Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content

In the current paper, a low-Si containing aluminium alloy (1.4-2.2% Si) was used to fabricate a complex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC), process. Microstructure and fracture characteristics were investigated. The cast material exhibited microstructural inhomogeneity, in particular macrosegregation in the form of liquid surface segregation bands in addition to sub-surface pore bands and gross centre porosity. Tensile specimen were taken from the cast components. Elongation and microstructural inhomogeneity were investigated and correlated. Fracture surfaces of the tensile specimen were examined under scanning electron microscope (SEM). The study showed that both near surface liquid segregation bands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss of ductility were gross centre porosity. This centre porosity was found to be a combination of trapped gas and insufficient, irregular feeding patterns.