Intermetallic particles in a strip-cast Al-FeMn-Si alloy

The microstructure of the strip-cast Al-Fe-Mn-Si alloy was characterized by a very fine dendritic network of the aluminum solid solution phase with the intermetallic phases mostly distributed at the dendrite boundaries. Three inter metallic compounds from the quaternary Al-Fe-Mn-Si system, alpha(e)-Al-12(Fe,Mn)(3)Si, Al3Fe and Al-6(Fe,Mn), were identified in the cast strip. Of these intermetallic com pounds, Al-6(Fe,Mn) phase has almost vanished while a, has dominated after extended holding at temperatures below 550 degrees C. Al3Fe, on the other hand, was only a minor phase at these temperatures. It was concluded from the X-ray diffraction and energy-dispersive X-ray spectroscopy analysis of a series of samples that an Al-6(Fe,Mn) to alpha(c) transformation was taking place in this temperature range along with some precipitation of secondary alpha(c) particles. alpha(c) which has become the dominating constituent with increasing temperatures until 550 degrees C, was gradually replaced by Al3Fe at still higher temperatures. Finally, after an 8 hour anneal at 600 degrees C, Al3Fe has become the dominant phase. There was hardly any change in the phase composition of the strip upon annealing treatments above 600 degrees C.