Evolution of microscopic strains, stresses, and dislocation density during in-situ tensile loading of additively manufactured AlSi10Mg alloy

Abstract

The AlSi10Mg alloy produced by laser powder bed fusion (LPBF) possesses a novel microstructure and higher mechanical properties compared with its casting counterpart. So far, the crystallographic orientation-dependent lattice strains, average phase stresses, and dislocation density during the tensile loading of the LPBF AlSi10Mg are not well understood. This fact is impeding further optimization of microstructure and mechanical properties. High energy synchrotron X-ray diffraction providing deep penetration capability and phase-specific measurements of various bulk properties of crystal materials is applied to investigate the LPBF AlSi10Mg under loading. The crystallographic orientation-dependent lattice strains and elastoplastic properties of the Al matrix are assessed. The average phase stresses are calculated to quantify load partitioning between the Al and Si phases. The nano-sized Si particles that bear high-stress are efficient strengthening particles. The maximum value of the average phase stress of Si reaches up to ~2 GPa. Based on the modified Williamson-Hall and the modified Warren-Averbach methods, the dislocation density and its evolution during the plastic deformation are determined. A multistage strain hardening behavior is detected in the Al matrix, which is associated with the interactions between the dislocations and the cell boundary network.