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采用OM,XRD,TEM等分析手段,并结合静、动态力学测试方法,研究了亚共析U-Nb合金激光焊接接头的微观结构和力学性能.结果表明,等温热处理下的亚共析U-Nb合金焊接基材为α-U+γ-U珠光体结构,激光焊缝在预热条件下为单相正交结构α’板条马氏体,非预热条件下为单相正交结构α’孪晶马氏体.两类焊接接头的抗拉强度皆约为400 MPa,远小于基材和焊缝组织强度,焊接接头未熔透和焊缝微观结构的断裂韧度较低是主要原因.比较基材和焊接接头的动态冲击压缩性能,相同冲击速率下,焊接接头应变率低于基材,而屈服强度高于基材.应变速率在2000~4000 s-1间,接头的流变应力均随应变速率的增加而增加,表现出明显的应变率强化效应,在2000 s-1应变速率下,接头发生了选择性塑性变形,绝热剪切带仅形成于基材和热影响区.
The microstructure and mechanical properties of the U-Nb alloy laser welded joints were studied by means of OM, XRD and TEM, combined with static and dynamic mechanical testing methods. The results showed that the eutectic U-Nb alloy welding substrate for the α-U + γ-U pearlite structure, the laser weld in the preheating conditions for single-phase orthogonal structure α ’lath martensite, non-preheating conditions for the single-phase positive Cross-structure α ’twin martensite.The tensile strength of the two types of welded joints are about 400 MPa, far less than the strength of the substrate and weld microstructure, weld joint is not penetrated and fracture microstructure fracture toughness is low Is the main reason.Compared with the dynamic impact compression of substrate and welded joint, the strain rate of welded joint is lower than that of the substrate at the same impact rate, and the yield strength is higher than that of the substrate.The strain rate is between 2000 ~ 4000 s-1, , The flow stress increases with the increase of strain rate and shows obvious strain rate strengthening effect. Under the strain rate of 2000 s-1, the joint undergoes selective plastic deformation, and the adiabatic shear band forms only on the substrate and heat Affected area.