title: Strengthening of Mg based alloy through grain refinement for orthopaedic application.
abstract: Magnesium is presently attracting a lot of interest as a replacement to clinically used orthopaedic implant materials, due to its ability to solve the stress shielding problems, biodegradability and osteocompatibility. However, the strength of Mg is still lower than the requirement and it becomes worse after it starts degrading fast, while being exposed in living body environment. This research explores the effectiveness of 'grain refinement through deformation', as a tool to modify the strength (while keeping elastic modulus unaffected) of Mg based alloys in orthopaedic application. Hot rolled Mg-3wt% Zn alloy (MZ3) has been investigated for its potential in orthopaedic implant. Microstructure, mechanical properties, bio-corrosion properties and biocompatibility of the rolled samples are probed into. Grain size gets refined significantly with increasing amount of deformation. The alloy experiences a marked improvement in hardness, yield strength, ultimate tensile strength, strain and toughness with finer grain size. An increment in accelerated corrosion rate is noted with decreasing grain size, which is correlated to the increased grain boundary area and mechano-chemical dissolution. However, immersion test in simulated body fluid (SBF) reveals reduction in corrosion rate after third day of immersion. This was possible owing to precipitation of protective hydroxyapatite (HA) layer, formed out of the interaction of SBF and the alloy. More nucleation sites at the grain boundary for fine grained samples help in forming more HA and thus reduce the corrosion rate. Human osteosarcoma cells show less viability and adhesion on grain refined alloy.
authors.affiliation: Biomaterials and Multiscale Mechanics Laboratory, Indian Institute of Technology Roorkee, Uttarakhand 247667, India; Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
authors.forename: Soumyaranjan
authors.initials: S
authors.lastname: Nayak
authors.affiliation: Nano-biotechnology Laboratory, Indian Institute of Technology Roorkee, Uttarakhand 247667, India; Centre for Nanotechnology, Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
authors.forename: Bharat
authors.initials: B
authors.lastname: Bhushan
authors.affiliation: Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
authors.forename: R
authors.initials: R
authors.lastname: Jayaganthan
authors.affiliation: Nano-biotechnology Laboratory, Indian Institute of Technology Roorkee, Uttarakhand 247667, India; Centre for Nanotechnology, Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
authors.forename: P
authors.initials: P
authors.lastname: Gopinath
authors.affiliation: Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
authors.forename: R D
authors.initials: RD
authors.lastname: Agarwal
authors.affiliation: Biomaterials and Multiscale Mechanics Laboratory, Indian Institute of Technology Roorkee, Uttarakhand 247667, India; Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Uttarakhand 247667, India; Centre for Nanotechnology, Indian Institute of Technology Roorkee, Uttarakhand 247667, India. Electronic address: debrupa.lahiri@gmail.com.
authors.forename: Debrupa
authors.initials: D
authors.lastname: Lahiri
mesh_terms: D020341:Absorbable Implants; D000497:Alloys; D045744:Cell Line, Tumor; D003343:Corrosion; D006801:Humans; D008274:Magnesium; D008422:Materials Testing; D009985:Orthopedics; D012516:Osteosarcoma / Q000473:pathology; D013718:Tensile Strength
chemical_list: D000497:Alloys; D008274:Magnesium
keywords: Bio-compatibility; Corrosion; Grain refinement; Hot rolling; Magnesium; Mechanical properties; Orthopaedic implant