Microstructure and mechanical properties of
melt-conditioned high-pressure die-cast Mg-Al-Ca alloy
melt-conditioned high-pressure die-cast Mg-Al-Ca alloy
(1. State Key Laboratory for Corrosion and Protection, Institute of Metal Research,
Chinese Academy of Sciences, Shenyang 110016, China;
2. Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, Uxbridge UB8 3PH, UK;
3. Graduate School of Chinese Academy of Sciences, Beijing 100049, China)
Chinese Academy of Sciences, Shenyang 110016, China;
2. Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, Uxbridge UB8 3PH, UK;
3. Graduate School of Chinese Academy of Sciences, Beijing 100049, China)
Abstract: A new shape casting process, melt-conditioned high-pressure die-casting (MC-HPDC) was developed. In this process, liquid metal was conditioned under intensively forced convection provided by melt conditioning with advanced shear technology (MCAST) unit before being transferred to a conventional cold chamber high-pressure die-casting (HPDC) machine for shape casting. The effect of melt conditioning was investigated, which was carried out both above and below the liquidus of the alloy, on the microstructure and properties of a Mg-Al-Ca alloy (AZ91D+2%Ca (mass fraction), named as AZX912). The results show that many coarse externally-solidified crystals (ESCs) can be observed in the centre of conventional HPDC samples, and hot tearing occurs at the inter-dendritic region because of the lack of feeding. With the melting conditioning, the MC-HPDC samples not only have considerably refined size of ESCs but also have significantly reduced cast defects, thus provide superior mechanical properties to conventional HPDC castings. The solidification behaviour of the alloy under different processing routes was also discussed.
Key words: Mg alloy; Mg-Al-Ca alloy; melt conditioning; grain refinement; solidification; die casting