Microstructure, texture and mechanical properties of 6061 aluminum laser beam welded joints

In the present study, laser beam welding was carried out with 6061 Al alloy plate to study the microstructural evolution under various welding heat input (ηP/v = 30 J/mm, 38 J/mm, 46 J/mm, and 58 J/mm). The width of the weld metals increased continuously with the heat input values. Quantitatively correlation of the microstructure distribution with welding parameters was developed based on the EBSD results. The weld metals mainly consisted of coarse columnar dendrites and equiaxed dendrites. The ratio of equiaxed dendrites which were controlled by constitutional supercooling and heterogeneous nuclei showed directly proportional relationship with the weld strength. Strong cube texture ({001}⟨100⟩) was observed in columnar dendrites, which showed harmful effect on the weld strength. Slight softening in heat affected zone due to recrystallization was identified by nanoindentation tests. All specimens failed in weld metal and the fracture surfaces showed the characteristics of ductile fracture.