Study on mechanical properties and corrosion behavior of Porous Magnesium alloy for biomedical application

Abstract

The trend in the applications of biomedical has been increasing for biodegradable implants material and the performance of an implant is highly related to the properties of the material. Relying on an excellent properties in high mechanical strength, metallic biomaterials is preffered to assist with repair or replacement of bone tissue that has become diseased or damaged. However, previously metallic biomaterials (stainless steel(316L), cobalt chromium alloy (Co-Cr-Mo and Co-Ni-Cr-Mo) and titanium alloy (Ti6Al4V)) are limited in terms of degradability and the presence of long term implants will leads harmful effect to human body due to mismatch between modulus of implant materials and surrounding bone tissue. Thus, magnesium (Mg) alloy is attractive to serve as implant materials due to its favorable properties such as, biodegradability and biocompatibility, its mechanical strength comparable to natural bone and light weight. Recently, porous material have attracted significant attentions in biomedical applications. The application of porosity into the implant will reduce the mismatch between metallic materials and surrounding bone tissue, as the porous structure able to provide stable biological fixation and enhance bone ingrowth through porous network. The present study was carried out to develop porous Mg alloy from elemental powder (Mg alloy and ammonium bicarbonate (NH4HCO3) through powder metallurgy method based on the space holder technique. This technique utilized two phase of sintering process which is to heat treated the sample at low temperature to burn out the space holder to create pores and eventually sintered at high temperature. The aims of this research are to investigate the effect of processing parameters on the porosity, density, microstructure and mechanical properties of fabricated porous Mg alloy body. An in vitro test was conducted using simulated body fluid (SBF) solution to determine the corrosion and biodegradable behavior of fabricated porous Mg alloy. A design of experiment (DOE) using Taguchi method was initially used to determine the effect of processing parameters (sintering temperature, heating rate and sintering time) on the mechanical performance of porous Mg alloy and the desired setting parameters to set up the experiment. It was found that sintering temperature contribute to the highest percentage followed by heating rate and sintering time. Higher sintering temperature, on the other hand, leads to a better mechanical performance of porous Mg alloy which is comparable to the cancellous bone. This observation is supported by compression, hardness, microstructure and x-ray diffraction (XRD) analysis. It should be noted that the range of compressive strength (1-15MPa), pore size (200-500μm) and porosity percentage (42%-64%) exhibited in this study for the fabrication of porous Mg alloy showed the typical range of values noted for materials used in biomedical applications. In vitro test demonstrated the ability of porous Mg alloy to degrade gradually under pH control. These findings suggest that, porous Mg alloy is suitable for biomedical applications.