EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Nanoparticles are known to play a crucial role in helping achieve excellent mechanical properties in advanced metal matrix composites fabricated by emerging selective laser melting (SLM) technology. Despite this, the understanding of their impacts on the evolution of microstructure and mechanical properties remains nebulous. In the present study, we adopted the SLM process to fabricate in-situ nano-TiB2 decorated AlSi10Mg composites with alternative TiB2 nanoparticle contents to investigate the effects of introduced nanoparticles on the SLM processability, microstructures, texture evolution and mechanical properties. Results show that nearly fully-dense TiB2/AlSi10Mg composite samples can be manufactured at the optimized SLM processing parameter due to the enhancing SLM processability by nano-TiB2 particles. Besides, increasing the nano-TiB2 addition can gradually transform the coarse columnar grain structure with <100> fiber orientation texture to fine equiaxed grain structure without preferred crystallographic texture due to the heterogeneous nucleation effect of nano-TiB2 particles. The elongated cellular sub-structure transforms to the equiaxed cellular sub-structure without obvious directionality. Additionally, the microhardness, tensile strength and ductility can be improved simultaneously by the addition of nano-TiB2 particles. With increasing TiB2 nanoparticles content, the tensile strength and microhardness increased in a stepwise manner while the ductility increased first and then decreased. Moreover, the SLMed TiB2/AlSi10Mg composites have superior tensile properties comparing to the previous SLMed AlSi10Mg alloy and their composites with the addition of other particles. The underlying mechanisms of strengthening are mainly attributed to grain boundary strengthening, dislocation density strengthening, load-bearing transformation strengthening, and Orowan strengthening. Meanwhile, the enhancing ductility in the composites is mainly attributed to higher relative density due to better SLM processability, less strain localization due to modified grain structure, high dislocation plasticity due to the intragranular nanoparticles. This study sheds light on SLM-produced nanoparticles decorated aluminium composites for the production of advanced materials.