Numerical modelling of porosity with combined gas and shrinkage effects in HPDC

High-pressure die casting is a manufacturing process in which near-net-shape components are produced rapidly under a pressurized environment. However, due to the relatively higher cooling rate prevailing during the process, isolated liquid pockets form at certain locations, leading to increased porosity formation. A one-dimensional deformable grid numerical model has been developed for predicting the evolution of a single pore in an elementary volume, which combines the diffusion model with the shrinkage affected growth. The model accounts for the change in pore size due to shrinkage and inter-granular growth. This model can provide predictions in representative volumes and be used for component level predictions by combining with a macroscopic model

Evolution of 3D microstructure and correlation with deformation behavior of as-cast Mg-4Zn-xCa alloys

In this study, X-ray microtomography results aided with fractography have been utilized to elucidate the effect of the distribution of the secondary phases on the damage mechanism of the Mg-4Zn-xCa (x = 0, 0.2, 0.4, 0.6, 1.0 wt%) alloys. The alloy Mg-4Zn exhibited a 2 -a phase microstructure comprising of alpha-Mg matrix and the second phase (MgZn), which converted to an interconnected network of Ca2Mg6Zn3 phase along grain boundaries with an increase in Ca content. The compressive strength increased with the increase in Ca content up to 0.4 wt% due to the formation of the Ca2Mg6Zn3 phase. However, it further decreased due to easier crack propagation through the 3D network of Ca2Mg6Zn3 at grain boundaries