Probing microstructural modification and hardness response in h-BN reinforced A356 aluminum matrix composites
Year: 2026
Type: article
Abstract: A356 Al–Si–Mg alloys are widely used in lightweight structural applications; however, their as-cast mechanical performance is strongly influenced by the morphology of dendritic α -Al, the interconnected eutectic Si-rich network, and casting-induced microstructural heterogeneity. In this study, A356 aluminum matrix composites containing 1 and 4 wt.% hexagonal boron nitride (h-BN) were fabricated by induction melting to investigate the effect of h-BN addition on microstructural evolution and localized hardness. The composites were characterized using x-ray diffraction (XRD), FESEM, Energy-dispersive spectroscopy (EDS) mapping, semiquantitative image analysis, and Vickers microhardness testing. XRD analysis showed that α -Al and Si remained the dominant crystalline phases, with no distinct reaction products detected. SEM observations and image analysis indicated that h-BN addition reduced the apparent continuity of the interdendritic eutectic Si-rich network, with the median major-axis length of the segmented Si-rich features decreasing from 3.38 µ m in the unreinforced A356 alloy to 3.14 µ m and 2.72 µ m in the composites containing 1 and 4 wt.% h-BN, respectively. EDS mapping qualitatively confirmed the presence of B-containing regions in the reinforced composites. The mean Vickers hardness increased from 57.5 HV to 64.4 HV and 71 HV with increasing h-BN content, corresponding to improvements of approximately 12% and 23.5%, respectively. The hardness enhancement is primarily attributed to eutectic Si network modification, with possible additional contributions from localized restriction of plastic deformation. Overall, the results establish a processing-microstructure-hardness relationship in cast A356/h-BN composites and demonstrate that h-BN addition improves localized deformation resistance through modification of the as-cast eutectic Si-rich network.
Source: Materials Research Express
Author: Mustafa Tekin
Institution: Yeditepe University
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,000
OpenAlex ID: W7204103713