The effect of chemical grain refinement and low superheat pouring on the structure of NRC castings of aluminium alloy Al–7Si–0.4Mg

摘要: Abstract The effect of the addition Al–5Ti–1B (wt.%) chemical grain refiners on nuclei generation for a range superheats during pouring in new rheocasting (NRC) aluminium alloy Al–7Si–0.4Mg has been investigated. contributions to density by refiner additions and impurity particles were quantified it was found that provides increasing number nucleation sites as superheat is decreased from 105 35 °C. However, at 15 °C, which are more typical NRC, similar both with without additions. At this superheat, equiaxed morphology globular rather than dendritic postulated size dependant upon coarsening mechanisms heterogeneous events. In agreement previous studies semi-solid processing, achievement fine structure led homogeneous casting being produced. mechanism macrosegregation observed these castings discussed explained ‘sponge effect’.