Metallurgical Structure and Mechanical Properties Test of Weld-Joint of Industrial Pure Zirconium

The element distribution, metallurgical structure and mechanical properties in different parts as base-zone, heat-treatment zone, and welded seam in butt-jointed seam of industrial pure zirconium R60702 welded with TIG was analyzed using optical microscope, electron probe and micro-hardness tester to study the relationship of microstructure and mechanical properties. The results show that different zones of the butt-jointed seam have different metallurgical structures: the crystalline grains in the base metal are equiaxed and surface textured; smaller and equiaxed grains in incomplete recrystallization zone create better mechanical properties in strength and plasticity; coarse grains are found in over-heated zone; and the casting organization with fibre structure is obtained in welded seam zone. The elements distribute uniformly in the butt-welded seam without obvious segregation. The hardness distribution in the butt-jointed seam between the base metal to the welded seam zone is depicted as W-shape: the maximum micro-hardness reaches 290 HV50 g at the position of welded seam, the minimum harness is located in the overheated zone with a value of 162 HV50 g, and the hardness of over-heated zone fall in between.