Microstructural heterogeneity and bonding strength of planar interface formed in additive manufacturing of Al-Mg-Si alloy based on friction and extrusion

Single-pass deposits of 6061 aluminum alloy with a single-layer thickness of 4 mm were fabricated by force-controlled friction-and extrusion-based additive manufacturing.The formation characteristics of the interface,which were achieved by using a featureless shoulder,were investigated and elucidated.The microstructure and bonding strength of the final build both with and without heat treatment were explored.A pronounced microstructural heterogeneity was observed throughout the thickness of the final build.Grains at the interface with Cu,{213}<111>,and Goss orientations prevailed,which were refined to approximately 4.0μm.Nearly all of the hardening precipitates were dissolved,resulting in the bonding interface displaying the lowest hardness.The fresh layer,subjected to thermal processes and plastic deformation only once,was dominated by a strong recrystallization texture with a Cube orientation.The previous layer,subjected twice to thermal processes and plastic deformation,was governed by P-and Goss-related components.The ultimate tensile strength along the build direction in asdeposited and heat-treated states could reach 57.0%and 82.9%of the extruded 6061-T651 aluminum alloy.