Exploring the Potential of Wire Fed Direct Energy Deposition of Aluminum–Boron Nitride Nanotube Composite: Microstructural Evolution and Mechanical Properties

Recent advancements have shown great promise in utilizing wire‐fed direct energy deposition (DED) for building aluminum alloy structures. However, utilizing the wire‐fed DED approach for fabricating metal matrix composite structures remains a significant challenge. Herein, a wire‐based additive manufacturing process is used to successfully produce a 1D boron nitride nanotube (BNNT)‐reinforced aluminum composite with high strength. Al‐BNNT electrode is developed in house. The microstructural changes that occur during layer‐by‐layer deposition are investigated. The grain morphology changes from equiaxed grains in the bottom layer to columnar grains in the top layer. BNNTs act as nuclei to promote the formation of equiaxed grains and interfacial compounds (AlN and AlB 2 ) during solidification. This results in improved strength, with Al‐BNNT composite exhibiting a tensile strength of 47 MPa, 2.3 times higher than its pure Al. Higher strength is attributed to the retention and uniform distribution of BNNT reinforcement in the melt pool, leading to effective load transfer. This study demonstrates the potential of additive manufacturing for producing high‐performance metal matrix composites with novel 1D reinforcements and improved multifunctional properties.