2024铝合金搅拌摩擦焊接头组织结构及力学性能

Microstructure and mechanical properties of the friction stir welding joints of 2024 aluminum alloy

采用搅拌摩擦焊工艺实现3 mm厚的2024铝合金焊接,对接头搅拌区的组织结构及力学性能进行分析。研究表明,焊核区主要由再结晶和搅拌的双重影响而形成的细小等轴晶组织构成;热机影响区受焊核区剪切力及热循环的影响,晶粒大小不均匀并伴有晶粒变形的现象。力学性能分析表明,接头显微硬度分布特征与金相组织结构一致;当焊接速度为300 mm/min时,接头的抗拉强度达到294 MPa,为母材的69%,接头的断裂形式为韧窝和沿晶断裂特征的韧性和脆性断裂;接头的焊接残余应力以纵向应力为主,纵向残余应力峰值出现在前进侧轴肩作用的边缘处,焊接速度为300 mm/min时峰值达到164.5 MPa。

The 2024 aluminiunl alloy of 3mm thickness was successfully joined by the friction stir welding.The microstructure in stir zone and mechanical properties of joints were observed and analyzed.Research indicated that the weld nugget （WN） was composed of refined and equiaxed grains formed by the dynamic rec, rystallization and mechanical stir.The shear force of weld nugget and welding thermal cycle had effect on the thenno-mechanically affected zone （TMAZ）.As a result,the grains size was un-tmiform,and grains deformation existed in the TMAZ.Mechanical property measurements demonstrate that the mierohardness distribution is correspondence with the metallurgy structure.When the welding traveling speed is 300 mmlmin,the peak tensile strength of the joint ean reach 294 MPa,as much as 69% of the base metal.The fracture analysis shows that the fracture mode of the joinls is mixed fracture of ductile and brittle with the dimple and intergranular fraeture.The residual stress of joints is main longitudinal residual stress.And the peak residual stress is located at the edge region in advancing processing side.When the welding traveling rate is 300 mm/min,the peak residual stress is 164.5 MPa.