Simultaneous enhancement of strength, ductility, and hardness of TiN/AlSi10Mg nanocomposites via selective laser melting

Metal additive manufacturing (AM) techniques, such as selective laser melting (SLM), enable the fabrication of advanced aluminum matrix composites (AMCs) with distinct microstructure and enhanced mechanical properties. In this study, an ultrasonic vibration technique together with SLM is employed to fabricate TiN/AlSi10Mg nanocomposites with alternative TiN nanoparticle contents (0, 2, 4, and 6 wt. %). The effects of TiN nanoparticles on the SLM processability, microstructure, texture evolution, recrystallization, and mechanical properties of TiN/AlSi10Mg are investigated. Results show that nearly fully-dense composite parts can be manufactured by enhancing the SLM processability. Increasing the TiN addition can gradually transform the crystallographic orientation from a strong (001) direction to a relatively random distribution that vanishes the preferred (001) texture. The continuous heterogeneous nucleation, recrystallization of alpha-Al grains, and Zener pinning along the grain boundaries occur during the SLM process due to the presence of the TiN nanoparticles, resulting in a significantly refined microstructure. The TiN nanoparticles are dominantly distributed along the Al grain boundaries, while rod-like nano-Si precipitates are well-dispersed inside the grains. Both TiN and nano-sized Si have well-bonded interfaces with the Al matrix. The optimal TiN content is found to be 4 wt.%, at which the additively manufactured specimens exhibit high tensile strength (492 +/- 5.5 MPa), high ductility (7.5 % +/- 0.29), and microhardness (157 +/- 4.9 HV) simultaneously. The underlying mechanisms of strength and ductility improvement are also elucidated. This study sheds light on the additive manufacturing of aluminum nanocomposites out of nanoparticles modified composite powder for the production of advanced materials with freeform microarchitectures.