Enhanced ductility in high-pressure die casting Mg-4Ce-xAl-0.5Mn alloys via modifying second phase

Abstract The tensile elongation of high-pressure die casting Mg-4Ce-xAl-0.5Mn alloy was significantly improved from 1% to 14% when the Al content was increased from 0 wt% to 3 wt%. Microstructural characterization and fractographic analyses were carried out to reveal the mechanism of ductility enhancement. With increasing Al content, the intermetallic particles evolve from the network-like Mg12Ce to fine acicular Al11Ce3 with a few small blocky Al2Ce and Al10Ce2Mn7 and to coarse Al11Ce3, large blocky Al2Ce and Al10Ce2Mn7. The network-like Mg12Ce, large and elongated Al2Ce and Al10Ce2Mn7 particles show the great tendency to cracking, while cracking of the small blocky Al2Ce and Al10Ce2Mn7 particles or fine acicular Al11Ce3 particles is relatively lag. In Mg-4Ce-0.5Mn alloy, microcracks propagate rapidly along the cracked Mg12Ce particles in the intergranular area. However, both the microcracks in Mg-4Ce-3Al-0.5Mn and Mg-4Ce-6Al-0.5Mn alloys need to penetrate into the grains to grow and coalesce together, which occurs only after certain plastic strain accumulating inside the grains.