ZK60-1Nd镁合金的组织结构及腐蚀行为

Microstructure And Corrosion Behavior Of ZK60-1Nd Magnesium Alloy

摘要:

通过扫描电镜(SEM),电化学工作站和盐水浸泡失重法研究了ZK60-1Nd镁合金的组织结构及在3.5wt % NaCl水溶液中的腐蚀行为。结果表明：ZK60-1Nd镁合金主要由基体α-Mg相,沿晶界分布的含有稀土Nd的粗大网状共晶组织以及在基体中弥散分布的细小棒状MgZn₂相组成。ZK60-1Nd镁合金在3.5wt % 的NaCl水溶液中的腐蚀速率为0.2 mg.cm_-2.h_-1；经过400 ℃保温96 h后,部分共晶相熔断成尺寸约为0.5 μm的颗粒,腐蚀速率降低到0.1 mg.cm_-2.h_-1；经过500 ℃保温8.0 h,网状共晶相熔化成分散块状,基体中细小棒状MgZn₂相溶解消失,Nd,Zn和Zr元素在基体中含量增加且分布均匀,腐蚀速率达到最低,为0.03 mg.cm_-2.h_-1。其耐蚀性能改善的主要原因为α-Mg基体中固溶态Nd元素含量的增加导致合金自腐蚀电位提高以及基体α-Mg中腐蚀微电偶数目的减少。

Abstract:

Microstructure and the corrosion behavior of ZK60-1Nd magnesium alloy in 3.5 wt % NaCl aqueous solution was studied by scanning electron microscope (SEM) , electrochemical workstation and brine weight loss method. The results indicate that the as-cast microstructure of ZK60-1Nd alloy is mainly composed of matrixα-Mg, a coarse network eutectic phase containing rare earth Nd distribute along the grain boundaries and the distribution of fine MgZn₂ phase in the matrix. The corrosion rate of ZK60-1Nd magnesium alloy in 3.5 wt % NaCl aqueous solution was 0.2 mg ? cm_-2 ? h_-1 in NaCl solution. After homogenization at 300 ℃ for 8.0 h , the microstructure was improved;after annealing at 400 ℃ for 96 h, A portion of the eutectic phase is fused to a particle with a maximum size of 1.5 μm and the corrosion rate is reduced to 0.1 mg.cm_-2.h_-1; After annealing at 500 ℃ for 8.0 h , fishbone eutectic phase composition of patchy, the MgZn₂ phase is dissolvedSintoSmatrix , the contents of Nd, Zn and Zr were increased and the distribution was uniform in the matrix , corrosion rate reached a minimum of 0.03 mg.cm_-2.h_-1. The main reason for the improvement of corrosion resistance is that the increase of the content of solid solution Nd in matrix α-Mg lead to the improvement of corrosion potential and the decrease in the number of micro galvanic corrosion.