Microstructure and phase formation in spray-deposited Al-18%Si-5%Fe-1.5%Cu alloy

Abstract

The Al alloy containing 18%Si, 5F%e and 1.5%Cu was spray-deposited using convergent-divergent nozzle geometry. Nitrogen gas was used as atomization medium. Microstructure and phase constitution of over-sprayed powders as well as spray deposit were studied. Spray-deposited alloy revealed 3- to 10-mum size particulates of primary Si phase co-existing with rectangular shape intermetallic -betaAl(5)SiFe and delta-Al4Si2Fe phases. This is in contrast to as cast alloy that exhibit 90- to 150-mum size particulates of primary Si phase and 120- to 500-mum size rods of Al-Fe-Si base intermetallic phases. X-ray diffraction results depicted presence of only delta-Al4Si2Fe phase in over-sprayed powders, whereas, spray-deposited alloy consisted both delta-Al4Si2Fe and beta-Al5SiFe phases. Energy-dispersive X-ray analysis also corroborates the presence of the above intermetallic phases. These results have been discussed in light of the mechanisms involved in the spray deposition process. (C) 2002 Published by Elsevier Science B.V.