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采用光学显微镜(OM),扫描电镜(SEM),能谱仪(EDS),X射线衍射(XRD)分析以及拉伸、全浸腐蚀等实验手段,研究了Mg-x Sn-2Al-1.5Zn-0.8Si(x=3,5,8;%,质量分数,下同)合金铸态下的组织和性能。结果表明:Sn元素与基体Mg生成Mg2Sn相,该相能阻断Mg2Si相的枝晶生长,并对铸态组织具有细化作用;随着Sn含量的增加,细化作用逐渐加强,但同时析出的Mg2Sn相增多,组织的均匀性下降。随着Sn的增加,合金延伸率逐渐减小,而抗拉强度呈现先升高后降低的趋势,过多的Sn对合金力学性能不利,Sn含量在5%时强韧性达到较佳配合;Sn含量为5%的合金耐高温性能较好,Sn含量为3%时耐高温性能较差。合金在腐蚀过程中,多数金属间化合物(Mg2Sn,Mg2(Si,Sn)和Mg2Si等)充当阴极相,Mg基体则充当阳极相,二者构成电偶腐蚀;Sn的加入使合金的耐蚀性能下降,特别是Sn含量超过5%时,耐腐蚀性能下降显著,腐蚀形貌特征从点蚀变为坑蚀。
The microstructures of Mg-xSn-2Al-1.5Zn-2Zn-xNi alloy were investigated by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) 0.8Si (x = 3,5,8;%, mass fraction, the same below) alloy microstructure and properties. The results show that the Mg2Sn phase is formed by Sn and matrix Mg, which can block the dendritic growth of Mg2Si phase and refine the as-cast microstructure. With the increase of Sn content, the refining effect gradually increases, Of the Mg2Sn phase increased, the uniformity of the tissue decreased. With the increase of Sn, the elongation of the alloy decreases gradually, but the tensile strength first increases and then decreases. Excessive Sn is unfavorable to the mechanical properties of the alloy, and the Sn content at 5% The alloy with the content of 5% has better high temperature resistance, and the high temperature resistance is worse when the content of Sn is 3%. During the corrosion process, most of the intermetallic compounds (Mg2Sn, Mg2 (Si, Sn) and Mg2Si) act as the cathode phase, and the Mg matrix acts as the anode phase, forming the galvanic corrosion. The corrosion resistance of the alloy In particular, when the content of Sn exceeds 5%, the corrosion resistance decreases significantly, and the corrosion morphology changes from pitting corrosion to pitting corrosion.