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Friction stir welding (FSW) was introduced to join laser powder bed fusion (LPBF) AlSi10Mg alloys in this study. Microstructure and texture evolution, microhardness distribution and tensile properties of the FSW joints were investigated. The evolution of grain size, grain boundary and misorientation angles distribution, dynamic recrystallization and crystallographic texture in various regions of the FSW joint concerning base metal (BM), thermo-mechanically affected zone (TMAZ), upper part of nugget zone (UPNZ) and low part of nugget zone (LPNZ) was characterized by using electron back-scattered diffraction (EBSD). The analysis reveals a strong texture evolution of shear components on the TMAZ, UPNZ and LPNZ as well as a fully recrystallized grain structure on the UPNZ and LPNZ. Additionally, a gradual evolution in Si-rich eutectic from continuous cellular networks in the BM to totally globularized particles in the UPNZ and LPNZ occurs in the FSW joint. The microhardness rapidly decreases to the TMAZ from the BM through heat affected zone (HAZ) reaching the lowest value of ∼65.0 HV at the TMAZ/NZ boundary. The FSW joint in LPBF AlSi10Mg alloys exhibits an ultimate tensile strength (UTS) of 247 MPa and an elongation-to-failure (EI) of 8.8%. The UTS of FSW joints is reduced compared to the BM, but the EI has been increased by 160%, implying an improvement in tensile ductility. [Display omitted] • Friction stir welding was introduced to weld laser powder bed fusion AlSi10Mg. • New shear textures of F, R-Goss and R-Cube components are developed in the FSW joint. • LAGBs are increased in the TMAZ, and a high fraction of HAGBs is developed in the NZ. • FSW of LPBF AlSi10Mg results in a gradual evolution of Si-rich phase morphology in the joint. • FSW of LPBF AlSi10Mg produces the highest UTS of 247.0 MPa and the maximum EI of 8.8%. [ABSTRACT FROM AUTHOR]

Autogenous laser welding of 5A90 Al–Li alloy sheets in a butt-joint configuration was carried out in this study. The microstructure characteristics of the weld metal and base metal in the horizontal surface and the transverse section of the welded joints were examined quantitatively using electron back scattered diffraction (EBSD) technique. The results show that the weld metal in the horizontal surface and the transverse section exhibits similar grain structural features including the grain orientations, grain shapes, and grain sizes, whereas distinct differences in the texture intensity and misorientation distributions are observed. However, the base metal in the horizontal surface and the transverse section of the joints reveals the obvious different texture characteristics in terms of the grain orientation, grain morphology, predominate texture ingredients, distribution intensities of textures, and grain boundary misorientation distribution, resulting in the diversity of the microhardness in the base metal and the softening of the weld metal. However, the degree of the drop in the hardness of the weld metal is highly correlated to the microtexture developed in the base metal. [ABSTRACT FROM AUTHOR]

The additive manufactured (AM) parts of aluminum alloys have been widely used in defense, aerospace, automotive and other industries. There is a growing demand for joining or repairing of the AM parts of aluminum alloys using welding technology. However, the problems of high porosity and joint softening are occurred when welding of aluminum alloy AM parts, which have become technical bottlenecks that need to be solved urgently. Laser welding of AlSi10Mg alloys fabricated by selective laser melting (SLM) with an addition of Er and Zr in the filler metal was carried out. The effect of Er and Zr addition on the porosity, microstructures and mechanical properties of the welded joints was investigated, and the contribute of Er and Zr addition to the yield strength (YS) of the welded joints was calculated. Compared that joints without Er and Zr addition, the average ultimate tensile strength (UTS) and YS of the welded joints with Er and Zr addition have been increased by 10.5% and 23.5%, respectively. The improved mechanical poverty of the welded joints is due to the refined α-Al grains and Si-rich cellular networks, and the reduced hydrogen pores occurred in the weld metal (WM) with the addition of Er and Zr. The YS calculation of the weld joints indicates the most important contribution to the YS is the enhancement effect of the Si-rich networks with Er and Zr. [Display omitted] • Filler metal with Er and Zr addition was introduced in laser welding of SLM AlSi10Mg alloys. • Er and Zr addition in Filler metal effectively reduces hydrogen pores generated in the WM. • Er and Zr addition in Filler metal greatly increases the UTS and YS of the welded joints. • Enhancing Si-rich network effect with Er and Zr addition is the most important contribution to the enhancement of YS. [ABSTRACT FROM AUTHOR]

Abstract: Al-4.7Mg-0.7Mn-0.3Er alloy plates were welded by laser beam welding (LBW) and tungsten inert gas (TIG). Mechanical properties and microstructures of both welded joints were analyzed. The results showed that the tensile strength of LBW joint was 315MPa, which was approximately 10% higher than that of TIG welded joint. This was attributed to the fine grains, dispersed primary Al3Er phase and low Mg evaporation in LBW weld. Equiaxed grains with average size of 30μm were obtained in the fusion zone, which were much smaller than that of 90μm in the fusion zone of TIG joint, due to the low heat input during LBW process. Moreover, finer primary Al3Er particles were uniformly distributed in the LBW joints, which resulted in a substantial increase of nucleation rate in LBW welds. In addition, it was also found that Mg concentrations in the fusion zones, in both TIG and LBW joints, were lower than that of the base one tested by EPMA. The burning loss rates of Mg in TIG and LBW joints were 36% and 22%, respectively. [Copyright &y& Elsevier]

Abstract: Butt joints of 3.0mm thick sheets of an Al–Li based alloy have been produced using Nd:YAG laser welding without filler metals. The hardness distribution and microstructure of the alloy and welded joints were investigated. The changes in the grain shapes, grain orientations, microtexture, and precipitates of the fusion zone were analyzed using optical microscope, electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that Nd:YAG laser welding leads to a change of the microhardness, grain shape, grain orientations, and a disappearance of the microtexture and precipitates. A narrow band of EQZ along the fusion boundary and a predominantly equiaxed dendritic structure are developed in the fusion zone. The formation of the predominately equiaxed dendritic grains is due to a heterogeneous nucleation mechanism aided by equilibrium A13Zr phases as well as the growth of pre-existing nuclei created by dendrite fragmentation, or by grain detachment resulted from Nd:YAG laser welding processes. In addition, Nd:YAG laser welding produces lower Vickers hardness than that of the base metal due to the decrease in the in quantity of δ′ precipitates in the fusion zone. [Copyright &y& Elsevier]

Laser welding of Q235 low carbon steel and 6061 aluminum (Al) alloy was carried out by using a dual beam fiber laser in keyhole welding mode in a steel-on-Al lapped configuration. The influence of processing parameters of power distribution ratios ( R s ) and dual beam laser distances ( d 1 ) on the weld shapes, microstructures of intermetallic compound (IMC) layers, microhardness and tensile resistance of the steel/Al joints was studied. Soundly welded steel/Al joints have been achieved by using dual beam laser keyhole welding at R s   = 0.67 and d 1  = 1.5 mm. The key factor affecting welding defects is the control of the penetration depth of the welds, and good weld shape has been achieved when the penetration depth of the welds is below 700 m. The formation of IMC phases consisted of Fe 4 Al 13 , Fe 2 Al 5 and FeAl 2 phases is only limited to the weld/Al interface when the steel/Al joint has a relatively low penetration depth of the welds in the steel/Al joint. The maximum tensile resistance of the steel/Al alloy joints of 115.6 N/mm is obtained under the conditions of R s  = 0.67 and d 1  = 1.5 mm. The fracture surface reveals a mixed failure occurred in the Al alloy leading to high tensile resistance of the steel/Al joints. [ABSTRACT FROM AUTHOR]