Al-Zn-Mg铝合金厚板搅拌摩擦焊接头组织与分层性能

Microstructure and layering properties of friction stir welded joint of Al-Zn-Mg aluminum alloy thick plate

采用搅拌摩擦焊方法对14 mm厚Al-Zn-Mg铝合金进行对接焊接,研究了沿厚度方向分层切片的横向拉伸和应力腐蚀性能,揭示搅拌摩擦焊接头分层力学和腐蚀性能的不均匀性。研究结果表明,焊核区为细小的再结晶组织,焊核区从上表层到下表层晶粒尺寸逐渐减小;接头两侧的热影响区存在明显软化区;接头分层的抗拉强度波动较小,在315～330 MPa之间,断裂位置均位于前进侧的软化区;接头上、下表层在四点弯曲试验中均未发生腐蚀断裂,接头上、下表层热影响区的腐蚀敏感性最高;晶内析出相发生粗化和晶界析出相连续分布,是导致热影响区力学性能和耐蚀性能降低的根本原因。

The 14 mm thick Al-Zn-Mg aluminum alloy was welded by friction stir welding. The transverse tensile and stress corrosion properties of the layered sections along the thickness direction were studied. The inhomogeneity of mechanical and corrosion properties of friction stir welded joints was revealed. The results showed that the nugget zone (NZ) was characterized by fine recrystallized structure, and the grain size of the NZ from the upper layer to the lower layer gradually reduced. There was obvious softening zone in the heat-affected zone (HAZ) on both sides of the welded joint. Tensile strength of the layered sections was 315-330 MPa. The fracture position located at the softening zone of the advancing side. In the four-point bending test, no corrosion cracking occurred at the welded joints. The highest corrosion sensitivity was exhibited in the HAZ. The coarsening of the precipitates in the crystal and the continuous distribution precipitates at the grain boundary were the basic reasons for the decrease of the mechanical properties and corrosion resistance in the HAZ.