“…3 ). The main reason is that the dislocation migration and therefore the dynamic recovery during HPT processing could be effectively inhibited by low temperature as well as by the Zener pinning from Sc atoms 26 . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…A big challenge for the application of NG metallic materials is the poor ductility 16 , 17 . Some tactics have been proposed to improve the ductility of bulk NG metals, including GB chemical/structural optimization and multi-length heterogeneity design 24 , 26 . In particular, dispersing nanosized particles in the grain interior via precipitation is an effective approach, because the intragranular particles can generate, pin down and thus accumulate dislocations within the grains 18 , 26 .…”
Section: Discussionmentioning
confidence: 99%
“…Some tactics have been proposed to improve the ductility of bulk NG metals, including GB chemical/structural optimization and multi-length heterogeneity design 24 , 26 . In particular, dispersing nanosized particles in the grain interior via precipitation is an effective approach, because the intragranular particles can generate, pin down and thus accumulate dislocations within the grains 18 , 26 . But uncontrollable intergranular precipitation preferentially occurred in the NG metals at low temperature (even room temperature) 20 , 22 , suppressing the intragranular precipitation.…”
Low-temperature decomposition of supersaturated solid solution into unfavorable intergranular precipitates is a long-standing bottleneck limiting the practical applications of nanograined aluminum alloys that are prepared by severe plastic deformation. Minimizing the vacancy concentration is generally regarded as an effective approach in suppressing the decomposition process. Here we report a counterintuitive strategy to stabilize supersaturated solid solution in nanograined Al-Cu alloys via high-density vacancies in combination with Sc microalloying. By generating a two orders of magnitude higher concentration of vacancies bonded in strong (Cu, Sc, vacancy)-rich atomic complexes, a high thermal stability is achieved in an Al-Cu-Sc alloy that precipitation is nearly suppressed up to ~230 °C. The solute-vacancy complexes also enable the nanograined Al-Cu alloys with higher strength, greater strain hardening capability and ductility. These findings provide perspectives towards the great potentials of solute-vacancy interaction and the development of nanograined alloys with high stability and well-performed mechanical properties.
“…3 ). The main reason is that the dislocation migration and therefore the dynamic recovery during HPT processing could be effectively inhibited by low temperature as well as by the Zener pinning from Sc atoms 26 . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…A big challenge for the application of NG metallic materials is the poor ductility 16 , 17 . Some tactics have been proposed to improve the ductility of bulk NG metals, including GB chemical/structural optimization and multi-length heterogeneity design 24 , 26 . In particular, dispersing nanosized particles in the grain interior via precipitation is an effective approach, because the intragranular particles can generate, pin down and thus accumulate dislocations within the grains 18 , 26 .…”
Section: Discussionmentioning
confidence: 99%
“…Some tactics have been proposed to improve the ductility of bulk NG metals, including GB chemical/structural optimization and multi-length heterogeneity design 24 , 26 . In particular, dispersing nanosized particles in the grain interior via precipitation is an effective approach, because the intragranular particles can generate, pin down and thus accumulate dislocations within the grains 18 , 26 . But uncontrollable intergranular precipitation preferentially occurred in the NG metals at low temperature (even room temperature) 20 , 22 , suppressing the intragranular precipitation.…”
Low-temperature decomposition of supersaturated solid solution into unfavorable intergranular precipitates is a long-standing bottleneck limiting the practical applications of nanograined aluminum alloys that are prepared by severe plastic deformation. Minimizing the vacancy concentration is generally regarded as an effective approach in suppressing the decomposition process. Here we report a counterintuitive strategy to stabilize supersaturated solid solution in nanograined Al-Cu alloys via high-density vacancies in combination with Sc microalloying. By generating a two orders of magnitude higher concentration of vacancies bonded in strong (Cu, Sc, vacancy)-rich atomic complexes, a high thermal stability is achieved in an Al-Cu-Sc alloy that precipitation is nearly suppressed up to ~230 °C. The solute-vacancy complexes also enable the nanograined Al-Cu alloys with higher strength, greater strain hardening capability and ductility. These findings provide perspectives towards the great potentials of solute-vacancy interaction and the development of nanograined alloys with high stability and well-performed mechanical properties.
“…Nowadays, various methods for increasing the ductility of UFG aluminum alloys are suggested. These methods may include the formation of bimodal [7][8][9], defect-free [10], and gradient [11,12] structures, etc. However, these approaches are technically difficult and have a number of restrictions in use.…”
A theoretical model is suggested that describes the effect of deformation temperature on the yield stress of an ultrafine-grained (UFG) Al-Cu-Zr alloy structured with severe plastic deformation. Within the model, nanoprecipitates (NPs) of Al2Cu act as sources of lattice dislocations in the presence of a number of extrinsic grain-boundary dislocations (EGBDs) near the NPs. It is shown that the number of EGBDs near the NPs decreases with a drop in the deformation temperature that increases the yield stress of the Al-Cu-Zr alloy. The proposed model is in good quantitative agreement with available experimental results.
“…In connection therewith, presently, a lot of attention is paid to develop scientificallybased approaches aimed at improving the plasticity of highstrength UFG-materials. The examples of these approaches include formation of a bimodal structure [5][6][7][8], introduction of nanosized precipitates of the secondary phase [9,10] and etc. [3].…”
The influence of the strain rate on the plasticization effect (PE) of ultrafine-grained (UFG) Al-1.47Cu-0.34Zr (wt%) alloy structured by high pressure torsion. A significant increase in plasticity (more than 2 times) while maintaining a high level of strength (ultimate tensile strength ~465 MPa) in the UFG alloy was achieved as a result of additional deformation-heat treatment (DHT), consisting of low-temperature annealing and a small additional deformation. It is shown that the PE after DHT is retained when the strain rate changes from 10-4 to 10-3 s-1 and decreases by half with its further increase to 10-2 s-1. The values of the strain-rate sensitivity coefficient for the UFG Al-1.47Cu-0.34Zr (wt%) alloy were determined in both states before and after DHT. Possible reasons of the PE suppression at high strain rates (≥10-2 s-1) are discussed. Keywords: aluminum alloys, severe plastic deformation, ultrafine-grained structure, strength, plasticity, strain-rate sensitivity.
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