OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Following heat treatment via annealing, conducted at a temperature of 400 °C, a further strengthening effect was demonstrated for both types of deformed samples. Notably, for samples that had undergone multidirectional forging, annealing contributed to a further increase in tensile strength by 30 MPa. Regarding the samples after rolling, annealing at the same temperature resulted in a more substantial additional increase in strength, amounting to 43 MPa. The performed analysis also revealed that SPD induces a significant increase in the yield strength of the bronze, relative to the characteristics of the samples formed after additive manufacturing. Multi-directional forging led to a substantial increase in yield strength (by 359 MPa), whereas the application of rolling produced an even more significant increase – 725 MPa Subsequent heat treatment via annealing, also demonstrated a positive influence on this parameter for all types of samples considered after SPD. In particular, for samples pre-processed by multi-directional forging, annealing contributed to a further increase in yield strength by 16 MPa. In the case of samples subjected to rolling, a similar annealing process resulted in a greater additional increase in yield strength, which amounted to 26 MPa. The application of multi-directional forging and rolling led to a reduction in the relative elongation of the bronze samples by 2.6 and 4.5 times, respectively, compared to the as-printed sample (Fig. 3, b). Annealing at 400 °C resulted in a minor increase in relative elongation of 1.1 % for the sample after multidirectional forging and 1.8 % for the sample after rolling. a b Fig. 3. Mechanical properties of Cu-Al-Si-Mn bronze samples Based on the experimental data, it was established that SPD significantly affects the strength and ductility of the printed Cu-Al-Si-Mn bronze samples. An increase in strength and a decrease in ductility are expected for an alloy with an FCC lattice, due to strain hardening mechanisms and structural refinement. Annealing has a minimal impact on the strength of the post-SPD samples, while their ductility improves by approximately 5–13.6 % compared to the deformed state. This is due to the influence on the structure and phase composition of the samples. On the one hand, annealing led to partial recrystallization of the structure and a reduction in the number of crystal lattice defects. On the other hand, the sizes of the structural elements remained at the submicron level. As a result, an increase in ductility and the retention of the material’s strength were achieved. The small increase in strength after annealing is associated with the cooperative contribution from grain boundary and dislocation strengthening mechanisms in the FCC alloy and has been previously noted for alloys with an ultrafine-grained structure [25–29]. In addition, the contribution to solid solution strengthening comes from the deformation-induced dissolution of secondary phase particles [30], as well as the possible precipitation of dispersed phases from the solution as a result of aging. Severe plastic deformation (SPD) through multi-directional forging followed by rolling increased the microhardness of the bronze by 46% and 80%, respectively, compared to the as-printed samples (Fig. 4). Annealing the multi-directionally forged sample at 400°C increased the microhardness from 2.05 GPa to
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