Abstract
The ignition resistance of AZ91 alloy is investigated during continuous heating experiments and when held at constant temperature in the semisolid range. It is found that during continuous heating, ignition takes place close to the liquidus temperature when a significant amount of liquid is present. Similarly, ignition occurs during an isothermal hold in the semisolid region, but after an incubation time that depends on the temperature. Resistance to burning is closely related to high temperature oxidation, which is particularly complex in the case of this alloy. The non-protective nature of the oxides together with the liquid oxidation and the possible role of Mg vapour seem to be the reasons for the AZ91 ignition.