钎料元素Al+Zn对镁合金钎焊接头显微组织和抗剪强度的影响

摘要

为了研究钎料元素Al+Zn对镁合金钎焊接头显微组织与抗剪强度的影响，以两种Al­Mg­Zn镁合金钎料对变形镁合金AZ31B进行了高频感应钎焊，研究两种Al­Mg­Zn镁合金钎料的显微组织、钎焊接头的显微组织及力学性能。结果表明：随着钎料中Al+Zn元素含量(质量分数)的增加，钎料的固相线和液相线温度也随之增加；在钎焊过程中两种 Al­Mg­Zn 镁合金钎料与母材 AZ31B 均发生强烈合金化作用，在钎缝中均生成α­Mg+β­Mg17(Al,Zn)12离异共晶组织，钎料的原始显微组织消失，且随着钎料中Al+Zn元素含量的增加，钎焊接头中的金属间化合物相β­Mg17(Al,Zn)12的体积分数和显微硬度也随之增加，同时钎焊接头力学性能随之降低。钎焊接头的断裂形式均为沿晶脆性断裂，断裂均产生在金属间化合物相β­Mg17(Al,Zn)12处。%In order to research effect of Al+Zn elements of the filler metal on microstructures and mechanical properties of magnesium alloy brazed joint, the wrought magnesium alloy AZ31B was joined using two kinds of Al­Mg­Zn filler metals by high­frequency induction brazing mode. The microscopic structure of the filler metal, microscopic structure and the mechanical properties of the brazed joint were studied. The results show that the solidus and liquidus temperatures of the filler metals are light increment when the contents of Al+Zn elements of the filler metals increase. The α­Mg+β­Mg17(Al,Zn)12 divorced eutectoid structure forms in the brazing region due to the intensive alloying between the molten two kinds of Al­Mg­Zn filler metals and the solid base metal AZ31B occurred in the brazing process. The original microscopic structure of the filler metals disappears completely after the brazing process. As contents of Al+Zn elements of the filler metal increase, the volume fraction and microhardness of intermetallic compoundβ­Mg17(Al,Zn)12 increase too, and the shear strength of the brazed joints decreases. The overlapped joints exhibit intergranular fracture mode, the fracture comes fromβ­Mg17(Al,Zn)12 hard brittle phase.