首页|Ag微合金化对Mg-Zn-Ca合金微观组织及腐蚀行为的影响

Ag微合金化对Mg-Zn-Ca合金微观组织及腐蚀行为的影响

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采用OM、SEM、电化学测试和析氢失重等方法研究了Ag微合金化对铸态Mg-2Zn-0.2Ca合金微观组织和腐蚀行为的影响.研究表明,ZX20合金(1.63±0.17mm/a)耐蚀性强于含Ag的ZXQ200合金(4.06±0.68 mm/a),这主要源于第二相和基体间的电位差差异.ZX20合金的枝晶臂间距(69.8±24.9μm)小于ZXQ200合金的枝晶臂间距(85.9±23.9 μm),这可能是ZXQ200合金局部腐蚀深度更大的原因之一.两种合金均由a-Mg和Ca2Mg6Zn3相组成且第二相体积分数相近,未发现富Ag相.Ag在第二相中的偏聚使得第二相与基体的电位差从约60 mV(ZX20合金)增加到约200 mV(ZXQ200合金),提高了合金的微电偶腐蚀驱动力,导致合金点蚀孕育期缩短和局部腐蚀位点增加.
Effect of Ag Micro-alloying on Microstructure and Corrosion Behavior of Mg-Zn-Ca Alloy
The effect of Ag micro-alloying on the microstructure and corrosion behavior of the as-casted Mg-2Zn-0.2Ca(ZX20)alloy were investigated by means of OM,SEM,electrochemical tests,and hydrogen evolution mass loss method.The results reveal that the addition of 0.5%(mass fraction)Ag af-fects adversely the corrosion resistance of ZX20 alloy.The corrosion rate increases from 1.63±0.17 mm/a for the ZX20 alloy to 4.06±0.68 mm/a for the Ag-containing alloy(ZXQ200),primarily due to the potential difference between the second phase and the matrix.The dendrite arm spacing of the ZX20 alloy(69.8±24.9 μm)is smaller than that of the ZXQ200 alloy(85.9±23.9 μm),potentially contributing to the greater local corrosion depth observed in the ZXQ200 alloy.The two alloys all consist of α-Mg and Ca2Mg6Zn3 phases with a similar volume fraction of the second phase,and no Ag-rich compounds have been detect-ed for the Ag-alloyed ones.However,the Ag segregation in the second phase results in a heightened po-tential difference between the second phase and the substrate,elevating it from approximately 60 mV(ZX20)to about 200 mV(ZXQ200).This segregation enhances the micro-galvanic corrosion driving force in the ZXQ200 alloy,resulting in a shorter pitting gestation period and an increase in local corrosion sites.

Mg-alloyAgsecond phasemicro-galvanic corrosion

尹洁、高永浩、易芳

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中南大学材料科学与工程学院 长沙 410083

中南大学湘雅口腔医学院 长沙 410000

镁合金 Ag 第二相 微电偶腐蚀

湖南省自然科学基金

2023JJ30673

2024

中国腐蚀与防护学报
中国腐蚀与防护学会 中国科学院金属研究所

中国腐蚀与防护学报

CSTPCD北大核心
影响因子:0.819
ISSN:1005-4537
年,卷(期):2024.44(5)