Study on microstructure and properties of Mg-Al-Si-Ca alloy by heat treatment

The effect of heat treatment on the microstructure and properties of Mg-4Al-0.25Si-0.3Ca alloy was systematically studied. The results showed that after solution treatment at 420 ℃ for 10 h and 500 ℃ for 3 h, then aging at 220 ℃ for 7.5 h, the shape of Mg2Si and CaMgSi phases changed from continuous to discontinuous, while the Mg17Al12 phased precipitated in the way of continuous precipitation in grains and discontinuous precipitation at grain boundaries during aging. The UTS of the alloy increased from 174.3 ± 4.0 MPa to 194.0 ± 5.0 MPa, and the corrosion current density decreased by 54%, The corrosion resistance was also improved, but the elongation decreased from 10.38 ± 0.37% to 9.1 ± 0.46%. •The Mg2Si phase and CaMgSi phase changed from continuous to discontinuous after 420 ℃ × 10 h, 500 ℃ × 3 h and 220 ℃ × 7.5 h.•After heat treatment, the UTS increased from 174.4 MPa to 194.0 MPa, the Icorr decreased, but the elongation decreased slightly.•The Mg17Al12 phase precipitated in two methods: intragranular continuous and grain boundary discontinuous precipitation.