Effect of assembly margin on laser weld formation for niobium tungsten alloy

Abstract

Based on the optimization experiment of laser welding process of niobium-tungsten alloy, the effects of assembly gap value and misalignment value on laser weld formation, microstructure and mechanical properties of Nb521 niobium-tungsten alloy were investigated by using variable gap method, equal gap method and equal misalignment value method. The results show that Nb521 niobium-tungsten alloy has good laser weldability. The maximum gap value margin of 1.0mm and 1.5mm thickness of base metal are about 22% and 10.6% of the base metal thickness, respectively. And the maximum misalignment value margin is about 30% and 33% of the base metal thickness, respectively. The welded joints are characterized by fine columnar crystal structure from the fusion zone to the center of the weld, and are little affected by assembly gap value and misalignment value. When the assembly gap value or misalignment value is not greater than the maximum margin, the welded joints are fractured in the base metal zone, which is far away from the weld. Therefore, the welded joints of Nb521 niobium-tungsten alloy by laser welding have excellent tensile mechanical properties at room temperature.