Simultaneously enhanced strength and ductility of Mg-Zn-Zr-Ca alloy with fully recrystallized ultrafine grained structures

Zheng, Ruixiao; Bhattacharjee, Tilak; Shibata, Akinobu; Sasaki, Taisuke; Hono, K.; Joshi, Mohit; Tsuji, Nobuhiro

doi:10.1016/j.scriptamat.2016.12.024

Cited by 123 publications

(37 citation statements)

References 31 publications

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“…Nevertheless, the ultra-fine grain size of TX22-280 sample (~0.65 mm) is comparable with that obtained by severely deformed Mg-alloys such as the HPT-ed and aged Mg-Zn-Zr-Ca alloy (~0.77 mm) [48]. When increasing the ram speed, the high-speed extruded samples can maintain the ultra-fine grained microstructures, with the average grain size slightly increasing from Fig.…”

Section: Microstructure Characterization Of As-extruded Mg Alloysupporting

confidence: 58%

Development of low-alloyed and rare-earth-free magnesium alloys having ultra-high strength

et al. 2018

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Developing ultra-high strength in rare-earth-free Mg alloys using conventional extrusion process is a great challenge. What is even more difficult is to achieve such a goal at a lower processing cost. In this work, we report a novel low-alloyed Mg-2Sn-2Ca alloy (in wt. %) that exhibits tunable ultra-high tensile yield strength (360e440 MPa) depending on extrusion parameters. More importantly, there is little drop in mechanical properties of this alloy even when it is extruded at a speed several times higher than those used in the reported high strength Mg alloys. Examination of as-extruded microstructures of this Cacontaining Mg alloy reveals that the ultra-high strength is mainly associated with the presence of surprisingly submicron matrix grains (down to~0.32 mm). The results suggest that the Ca addition promotes accumulations of the pyramidal dislocations, which eventually transform into the low angular grain boundaries (LAGBs). The high number density of LAGBs separate the a-Mg matrix via either discontinuous dynamic recrystallization (DDRX) mechanism in the early stage or the continuous dynamic recrystallization (CDRX) mechanism in the later stage of extrusion, which effectively enhances the nucleation rates of the DRXed grains. More importantly, large amount of Ca segregation along LAGBs, accompanied with dynamically precipitated Mg 2 Ca nano-phases, are detected in the present nonseverely deformed samples. It is the combination of solute segregations and numerous Mg 2 Ca nanoprecipitates that contributes to the formation of the ultra-fine grains via pinning mechanism. The ultrafine grains size, Ca enrichment in most LAGBs, and residual Mg 2 Ca nano-precipitates would in turn contribute significantly to the enhancement of the yield strength of the as-extruded Mg-2Sn-2Ca (wt.%) alloy. The low content of alloying elements and the fast one-step extrusion process render the present alloys low-cost and thus have great potential in large-scale industry applications.

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Section: Microstructure Characterization Of As-extruded Mg Alloysupporting

confidence: 58%

Development of low-alloyed and rare-earth-free magnesium alloys having ultra-high strength

et al. 2018

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“…Also, a short annealing after HPT processing may increase the ductility. For example, an increase in strength and a remarkably uniform elongation of 20.5% was reported in a ZKX600 alloy processed by HPT and subjected to a 1 min annealing treatment at 300 °C and an increase in elongation was reported also in a ZK60 alloy processed by HPT and annealed for 20 min at 200 °C …”

Section: Mechanical Propertiesmentioning

confidence: 93%

Processing Magnesium and Its Alloys by High‐Pressure Torsion: An Overview

Figueiredo

Langdon

2018

Adv Eng Mater

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Magnesium and its alloys have attracted significant attention in recent years because they display high strength-to-density ratios, they are biodegradable and they provide a potential for hydrogen storage. Many investigations have examined the effect of high-pressure torsion processing on the microstructures and properties of these materials so that numerous reports are now available. This overview provides a summary of the observations reported to date on the structure and mechanical property evolution including the nature of grain refinement, the grain boundary misorientation distributions, texture evolution, and the minimum grain size. For convenience, the mechanical properties are separated into hardness, tensile behavior, and superplastic properties. It is shown that the mechanism of grain refinement differs from other metallic materials processed by severe plastic deformation but high strength may be achieved in magnesium alloys and exceptional ductility in pure magnesium. Hydrogen storage and corrosion behavior are also examined together with a discussion of recent attempts to produce magnesium-based nanocomposites through processing by high-pressure torsion.

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“…27) Recently, the coexistence of high strength and high ductility was confirmed in fully recrystallized structures of some alloys which had unimodal grain size distributions with sub-micrometer grain sizes. 28,29) An unimodal fully-recrystallized grain-structure with a mean grain size of 400 nm was formed in a high-Mn austenitic steel specimen after cold-rolling by 92% thickness reduction and subsequent annealing at 650°C. 28) The specimen showed the coexistence of high strength and high ductility in tensile tests at room temperature.…”

Section: Coexistence Of High Strength and High Ductilitymentioning

confidence: 99%

“…The coexistence of high strength and high ductility was also observed in a MgZnZrCa alloy specimen heavily deformed by HPT and subsequently annealed at 300°C or 400°C for 1 min. 29) Unimodal UFG structures with average grain sizes of several hundreds nm were formed by the inhibition of grain growth which was due to the fine second phase particles in the Mg-alloy. The fully recrystallized structures were naturally free from dislocations inside grains.…”

Section: Coexistence Of High Strength and High Ductilitymentioning

confidence: 99%

Texture and Mechanical Properties of Al–Mg Alloy with Unimodal and Bimodal Grain-Structures Formed by Accumulative Roll Bonding and Annealing

Kashihara

Tsuji

2018

Mater. Trans.

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The structural and mechanical properties of a commercial A5052 aluminummagnesium alloy processed by accumulative roll bonding (ARB) and subsequent annealing were investigated. Unimodal and bimodal grain-structures were formed in the ARB-processed specimens by annealing at 250°C and 300°C, respectively. In the specimen ARB-processed and annealed at 300°C, {001} ©100ª cube orientation became the main texture component which corresponded to coarse recrystallized grains in the bimodal grain-structures. The preferential formation of the cube texture could be explained by existing theories regarding stored energy and grain boundary mobility. High strength and high ductility was both managed in the specimens with bimodal grain-structures as well as those with unimodal grain-structures. In order to achieve both high strength and high ductility in bimodal grain-structures, the area fraction of coarse grains to fine grains played a critical role. It was also suggested in this study that bimodal structures were not only the structure to provide the coexistence of high strength and high ductility.

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Simultaneously enhanced strength and ductility of Mg-Zn-Zr-Ca alloy with fully recrystallized ultrafine grained structures

Cited by 123 publications

References 31 publications

Development of low-alloyed and rare-earth-free magnesium alloys having ultra-high strength

Development of low-alloyed and rare-earth-free magnesium alloys having ultra-high strength

Processing Magnesium and Its Alloys by High‐Pressure Torsion: An Overview

Texture and Mechanical Properties of Al–Mg Alloy with Unimodal and Bimodal Grain-Structures Formed by Accumulative Roll Bonding and Annealing

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