Improvement of microstructure and mechanical properties of Al?Cu?Li?Mg?Zn alloys through water-cooling centrifugal casting technique
The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated. Experimental results demonstrated that compared with the gravity casting technique,the water-cooling centrifugal casting technique significantly reduces porosity,refines α(Al) grains and secondary phases,modifies the morphology of secondary phases,and mitigates both macro-and micro-segregation. These improvements arise from the synergistic effects of the vigorous backflow,centrifugal field,vibration and rapid solidification. Porosity and coarse plate-like Al13Fe4/Al7Cu2Fe phase result in the fracture before the gravity-cast alloy reaches the yield point. The centrifugal-cast alloy,however,exhibits an ultra-high yield strength of 292.0 MPa and a moderate elongation of 6.1％. This high yield strength is attributed to solid solution strengthening (SSS) of 225.3 MPa,and grain boundary strengthening (GBS) of 35.7 MPa. Li contributes the most to SSS with a scaling factor of 7.9 MPa·wt.％−1. The elongation of the centrifugal-cast alloy can be effectively enhanced by reducing the porosity and segregation behavior,refining the microstructure and changing the morphology of secondary phases.
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