Contents lists available at ScienceDirect Journal of the Mechanical Behavior of Biomedical Materials journal homepage: www.elsevier.com/locate/jmbbm Stress corrosion cracking and corrosion fatigue characterisation of MgZn1Ca0.3 (ZX10) in a simulated physiological environment Sajjad Jafari a, ⁎ , R.K. Singh Raman a,b , Chris H.J. Davies a , Joelle Hofstetter c , Peter J. Uggowitzer c , Jörg F. Löffler c a Department of Mechanical & Aerospace Engineering, Monash University (Melbourne), VIC 3800, Australia b Department of Chemical Engineering, Monash University (Melbourne), VIC 3800, Australia c Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland ARTICLE INFO Keywords: Biodegradable implants Magnesium alloys Stress corrosion cracking Corrosion fatigue Twinning ABSTRACT Magnesium (Mg) alloys have attracted great attention as potential materials for biodegradable implants. It is essential that an implant material possesses adequate resistance to cracking/fracture under the simultaneous actions of corrosion and mechanical stresses, i.e., stress corrosion cracking (SCC) and/or corrosion fatigue (CF). This study investigates the deformation behaviour of a newly developed high-strength low-alloy Mg alloy, MgZn1Ca0.3 (ZX10), processed at two different extrusion temperatures of 325 and 400 °C (named E325 and E400, respectively), under slow strain tensile and cyclic tension-compression loadings in air and modified simulated body fluid (m-SBF). Extrusion resulted in a bimodal grain size distribution with recrystallised grain sizes of 1.2 μm ± 0.8 μm and 7 ± 5 μm for E325 and E400, respectively. E325 possessed superior tensile and fatigue properties to E400 when tested in air. This is mainly attributed to a grain-boundary strengthening mechanism. However, both E325 and E400 were found to be susceptible to SCC at a strain rate of 3.1×10 −7 s −1 in m-SBF. Moreover, both E325 and E400 showed similar fatigue strength when tested in m-SBF. This is explained on the basis of crack initiation from localised corrosion following tests in m-SBF. 1. Introduction Traditional implant materials, such as stainless steels, titanium alloys and cobalt–chromium alloys, possess excellent load-bearing capacity and resistance to wear, corrosion, and fatigue (Niinomi et al., 2012; Okazaki and Gotoh, 2008). However, when deployed as temporary implants, keeping them in the body beyond their recom- mended timeframe is disadvantageous, and removal surgery is re- quired after the healing process. This increases health care costs and inconvenience to patients. Using magnesium (Mg) alloys as potential materials for temporary implants has recently attracted attention as they are biodegradable and can dissolve completely in the body (Staiger et al., 2006; Witte, 2010). For such applications, Mg alloys must fulfil certain electrochemical, biocompatibility and mechanical require- ments. Magnesium is biocompatible and essential to human metabo- lism with the added advantage of its biodegradable behaviour elim- inating the need for a second surgical procedure. It also possesses mechanical properties close to those of bone, reducing stress shielding effects under load-bearing conditions, which is a serious concern with traditional alloys (Kraus et al., 2012; Saris et al., 2000; Witte et al., 2005). Despite these advantages, Mg alloys have rarely been used in body implants. This is predominantly due to their rapid degradation in the physiological environment, with unacceptably poor mechanical integrity before the bone has healed sufficiently (Kannan and Raman, 2008; Song, 2007). Implants in general are subjected to acute dynamic loadings during normal physical activities (Gu et al., 2010). Such loadings, along with the corrosive physiological environment, pose the threat of stress corrosion cracking (SCC) and corrosion fatigue (CF) (Antunes and de Oliveira, 2012; Singh Raman et al., 2015). Several adverse incidents involving the SCC and CF of traditional implants in the body environ- ment have been reported (Amel-Farzad et al., 2007; Sivakumar and Rajeswari, 1992). Mg alloys are also susceptible to SCC and CF in simulated body fluids (SBF) (Choudhary and Raman, 2012; Choudhary et al., 2014; Gu et al., 2010; Jafari et al., 2015b). Therefore, it is important to identify Mg alloys that confer a combination of strength and corrosion resistance in human body fluid without causing body fluid-assisted cracking such as SCC or CF. Due to the potential http://dx.doi.org/10.1016/j.jmbbm.2016.09.033 Received 23 May 2016; Received in revised form 15 September 2016; Accepted 27 September 2016 ⁎ Correspondence to: Department of Mechanical & Aerospace Engineering, Department of Chemical Engineering, Bldg 37, Monash University – Clayton Campus (Melbourne), VIC 3800, Australia. E-mail address: [email protected] (S. Jafari). Journal of the mechanical behavior of biomedical materials 65 (2017) 634–643 1751-6161/ Crown Copyright © 2016 Published by Elsevier Ltd. All rights reserved. Available online 28 September 2016 crossmark
Stress corrosion cracking and corrosion fatigue characterisation of MgZn1Ca0.3 (ZX10) in a simulated physiological environment
May 17, 2023
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