Accumulative extrusion bonding of Mg-Mn-Ca/FA+GNP hybrid biocomposite: On microstructure evaluation, mechanical and corrosion properties

Mg alloys have limitations for biomedical applications due to high corrosion rate and low strength. In this study, magnesium alloy (Mg-0.5Ca-0.8Mn (wt%)) and it's composite reinforced to fluorapatite (FA) and graphene nanoplate (GNP) were produced through several stages including pre-dispersion, mechanical stirring, re-melting under Ar atmosphere, and accumulative extrusion bonding at 120o channels (AEB process). Mechanical prop-erties such as tensile strength and corrosion behavior were investigated by electrochemical impedance tests and hydrogen release in simulated body fluid (SBF). Microstructural variations such as reinforcement dispersion and grain size were assessed by optical microscopy and scanning electron microscopy (FESEM). The results indicated an improvement in dispersion and uniform distribution of the reinforcement particles as well as a homogenous microstructure with increasing the AEB passes. With adding reinforcements and after 3-pass of AEB process, the average grain size of the base alloy and its composite decreased from 450 and 175-1.55 mu m and 851 nm, respectively. So, the yield and ultimate strengths of the composite increased from 63 and 172 MPa to 270 and 386 MPa compared to the base alloy, as contribution of adding reinforcements in strengths increase was almost 26 % and 14 %, respectively. The corrosion resistance of the homogenized alloy was improved from 1.1 to 4.02 k ohm. Cm2 with addition of reinforcements and a considerable increase to 18.55 k ohm. Cm2 was obtained with a special improvement in corrosion rate (0.057 mm/year) after 3-pass of AEB process.

Automated summary

In this study, a magnesium alloy composite reinforced with fluorapatite and graphene nanoplate was produced through accumulative extrusion bonding (AEB) process. The addition of reinforcements improved the tensile strength and corrosion behavior of the alloy, as well as the uniformity of grain size.