The role of defects on tensile deformation and fracture mechanisms of AM AlSi10Mg alloy at room temperature and 250 °C

This paper studied the tensile deformation and fracture mechanisms of a laser powder bed fusion (L-PBF) built AlSi10Mg alloy at room temperature (RT) and 250 °C via X-ray microtomography (XCT) and fractography. The mechanical tests have shown a distinct contrast on the bulk strength and ductility between the two temperatures. It was found that the temperature influences the tensile fracture behaviour via primarily facilitating the plastic deformation, leading to the significant enlargement and elongation of the defects within the necked region. Additionally, the tensile fracture path involves less preferential propagations along the melt pool boundaries (MPBs), due to the loading direction and the less distinct solidification structure arising from the stress relief treatment. In terms of fracture mechanisms, at RT, defects coalesce to form microcracks, propagate in a quasi-zig-zag path and finally lead to a classical cup-cone fracture. While at 250 °C, defects elongate under local plastic straining and then coalesce through microvoiding as the hydrostatic constraint becomes significant due to necking, and finally lead to a ductile fracture.