Corrosion behavior and cytocompatibility of nano-grained AZ31 Mg alloy
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The high corrosion rate of Mg alloys has hindered their wider use in orthopedic applications. In order to decrease the corrosion rate and to improve the bioactivity, a modified nanocrystalline (NC) surface layer with an average grain size of 70 nm and a thickness of 70 μm on the topmost surface of coarse-grained (CG) AZ31 alloy was successfully achieved by means of a surface nanocrystallization technique called sliding friction treatment (SFT). It showed that the extreme grain refinement in NC layer was favorably capable of enhancing the protective efficiency of the corrosion product layer and alleviating the susceptibility to localized corrosion. Moreover, SFT-induced second-phase particles fragmentation also helped to hinder micro-galvanic corrosion. Resultantly, the NC sample exhibited notably enhanced corrosion resistance as compared to the CG counterpart (e.g., the average hydrogen evolution rate of AZ31 during 170 h immersion in simulated body fluid (SBF) solution was reduced from 0.12 to 0.068 mL cm−2 h−1 after SFT processing). Meanwhile, the in vitro results confirmed that SFT processing enhanced the cytocompatibility of AZ31 Mg alloy to osteoblasts, which also benefited from the improved corrosion resistance induced by grain size reduction. Therefore, our study suggests a promising approach for the fabrication of biodegradable Mg alloy with modified properties.
This work was supported by National Natural Science Foundation of China (Grant Nos. 51701166, 51701163 and 81501858), State Key Laboratory for Advanced Metals and Materials of China (2017-Z01), CAS “Light of West China” Program (XAB2017AW12), Scientific Research Program in Weiyang District of Xi’an (201820) and Innovation team in key areas of Shaanxi Province (2016KCT-30).
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Conflict of interest
The authors declare that they have no conflict of interest.