Characterization of the effects of process parameters on macrosegregation in a high-pressure die-cast Magnesium alloy

Normal and inverse solute segregations have been reported to occur in several Al-alloys as well as in some other nonferrous alloys. Nonetheless, these phenomena have not been studied in high-pressure die-cast (HPDC) Mg-alloys. This contribution reports an experimental metallographic evidence of inverse surface macrosegregation in a HPDC AM60 Mg-alloy and the effects of process parameters on the extent of inverse segregation. It is observed that low gate velocity, low liquid metal temperature before casting, and application of intensification pressure lead to high extent of inverse macrosegregation at the cast surfaces of HPDC AM60 Mg-alloy. Unfortunately, this combination of HPDC process parameters is also often utilized to achieve low micro-porosity levels. Consequently, in such cases, the beneficial effects of low levels of micro-porosity on the fracture related mechanical properties might be nullified by the adverse effects of enhanced macrosegregation.