Deformation mechanisms of pure Mg materials fabricated by using pre-rolled powders

Shen, Jianghua; Imai, Hisashi; Chen, Biao; Ye, X.; Umeda, Junko; Kondoh, Katsuyoshi

doi:10.1016/j.msea.2016.02.027

Cited by 17 publications

(6 citation statements)

References 68 publications

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“…Also, the significant grain growth occurring during high-temperature post-treatments may alter the materials properties. In contrast, the powder metallurgy (PM) processes represent an effective way for mechanical improvement through reduction in segregation scale, improvement in densification and microstructural refinement [ 19 , 20 , 21 ]. One of the major drawbacks of the PM process in Mg is the lack of ductility inherited from the presence of oxides at the surface of the powder particles which are difficult to remove during “conventional” sintering [ 20 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Strain Heterogeneities on Microstructure, Texture, Hardness, and H-Activation of High-Pressure Torsion Mg Consolidated from Different Powders

et al. 2018

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Severe plastic deformation techniques, such as high-pressure torsion (HPT), have been increasingly applied on powder materials to consolidate bulk nanostructured materials. In this context, the aim of the present study is to compare the plastic deformation characteristics during HPT of two distinct Mg-based powder precursors: (i) atomized micro-sized powder and (ii) condensed and passivated nanopowder. Dynamic recrystallization could take place during HPT consolidation of the atomized powder particles while the oxide pinning of the grain boundaries restricted it for the condensed powder. Consequently, there have been substantial differences in the development of the microstructure, texture, local strain heterogeneities, and hardness in the two types of consolidated products. Different types of local strain heterogeneities were also revealed in the consolidated products. The associated diversity in microstructure within the same consolidated product has been demonstrated to have an effect on the hydrogen activation kinetics to form hydrides for these Mg-based materials that could be suitable for solid state H-storage applications.

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Section: Introductionmentioning

confidence: 99%

Effect of Strain Heterogeneities on Microstructure, Texture, Hardness, and H-Activation of High-Pressure Torsion Mg Consolidated from Different Powders

et al. 2018

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“…Good mechanical properties of magnesium and its alloys can be furthermore significantly upgraded by decreasing the grain size, nowadays performed mainly via severe plastic deformation (SPD) techniques [3,5], powder metallurgy (PM) processing [1,2,6,7] or by a combination of both methods. Decreasing the metallic grain size within the material volume, either by alloying elements, SPD methods, such as extrusion, equal channel angular pressing (ECAP) and high-pressure torsion (HPT) or PM, leads to increase of hardness, tensile and yield strength, but the plasticity of the material was shown to be decreased [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Decreasing the metallic grain size within the material volume, either by alloying elements, SPD methods, such as extrusion, equal channel angular pressing (ECAP) and high-pressure torsion (HPT) or PM, leads to increase of hardness, tensile and yield strength, but the plasticity of the material was shown to be decreased [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

Zapletal

Březina

Krystýnová

et al. 2017

Metals

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Magnesium with its mechanical properties and nontoxicity is predetermined as a material for biomedical applications; however, its high reactivity is a limiting factor for its usage. Powder metallurgy is one of the promising methods for the enhancement of material mechanical properties and, due to the introduced plastic deformation, can also have a positive influence on corrosion resistance. Pure magnesium samples were prepared via powder metallurgy. Compacting pressures from 100 MPa to 500 MPa were used for samples' preparation at room temperature and elevated temperatures. The microstructure of the obtained compacts was analyzed in terms of microscopy. The three-point bending test and microhardness testing were adopted to define the compacts' mechanical properties, discussing the results with respect to fractographic analysis. Electrochemical corrosion properties analyzed with electrochemical impedance spectroscopy carried out in HBSS (Hank's Balanced Salt Solution) and enriched HBSS were correlated with the metallographic analysis of the corrosion process. Cold compacted materials were very brittle with low strength (up to 50 MPa) and microhardness (up to 50 HV (load: 0.025 kg)) and degraded rapidly in both solutions. Hot pressed materials yielded much higher strength (up to 250 MPa) and microhardness (up to 65 HV (load: 0.025 kg)), and the electrochemical characteristics were significantly better when compared to the cold compacted samples. Temperatures of 300 • C and 400 • C and high compacting pressures from 300 MPa to 500 MPa had a positive influence on material bonding, mechanical and electrochemical properties. A compacting temperature of 500 • C had a detrimental effect on material compaction when using pressure above 200 MPa.

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“…Our MD simulation results capture the critical feature of faster TT propagation compared to twin thickening [34,[41][42][43][44] and isolate the importance of disconnections in this process, but also allow for the development of a general model for twin embryo growth. A quantitative description of the evolution of twin length and thickness allows us to connect MD models on the nanoscale to experimental work that usually reports on a much larger length-scale.…”

Section: Discussionmentioning

confidence: 67%

Disconnection-Mediated Twin Embryo Growth in Mg

Turlo

Beyerlein

et al. 2019

SSRN Journal

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While deformation twinning in hexagonal close-packed metals has been widely studied due to its substantial impact on mechanical properties, an understanding of the detailed atomic processes associated with twin embryo growth is still lacking. Conducting molecular dynamics simulations on Mg, we show that the propagation of twinning disconnections emitted by basalprismatic interfaces controls the twin boundary motion and is the rate-limiting mechanism during the initial growth of the twin embryo. The time needed for disconnection propagation is related to the distance between the twin tips, with widely spaced twin tips requiring more time for a unit twin boundary migration event to be completed. Thus, a phenomenological model, which unifies the two processes of disconnection and twin tip propagation, is proposed here to provide a quantitative analysis of twin embryo growth. The model fits the simulation data well, with two key parameters (twin tip velocity and twinning disconnection velocity) being extracted. In addition, a linear relationship between the ratio of twinning disconnection velocity to twin tip velocity and the applied shear stress is observed. Using an example of twin growth in a nanoscale single crystal from the recent literature, we find that our molecular dynamics simulations and analytical model are in good agreement with experimental data.

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Deformation mechanisms of pure Mg materials fabricated by using pre-rolled powders

Cited by 17 publications

References 68 publications

Effect of Strain Heterogeneities on Microstructure, Texture, Hardness, and H-Activation of High-Pressure Torsion Mg Consolidated from Different Powders

Effect of Strain Heterogeneities on Microstructure, Texture, Hardness, and H-Activation of High-Pressure Torsion Mg Consolidated from Different Powders

Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

Disconnection-Mediated Twin Embryo Growth in Mg

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