Zn对钢/铝异种金属搅拌摩擦焊接头界面组织及性能的影响

采用离子喷涂方法在钢侧喷涂厚度为0.4 mm的Zn粉,对厚度同为3 mm的6005A-T6铝合金与S420MC钢板进行搭接搅拌摩擦焊实验。采用金相显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)和显微硬度等方法研究Zn对焊缝界面形貌、微观组织结构、力学性能及界面生长的影响。结果表明:无Zn层钢/铝接头和有Zn层钢/铝接头均在界面处形成了搅拌焊特有的"飞边",并延伸至铝基体中形成机械咬合接头,界面处均有AlFe,AlFe3,Al13Fe4金属间化合物产生。有钢质颗粒弥散分布在无Zn层的钢/铝接头的铝基体中。Zn的添加降低了界面反应层厚度,钢/铝搅拌摩擦焊界面结合方式为"机械+冶金"。接头断裂位置均在界面处,无Zn层钢/铝断裂接头为典型的"韧-脆"混合型断裂,有Zn层钢/铝接头为韧性断裂。最高显微硬度值从无Zn层接头的388HV降低到有Zn层接头的210HV。

Effect of Zn on interfacial microstructure and properties of steel/aluminum dissimilar metal friction stir welded joints

Zn powder with a thickness of 0.4 mm was sprayed on the steel side by ion spraying method The lap welding was carried out on the 3 mm thickness 6005A-T6 aluminum alloy and 3 mm thickness S420MC steel plate using FSW(friction stir welding).The effects of Zn on the interface morphology,microstructure,mechanical properties and interfacial growth of weld were studied by means of(XRD)and microhardness of(OM),scanning electron microscope(SEM),X-ray diffractometer and microhardness.The results show that both the steel/aluminum joint without Zn layer and the steel/aluminum joint with Zn layer form the special"flying edge"of friction stir welding at the interface and extending into aluminum matrix to form the joint of mechanical occlusion,AlFe,AlFe3,Al13Fe4 intermetallic compounds are produced at the interface.Steel particles are dispersed in aluminum matrix of steel/aluminum joint without Zn layer.The maximum tensile and shear load of the joint increase from 4826 N to 5628 N at the interface.The non-Zn layer steel/aluminum fracture joint is a typical"tough-brittle"hybrid fracture,and the Zn layer steel/aluminum joint is brittle fracture.The maximum microhardness value reduces from 388HV without Zn layer joint to 210HV with Zn layer joint.