Corrosion fatigue of a magnesium alloy in modified simulated body fluid Sajjad Jafari a , R.K. Singh Raman a,b,⇑ , Chris H.J. Davies a a Department of Mechanical & Aerospace Engineering, Monash University (Melbourne), VIC 3800, Australia b Department of Chemical Engineering, Monash University (Melbourne), VIC 3800, Australia article info Article history: Available online xxxx Keywords: Implant materials Magnesium alloys Environmental cracking High cycle fatigue Hydrogen embrittlement abstract For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to establish their resistance to body fluid-assisted cracking. In this paper the fatigue behav- iour of a common magnesium alloy, AZ91D, is studied in air and in modified simulated body fluid (m-SBF), and the effect of different electrochemical conditions on corrosion fati- gue life is investigated. The alloy was found to be susceptible to corrosion fatigue. Results suggest inclusions and corrosion pits to be the crack initiation sites, and hydrogen embrit- tlement to play a dominant role in cracking of AZ91D Mg alloy in m-SBF. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Metallic biomaterials such as titanium alloys, stainless steels and cobalt-chromium alloys are widely used implant mate- rials due to their corrosion resistance and strength [1,2]. However, when these materials are used as temporary implants, their retention in the body becomes unnecessary after they have fulfilled their function, and a removal surgery is required which increases the health care cost as well as inconvenience to the patient [3]. Moreover, the mechanical properties of these alloys are considerably different from those of human bone which results in the problem of ‘stress shielding’ and consequent reduction in bone density [4]. Magnesium (Mg) alloys are suitable as potential temporary biomedical implants because they are biodegradable and can completely dissolve in the body [5–8], which eliminates the need for secondary surgery to remove an implant. Magnesium is also biocompatible, is essential to human metabolism, and in addition any excess Mg is harmlessly excreted [4,9]. Further- more magnesium has mechanical properties much closer to bone and this mitigates stress shielding [8]. These properties make magnesium and its alloys suitable as temporary orthopaedic implants (e.g. bone plates and screws) and cardiovascular implants (e.g. stents). In spite of these advantages Mg alloys have found very little actual use in implants, primarily because they tend to corrode too quickly in chloride solutions including physiological environments and therefore lose their mechan- ical integrity before accomplishing their purpose [10–13]. Orthopaedic and cardiovascular implants generally experience cyclic loading [14,15], which along with the corrosive physiological environment can cause corrosion assisted cracking. Depending on the nature of loading, corrosion assisted cracking includes stress corrosion cracking (tensile loading) and corrosion fatigue (cyclic loading). Stress corrosion cracking (SCC) of Mg alloys has been widely investigated including in physiological environments [16–20] but corrosion fatigue (CF) http://dx.doi.org/10.1016/j.engfracmech.2014.07.007 0013-7944/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Mechanical & Aerospace Engineering, Bldg 31, Monash University – Clayton Campus (Melbourne), VIC 3800, Australia. Tel.: +61 399053671. E-mail address: raman.singh@monash.edu (R.K. Singh Raman). Engineering Fracture Mechanics xxx (2014) xxx–xxx Contents lists available at ScienceDirect Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech Please cite this article in press as: Jafari S et al. Corrosion fatigue of a magnesium alloy in modified simulated body fluid. Engng Fract Mech (2014), http://dx.doi.org/10.1016/j.engfracmech.2014.07.007