Synergistic effects of in-situ TiB2 on grain structure and strength of Al-4.5Cu alloys

Abstract

In-situ Al-4.5 wt%Cu-xTiB2 (x = 3-12 wt%) composites were synthesized to achieve simultaneous microstructural refinement and mechanical strengthening. Multi-scale characterization reveals that TiB2 forms uniformly within the Aluminium matrix without parasitic phases, while effectively modifying the morphology and distribution of Al2Cu precipitates. Increasing TiB2 content results in pronounced grain refinement, enhanced highangle grain boundary fraction, and texture randomization, supported by EBSD and TEM analyses. Sub-micron TiB2 particulates with clean interfaces generate dense dislocation networks and promote heterogeneous nucleation, activating synergistic strengthening via grain refinement, Orowan looping, precipitation hardening, and load transfer. Tensile testing shows a substantial improvement in yield and ultimate strengths, particularly after T6 aging, with optimum strength-ductility balance achieved at 6-9 wt% TiB2. These findings demonstrate an efficient pathway for tailoring high-performance Al-Cu matrix composites for lightweight structural applications.