Solidification Analysis of Al-Si Alloys Modified with Addition of Cu Using In-Situ Neutron Diffraction

The potential of application of in-situ neutron diffraction for studies of solidification of Al alloys have been previously reported by the authors for the binary hypereutectic A-Si system. This illustrated the potential of neutron diffraction for high resolution melt analysis at near-liquidus temperatures required for advanced studies of grain refining, eutectic modification, etc. The solid and liquid volume fractions were determined based on the change of intensity of neutron diffraction peaks over the solidification interval. The path of non-equilibrium solidification for the alloy modified with addition of copper and magnesium is very complex. Phase diagrams and FactSage-based computations give only approximate kinetics of solid phase(s) evolution during cooling and solidification. On the other hand, in-situ neutron diffraction, coupled with the results of thermal analysis, provides non-biased experimental data on phase evolution; for example, on formation of FCC Al-Cu-Si and diamond silicon during solidification of hypereutectic Al-Si-Cu alloy.