The formations and fracture behavior of the AA2A14-T6 aluminum alloy friction stir welded (FSWed) joints are investigated under different ratios of rotational speed to welding speed (n/v). The relationship between the viscous layer (δ) and the rheological layer (ξ) is the key factor to determine the welding quality of joints. When δ < ξ, loose microstructure, needle-like, dispersive, or through void is generated in the joint as the n/v decreases. When δ ≥ ξ, the defect-free joints can be obtained. The through void greatly weakens the tensile properties, and the tensile specimens fracture in the stir zone (SZ). Other defects mainly influence the ultimate strength and the elongation, and the joints fracture at the SZ/thermo-mechanically affected zone or the base material/heat-affected zone (BM/HAZ). The defect-free joints have the largest tensile properties and fracture at the BM/HAZ. Based on the above analysis, the reasonable quality assessment criteria of the FSWed joint need to combine with four aspects: internal formation, strength, plasticity, and fracture behavior. Meanwhile, according to the reasonable matching relationship between δ and ξ, the critical conditions of FSW process parameters for the 2A14-T6 aluminum alloy can be obtained.

研究了AA2A14-T6铝合金搅拌摩擦焊接（FSWed）接头在不同转速对焊接速度（n / v）的比率下的形成和断裂行为。粘性层（δ）和流变层（ξ）之间的关系是决定接头焊接质量的关键因素。当δ  <  ξ时，随着n / v的降低，在接头中会产生松散的微观结构，针状，分散或贯通空隙。当δ  ≥  ξ，可以获得无缺陷的接头。通孔大大削弱了拉伸性能，并且拉伸试样在搅拌区（SZ）断裂。其他缺陷主要影响极限强度和伸长率，并且接头在SZ /热机械影响区或基材/热影响区（BM / HAZ）处断裂。无缺陷的接头在BM / HAZ处具有最大的拉伸性能和断裂。基于以上分析，FSWed接头的合理质量评估标准需要结合四个方面：内部构造，强度，可塑性和断裂行为。同时，根据δ与ξ之间的合理匹配关系，可以获得2A14-T6铝合金FSW工艺参数的关键条件。