International Journal of Refrigeration

Abstract 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.

Abstract The effects of 0.12wt%Sr additive on some material properties of Al-12Si+10wt%Zn alloy were examined in this study. Al-12Si+10wt%Zn and Al-12Si+10wt%Zn+0.12wt%Sr alloys were manufactured by permanent mold casting. Microstructures of these alloys were examined with both optic and scanning electron microscopes. Phases in the alloys were identified by energy-dispersive spectroscopy and X-ray diffraction analyses. Hardness measurements were performed with the Brinell method. Mechanical and tribological properties of the alloys were investigated with tensile and friction-wear tests, respectively. The microstructure of the Al–12Si+10wt%Zn alloy consists of α-Al, eutectic Al-Si mixture, primary Si and β phases. Al-12Si+10wt%Zn+0.12wt%Sr alloy includes the Al-Zn-Fe-Si and Sr-Al-Si phases in addition to phases observed in the Al-12Si+10wt%Zn alloy. Sr addition resulted in the eutectic silicon particles becoming thinner and a spherical-like shape. The Sr addition to the Al-12Si+10wt%Zn alloy caused the hardness, yield strength and tensile strength to increase from 97 HBN to 138 HBN, 163 MPa to 233 MPa and 215 MPa to 240 MPa, respectively. The addition of Sr also caused coefficient of friction and wear volume of the Al-12Si-10Zn alloy to decrease from 0.5189 to 0.4621 and 4.488 mm3 to 4.025 mm3, respectively. Effects of Sr additive on the material properties of the Al-12Si+10wt%Zn alloy were discussed based on the microstructural changes.