Simulation-assisted investigation of TiB2-distribution-regulated T6 aging response in ultrasonic-assisted cast ZL205A/TiB2 aluminum matrix composites

This study investigates the effect of ultrasonic-assisted casting on the T6 aging response, precipitation behavior, and mechanical properties of in-situ TiB 2 -reinforced ZL205A aluminum matrix composites. TiB 2 reinforcement and ultrasonic melt treatment are standard methods for microstructural refinement in aluminum matrix composites. However, the role of ultrasonic-induced TiB 2 redistribution in governing the subsequent aging behavior of Al-Cu-based alloys has received limited attention. To address this issue, three material conditions were prepared: unreinforced ZL205A alloy (ZL205A), non-ultrasonically treated ZL205A/2.0 wt% TiB 2 composite fabricated by mechanical stirring (NUT composite), and ultrasonically treated ZL205A/2.0 wt% TiB 2 composite treated at 800 W for 3 min (UT composite). The age-hardening behavior, SEM/EDS microstructures, TEM precipitation features, tensile properties, and fracture morphologies were systematically characterized. In addition, a mechanism-oriented counterfactual 2D RVE simulation was introduced to evaluate the influence of TiB 2 spatial distribution on the θ′-related precipitation tendency during aging while keeping the TiB 2 content, particle size, heat-treatment condition, and model parameters unchanged. The results show that the optimum aging condition shifted from 160 °C for 24 h for the unreinforced ZL205A alloy to 170 °C for 24 h for the ZL205A/2.0 wt% TiB 2 composites. Under the peak-aged condition, the UT composite achieved the highest hardness of 138.4 ± 3.5 HV and ultimate tensile strength of 383 MPa, corresponding to increases of 9.0% and approximately 29.0%, respectively, compared with the peak-aged ZL205A alloy. TEM observations revealed nanoscale Al 2 Cu-related precipitates, and the UT composite exhibited a more favorable precipitation distribution. Counterfactual representative volume element (RVE) simulations demonstrated that the dispersion of TiB 2 via ultrasonic treatment (UT) attenuated the coefficient of variation (CV) for θ′ precipitation propensity from 2.738 to 2.068. Simultaneously, the uniformity index improved from 0.268 to 0.327 compared to the agglomerated configuration observed without ultrasonic treatment (NUT). Spatial-homogenization ablation further confirmed that this improvement originated mainly from the redistribution of TiB 2 -related source regions rather than from changes in material parameters. These findings demonstrate that ultrasonic-assisted casting improves the T6 response of in-situ ZL205A/2.0 wt% TiB 2 composites by reducing TiB 2 agglomeration, promoting a more homogeneous precipitation tendency, and enhancing the combined effects of particle reinforcement and precipitation strengthening.