Effect of minor additions of graphene and copper on magnesium alloy AZ31 by stir casting

The primary aim of this study is to develop a biocompatible magnesium alloy (AZ31) composite by stir casting. This composite incorporates a low content of graphene (0.1 wt%) and copper (0.15 and 0.3 wt%) into AZ31 by stir casting to form lightweight but corrosion-resistant materials. The properties of the resulting composites were assessed through various tests, including microstructural analysis, hardness measurements, compression testing, and corrosion evaluation via electrochemical methods and immersion tests. Additionally, samples were in-vitro tested for Wharton's Jelly Mesenchymal Stem Cells. Results demonstrated that the Al and Zn out-precipitate from the Mg matrix to form second-phase particles at the grain boundaries. Both C and Cu tend to disperse inside the composites, but Cu is also coupled with Al and Zn in the particles. These particles make the cast composites more ductile with higher ultimate compressive strength increased from 360.52 +/- 14.00 to 382.43 +/- 6.70 MPa, and maximum strain from 18.34 +/- 1.77 to 22.44 +/- 0.83 %. The dispersed Cu and graphene also help to enhance the corrosion resistance with higher open circuit potentials and larger impedance semi-circles. The immersion test shows a limited increase of pH values from (similar to 7.4-similar to 8.4-8.6) in Hank's solution after 15 days. The in-vitro cell culture shows the composites have low toxicity, with cell viability maintained at 88-95 % as compared to the blank culture media. These findings could be beneficial to future studies on the composite of AZ31.