微量钪对Al-Zn-Mg-Zr热轧板搅拌摩擦焊接头组织与性能的影响

Effects of minor Sc on microstructure and mechanical properties of Al-Zn-Mg-Zr hot rolled plate

采用硬度测试、室温拉伸性能测试、金相显微和透射电镜研究微量钪对Al-Zn-Mg-Zr热轧板搅拌摩擦焊接头组织与性能的影响。结果表明:微量钪使Al-Zn-Mg-Zr合金母材的抗拉强度和屈服强度分别提高22MPa和42MPa,使焊接接头的抗拉强度和屈服强度分别提高19MPa和33MPa;焊核处硬度的提高来源于搅拌摩擦引起的细晶强化、固溶强化以及第二相的弥散强化,热影响区硬度的降低则是由于焊接热循环引起的析出相的粗化;微量钪使Al-Zn-Mg-Zr合金母材及焊接接头强度的提高的主要原因是细晶强化和Al3(Sc,Zr)粒子的析出强化。

The effects of minor Sc on the microstructures and mechanical properties of friction stir welding（FSW） joint of Al-Zn-Mg-Zr alloy were studied by hardness test,tensile property test,optical microscope（OM） and transmission electron microscope（TEM） analysis.The results show that minor Sc can increase the tensile strength and yield strength of Al-Zn-Mg-Zr based alloys by 22 MPa and 42 MPa and those of FSW joints by 19 MPa and 33 MPa,respectively.The strengthening of weld nugget attributes to grain refinement strengthening,solution strengthening and precipitation strengthening caused by friction stir welding.The decrease of strength in head affected zone（HAZ） is due to coarsening of precipitated phase.The fine grain strengthening and precipitation strengthening of Al3（Sc,Zr） should be responsible for the strengthening of base alloy and the joint of Al-Zn-Mg-Zr alloy with minor Sc.