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Laser welding/brazing of AA5182 Al to ZEK100 Mg in a lap joint configuration was performed by using a Ni interlayer. The stick-out width of Ni interlayer (WNi) had significant effects on the weld appearance, interfacial microstructure and joint strength of laser Al/Mg joints. Weld defects including porosity and crack were largely reduced with the increase of WNi from 2 to 6 mm, but a fracture occurred at the Mg/Ni interface when it increased to 8 mm which led to an immediate failure after welding. Mg–Al, Mg–Ni and minor Al-Ni IMCs were observed at the Mg/Ni interfacial region. The joint strength first increased and then decreased with the rising WNi, which was mainly determined by the width of Mg-Ni IMCs. [ABSTRACT FROM AUTHOR]

The experiment was conducted on the 907A high strength steel T-joint weldment with double pass laser based on the fiber laser welding system. The welds were fully characterized by means of metallography, microhardness and tensile test. It can be concluded that when the welding speed and defocus amount remain unchanged, the width and penetration of two weld beads increase with the increase of laser power. Uniform thin lathy martensite was found in the weld seam, which may have something to do with the preheating by the first scan and the effect of heat treatment of the second pass laser. Residual austenite and a small amount of carbides were found in the heat affected zone (HAZ). The microhardness of weld seam and HAZ are all higher than the base metal. Dimple and cleavage steps feature were easy to be found from the fractograph of the tensile samples, which can be concluded that ductile-brittle compound fracture was reached. [ABSTRACT FROM AUTHOR]