摘要
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a—U＋y-U珠光体结构，激光焊缝在预热条件下为单相正交结构a板条马氏体，非预热条件下为单相正交结构a李晶马氏体．两类焊接接头的抗拉强度皆约为400MPa，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2000-4000s。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2000S。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 microstructures and mechanical properties of hypoeutectoid U-Nb alloy laser welded joint were investigated by optical microscopy （OM）, X-ray diffractometer （XRD）, transmission electron microscopy （TEM）, split hopkinson pressure bar （SHPB） and other analysis apparatus. The results show that the microstructure of hypoeutectoid U-Nb alloy base metal is a-U＋）,-U lamellar pearlite under isothermal heat treatment, while the laser welding seam is composed of a＇ lath martensite for pre-heated or a＇ twin martensite for no pre-heated with orthogonal crystal structure. The quasi-static tensile strength of welded joint （about 400 MPa） is much less than base metal and microstructures of weld, for the main reason of incomplete penetration weld and low fracture toughness. Between dynamic impact loading for base and welded joint, the strain rate of welded joint is lower than base metal, and the yield strength of welded joint is higher. Also, the compressive stress-strain curves indicated that the flow stresses for welded joint increased with the increase of strain rate and the obvious effect of strain rate hardening has been observed. At strain rate of 2000 s-1, selected plastic deformation taking place in welded joint is due to the tremendous difference mechanic properties between weld seam and base metal, and the adiabatic shear band（ASB） only appears in the rest of welded joint.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第3期379-386,共8页
Acta Metallurgica Sinica
基金
中国工程物理研究院发展基金资助项目2011B0301055~~
关键词
亚共析U-Nb合金
激光焊接
微观结构
力学性能
动态压缩
hypoeutectoid U-Nb alloy
laser welding
microstructure
mechanical property
dynamic compression
