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在横向速度为8~31.5 mm/min、搅拌速度为400~800 r/min条件下对厚度为8 mm的2024-T351铝合金板进行搅拌摩擦焊接实验。为了考察焊接样品的各项性能,对焊接样品进行金相分析、维氏硬度和XRD(确是残余应力)测试。为了得到样品的残余应力和应力强度因子(SIF),对样品的搅拌摩擦焊接过程进行有限元分析。基于标准测试方法研究焊接样品的断裂和疲劳行为,焊接样品在焊核区出现初始裂纹且裂纹沿焊接方向扩展;同时采用剪切散斑干涉方法对焊接样品的断裂行为进行进一步研究。结果表明:横向速度和搅拌速度影响样品的断裂韧性和疲劳裂纹生长速率。搅拌摩擦焊使样品的最大断裂荷载和断裂韧性降低了18%~49%。较低的横向速度使焊接接头的断裂韧性稍许降低。在较高的横向速度或较低的搅拌速度下,焊接接头缺陷的增加可导致较低的断裂韧性。在较低应力强度因子差值(ΔK≤13 MPa·m~(1/2))条件下,所有焊接样品的疲劳裂纹扩展速率比其基体合金的疲劳裂纹扩展速率慢;而在较高的ΔK值条件下,焊接样品的疲劳裂纹扩展速率比基体合金的疲劳裂纹扩展速率快得多。
The friction stir welding experiment was carried out on 2024-T351 aluminum alloy plate with thickness of 8 mm under the conditions of lateral speed of 8 ~ 31.5 mm / min and stirring speed of 400 ~ 800 r / min. In order to examine the performance of the welded samples, the welded samples were examined by metallography, Vickers hardness and XRD (indeed residual stress). In order to obtain the sample residual stress and stress intensity factor (SIF), the finite element analysis of the sample friction stir welding process. The fracture and fatigue behaviors of the welded samples were studied based on the standard test methods. The initial cracks and the cracks propagating along the welding direction were observed in the weld samples. The fracture behavior of the welded samples was further studied by shear speckle interference method. The results show that the transverse velocity and stirring speed affect the fracture toughness and fatigue crack growth rate. Friction stir welding reduced the maximum fracture load and fracture toughness of the samples by 18% -49%. The lower transverse velocity slightly reduces the fracture toughness of the welded joint. At higher lateral speeds or lower agitation speeds, the increase in weld joint defects can lead to lower fracture toughness. The fatigue crack growth rate of all the welded samples is slower than the fatigue crack growth rate of the base alloy at the lower stress intensity factor difference (ΔK≤13 MPa · m ~ (1/2)), while at higher ΔK The fatigue crack growth rate of the welded samples is much faster than that of the matrix alloy under the condition of value.