In recent years, high - performance Al - Mg alloys modified by Sc/Zr (i.e., Al - Mg - Sc - Zr alloys, Scalmalloy®) have attracted extensive attention from researchers, especially in the field of additive manufacturing. Among them, the addition amount of Sc usually exceeds 0.6%, and the expensive raw materials greatly increase the production cost, which has become the main obstacle in the development of such alloys. Based on this background, in this study, Sc, Zr and TiB₂ particles were simultaneously introduced into the Al - Mg matrix. The purpose was to use the heterogeneous structure to replace part of the Sc content, and to prepare high - performance Al - Mg - based alloys with controllable microstructures while reducing costs.
Through a series of experiments and analyses, we have the following findings: During the hot deformation process, spherical Al₃(Sc,Zr) precipitates with a size of 5 - 10 nm and a dispersed distribution play a Zener pinning role for dislocations, which increases the proportion of low - angle grain boundaries (LAGBs) and inhibits the dynamic recrystallization (DRX) process. Meanwhile, the introduction of TiB₂ particles induces the particle - stimulated nucleation (PSN) effect, which accelerates the DRX process and refines the microstructure, further increasing the LAGBs content and the proportion of continuous dynamic recrystallization (CDRX). In addition, the addition of TiB₂ greatly weakens the anisotropy of the material, inhibits the growth of DRX grains, thereby broadening the subsequent processing window and providing more potential applications for the material.
From the perspective of microstructure, taking the EBSD results as an example, the grains of the MO sample are composed of elongated deformed grains and equiaxed grains, and LAGBs exist in the deformed grains; after adding TiB₂ particles, the LAGBs in the MSZT sample increase, and the DRX proportion also increases. In terms of texture, TiB₂ particles and Al₃(Sc,Zr) precipitates not only affect the grain morphology but also cause texture changes. For example, the proportion of {111} texture in the MSZ sample reaches 88.8%, while the {111} texture intensity in the MSZT sample is weaker. In terms of mechanical properties, the grain structure of the prepared alloy is refined, and the anisotropy of the material is significantly reduced. For example, the ultimate tensile strength (UTS) and yield strength (YS) of the MSZT sample are increased by 26.2% and 40.9% respectively compared with the matrix, and the ductility reaches 16.6%, showing an excellent balance between strength and ductility. Grain - boundary strengthening, dislocation strengthening and Orowan strengthening are the main strengthening mechanisms, accounting for 22.4%, 24.9% and 52.7% respectively.
In summary, the introduction of trace Sc/Zr/TiB₂ has a significant impact on the recrystallization and strengthening behavior of Al - Mg alloys through the synergistic effect of multiple mechanisms, providing new ideas and methods for the production of high - performance aluminum alloy products.