AM60压铸镁合金表面ZrO_2微弧氧化陶瓷层的制备方法研究

为了改善镁合金的微弧氧化膜层的性能,利用两步法在AM60压铸镁合金表面制备了ZrO_2微弧氧化膜层.研究了膜层在恒电压控制方式下的生长规律,测量了膜层在w(NaCl)=3.5%溶液中的极化曲线,分析了膜层的物相组成.结果表明:在400 V恒压微弧氧化处理时,微弧氧化膜层的平均生长速度最高可达3.5 μm/min:试样在w(NaCl)=3.5%溶液中的极化曲线显示,镁合金经过两步法在锆盐溶液中微弧氧化后,其腐蚀电位正移,腐蚀电流降低,腐蚀速度大幅降低,其耐蚀性得到了大幅度提高.两步法制备微弧氧化膜层主要由ZrO_2、ZrP_2、Mg_3(PO_4)_2、MgF_2相组成,在溶液中添加的Zr元素可以通过微弧氧化处理时的复杂反应进入膜层中,膜层表现出的优异耐蚀性主要源于膜层中存在ZrO_2陶瓷.

Study on Preparing Method of ZrO_2 Micro-arc Oxidation Films on AM60 Die-casting Mg Alloys Surface

The ZrO_2 micro-arc oxidation (MAO) films were prepared with two-step process. The growth law of films was studied under constant voltage control mode. The polarization curves of MAO films in 3.5% NaCl solution were measured and the phase constituent of the films was analyzed. The results show that the average growth rate of the films can reach 3.5 μm/min when the constant voltage is 400V. The polarization curves show that the corrosion voltage increases and the corrosion rate decreases substantially. Those means that the corrosion resistance of AM60 die-casting magnesium alloys is increased by MAO processing in Zr~(4+) salt solution. The films mainly consist of ZrO_2, ZrP_2, Mg_3 (PO_4)_2, MgF_2 phases. Zr element added in the MAO solution can access the films by MAO actions. The increase of corrosion resistance of the films is because of the ZrO_2 phase in it.