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

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-μm size particulates of primary Si phase co-existing with rectangular shape intermetallic β-Al5SiFe and δ-Al4Si2Fe phases. This is in contrast to as cast alloy that exhibit 90- to 150-μm size particulates of primary Si phase and 120- to 500-μm size rods of Al–Fe–Si base intermetallic phases. X-ray diffraction results depicted presence of only δ-Al4Si2Fe phase in over-sprayed powders, whereas, spray-deposited alloy consisted both δ-Al4Si2Fe and β-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.