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Most industrial alloys contain a matrix phase and dispersed second-phase particles. Several thermomechanical processing (TMP) steps are usually needed to produce a final product, during which recrystallization and its related phenomena may take place. Second-phase particles may retard or accelerate recrystallization, depending on their size and spatial distribution, the TMP conditions, among others. Besides their effect on recrystallization kinetics, the introduction of second-phase particles creates additional interfaces within the matrix, it also modifies the grain structure and crystallographic texture after recrystallization, which then either improves or deteriorates the associated mechanical properties of the investigated materials. The interactions between second-phase particles and recrystallization are further complicated when these particles are not stable. In addition to particle coarsening, they can also precipitate out or dissolve into the matrix before, simultaneously with or after recrystallization. This review article attempts to summarize the recent progresses on the complex interaction between second-phase particles and recrystallization and the science behind them. This double-edge effect of second-phase particles on recrystallization behaviour and mechanical properties of metallic materials is still far from being clear. A better understanding of this issue is of high academic and industrial interests, since it provides potential freedom for TMP design and microstructure control.
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... In the particle-containing materials, the void formation at second phase particles may attribute to a fracture. Based on the report of Huang et al. [71] , a critical stress for the void nucleation is proportional to the r − 1/2 ( r presents the average radius of spherical particles). This suggests that the oc-currence of voids needs a larger stress in the materials with finer particles. ...
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The fundamental research on thermo-mechanical conditions provides an experimental basis for high-performance Mg-Al-Ca-Mn alloys. However, there is a lack of systematical investigation for this series alloys on the hot-deformation kinetics and extrusion parameter optimization. Here, the flow behavior, constitutive model, dynamic recrystallization (DRX) kinetic model and processing map of a dilute rare-earth free Mg-1.3Al-0.4Ca-0.4Mn (AXM100, wt.%) alloy were studied under different hot-compressive conditions. In addition, the extrusion parameter optimization of this alloy was performed based on the hot-processing map. The results showed that the conventional Arrhenius-type strain-related constitutive model only worked well for the flow curves at high temperatures and low strain rates. In comparison, using the machine learning assisted model (support vector regression, SVR) could effectively improve the accuracy between the predicted and experimental values. The DRX kinetic model was established, and a typical necklace-shaped structure preferentially occurred at the original grain boundaries and the second phases. The DRX nucleation weakened the texture intensity, and the further growth caused the more scattered basal texture. The hot-processing maps at different strains were also measured and the optimal hot-processing range could be confirmed at the deformation temperatures of 600∼723 K and the strain rates of 0.018∼0.563 s⁻¹. Based on the optimum hot-processing range, a suitable extrusion parameter was considered as 603 K and 0.1 mm/s and the as-extruded alloy in this parameter exhibited a good strength-ductility synergy (yield strength of ∼ 232.1 MPa, ultimate strength of ∼ 278.2 MPa and elongation-to-failure of ∼ 20.1%). Finally, the strengthening-plasticizing mechanisms and the relationships between the DRXed grain size, yield strength and extrusion parameters were analyzed.
... In the past 20 years, in the direction of development and preparation technology of steel materials, the thermomechanical control process (TMCP) combined with severe plastic deformation (SPD) has been widely adopted to develop good crystal structures with good mechanical properties [8][9][10]. Recently, a method of fabricating ultrafine elongated grain structure through multi-pass caliber rolling is developed [11]. ...
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... It was reported that aluminum alloys have a higher stacking fault energy than copper alloys. 8,9 As a result, copper alloys highly restrict the recovery and cause a high density of dislocations in ECAP processed samples. 10 The microstructure of ECAP processed brass samples is more refined than that of the initial brass alloy. ...
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An impeccable, authoritative, yet refreshingly lucid work on the development of nanocrystalline materials, this book is the first definitive step to understanding the relationship between the properties of nanomaterials and their microstructure. Thousands of papers have been published that concentrate on the comprehension of the strength and ductility of such materials in order to maximize both. Moving beyond reiterating just the strength, toughness, and stability of these materials, this compendium provides much analysis to better understand the crystal grain and grain boundary bases that determine property behaviors over a range of temperatures and applied loading rates. The original relation that connects grain size and strength, known as the Hall-Petch relation, is studied in the nanometer grain size region. The breakdown of such a relation is a challenge. Why and how to overcome it? Is the dislocation mechanism still operating when the grain size is very small, approaching the amorphous limit? How do we go from the microstructure information to the continuum description of mechanical properties? The book effectively answers these questions, besides many others that have made nanocrystalline materials an object of unprecedented interest of late.
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