Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Chair/Advisor

Dr. Hongseok Choi

Committee Member

Dr. Cameron Turner

Committee Member

Dr. Xin Zhao

Abstract

A356 (Al–7Si–0.3Mg) aluminium alloy is widely used in automotive and aerospace applications due to its low density and good castability; however, its relatively low strength limits its use in high-load structural components. This study focuses on enhancing the mechanical performance of A356 through the incorporation of hybrid silicon carbide (SiC) reinforcements consisting of micron-sized and nano-sized particles.

The primary objective of this work is to develop a reinforcement-rich composite that can be used as a master composite for controlled and scalable addition of hybrid reinforcements into the base alloy. A hybrid reinforcement composition of 5 vol.% micro-SiC and 1 vol.% nano-SiC was selected to combine the load-bearing capability of microparticles with the strengthening effects of nanoparticles.

To prepare the reinforcement-rich composite, two processing approaches were investigated: hybrid mixing and double capsulate feeding. Microstructural analysis using SEM and EDS revealed that the hybrid mixing method resulted in a more uniform dispersion of hybrid particles within the matrix compared to the double capsulate approach. Based on these observations, the reinforcement-rich composite produced via hybrid mixing was selected for further processing.

This reinforcement-rich composite was then diluted with the base A356 alloy to achieve a final reinforcement content of 3 vol.% SiC, forming the master composite. For comparison, a separate composite with the same 3 vol.% hybrid reinforcement was also prepared using the double capsulate feeding method.

Mechanical and microstructural evaluation showed that both methods significantly improved the strength and ductility of A356 alloy. While the double capsulate method exhibited slightly superior mechanical properties, the improvement was marginal. In contrast, the master composite approach demonstrated a more practical and scalable solution for industrial applications due to its simpler processing and effective reinforcement distribution.

Overall, this study establishes that the master composite approach, developed through hybrid mixing of micro–nano reinforcements, provides an efficient and scalable pathway for producing high-performance aluminium matrix composites with enhanced mechanical properties.

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