Electron beam weldability of pure magnesium and AZ31 magnesium alloy

Abstract

Pure magnesium and AZ31 alloy plates with 4 mm thickness were butt welded without addition of filler wire using a high voltage electron beam welding machine. Effect of welding speed on the electron beam weldability was investigated by the microstructural observation and mechanical properties. Regardless of the base metal, the welded joints were almost free from welding defects and showed good bead appearance at appropriate welding condition. The arcing phenomena did not occur at every welding speeds. Microstructure of the fusion zone of pure magnesium welded joint was coarse, and typical epitaxial growth of columnar grains was observed at fusion boundary. The very fine crystal grains were observed in the fusion zone of AZ31 alloy welded joint. Hardnesses of both fusion zone and heat affected zone of the welded joint are nearly equal to that of each base metal. Regardless of the welding speed, both tensile strength and impact value of the welded joint show same value to those of the base metal, but the elongation of the welded joint is inferior to that of the base metal. From both of the tensile test and impact test, welded joint of pure magnesium were fractured at the center of the fusion zone, but in case of AZ31 alloy welded joint, crack occurred at fusion boundary and it propagated through the fusion zone.