Mg-based alloys with Y, Ca and Al reaching exceptional ignition resistance and suppressed flammability

Magnesium alloys are increasingly pivotal in automotive and aerospace engineering due to their superior strength-to-weight ratio. This rising prominence necessitates advancements in their mechanical characteristics, such as tensile strength, ductility, and fatigue endurance, alongside enhanced control over their interaction with oxygen. A critical phenomenon in this context is the ignition of magnesium in oxygen-rich environments at high temperatures. This exothermic reaction induces a rapid temperature surge, potentially reaching 3000 degrees C, leading to the catastrophic disintegration of magnesium alloy components. Consequently, research in magnesium technology also focuses on augmenting the ignition threshold and diminishing the material's combustibility. This expansion in the application scope for magnesium alloys in the aviation and aerospace sectors hinges on developing novel alloy compositions. Elements like yttrium (Y), rare-earth elements, and calcium (Ca) are under exploration for their potential to bolster ignition resistance in magnesium alloys. However, the impact of these elements on ignition and flammability is highly dependent on their concentration and the overall alloy chemistry. Four magnesium alloys, integrating yttrium, calcium, and aluminium - a conventional element in commercial alloys - were synthesised in the study under discussion through casting and thermal processing. These alloys were methodically examined for microstructural evolution and their resistance to ignition and flammability. The results demonstrated that when appropriately balanced with yttrium, aluminium is a viable alloying element in magnesium alloys without significantly compromising ignition resistance. The alloy WAX211 exhibited the highest ignition temperature of 940 degrees C, attributed to the synergistic effects of calcium and yttrium and the formation of a highly stable protective oxide layer.