Microstructural evolution of previously deformed AZ91D magnesium alloy during partial remelting

摘要

Based on the Kissinger model, the eutectic melting activation energy of AZ91 D alloy deformed by equal channel angular extrusion (ECAE) is calculated by using differential scanning calorimetry (DSC) experiments. The microstructure evolution of AZ91D alloy, produced by the combined effects of ECAE and subsequent partial remelting, is also investigated. The results show that with increasing numbers of extrusion passes, the eutectic melting activation energy of ECAE-formed alloy decreases. Isothermal holding experiments reveal that the two-pass ECAE predeformation and then partial remelting process can produce ideal, fine semi-solid microstructure, in which spheroidal alpha-Mg grains have a little of entrapped liquid. The degree of grain spheroidization depends on holding time and liquid fraction during isothermal holding.