Abstract:Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current, pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry. The microstructure and mechanical properties of the weldments were also investigated. Relationships between the parameters and weld bead geometry were found. High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at (I) high pulse energy (25 J) and high average peak power (4.2 kW) and (II) low pulse energy (17.6 J) and low average peak power (2.8 kW). The weld joint formed at lower heat energy input exhibited finer dendritic grain structure. Mg vapourisation and hard phase compound (Al_0.5Fe₃Si_0.5) formation decreased in the weld joint formed at lower heat energy input. Consequently, the tensile strength of the weldment formed at lower heat energy input (168 MPa) is by a factor of 1.15 higher but showed ~29% decrease in hardness (111 HV_0.1) at the joint when being compared with the weldment formed at higher heat energy input. Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.

Key words: pulse laser welding; aluminium alloy; thin sheet; microstructure; mechanical properties; solidification cracking; intermetallic compound