异种厚度Nb521铌钨合金激光焊接工艺

为了给Nb521铌钨合金大型薄壁结构件的工程化应用提供参考，积累Nb521铌钨合金激光对接焊缝的基础数据，通过预置装配错边和装配间隙，开展了异种厚度Nb521铌钨合金的激光焊接工艺试验，研究了装配条件对铌钨合金激光焊接头的焊缝成形、微观组织及力学性能的影响。结果表明，Nb521铌钨合金具备良好的激光焊接工艺性；1.0 mm+1.5 mm厚Nb521铌钨合金激光对接焊缝允许的最大装配错边和最大装配间隙均为0.3 mm，即不超过较薄母材厚度的30%；Nb521铌钨合金激光焊缝金相组织为典型的铸态组织，两侧柱状晶通过联生结晶方式向焊缝中心相对生长，热影响区宽度为0.3～0.4 mm；装配错边和装配间隙对焊缝微观组织的影响较小；当装配错边和装配间隙不超过允许的最大值，均可获得均匀美观的双面焊缝成形；接头具备良好的综合力学性能，拉伸试样断裂于母材，为典型的韧性断裂特征。创新点： (1)引入激光焊实现了异种厚度Nb521铌钨合金对接焊，接头具备良好的综合力学性能。(2)分析了装配错边和装配间隙对1.0 mm+1.5 mm厚Nb521铌钨合金激光对接焊缝的影响，获得了装配阈值。

Laser welding process of Nb521 Nb-W alloys with different thickness

In order to provide reference for engineering application of Nb521 Nb-W alloy large and thin-wall structural components and accumulate basic data of Nb521 Nb-W alloy laser butt weld, laser welding process test of Nb521 Nb-W alloy with different thickness was carried out by presetting assembly misalignment and assembly gap, and effects of assembly condition on formation of weld, microstructure and mechanical properties of laser welded joints were researched. The results showed that Nb521 Nb-W alloy had excellent laser welding processability. Acceptable maximum assembly misalignment and maximum assembly gap of 1.0 mm+1.5 mm Nb521 alloys laser butt weld was both 0.3 mm, which was less than 30% thickness of thinner base metal. Metallographic structure of Nb521 Nb-W alloy laser weld was typical as-cast microstructure, columnar crystals on both sides grew relatively towards weld center through epitaxial solidification, and width of heat affected zone was 0.3～0.4 mm. Assembly misalignment and assembly gap had little effect on microstructure of weld. When assembly misalignment and assembly gap did not exceed the maximum acceptable value, uniform and beautiful formation of weld on both sides could be obtained. Welded joints had good and comprehensive mechanical properties, tensile smples fractured on base metal and showed a typical characteristic of ductile fracture.Highlights: (1) Laser welding process was introduced to achieve butt welding of Nb521 Nb-W alloys with different thickness, and welded joints had good and comprehensive mechanical properties.(2) Effects of assembly misalignment and gap on laser weld of 1.0 mm+1.5 mm Nb521 Nb-W alloys were analyzed, and assembly threshold was achieved.