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对AZ31B 镁合金焊接接头和热影响区的疲劳裂纹扩展行为进行研究,分析了焊接接头[L-T(W)]和热影响区的紧凑拉伸试验[C(T)],其中热影响区的C(T)试验包括焊缝平行于挤压方向[T-L(H)] 和垂直于挤压方向 [L-T(H)]两种。结果表明:对于L-T(W) 试样,裂纹沿挤压方向扩展,裂纹扩展经历先快后慢的扩展过程;T-L(H) 试样裂纹平行于缺口方向扩展,L-T(H)试样裂纹为平行于缺口方向和与缺口成一定角度两种扩展方向,裂纹扩展经历先慢后快的扩展过程。裂纹尖端扩展为穿晶和沿晶的混合模式,疲劳断口为准解理特征的脆性断口。
The fatigue crack propagation behaviors of AZ31B magnesium alloy welded joint and heat affected zone were studied. The compact tensile test [C (T)] of welded joint [LT (W)] and heat affected zone was analyzed. The C (T) test includes two parallel weld lines [TL (H)] and perpendicular to the direction of extrusion [LT (H)]. The results show that for the LT (W) specimen, the crack propagates along the direction of extrusion and the crack propagates faster and then slower. The cracks of TL (H) specimen extend parallel to the notch. The crack of LT (H) Parallel to the notch and notch at an angle to the two expansion directions, the crack propagation experienced slow first slow expansion process. The crack tip is extended to a mixed mode of transgranular and intergranular, and the fracture of fatigue is a brittle fracture characterized by quasi-cleavage.