Microstructural basis for improved corrosion resistance and mechanical properties of fabricated ultra-fine grained Mg-Akermanite composites

In the present research, a composite with a magnesium alloy (WE43) as the matrix and Akermanite as the bioactive and reinforcing agent was fabricated by friction stir processing (FSP), resulting in a microstructure with uniformly distributed fine grains, second-phase particles and micro-sized Akermanite particles. The effect of an addition of Akermanite to the alloy on the mechanical properties and corrosion resistance of the resulting composite was investigated. The compressive strength and ductility of the composite were found to be significantly higher than those of the monolithic WE43 alloy. The value of yield strength of the WE43 sample increased from 75 MPa up to 119 and 225 MPa for WE43-6P and WE43-A-6P samples, respectively. Also, the value of the ultimate compressive strength of the WE43 sample increased from 210 MPa up to 240 and 362 MPa for WE43-6P and WE43-A-6P samples, respectively. The value of elongation for WE43, WE43-6P, and WE43-A-6P samples were 4.5%, 16%, and 22%, respectively. The EIS test showed that the corrosion mechanism of WE43 sample is a combination of localized pitting and uniform corrosion, which shifted towards more uniform corrosion with higher corrosion resistance by applying FSP and adding Akermanite powder. The potentiodynamic polarization and in vitro immersion tests confirmed this finding, as evidenced by the increase in polarization resistance from 0.192 for the monolithic WE43 alloy up to 0.339 and 0.609 kΩ/cm² for WE43-6P and WE43-A-6P samples, respectively. The mass loss rate of the WE43 sample decreased from 20.82 to 10.13 mm per year for the WE43-A-6P sample after 312 h immersion in SBF solution. All tests approved that by applying FSP and adding Akermanite to WE43, the corrosion resistance in the SBF solution could be significantly enhanced.