Hot extrusion of SiCp/Al-Cu composites: optimizing mechanical properties through microstructural control

Abstract

The solid-state processing and utilization of light-metal-based composites align with green policies by reducing the weight of components and employing lower processing temperatures compared to traditional metallurgical methods. This study explores the incorporation of SiC particles at concentrations of 5 and 10 wt.% into an Al4Cu matrix through powder mixing, compaction at 235 MPa, hot extrusion, and sintering at 600 °C in a nitrogen atmosphere. The resulting microstructure, hardness, compressive strength, and flexural strength of the composites were evaluated. During extrusion, the composite underwent plastic deformation, leading to cracking and fragmentation of the SiC particles within the matrix. Therefore, evenly distributed reinforcing particles with a diameter much smaller than the originally introduced ceramic particles were observed. Recrystallization also occurred, with Al2Cu precipitates forming on grain boundaries and nanosized Al2O3 oxides observed in porous areas and at matrix-reinforcement interphase boundaries. The composite containing 5 wt.% SiC exhibited the highest compressive strength of 305 MPa, while the composite with 10 wt.% SiC achieved the highest flexural strength of 889 MPa. However, non-deformable SiC particles crack before reaching maximum strength due to stress concentration at their sharp edges, initiating microcracks in the matrix. Microstructural analysis further revealed that SiC particles tend to crack during hot extrusion, reducing their effectiveness in stress transfer. The hardness remained constant at 78 HV1, irrespective of SiC content. These findings demonstrate that the addition of SiC particles significantly enhances the mechanical properties of Al4Cu composites, making them promising materials for lightweight and high-strength applications.