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对1.8 mm厚AZ91镁合金和1.2 mm厚6016铝合金平板试件进行激光搭接焊试验,利用体视显微镜、卧式金相显微镜、扫描电镜、X射线衍射仪、电子显微硬度仪、微机控制电子万能试验机等手段研究镁/铝焊缝的表面成形性、接头区域的金相组织、界面元素分布、断口形貌、主要物相、显微硬度与接头力学性能。结果表明:激光功率1900 W,焊接速度50 mm/s,离焦量f为0,Ar气保护气体流量为15 L/min时,焊缝表面成形性良好,热影响区窄,晶粒细化;焊接接头平均抗拉强度和抗剪强度分别为13.99和12.79 MPa,镁侧和铝侧焊缝硬度均高于母材;剪切断口较平坦、光滑,出现相互平行的疲劳条纹;拉伸断口存在较多高度不一致的解理台阶,呈脆性断裂特征;镁/铝焊缝界面存在Mg17Al12、Mg2Al3主要物相,其中Mg17Al12脆性相高温下比Mg2Al3延性相结构稳定,是镁/铝焊接接头呈现脆性特征和较难实现焊接的主要原因。
The laser lap welding test was carried out on a 1.8 mm thick AZ91 magnesium alloy and a 1.2 mm thick 6016 aluminum alloy flat plate specimen using a stereomicroscope, a horizontal optical microscope, a scanning electron microscope, an X-ray diffractometer, an electron microhardness tester, Control electronic universal testing machine and other means to study the surface formability of magnesium / aluminum weld, metallographic structure of joint area, interface element distribution, fracture morphology, major phase, microhardness and mechanical properties of joints. The results show that when the laser power is 1900 W, the welding speed is 50 mm / s, the defocus amount is 0, and the flux of Ar shielding gas is 15 L / min, the weld formability is good, the heat affected zone is narrow, The average tensile strength and shear strength of welded joints were 13.99 and 12.79 MPa, respectively. The hardness of magnesium and aluminum side welds was higher than that of base metal. The shear fracture was flat and smooth with parallel fatigue stripes. There are many highly inconsistent cleavage steps with brittle fracture characteristics. The main phases of Mg17Al12 and Mg2Al3 exist in the interface of Mg / Al weld. The Mg17Al12 brittle phase is more stable than the Mg2Al3 ductile phase at high temperature and is brittle Features and harder to achieve welding the main reason.