Effects of submicron-sized TiC particles on the microstructure modification and mechanical properties of Al-Si-Mg alloy

Abstract

The microstructure evolution and mechanical properties of Al-7Si-0.35Mg alloy with varied amounts of submicron-sized TiC particles addition were investigated. The results indicated that the TiC addition decreased the critical undercooling for α-Al nucleation and refined secondary dendritic arms and grain sizes, meanwhile the flaky eutectic phases were modified into fibrous morphology. With increasing TiC addition, the mechanical properties of aged composites were firstly increased and decreased with further addition. The composite with 0.3 wt% TiCP exhibited the optimal combination of mechanical properties, with simultaneously enhancements in ultimate tensile strength, 0.2 % yield strength, and elongation from 293 MPa, 220 MPa, and 7.7 % to 315 MPa, 240 MPa, and 16.3 %, respectively. These improvement in mechanical properties are mainly attributed to microstructure refinement and Si phase modification due to proper TiC addition. While a high content of TiC addition caused aggregation and resulted in the formation of coarsen undissolved Al-Mg-Si-Fe phase and needle-like Al-Si-Ti intermetallic compounds, as a result, the ductility and strength were decreased.