等通道转角挤压对生物Mg-Zn-Ca合金显微组织与腐蚀行为的影响

Effects of ECAP on the microstructure and corrosion behavior of biomedical Mg-Zn-Ca alloy

摘要:

本文旨在探讨等通道转角挤压(equal-channel-angular-pressed,简称ECAP) 对生物医用Mg-3Zn-0.2Ca合金的显微组织以及腐蚀行为的影响。通过A路线对铸态Mg-3Zn-0.2Ca合金进行了1-4道次的剪切挤压变形。采用光学显微组织观察、X射线反射法、电化学等手段研究了挤压道次对镁合金显微组织、织构以及腐蚀行为的影响,也特别关注了ECAP对试样的不同截面方向的显微组织演变以及模拟体液(simulated body fluid,简称SBF)电化学腐蚀行为的影响。实验结果表明：ECAP变形后铸态Mg-3Zn-0.2Ca镁合金晶粒尺寸逐渐细化,变形后镁合金呈现出与ED方向呈一定角度的<0 0 2>面剪切织构；随着挤压道次增加,合金的耐蚀性先增加后降低。等通道转角挤压对合金耐蚀性的影响是晶粒尺寸、晶体缺陷和织构变化的综合效果；ECAP变形后合金不同截面方向呈现不同的耐蚀性,沿TD方向截面的耐蚀性优于另两个方向的截面。

关键词:ECAP;医用Mg-3Zn-0.2Ca合金;显微组织;腐蚀行为

Abstract:

The purpose of this paper is to explore the effects of equal-channel angular pressed (ECAP) process on the microstructure and corrosion behavior of biomedical Mg-Zn-Ca Alloy. As-cast Mg-3Zn-0.2Ca alloy was extruded for 1-4 passes by ECAP using route A process. The influences of ECAP process on the microstructure, texture and corrosion behavior of Mg-3Zn-0.2Ca alloy were investigated by optical microstructure observation, X-ray reflection and electrochemical methods. Particularly, the effects of ECAP process on the microstructure evolution and electrochemical corrosion behavior in simulated body fluid on the different cross-section of ECAPed alloy. The results indicated that with increasing ECAP passes, grain size of Mg-3Zn-0.2Ca alloy gradually refined, and (0002) basal texture emerged after ECAP 4 passes. With increasing ECAP passes, the corrosion resistance of Mg-3Zn-0.2Ca alloy increased firstly and then decreased. The influence of ECAP process on corrosion resistance of Mg-3Zn-0.2Ca was the combined action of grain size, crystal defect and texture. The corrosion resistance of ED, TD and ND cross-section of ECAPed alloy were different, and the corrosion resistance of TD section is superior to the other two directions.

Key words:ECAP process; Mg-3Zn-0.2Ca alloy; microstructure; texture; corrosion behavior