Abstract
Magnesium (Mg) and its alloys can degrade gradually up to complete dissolution in the physiological environment. This property makes these biomaterials appealing for different biomedical applications, such as bone implants. In order to qualify Mg and its alloys for bone implant applications, there is a need to precisely model their degradation (corrosion) behavior in the physiological environment. Therefore, the primary objective develop a model that can be used to predict the corrosion behavior of Mg-based alloys in vitro, while capturing the effect of pitting corrosion. To this end, a customized FORTRAN user material subroutine (or VUMAT) that is compatible with the finite element (FE) solver Abaqus/Explicit (Dassault Systèmes, Waltham, MA, USA) was developed. Using the developed subroutine, a continuum damage mechanism (CDM) FE model was developed to phenomenologically estimate the corrosion rate of a biocompatible Mg–Zn–Ca alloy. In addition, the mass loss immersion test was conducted to measure mass loss over time by submerging Mg–Zn–Ca coupons in a glass reactor filled with simulated body fluid (SBF) solution at pH 7.4 and 37 °C. Then, response surface methodology (RSM) was applied to calibrate the corrosion FE model parameters (i.e., Gamma (γ), Psi (ψ), Beta (β), and kinetic parameter (Ku)). The optimum values for γ, ψ, β and Ku were found to be 2.74898, 2.60477, 5.1, and 0.1005, respectively. Finally, given the good fit between FE predictions and experimental data, it was concluded that the numerical framework precisely captures the effect of corrosion on the mass loss over time.
Highlights
Magnesium (Mg)-based alloys are attractive for bone implant applications, as they corrode gradually in vivo with an appropriate host response, and degrade completely after the healing of the bone tissue [1,2,3]
When compared with other metallic materials, Mg-based alloys, either crystalline or amorphous, do not significantly interfere with magnetic resonance imaging (MRI), allowing for the accurate assessment of the device function and surgical outcome to be made after the surgery [6]
Amorphous Mg-based alloys have been studied for bone fixations applications due to their superior strength and corrosion resistance in comparison with traditional crystalline Mg-based alloys [2,7]
Summary
Magnesium (Mg)-based alloys are attractive for bone implant applications, as they corrode gradually in vivo with an appropriate host response, and degrade completely after the healing of the bone tissue [1,2,3]. These alloys can be designed to degrade within a desired period of time through alloying elements and coating techniques, allowing for the regeneration of the surrounding soft or hard tissues [4,5]. While Mg-based alloys provide the unique property of enhancing the cell attachment and proliferation through generating magnesium-containing calcium phosphate, , they are considered biocompatible in vivo alloys that can receive acceptable responses from the host environment [14,15,16]
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