Influence of pre-weld heat treatment temperatures and AlSi10Mg-Er-Zr filler powder on microstructure and mechanical properties of welded joints produced using laser metal deposition for L-PBF AlSi10Mg alloys

This study investigates the influence of pre-weld heat treatment (PWHT) temperatures (250 ~ 400 ℃) on laser metal deposition (LMD) welding of laser powder bed fusion (L-PBF) AlSi10Mg alloys using novel AlSi10Mg-Er-Zr filler powders, with particular emphasis on porosity characteristics, mechanical performance, and microstructural evolution of the welded joints. Results show that elevated PWHT temperatures effectively mitigated hydrogen porosity, reducing both pore density and maximum diameter. The synergistic combination of low PWHT temperatures at 250 ~ 280 ℃ using AlSi10Mg-Er-Zr filler powder demonstrated superior mechanical enhancement, achieving 4.3 ~ 7.2% improvement in ultimate tensile strength (UTS) and 3.8 ~ 94.6% increase in elongation at fracture (EF) compared to the conventional AlSi10Mg filler powder. Welded joints produced using AlSi10Mg-Er-Zr filler powder at 280 ℃ PWHT yielded the optimal mechanical performance, achieving a remarkable balance between strength and ductility with an UTS of 259.0 MPa and EF reaching 10.9%. The synergistic combination of AlSi10Mg-Er-Zr filler powder and PWHT not only enhanced microstructure improvement through substantial grain refinement, increased proportions of high-angle grain boundaries (HAGBs), Σ3 grain boundaries, and hard-oriented grains, but also reduced hydrogen porosity in the welds, collectively contributing to the superior mechanical performance of L-PBF AlSi10Mg welded joints.