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采用扫描电镜及X射线衍射仪对铸态Mg-4Zn-1Ca(wt%)合金的微观组织和相组成进行分析。利用电化学噪声测试,通过时域和频域分析方法研究了合金在0.9%Na Cl溶液中的腐蚀行为。结果表明,Mg-4Zn-1Ca合金由α-Mg固溶体和(α-Mg+Ca2Mg6Zn3)共晶组成;在电化学腐蚀过程中,作为阴极的Ca2Mg6Zn3相,与基体构成电偶腐蚀,加速了基体的腐蚀。在浸泡腐蚀的全过程中,电流噪声功率谱密度曲线高频线性部分的斜率近于-20 d B/(°),表明合金发生了局部腐蚀。合金的腐蚀过程可分为三个阶段,即阳极溶解过程、腐蚀产物层的反复破裂与修复过程,以及逐渐增强的腐蚀产物层对合金的保护作用。
The microstructure and phase composition of as-cast Mg-4Zn-1Ca (wt%) alloy were analyzed by scanning electron microscopy and X-ray diffraction. Using electrochemical noise test, the corrosion behavior of the alloy in 0.9% NaCl solution was studied by time-domain and frequency-domain analysis. The results show that the Mg-4Zn-1Ca alloy is composed of α-Mg solid solution and (α-Mg + Ca2Mg6Zn3) eutectic. During the electrochemical corrosion process, the Ca2Mg6Zn3 phase, which is the cathode, forms galvanic corrosion with the matrix and accelerates the growth of the matrix corrosion. In the whole process of immersion corrosion, the slope of the high frequency linear part of the current noise power spectral density curve is close to -20 d B / (°), indicating that the alloy has been locally etched. The corrosion process of the alloy can be divided into three stages, namely the anodic dissolution process, the repeated rupture and repair process of the corrosion product layer, and the gradual enhancement of the protective effect of the corrosion product layer on the alloy.