2010 Volume 51 Issue 8 Pages 1371-1380
This paper describes the assimilation mechanism of Mn-Al compacts in liquid Mg, utilizing procedures that have been employed successfully in studying assimilation mechanisms in other liquid metals. Two critical steps were identified in the assimilation process: (1) melting of some Mn-Al reaction products and (2) mass transfer of phases with the high Mn content from the reaction sites into the Mg bath. The assimilation process was divided into three stages: incubation stage, intermetallic reaction stage, and homogenization stage. Compact swelling was observed during the intermetallic reaction stage. Yet, contrary to the currently-held prevalent view, it was determined that compact swelling was not due primarily to the formation of new intermetallic phases. Rather, swelling is due to the existence of a large amount of porosity initially in the compact which becomes greatly augmented with the large heat released during the Mn-Al exothermic intermetallic reactions.
