Refining SiCp in reinforced Al–SiC composites using equal-channel angular pressing

• The composites of Al–SiC were successfully fabricated and ECAPed up to 12 passes.
• Applying ECAP for the composites in order to reduce porosity%.
• Refining of SiCp by breakage of the coarse particles was achieved.
• Mechanical properties of ECAPed composite were about threefold those of as-cast.

Aluminum–silicon carbide composite (Al–SiCp) is one of the most promising metal matrix composites for their enhanced mechanical properties and wear resistance. In the present study, Al–SiC (average size 55 μm) composites with 5% and 10% by volume were fabricated by stir casting technique. The equal-channel angular pressing (ECAP) was then applied on the cast composites at room temperature in order to study the effect of ECAP passes on the SiCp size and distribution. The ECAP process was successfully carried out up to 12(8) passes for Al–5%(10%)SiC samples. Microstructure study revealed that the highest refinement by breakage of SiCp was achieved after the first ECAP pass and that further refinement took place in the next passes. More breakage of the SiCp was found in the composite richer in reinforcing particles so that the SiCp reached approximately 1 μm in the Al–10%SiC after 8 passes and 4 μm in Al–5%SiC after 12 ECAP passes. The distribution of SiC reinforcement particles also improved after applying ECAP. The factors including decrease in reinforcing particle size, improvement in their distribution, decrease in porosity in addition to strain hardening and grain refining of the matrix resulted in enhancement of tensile and compressive strengths as well as hardness by more than threefold for the Al–5%SiC after 12 passes and for Al–10%SiC after 8 passes compared to the cast composites. Additionally, the composite remained ductile after the ECAP process. The fracture surface indicated good bond between the matrix and the reinforcement.