Correlation Between Microstructure and Corrosion Resistance of Magnesium Alloys Prepared by High Strain Rate Rolling
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JMEPEG DOI: 10.1007/s11665-017-2918-x
Correlation Between Microstructure and Corrosion Resistance of Magnesium Alloys Prepared by High Strain Rate Rolling Jihua Chen, Guanqing Chen, Hongge Yan, Bin Su, Xiaole Gong, and Bo Zhou (Submitted February 26, 2017; in revised form June 20, 2017) Microstructure and corrosion resistance in HankÕs solution of four magnesium alloys (pure Mg, ZK60, Mg4Zn and Mg-4Zn-0.3Ca) prepared by high strain rate rolling (HSRR) and conventional rolling (CR) are comparatively investigated. The HSRR alloy exhibits better bio-corrosion resistance than the CR alloy. The HSRR ZK60 alloy has finer grains, higher dynamic recrystallization (DRX) extent, lower twin fraction, coarser residual second-phase particles, finer and denser nanometer b1 precipitates, lower residual compressive stress and stronger basal texture than the CR alloy. The average corrosion rate of the HSRR ZK60 sheet after 90-day immersion in HankÕs solution is 0.17 mg cm22 d21, about 19% lower than that of the CR sheet. Its corrosion current density is 30.9 lA/cm2, about 45% lower than that of the CR sheet. Biocorrosion resistance enhancement by HSRR can be mainly ascribe to the reduced grain size, the relatively adequate DRX, non-twinning, the coarser residual second-phase particles, the finer and denser nanometer precipitates and the slightly stronger (0001) texture. Keywords
corrosion resistance, high strain rate rolling microstructure, nanometer precipitate, wrought magnesium alloy
1. Introduction Magnesium (Mg) and its alloys have been investigated since as early as 1878 for their potential use as a biomaterial (Ref 1). However, pure Mg corrodes too rapidly in vivo, losing mechanical integrity before the tissue has sufficiently healed (Ref 2). Several measures such as alloying, change in the processing histories and surface modification have been adopted to improve the biodegradation property. The processing histories have significant influences on the bio-corrosion resistance of magnesium alloys. According to Wang H et al., the biodegradation rate of AZ31 in HankÕs solution can be significantly reduced by mechanical processing and the desirable retardation of the excessively rapid degradation can be provided by hot rolling, but additional ECAP processing does not lead to further deceleration of corrosion (Ref 3). Shervin Eslami Harandi et al. have investigated the effect of forging process parameters on a binary Mg-1Ca alloy as a biodegradable bone implant material and have found that more hydroxyapatite product is generated in the alloy exposed to the SBF by elevating forging temperature during corrosion process while increasing Jihua Chen, Guanqing Chen, Hongge, and Yan Bin Su, School of Materials Science and Engineering, Hunan University, Changsha 410082, China; and Hunan Provincial Key Laboratory of Spray Deposition Technology and Application, Hunan University, Changsha 410082, China; Xiaole Gong and Bo Zhou, School of Materials Science and Engineering, Hunan University, Changsha 410082, China; Contact e-mails: [email protected]
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