含Al2Ca相和Mg2Ca相Mg−Al−Ca−Mn合金经等通道转角挤压加工后的腐蚀性能

Corrosion properties of ECAP-processed Mg-Al-Ca-Mn alloys with separate Al2Ca and Mg2Ca phases

为了研究Al_(2)Ca相和Mg_(2)Ca相对Mg−Al−Ca−Mn合金腐蚀行为的影响,采用金相显微镜、扫描电子显微镜、浸泡和电化学测试对仅含Al_(2)Ca相(2Ca)和仅含Mg_(2)Ca相(4Ca)的铸态及ECAP态合金进行研究。在腐蚀初期,两种铸态合金的腐蚀速度比ECAP合金的慢。随着腐蚀时间的延长,ECAP合金的腐蚀程度变得比铸态合金轻微,这主要归因于ECAP合金中第二相的有效细化及分散。此外,2Ca合金的腐蚀程度始终小于4Ca合金,表明Al_(2)Ca相比Mg_(2)Ca相更有利于提高Mg−Al−Ca−Mn合金的耐腐蚀性能。最后,根据合金腐蚀表面的形貌观察和电化学测试结果,对由Al_(2)Ca相和Mg_(2)Ca相的分布和形貌引起合金的不同腐蚀机理进行讨论。

To investigate the effect of separate Al_(2)Ca and Mg_(2)Ca phases on the corrosion properties of Mg−Al−Ca−Mn alloys,OM,SEM,immersion and electrochemical tests were conducted on the as-cast and ECAP Al_(2)Ca-containing(2Ca)and Mg_(2)Ca-containing(4Ca)alloys.At the beginning of corrosion,the two as-cast alloys are corroded slowly compared with ECAP alloys.With prolonging the corrosion time,the corrosion of ECAP alloys becomes slighter than that of as-cast alloys,which is mainly ascribed to the dispersion and refinement of the second phase in ECAP alloys.Moreover,the corrosion degree of 2Ca alloys is always slighter than that of 4Ca alloys,suggesting that Al_(2)Ca phase is more beneficial to the enhancement of corrosion resistance of Mg−Al−Ca−Mn based alloys than Mg_(2)Ca phase.Finally,based on the examinations of corrosion surface and electrochemical testing results,different corrosion mechanisms caused by the distributions and morphology of Al_(2)Ca and Mg_(2)Ca phases are discussed.