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利用X射线衍射、金相显微镜、力学性能测试、腐蚀质量损失法、电化学极化曲线和电化学阻抗测试研究了Bi含量对Mg-4Zn-Y合金的组织、力学性能以及在3.5%的NaCl溶液中的腐蚀行为的影响。结果表明,Mg-4Zn-Y-xBi(x=0、0.5、1、2)合金的铸态组织主要由基体α-Mg、三元I相(Mg3Zn6Y)和Y5Bi3组成,Bi的加入使合金晶界上半连续网状分布的I相变为分散的颗粒状,Y5Bi3相的数量随着Bi含量的增加而增多,尺寸也逐渐粗化。合金室温和高温(150℃)时的抗拉强度、屈服强度和伸长率先随Bi含量的增加而增大,但当Bi含量过多时(2.0%),合金的综合力学性能反而下降。Mg-4Zn-Y-xBi合金的耐蚀性能随着Bi含量的增加而降低,其腐蚀速率为Mg-4Zn-Y合金的2～3倍。当Bi的加入量为2%时,合金的腐蚀电流达到最大,为0.913mA,耐蚀性能最差。
The microstructure and mechanical properties of Bi-doped Mg-4Zn-Y alloy were studied by X-ray diffraction, metallographic microscope, mechanical property test, corrosion mass loss method, electrochemical polarization curve and electrochemical impedance spectroscopy. Effect of Corrosion Behavior in Solution. The results show that the as-cast microstructure of Mg-4Zn-Y-xBi (x = 0,0.5,1,2) alloy mainly consists of matrix α-Mg, ternary I phase (Mg3Zn6Y) and Y5Bi3. The I phase in the upper semi-continuous network changes to dispersed granularity. The amount of Y5Bi3 phase increases with the increase of Bi content, and the size gradually becomes coarse. The tensile strength, yield strength and elongation of the alloy increase with increasing Bi content at room temperature and high temperature (150 ℃). However, the overall mechanical properties of the alloy decrease when the Bi content is too high (2.0%). The corrosion resistance of Mg-4Zn-Y-xBi alloy decreases with the increase of Bi content, and the corrosion rate of Mg-4Zn-Y-xBi alloy is 2 to 3 times that of Mg-4Zn-Y alloy. When the addition of Bi is 2%, the corrosion current of the alloy reaches the maximum, 0.913mA, the worst corrosion resistance.