Microstructural features associated with spray atomization and deposition of Al-Mn-Cr-Si alloy

An inert gas atomization process was employed in production of rapidly soli dified powders as well as disc-shape preform by spray deposition of an Al(7 )5Mn(1)0Cr(5)Si(1)0 alloy. Microstructural features of atomized powders and spray deposited preforms were evaluated by scanning and transmission elect ron microscopy and X-ray diffractometry techniques. Solidification structur e of powders revealed cellular and dendritic morphology, depending on their size. The interdendritic regions consisted of second phase particles. In c ontrast the spray formed alloy exhibited microstructural homogeneity with d istribution of ultra-fine second phase particles of intermetallic compound. The structure of second phase intermetallics was identified as a cubic alp ha -Al(Mn,Cr)Si, in both the atomized powders and the spray-deposits. The f ormation of cubic phase is discussed as rational approximant structure of a n icosahedral quasicrystal. (C) 2001 Kluwer Academic Publishers.