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ORIGINAL ARTICLE

Tailoring ZE41 Mg Alloy by Friction Stir Processing for Biomedical Applications: Role of Microstructure on the Degradation and Mechanical Behavior in Simulated Body Fluids B. Kiran Babu1,2 • A. Jawahar Babu3 • G. Ranga Janardhana1

Received: 16 June 2020 / Accepted: 11 September 2020 Ó The Indian Institute of Metals - IIM 2020

Abstract ZE41 magnesium alloy has been processed by friction stir processing (FSP) with an aim to investigate the role of microstructure on the degradation behavior and mechanical response targeted for temporary orthopedic implant applications. Grain size reduction was achieved in the ZE41 Mg alloy from 107 ± 6.7 lm to 3.5 ± 1.5 lm after FSP. Increased hardness up to 30% was measured in the stir zone of FSPed sample. From the immersion studies done in simulated body fluids (SBFs) for 72 h, decreased weight loss was measured for the FSPed ZE41 compared with unprocessed alloy due to deposition of more Ca/P mineral phase. From the tensile tests, higher ultimate tensile strength was measured for FSPed ZE41 alloy compared with unprocessed alloy. Furthermore, the tensile specimens were exposed to corroding medium SBF for 72 h and then tensile tests were carried out. Result demonstrated the combined effect of grain refinement, decreased intermetallic phase and formation of supersaturated grains on sustaining the improved mechanical properties after degradation which demonstrated the promising role of modified microstructure by FSP on enhancing the strength of ZE41 Mg alloy in the presence of simulated physiological environment. & B. Kiran Babu [email protected] 1

Department of Mechanical Engineering, Jawaharlal Nehru Technological University Kakinada, Kakinada, Andhra Pradesh 533003, India

2

Department of Mechanical Engineering, Usha Rama College of Engineering and Technology, Telaprolu, Andhra Pradesh 521109, India

3

Department of Mechanical Engineering, Gudlavalleru Engineering College, Gudlavalleru, Andhra Pradesh 521356, India

Keywords Mg alloy
Biomaterials
Grain refinement
FSP
Tensile strength
Degradation

1 Introduction Developing magnesium (Mg)-based biomaterials has become one of the important research fields in the biomedical research for the past two decades. Iron and Mg are the two metallic systems that have been widely investigated as promising materials targeted for degradable cardiovascular stent and orthopedic implant applications [1, 2]. Owing to its biocompatibility, nontoxicity and mechanical properties close to the natural human bone, Mg has become a promising choice to develop implants for orthopedic and cardiovascular applications. However, uncontrolled and rapid degradation due to the aggressive nature of physiological environment is the main limitation of Mg which has attracted the attention of several research groups across the globe to develop new alloys to control the Mg degradation. Earlier studies were focused on the commercial grade Mg alloys to tailor them as implant materials [2]. AZ series alloys (AZ31, AZ61 and AZ91 Mg a