Influence of Sn Addition on the Ignition Resistance and Microstructural Evolution of Non-Flammable Mg-9Al-0.8Zn-0.1Mn-0.3Ca-0.2Y Alloy

This study investigates the influence of tin (Sn) addition on the ignition resistance and microstructural evolution of Mg-9Al-0.8Zn-0.1Mn-0.3Ca-0.2Y (AZXW9100) magnesium alloy. The AZXW9100 alloy without Sn exhibited a high ignition temperature of approximately 720 °C, significantly exceeding the melting point of magnesium, indicating superior ignition resistance. However, with increasing Sn content, the ignition temperature decreased, with the AZXW9100-4Sn alloy showing a reduction of about 120 °C. Microstructural analysis revealed that calcium (Ca) in the Mg₁₇Al₁₂ phase improves thermal stability and ignition resistance by forming protective oxide layers such as MgO, MgAl₂O₄, and CaO. However, Sn addition promotes the formation of the MgSnCa phase, depleting Ca from the Mg₁₇Al₁₂ phase, resulting in reduced thermal stability. High-temperature oxidation experiments further confirmed that increased Sn content leads to the formation of low-melting phases, accelerating oxidation and lowering the ignition temperature. These findings suggest that while Sn addition can enhance certain mechanical properties, it negatively affects ignition resistance when present in excess. To optimize the performance of AZXW-series alloys, particularly for safety–critical applications, careful control of both Sn and Ca content is essential.