3D local atomic structure evolution in a solidifying Al-0.4Sc dilute alloy melt revealed in operando by synchrotron X-ray total scattering and modelling

Using synchrotron X-ray total scattering and empirical potential structure refinement modelling, we studied systematically in operando condition the disorder-to-order local atomic transition a pure Al dilute Al-0.4Sc alloy melt temperature range from 690 °C to 657 °C. In liquid state, icosahedral short-range ordered Sc-centred polyhedrons form most of them with coordination number 10–12. As is cooled semisolid become more connected atom clusters via vertex, edge face-sharing. These exhibit partially face-centred-cubic symmetry. The medium-range face-sharing are proved be “precursors” L12 Al3Sc primary phases liquid-solid coexisting state.