基于数字图像相关（DIC）方法对2A12-T4铝合金搅拌摩擦焊（FSW）接头拉伸过程的非均匀变形行为进行分析，然后采用等应力假设方法研究了接头的局部力学性能，并与横向拉伸试验得到的整体力学性能进行对比。结果表明：基于DIC方法可知，拉伸过程中接头内部存在较大的应变梯度，采用等应力假设方法计算得到的母材局部真应力-真应变数据与试验得到的真应力-真应变曲线相吻合，验证了等应力假设方法的准确性；计算得到前进侧距焊缝中心6.5 mm处热影响区的真应力-真应变曲线更接近于接头的，热机影响区与热影响区交界处的屈服强度最低，为接头力学性能最薄弱区域；接头高强度区对低强度区存在约束效应，导致接头的整体力学性能优于最薄弱区域的局部力学性能。

The inhomogeneous deformation behavior of friction stir welding (FSW) 2A12-T4 aluminum alloy joint during tension was analyzed on the basis of digital image correlation (DIC) method. The local mechanical properties of the joint were then studied by the iso-stress assumption method, and compared with global mechanical properties obtained by the transverse tensile test. The results show that there was a large strain gradient inside the joint during tension by the DIC method. The local true stress-true strain data of base metal obtained by iso-stress assumption method was consistent with the true stress-true strain curve by the test, which verified the accuracy of the iso-stress assumption method. The calculated local true stress-true strain curve of heat affected zone at the distance of 6.5 mm from the weld center on advancing side was closer to the tensile properties of the joint. The yield strength of the junction of thermal-mechanically affected zone and heat affected zone was the smallest, and this position was the weakest area of the joint. The high strength area of the joint had constrains on the low strength area, which led to the better mechanical properties of the joint than the local mechanical properties of the weakest area.