Exploring the microstructural and mechanical response of aluminum composites reinforced with SiN: A novel hybrid microwave sintering approach

This study investigates the microstructural and mechanical behavior of AA7075 aluminum matrix composites reinforced with varying weight percentages (1–8 wt%) of silicon nitride (SiN), processed via high- energy ball milling and hybrid microwave sintering. Microstructural characterization revealed uniform SiN dispersion and strong matrix–particle interfaces up to 6 wt%, while higher loadings led to agglomeration. Mechanical testing demonstrated significant improvements in tensile strength (149 MPa), compressive strength (237 MPa), and hardness (107 HV) at 6 wt% SiN, attributed to Orowan looping, load transfer, grain refinement, and Zener pinning mechanisms. Beyond this threshold, reinforcement agglomeration adversely affected performance. The results confirm that hybrid microwave sintering is a viable and energy-efficient route for producing high-strength aluminum-based composites, with 6 wt% SiN identified as the optimum reinforcement level.