Optimum evaluation for electron beam weldments of AZ61A-F extruded plates

Abstract

Recently there has been a renewed interest in magnesium alloys because of their extensive applications in industries, such as computing, communications, consumer electronics, aerospace, and traffic. However, the plastic deformation of these alloys is restricted because HCP magnesium has fewer dislocation slip systems. This limitation can be circumvented by dividing shape-complicated workpieces into several more easily made parts, which are then combined into one. Due to the interaction between material properties and welding conditions, there are various kinds of defects in the welds of magnesium alloys, and these defects cause obvious stress concentrations and serious material damage. This study used a custom-made 11-mm-thick AZ61A extruded plate. By operating and comparing the variable parameters of electron beam welding (EBW), the condition was optimized for ultimate tensile strength (UTS) at 100 mA, 50 kV, 60.6 mm/s, and a focal position at the bottom of the workpiece. Under these conditions, ultimate tensile strengths of 83% and 96%, respectively, were obtained for the base metal in weldments with and without stress concentrators on their surface. For worse conditions such as 100 mA, 45 kV, 86.0 mm/s, and a focal position at the bottom, the UTS of electron beam weldments for AZ61A-F plates was reduced by the three factors of root concavity, heat-affected zone (HAZ), and cavities.