Strain Induced Segregations in Severely Deformed Materials

Abstract

Severely deformed materials intrinsically contain a large density of crystalline defects like dislocations or boundaries. The interactions between solute atoms or impurities with these defects play a key role in the grain refinement mechanisms as they affect dynamic recovery. This short review manuscript focusses on grain boundary segregations resulting from severe plastic deformation. The important contribution of atom probe tomography for the quantitative characterization of such segregations in various metallic alloys is at first highlighted. Then, a special emphasis is given on the physical mechanisms leading to strain induced segregations and on the connection that is sometimes observed with dynamic precipitation during severe plastic deformation. The last section is devoted to the influence of such grain boundary segregations in ultrafine grained alloys on the mechanical properties and on the thermal stability. [

Achieving highly strengthened Al–Cu–Mg alloy by grain refinement and grain boundary segregation

“…Interestingly, the precipitation sequence usually takes a diffe rent type, with the easy nucleation of stable phase without the classical sequence 3 (through formation of Guinier-Preston-Bagarysatsky (GPB) zones [26]). Besides, strain-induced segregations of solute atoms along GBs have been reported in the Al-Cu system [27,28] and other alloys [29]. In addition, three dimensional atom probe tomography (APT) by Sha et al [30] showed that such segregation of Cu and Mg also occurred during aging in an A2024 alloy.…”

“…In addition, three dimensional atom probe tomography (APT) by Sha et al [30] showed that such segregation of Cu and Mg also occurred during aging in an A2024 alloy. They could efficiently stabilize UFG structures but also contribute to strengthening [29].…”

Understanding the role of Ca segregation on thermal stability, electrical resistivity and mechanical strength of nanostructured aluminum

“…At this stage, the original sub-micrometer Ca filaments (dCa < 1m) are greatly elongated with a thickness dCa*  dCa /  of only 5 nm or less. Thus, at larger levels of deformation, Ca filaments are so much elongated that they start to dissolve in the fcc Al matrix as observed in other immiscible systems [31][32][33][34][35][36]. It starts at the HPT disc periphery where the shear strain is larger, and it progressively reaches the whole sample, leading to a progressive decrease and vanishing of Ca peaks on XRD spectra (Fig.…”

“…The aim of the present work was to investigate both the influence of segregations and of intermetallic phases in a nanostructured Al-Ca alloy. To reach this goal, it was assumed that the co-deformation of fcc Al and fcc Ca phases could lead to mechanical mixing, promote the nanoscaled structure formation and segregation of the minor element (namely Ca) along grain boundaries, as observed in various immiscible systems [31][32][33][34][35][36]. Thus, a bi-metallic composite material made of fcc Al and fcc Ca phases [37] has been processed by High-Pressure Torsion (HPT) at various strains.…”

Модель Растворения Пор На Границах Зерен При Отжиге Ультрамелкозернистого Алюминиевого Сплава

“…Известно также, что выделение второй фазы в таких материалах может улучшать их механические характеристики [2]. В экспериментах [3][4][5] отмечалось ускоренное выделение второй фазы в УМЗ-материалах, полученных методами интенсивной пластической деформации. Например, в алюминиевом УМЗ-сплаве Al−Zr, полученном методом интенсивной пластической деформации и затем отожженном при температуре 230 • C, наблюдалось значительное количество наноразмерных выделений фазы Al 3 Zr [5].…”