Additional modes of deformation twinning in magnesium

Reed-Hill, R.E.; Robertson, W. D.

doi:10.1016/0001-6160(57)90074-3

Cited by 239 publications

(91 citation statements)

References 4 publications

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“…The primary reason for this pronounced difference may lie in the fact that the critical stress for twin formation in the AZ31 alloy is rather low. 27) For some other alloys, e.g. Al-7%Si alloys, 9) no twins were revealed during EMV processing even when a larger vibration force (J e ϭ120 A and B 0 ϭ10 T) was imposed; this twin-free feature is similar to that observed in forced convection for Al-6.5%Si alloys 23) because of the very high stacking fault energy of aluminum.…”

Section: Discussionmentioning

confidence: 75%

Solidification Behavior of AZ31 Magnesium Alloys Using an Electromagnetic Vibration Technique

Tamura

Miwa

2008

ISIJ Int.

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The commercial magnesium-based AZ31 alloy was solidified in a static magnetic field when an alternating electric current, perpendicular to the direction of the magnetic field, passes through the alloy. In this case, the periodical Lorentz force is generated, making the conductor vibrate centering on the initial equilibrium position. In this paper, we investigated the microstructure evolution of the alloy as a function of vibration frequency, magnetic flux density and electric current, respectively. The solidification behavior was discussed and the mechanism for the formation of the microstructure was proposed when considering the electrical properties of solid and liquid at high temperature. Because the electrical resistivity of liquid in the mushy zone is about twice that of the solid, this significant difference drives the solid to move faster than the liquid and thus generating a leading displacement for the solid over the liquid even within one vibration cycle. The uncoupled movement between the solid and liquid also gives rise to melt flow, which may be the reason to segment dendrites into fine particles. Meanwhile, the uncoupled movement makes it difficult to establish a steady state for solute redistribution during solidification and thus favoring equiaxed structures instead of dendrites. Considering these two factors, we examine the solidification behavior of the alloy separately when vibration frequency, magnetic flux density, and electric current are set as independent variables and the microstructure evolution as a function of these processing parameters can be well interpreted.KEY WORDS: AZ31 magnesium alloy; microstructure formation; electromagnetic vibration; melt flow; solute redistribution. structure and thus having a fewer slip planes than those with a cubic structure. The anisotropic characteristic in deformation is rather pronounced for alloys with coarse structures and it is not favorable for a uniform deformation. However, the anisotropic feature can be greatly minimized by refined grains that randomly distribute throughout the entire volume, which is beneficial to have a uniform deformation during plastic processing. Moreover, a refined structure makes it possible to process at ambient temperature and thus reducing the production cost. StJohn et al. 17) summarized the influence of refined microstructures in Mg alloys on mechanical and chemical properties. Hence, a grain-refined structure of a solidified ingot is desirable from the viewpoint of industrial application even for the wrought AZ31 alloy.The EMV technique has been demonstrated to be effective in producing grain-refined structures for alloys. In comparison with other approaches for the production of fine structures, e.g., rapid melt quenching and external incubation, a bulk ingot can be fabricated without any external additives during EMV processing. Furthermore, no attenuation in vibration intensity can be inferred throughout the entire volume of the sample provided that electric current can pass through the conductor uniformly,...

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Section: Discussionmentioning

confidence: 75%

Solidification Behavior of AZ31 Magnesium Alloys Using an Electromagnetic Vibration Technique

Tamura

Miwa

2008

ISIJ Int.

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“…This can be attributed to the deformation driven by slipping of atomic planes at elevated temperatures. It has been earlier found that non-basal slip system activates at elevated temperature and it improves the ductility of Mg Alloys [24][25][26][27][28][29][30][31][32]. The evidence of slip induced deformation is clearly observed as parallel lines within the grains (Fig.…”

Section: Mechanical Propertiesmentioning

confidence: 91%

Effect of melt conditioning on heat treatment and mechanical properties of AZ31 alloy strips produced by twin roll casting

Das

Barekar

Fakir

et al. 2015

Materials Science and Engineering: A

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In the present investigation, magnesium strips were produced by twin roll casting (TRC) and melt conditioned twin roll casting (MC-TRC) processes. Detailed optical microscopy studies were carried out on as-cast and homogenized TRC and MC-TRC strips. The results showed uniform, fine and equiaxed grain structure was observed for MC-TRC samples in as-cast condition. Whereas, coarse columnar grains with centreline segregation were observed in the case of as-cast TRC samples. The solidification mechanisms for TRC and MC-TRC have been found completely divergent. The homogenized TRC and MC-TRC samples were subjected to tensile test at elevated temperature (250 to 400C). At 250C, MC-TRC sample showed significant improvement in strength and ductility. However, at higher temperatures the tensile properties were almost comparable, despite of TRC samples having larger grains compared to MC-TRC samples. The mechanism of deformation has been explained by detailed fractures surface and sub-surface analysis carried out by scanning electron and optical microscopy. Homogenized MC-TRC samples were formed (hot stamping) into engineering component without any trace of crack on its surface. Whereas, TRC samples cracked in several places during hot stamping process.

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“…Among these types of twinning, the {10-12}-type (‹c›-axis tension) twins form easily at the beginning of plastic deformation, since its CRSS is the lowest and has a similar order as that in the basal plane. 5,6 The twinning is formed by the concentrated stress due to the dislocation pile-up, as reported in 3 . When the magnitude of the stress concentration is larger than the nucleation stress, twinning is thought to form at an adjacent grain.…”

Section: Introductionmentioning

confidence: 87%

“…4 Therefore, in practice, the mean free path of the dislocations should incorporate terms representing the effects of both the grain size and the presence of any twins. Several types of single-and doubletwinning such as {1011}, {1012}, {1013}, {1011}-{1012} and {1013}-{1012} are formed in magnesium and its alloys, [5][6][7] and the crystallographic relation of the lattice rotates around the ‹1120› direction by 56°, 86°a nd 64°for these types of single twinning formation. Among these types of twinning, the {10-12}-type (‹c›-axis tension) twins form easily at the beginning of plastic deformation, since its CRSS is the lowest and has a similar order as that in the basal plane.…”

Section: Introductionmentioning

confidence: 99%

The effect of thermo-mechanical processing on the structure, static mechanical properties and fatigue behaviour of pure Mg

Kubásek¹,

Vojtěch²,

Dvorský³

2017

Mater. tehnol.

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Magnesium alloys find important applications in automotive, aircraft and space industries. Magnesium itself is also a key component in biodegradable metallic materials considered for applications in medicine. Although there are many studies that include the mechanical behaviour of pure Mg and its alloys after different thermomechanical processing, there is a huge impact of the processing method on the observed properties. Based on these facts, predicting the final properties is difficult. This paper deals with the preparation of pure Mg using a classic extrusion method with a low extrusion ratio, slow extrusion rate and low temperature. These parameters were selected to prevent an excessive grain size and to obtain optimal mechanical properties. The prepared materials were subsequently heat treated under different conditions and the relations between the grain size, texture strength and mechanical properties were studied. As well as static mechanical tests in tension and compression, fatigue tests were also performed. Finally, the obtained data were fitted using the Hall-Petch relation and the results were compared with the literature. The observed results confirmed the significant effect of processing on the mechanical properties with a strong impact on the Hall-Petch behaviour. Keywords: magnesium, mechanical properties, texture, Hall-Petch relation Magnezijeve zlitine so pomembne za uporabo v avtomobilski, letalski in vesoljski industriji. Magnezij je tudi klju~na komponenta v biorazgradljivih kovinskih materialih za uporabo v medicini.^eprav obstaja mnogo {tudij, ki vklju~ujejo mehansko obna{anje~istega Mg in njegovih zlitin po razli~nih termomehanskih obdelavah, je velik vpliv metode obdelovanja na opazovane lastnosti. Na osnovi tega je te`ko napovedovati kon~ne lastnosti. Ta~lanek obravnava pripravo~istega Mg s klasi~no metodo ekstruzije z majhnim razmerjem ekstruzije, majhno hitrostjo ekstruzije pri nizki temperaturi. Ti parametri so bili izbrani, da se prepre~i prekomerna rast zrn in da se dose`e optimalne mehanske lastnosti. Pripravljeni material je bil pozneje toplotno obdelan pri razli~nih pogojih in {tudirane so bile odvisnosti med velikostjo zrn, teksturo in mehanskimi lastnostmi. Razen stati~nih mehanskih preizkusov, nateznih in tla~nih, so bili izvedeni tudi preizkusi utrujanja. Na koncu so bili dobljeni podatki primerjani s Hall-Petchevim razmerjem in dobljeni rezultati so bili primerjani s podatki iz literature. Dobljeni rezultati so potrdili mo~an vpliv obdelave na mehanske lastnosti, z mo~nim vplivom na Hall-Petchevo razmerje.

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Additional modes of deformation twinning in magnesium

Cited by 239 publications

References 4 publications

Solidification Behavior of AZ31 Magnesium Alloys Using an Electromagnetic Vibration Technique

Solidification Behavior of AZ31 Magnesium Alloys Using an Electromagnetic Vibration Technique

Effect of melt conditioning on heat treatment and mechanical properties of AZ31 alloy strips produced by twin roll casting

The effect of thermo-mechanical processing on the structure, static mechanical properties and fatigue behaviour of pure Mg

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