METALLURGICAL REACTIONS IN 2 INDUSTRIALLY STRIP-CAST ALUMINUM-MANGANESE ALLOYS

Precipitation, phase transformation, subgrain growth, and recrystallization that occur during heat treatment of two strip-cast, cold-rolled, high manganese. aluminum alloys have been studied mainly by transmission electron microscopy (TEM). The alloys differ in silicon content. The isothermal heat treatments have been performed in a salt bath at temperatures between 330 degrees C and 530 degrees C for times up to 1000 hours. Size distributions for each type of secondary particle have been determined. After short annealing times, small quasicrystals precipitated and subsequently transformed to ct phase. The densities of these precipitates controlled dislocation movement and regulated subgrain sizes. Prolonged heating resulted in peritectoid reactions to Al6Mn or Al12Mn. Recrystallization, which is associated with the formation of Al12Mn, is advanced by increasing the silicon content; the nucleation and growth of Al12Mn occurs only at the expense of other phases that stabilize the subgrain network.