Stress corrosion cracking of an extruded magnesium alloy (ZK21) in a simulated body fluid

• Published in: Engineering fracture mechanics 2018-10, Vol.201, p.47-55
• Main Authors: Jafari, Sajjad, Raman, R.K. Singh, Davies, Chris H.J.
• Format: Article
• Language: English
• Subjects: Anodic dissolution; Biocompatibility; Biomedical materials; Body fluids; Corrosion fatigue; Corrosion resistance; Corrosion tests; Crack propagation; Extrusion rate; Fatigue cracking; Fatigue failure; Fracture mechanics; Hydrogen; Hydrogen embrittlement; In vitro methods and tests; Magnesium; Magnesium alloy; Magnesium base alloys; Materials selection; Mechanical properties; Medical devices; Medical electronics; Slow strain rate; Stress corrosion cracking; Surgical implants
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2018.09.002

•ZK21 magnesium alloy was found to be susceptible to Stress Corrosion Cracking (SCC).•SCC occurred even in the absence of an externally applied load.•Fractured surface of pre-immersed and strained in the air samples showed presence of corrosion products.•A mixed-mode mechanism involving dissolution and hydrogen embrittlement was responsible for cracking. Magnesium (Mg) alloys are attractive candidate materials for resorbable implants including cardiovascular and orthopaedic medical devices e.g., stents and bone plates/screws. Bioresorbable implants provide a temporary support for the malfunctioned tissue/bone to heal and then completely degrade in the body. In such uses the implant material must possesses an adequate resistance to cracking such as corrosion-assisted-cracking fractures including stress corrosion cracking (SCC) and corrosion fatigue (CF). This study evaluates SCC of an extruded Mg alloy, ZK21, using slow strain rate tensile (SSRT) testing at a strain rate of 3.1 × 10−7 in modified simulated body fluid (m-SBF) at 37 °C. SCC tests under different electrochemical conditions suggest that the alloy is susceptible to SCC with a substantial decrease in mechanical properties.