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 Microstructure and Corrosion Behavior of Biomedical Mg-Zn-Ca Alloy

旨在探讨等通道转角挤压(equal-channel-angular-pressed,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。对铸态Mg-3Zn-0.2Ca合金进行了1,2,4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(simulatedbodyfluid,SBF)电化学腐蚀行为的影响。结果表明:ECAP变形后铸态Mg-3Zn-0.2Ca镁合金晶粒逐渐细化,变形后镁合金呈现出与挤压方向呈一定角度的<002>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,垂直于挤压方向截面的耐蚀性优于另2个方向截面的耐蚀性。

The paper explored the effects of equal-channel angular pressing（ECAP） process on the microstructure and corrosion behavior of biomedical Mg-3Zn-0.2Ca alloy.As-cast Mg-3Zn-0.2Ca alloy was extruded for 1,2 and 4 passes by ECAP.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 was investigated in simulated body fluid on the different cross-section of ECAPed alloy.The results indicate that with increasing ECAP passes,grain size of Mg-3Zn-0.2Ca alloy are gradually refined,and（0002） basal texture emerges after ECAP 4 passes.With increasing ECAP passes,the corrosion resistance of Mg-3Zn-0.2Ca alloy increases firstly and then decreases.The influence of ECAP process on corrosion resistance of Mg-3Zn-0.2Ca is a combined action of grain size,crystal defect and texture.The corrosion resistance of ED,TD and ND cross-section of ECAPed alloy is different,which of TD section is superior to that of the other two directions.