Formation, microstructure, and performance of laser-welded 6061 Al alloy joint with Ti3AlC2 additive.

Aluminum alloy is the optimum material for weight reduction and widely used in a lot of industries including automobile, rail transportation, aerospace, and so on. Ternary Ti₃AlC₂ powder was adopted in this study to improve the laser welding quality of 6061 Al alloy. Addition of the Ti₃AlC₂ powder could increase the width and stability of the molten pool, which was beneficial to inhibit the formation of defects such as pore, spatter, rugged surface, sagging, and undercut. Reaction products of Ti₃AlC₂ powders including Ti₃Al_xC₂, TiAl_3, and TiC impeded the growth of dendrites and could serve as nucleating agent, resulting in the formation of massive isometric crystals and dispersed precipitates. The refinement strengthening and dispersion strengthening could impede the extension of deformation and made up the influences of uneven melting loss of alloying elements, leading to the increase and uniformity of weld hardness from 53.1 HV_0.2 to 74.9 HV_0.2. Both of the welded joints with and without assistant powder fractured at the welds. Elimination of pores increased the loading area of weld while generation of precipitates impeded the extension and connection of dimples, leading to the improvement of tensile strengths from 191.0 to 232.5 MPa and displacements from 0.95 to 1.59 mm. [ABSTRACT FROM AUTHOR]