Influence of hot rolling parameters on microstructure and biodegradability of Mg-1Ca alloy in simulated body fluid

Binary Mg-1Ca alloy has been considered as a potential material for implant applications due to its non-toxic and biodegradable properties. However, the high corrosion tendency of the alloy, as a serious drawback, limited its practical efficiency. In this study, the effect of hot rolling on biodegradability of Mg-1Ca was investigated as a process to improve the microstructure and corrosion resistance of the alloy in simulated body fluid. The as-cast alloy was rolled to various reduction levels at different temperatures. Optical and scanning electron microscopy together with energy dispersive X-ray spectroscopy and X-ray diffraction analysis were used characterize the microstructure of the as-cast and rolled samples. Immersion and potentiodynamic polarization tests were performed to examine the electrochemical and corrosion behavior of the samples in simulated body fluid. The results showed that the high corrosion tendency of as-cast Mg-1Ca was remarkably reduced by the hot rolling process due to the microstructure refinement. It was found that the corrosion rate of the samples which experienced higher reduction percentages decreased to some extent. However, the weight loss results indicated that the rolling process at higher temperatures caused more corrosion products to emerge on the surface of the samples. It can be associated with the accumulation and growth of Mg2Ca phase at the grain boundaries

The properties of hot rolled binary magnesium calcium alloy for use as a biodegradable material within bone

Binary Mg-Ca alloys with various Ca contents were fabricated under controlled condition. X-ray diffraction (XRD) analysis and optical microscopy observations showed that Mg-Ca (x= 1-5 wt %) alloys were composed of two phases, a (Mg) and MgzCa. The results of hardness test and in vitro corrosion tests indicated that the mechanical properties could be adjusted by controlling the Ca content and processing treatment. Increasing Ca results in higher corrosion rate and hardness. In spite of higher hardness, low Ca content materials were selected due to lower corrosion rate. The corrosion test in simulated body fluid (SBF) indicated that temperature and thickness reduction strongly affected the corrosion behaviours. In the vitro, corrosion suggested that a mixture of Mg (OH)2 and hydroxyapatite formed on the surface of Mg-ICa alloy with the extension of immersion period time of 100h.. Corrosion resistance fluctuated at different temperatures and thickness reduction as a result of electrochemical, immersion and weight loss testing

Effect of calcium content on the microstructure, hardness and in-vitro corrosion behavior of biodegradable Mg-Ca binary alloy

Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (%)) was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg2Ca phase was observed in a-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg2Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg2Ca is a good candidate for bio-implant applications