Role of Al modification on the microstructure and mechanical properties of as-cast Mg-6Ce alloys

摘要

The effect of Al additions on grain refinement and mechanical properties of Mg-6Ce alloys has been investigated. Greatly grain coarsening were obtained when Al content are 1% and 2%, mainly due to both the weakening of the segregation effect of Ce solute and the lack of the effective nucleation sites. However, an addition of 3～5% Al into the Mg-6Ce melt promotes the in situ formation of Al_2Ce particles and reduce the grain size. Furthermore, active Al_2Ce particles were observed at the centers of many refined grains. Crystallographic calculations confirmed that Al_2Ce particles were effective grain refiners for α-Mg. The finest grains were achieved at 5% Al addition level, which corresponds to the size of 7～10 μm with the highest number density of the active particles. The reasons of improvement of both the strength and ductility of the Mg-6Ce alloy containing Al were fine grain size and secondary phase strengthening.