Simultaneously enhancing strength and ductility of laser directed energy deposited TiB2/AlSi10Mg by inducing dispersed Mg2Si precipitation and reducing strain concentration

Abstract

Laser directed energy deposition (L-DED) has been widely used in metal additive manufacturing due to its advantages in terms of large dimensions and high forming speed. However, the limited mechanical properties and ductility of components have hindered the broader application of this technology. In this research, we have achieved a simultaneous enhancement of yield strength and elongation in TiB₂/AlSi10Mg composites after T6 heat treatment fabricated by blue l-DED technology. The T6 heat-treated TiB₂/AlSi10Mg composites exhibit a yield strength, tensile strength, and elongation of approximately 289.4 MPa, 431.3 MPa, and 12.3 %, respectively, representing exceptionally high values. An in-situ imaging technique utilizing X-ray computed tomography (CT) is firstly implemented to explore the evolution of defects, TiB₂ particles, and microcracks during the deformation process. In the process of plastic deformation, new voids nucleate at the interface between the Al matrix and TiB₂ particles with a large size (>25 μm), leading to damage accumulation. Furthermore, based on the modified Gurson-Tvergaard model, a new critical strain value of TiB₂ particles (∼8 %) for void nucleation is proposed. After T6 heat treatment, no significant grain coarsening occurs due to the “pinning” effect of TiB₂ particles on the grain boundaries. Lots of fine dispersed Mg₂Si phases (quantity density about 3.1 × 10¹⁵ m^-2) show more obvious precipitation strengthening. This research provides valuable insights to further promote the development of high-performance aluminum matrix composites by the l-DED process.