Microstructural modifications induced during spray deposition of Al–Si–Fe alloys and their mechanical properties

In the present investigation, different Al alloys such as Al–6.5%Si, Al–18%Si, Al–5%Fe and Al–18%Si–5%Fe–1.5%Cu (wt.%) were spray deposited and the over-spray powder particles were collected. The spray formed materials as well as their as-cast counterparts were extruded at 480 °C using an area reduction ratio of 6:1. The microstructural features of alloys and the over-sprayed powder particles were examined. The extruded alloys were tested for the tensile properties at a cross-head speed of 0.5 mm min−1. The alloys showed drastic refinement of primary phase and modification of the second phase after spray deposition. Over-spray powder particles showed varied microstructure depending upon the size. Powder microstructures suggested high undercooling experienced by the droplets. The Al–5Fe alloy exhibited partitionless solidification in over-sprayed powder particles. In some cases, non-twinned dendrites were also observed. The mechanical properties of the spray deposited and extruded alloys showed considerable improvement in strength and ductility compared to their as-cast counterparts. This property enhancement is attributed to the unique microstructural features generated during spray deposition process. The results of this investigation have been discussed in light of the microstructural features of the alloys.