长周期有序堆垛相对Mg-Gd-Y-Zn-Zr合金腐蚀行为的影响

Effect of Long-Period Stacking Ordered (LPSO) Phases on the Corrosion Behavior of Mg-Gd-Y-Zn-Zr Alloys

研究不同长周期有序堆垛(LPSO)相含量对Mg-Gd-Y-Zn-Zr合金腐蚀行为的影响,对于新型高强耐蚀镁合金的设计具有重要的指导意义。为此,通过金相观察、SEM形貌及能谱分析、电化学测试及浸泡试验等手段考察了Mg-Gd-Y-Zn-Zr合金在5%NaCl溶液中的电化学及腐蚀行为,以确定不同LPSO相含量对镁合金抗蚀性能的影响。结果表明:Zn元素对Mg-Gd-Y-Zn-Zr合金中LPSO相的形成和分布起决定性的作用,当合金中不含Zn元素时,不会形成LPSO相;随着Zn元素的增多,LPSO相的体积分数不断增加,形态从薄片层状向块状转变。腐蚀过程中首先在合金基体表面形成一层均匀连续的腐蚀产物层,随Zn含量增加合金表面腐蚀产物层的厚度降低,合金腐蚀形态从全面腐蚀向局部腐蚀转变;LPSO相在局部腐蚀过程中充当腐蚀微电池的阴极,加速合金基体的腐蚀溶解。

It is meaningful to study the effect of long-period stacking ordered( LPSO) phases content on the corrosion behavior of Mg-Gd-Y-Zn-Zr alloys for designing novel high-strong anti-corrosive Mg alloys. In this work,the electrochemical and corrosion behaviors of Mg-Gd-Y-Zn-Zr alloy in 5% Na Cl aqueous solution were analyzed by metallographic observation,SEM,EDS,electrochemical test and immersion experiment,further confirming the effect of LPSO content on the corrosion resistance. Results showed that the Zn element played a dominant role in the formation and distribution of the LPSO phase in the Mg-Gd-Y-Zn-Zr alloys,there was no LPSO phase formed in the alloy when no Zn element was added. The volume fraction of the LPSO phase increased and the morphology changed from lamellar to bulk with the increase of Zn concentration. Moreover,during the corrosion process,an uniform and continuous corrosion product layer was formed on the surface of the alloy substrate. when the addition of Zn increased,the thickness of the corrosion product layer decreased,and the corrosion morphology of the alloys changed from general corrosion to local corrosion. Besides,the LPSO phase acted as the cathode of corrosion micro-cell during local corrosion process,accelerating the corrosion and dissolution of the alloy substrate.