Influence of Dispersoid Content on Compressibility, Sinterability and Mechanical Behaviour of B₄C/BN Reinforced Al6061 Metal Matrix Hybrid Composites Fabricated via Mechanical Alloying

In the present work, x wt% B₄C (x = 2, 4, 6, 8) and 2 wt% BN reinforced aluminum 6061 metal matrix hybrid composites were synthesized by mechanical milling for 10 h. The milled powders were consolidated by cold uniaxial compaction at various compression pressure (200–800 MPa) and then sintered at various temperatures (400–600 °C). Microstructural characterization of the milled powders and the fabricated composites were performed by X-ray diffraction, scanning electron microscope, and energy dispersive spectroscopy techniques. The effect of B₄C/BN reinforcements on the densification of the milled powders was studied in terms of compressibility and sinterability. The mechanical properties, specifically the green compressive strength, and hardness of the composites were also investigated. The empirical relations formulated by Heckel, Panelli-Filho, and Ge were used to plot the compressibility curves of the developed composites to study the compressibility behavior of the milled powders. The densification co-efficient (K) of the powders and sinterability behavior of the composites decreased with an increase in B₄C reinforcement. B₄C particles prevented the grain growth by seizing the grain boundary, resulting in refinement of grains and enhancement in mechanical properties The maximum compressive strength of 249 MPa and hardness of 184 HV was observed for the sample Al6061–8 wt% B₄C–2 wt% BN compressed at 800 MPa and sintered at 600 °C.