Investigation of microstructure, mechanical properties and corrosion behaviour of As-cast Mg-4Sn-2Al-X (X=0.5 Ca and 0.25 Mn) alloys

In this study, 0.5 wt. % of Ca, and 0.25 wt. % Mn was added to Mg-4Sn-2Al alloy, and its mechanical and corrosion properties were investigated. Production was carried out by gravity casting under a controlled atmosphere. Microstructures were investigated using SEM/EDS and XRD. In addition to the microstructure, the effects of alloying element addition on tensile properties, hardness, fracture surfaces, strain hardening exponent, anisotropy coefficients, corrosion microstructures, and corrosion rates were also investigated. According to the results obtained, Mg–4Sn–2Al–0.5Ca, and Mg–4Sn–2Al–0.25Mn alloys showed lower mechanical properties than Mg–4Sn–2Al alloys. While the ultimate tensile strength was 131 MPa for the Mg-4Sn-2Al alloy, this value decreased to 92.5 MPa with the addition of Ca, and to 102 MPa for the Mg-4Sn-2Al–0.25Mn alloy. Also, the strain hardening coefficient for Mg-4Sn-2Al alloy was 0.35, while it decreased to 0.28 with the addition of Ca. With the addition of Mn, it gave a value of 0.36, which is almost the same as Mg-4Sn-2Al alloy. When the anisotropy coefficients are examined, the anisotropy coefficient of Mg-4Sn-2Al alloy, which was 0.83, increased to 0.872 with the addition of Ca, and 1.293 with the addition of Mn. According to the results obtained from potentiodynamic and immersion corrosion tests, the Mn doped alloy showed the highest corrosion resistance in both tests. The corrosion rate of the Mn doped alloy was 18.96 mpy according to potentiodynamic results and 65.32 mpy according to immersion test results.