7A52铝合金搅拌摩擦焊接头第二相的形貌及相组成

摘要

In order to further research the properties of the high strength aluminum alloy friction stir welded (FSW) joint, the second phases in the joint must be characterized clearly. The optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope were used to observe the type, quantity, shape, size and distribution of the second phases in the 7A52 alloy FSW joint. The research results indicate that the second phases in the base material are mainly composed of coarse Al6(Mn, Fe) along rolling direction, Mg2Si, fine n' phase (MgZn2) and η phase (MgZn2). In addition, both α-Al12(Fe, Mn)3Si and Mg2Si phases distribute dispersively in other zones. The T (Mg32(Al, Zn)49), Al6Mn and S (Al2CuMg) phases appear mainly in the dynamic recrystallization zone (DRZ). The zonal Al6Mn phase distributes continuously along the grain boundaries in the thermo-mechanically affected zone (TMAZ). The -n phase inside the grains becomes coarser, and fragmentates from long strip to ellipsoid shape. The precipitate free zone (PFZ) appears at grain boundaries in TMAZ. Compared with the base material, the morphology and distribution of the η' phase has no obvious change while the η phase coarsens significantly in the heat affected zone (HAZ). Compared with the TMAZ, the zonal Al6Mn phase distributes still along the grain boundaries and the S phase appears inside the grains in the HAZ.%为进一步研究高强铝合金搅拌摩擦焊接头的性能,必须对接头中的第二相进行明确表征.采用光学显微镜、扫描电镜及能谱、透射电镜对7A52铝合金搅拌摩擦焊接头第二相的种类、数量、形状、大小、分布进行了观察.结果表明,基材的第二相组成主要为沿轧制方向分布的粗大Al6(Mn,Fe)和Mg2Si,细小的η'相(MgZn2)和η相(MgZn2),其他各区均弥散分布α-Al12(Fe,Mn)3Si和Mg2Si.动态再结晶区主要包含T相(Mg32(Al,Zn)49)、Al6Mn、S相(Al2CuMg).热机影响区晶界处连续分布条带状Al6Mn,η相发生粗化,分布在晶粒内部,由原来的长条状破碎成椭球状,晶界有无沉淀析出带.热影响区与基材相比,η'相形貌和分布状况并无明显变化,η相明显粗化;与热机影响区相比,Al6Mn仍然在晶界处呈条带状分布,晶内有S相存在.