On the deformation behavior of heterogeneous microstructure and its effect on the mechanical properties of die cast AZ91D magnesium alloy

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting (HPDC) process, and samples of AZ91D magnesium alloy with different microstructure mainly consisting of alpha-Mg grains, /3-phase and porosities were obtained. According to the grain orientation analysis, the predominant deformation behavior in alpha-Mg grains was dislocation slip, supplemented by deformation twinning. Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size of alpha-Mg grains in the microstructure was finer and more uniform. During the in situ tensile deformation test, cracks were observed to initiate from gas-shrinkage pore and island-shrinkage, and two main crack propagation mechanisms, porosity growth and coalescence were found accordingly. When the crack was in contact with the /3-phase, it would pass through and fracture the network/3-phase, whereas bypass the island /3-phase by detaching it from the surrounding alpha-Mg grains. Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties, which was the combined effect of matrix alpha-Mg grains, /3-phase, and porosities.(c) 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

This study investigates the effect of flow distributor improvement on the microstructure and mechanical properties of AZ91D magnesium alloy samples obtained through high pressure die casting. The results reveal that samples with a more homogeneous microstructure demonstrate higher mechanical properties.