing 0, 0.5, 1, 2 and 3 wt% Gd were studied for their microstructure and high-temperature behaviour. Mechanical properties of the composites were investigated in the temperature range 25–250°C. Gd addition resulted in the modification of the primary Mg2Si particles, reduction of their average size and volume fraction, and formation of new Mg3Si2Gd2 and Mg5SiGd intermetallic phases and solid solution of Gd in the Mg matrix. The composite with 1% Gd addition showed the highest strength due to the presence of finer Mg2Si particles with polygonal morphology. Higher Gd contents decreased the strength, due to the coarsening of the Mg2Si particles, caused by the over-modification effect of Gd.