MICROSTRUCTURE AND PROPERTIES OF LASER-WELDED BUTT JOINTS OF AlSi1MgMn ALUMINIUM ALLOY

Abstract

The process of autogenous laser welding of butt joints of aluminium alloy AlSi1MgMn plates with thickness of 3.0 mm was investigated. The Yb:YAG disk laser was used in the study. The aim was to determine the influence of the basic parameters of laser welding on the joint quality, fusion zone geometry, microhardness distribution across the butt joint, structure and microstructure of fusion zone (FZ) and heat affected zone (HAZ) was studied and determined. The chemical composition of the base metal was determined by spark emission spectroscopy, while the phase constituents were determined by XRD analysis. Results of the study have shown that the geometry of welds is proper without excessive imperfections. No voids were found the FZ. However, weld face of the joints are slightly convex, while the roots are slightly concave. Microscopic observations showed no discontinuities in the fusion zone of the welds. A significant decrease in hardness in the FZ was observed. The hardness in the FZ of the test joints is approx. 67÷70 HV0.1. The fracture of the samples during tensile tests occurred in the FZ or at the boundary FZ/HAZ, and the tensile strength was ranged from 200MPa to 220MPa.