Microstructure and mechanical properties of Mg–Al–Zn alloy sheets severely deformed by asymmetrical rolling

Kim, Woo Jin; Lee, J.B.; Kim, W.Y.; Jeong, Hyo‐Tae; Jeong, Hye Gwang

doi:10.1016/j.scriptamat.2006.09.034

Cited by 217 publications

(80 citation statements)

References 11 publications

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“…As the particle size is smaller and the particle distribution is more uniform in the HRDSR-processed 1CaAZ31, the inter-particle spacing in the HRDSR-processed alloy should be smaller. According to the constant structure-creep relation, in which sub-grain size is determined by inter-particle spacing, the following relationship holds at a given stress: [15] _ e / l 3 (1) where l is the sub-grain size. By using this relation, the l value of the HRDSR-processed alloy was calculated to be smaller than that of the extruded alloy by a factor of 0.65-0.7.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] Early investigations of the microstructures of the AZ31, [1] AZ61 [2] and AZ91 alloys [3] produced by HRDSR led to the recognition that this processing method is capable of reducing the grain size of Mg alloys to the sub-micrometer level achieved using equal-channel angular pressing (ECAP) with multiple passes. Like many Mg alloys processed by ECAP, [4,5] the HRDSRprocessed AZ61 and AZ91 alloys [2,3] exhibited excellent superplasticity at relatively low temperatures (473-523 K).…”

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confidence: 99%

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Achieving Low Temperature Superplasticity from Ca‐Containing Magnesium Alloy Sheets

Kim

Lee

2009

Adv Eng Mater

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High-speed-ratio differential speed rolling (HRDSR) is a newly developed procedure in which a material, in either plate or sheet form, is subjected to severe plastic deformation by inducing a large shear deformation during rolling for a large thickness reduction of 60$70% in a single pass. [1][2][3] Early investigations of the microstructures of the AZ31, [1] AZ61 [2] and AZ91 alloys [3] produced by HRDSR led to the recognition that this processing method is capable of reducing the grain size of Mg alloys to the sub-micrometer level achieved using equal-channel angular pressing (ECAP) with multiple passes. Like many Mg alloys processed by ECAP, [4,5] the HRDSRprocessed AZ61 and AZ91 alloys [2,3] exhibited excellent superplasticity at relatively low temperatures (473-523 K). The superplasticity of the HRDSR-processed AZ31 alloy was, however, not so impressive at similar temperatures, despite it being processed under identical experimental conditions as for the AZ61 and AZ91 alloys. The result was attributed to the presence of a relatively small volume fraction of a second phase (b-Mg 17 Al 12 ) in AZ31, which affects grain refining and growth during deformation. [6] It is well known that addition of Ca to magnesium is effective in the grain refining of magnesium castings. [7] However, there have been few reports on the superplastic behavior of Mg-Al-Ca alloys, since the effective break-up of coarse (Al, Mg) 2 Ca phase, in the form of a continuous network in grain boundaries of matrix, is not easy through conventional thermo-mechanical working routes. [8] In a previous work, [9] the effect of high-frequency electromagnetic forces on the surface quality and microstructure of a 1 wt.-% Ca-AZ31 billet was examined. Under optimum processing conditions, high-surface-quality billets with a homogeneous microstructure consisting of fine equiaxed grains (L ¼ 40-50 mm, where L is the linear intercept grain size) and a thin layer of (Al, Mg) 2 Ca phase distributed along the grain boundaries could be obtained. During the subsequent hot extrusion process, significant grain refinement (L ¼ 2.1 mm) and effective break-up of the (Al, Mg) 2 Ca phase took place. The extruded 1 wt.-% Ca-AZ31 exhibited high-strain-rate superplasticity at 573 and 673 K, at which temperatures tensile elongations larger than 550% were achieved at 10 À2 s À1 . [10] In this work, we applied the HRDSR technique to extruded 1 wt.-% Ca-AZ31 plates in order to produce sheets capable of exhibiting superplasticity at warm temperatures (473-523 K), in the range where most forming operations on magnesium alloy sheets are conducted in practice. The use of superplastic magnesium alloy sheets is exciting since it provides accommodation for a higher degree of design freedom in making magnesium components. ExperimentalA cylindrical AZ31 (Mg, 3 wt.-%Al, 1 wt.-% Zn) billet with 1 wt.-% Ca added (denoted 1CaAZ31) was produced by electromagnetic casting in the presence of electromagnetic stirring; details of this casting technique are available elsewhere. [9] Billets with ...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Achieving Low Temperature Superplasticity from Ca‐Containing Magnesium Alloy Sheets

Kim

Lee

2009

Adv Eng Mater

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“…Rods extruded at the relatively low ratios of 2.4 and 4.7 were subjected to warm rolling at 473 K for a thickness reduction from 7.0 or 5.1 to 3.0 mm through 1-2 passes by conventional rolling. After rolling, the materials were subjected to high-ratio differential speed rolling (HRDSR 7,8) ) with a roll speed ratio of 2, and a nal thickness of 1 mm was obtained. During the HRDSR process, the surface temperature of the rolls was maintained at 473 K, and the samples were not preheated between passes.…”

Section: Methodsmentioning

confidence: 99%

Accelerated Formation of an Ultrafine-Grained Microstructure in Closed-Cell Aluminum Foam after Extrusion and Differential Speed Rolling

Kim

Utsunomiya

2017

Mater. Trans.

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Plastic deformation by extrusion and high-ratio differential speed rolling on closed-cell aluminum foams resulted in the formation of ultra ne grains in the densi ed matrix. The microstructure had an average grain size of 1.30 μm and a fraction of high angle boundaries of 0.7. Under the same processing condition, only dynamic recovery occurred in the bulk aluminum. During deformation of the foam, continuous dynamic recrystallization accelerated at the cell walls due to the occurrence of a high degree of severe plastic deformation there. The bonded interfaces created by pore closure also provided a number of sites of high angle grain boundaries, thereby contributing to the grain re nement.

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“…The third way to improve the mechanical behaviour of Mg alloys is based on modifying the texture, which has an important influence on the ductility and on the plastic anisotropy [31][32][33][34][35][36][37][38][39][40][41][42]. Depending on the processing route followed, different types of textures are obtained.…”

Section: Introductionmentioning

confidence: 99%

“…During extrusion, the c-axes align perpendicular to the extrusion direction. Considerable efforts have been devoted to develop novel textures by innovative processing techniques such as asymmetric rolling [40][41][42]. If a tensile test is carried out in a rolled Mg sheet along an in-plane direction, basal slip becomes difficult and non-basal deformation modes become active.…”

Section: Introductionmentioning

confidence: 99%

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

Srinivasarao¹,

Valle²,

Ruano³

et al. 2012

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The work carried out by the authors over the last decade on the processing, microstructural characterization and the mechanical behaviour of Mg alloys is reviewed. In particular, the potential for grain refinement and for the development of specific textures of large strain hot rolling (LSHR), equal channel angular pressing (ECAP) and accumulative roll bonding (ARB) is discussed. The recrystallization and the deformation mechanisms predominant in Mg alloys are analysed as a function of the grain size and the texture in a wide range of stresses, strain rates and temperatures. Finally, the feasibility of superplastic forming of Mg alloys was examined, taking into account the influence of factors such as grain size stability and microstructural heterogeneities.K e y w o r d s : magnesium alloys,

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Microstructure and mechanical properties of Mg–Al–Zn alloy sheets severely deformed by asymmetrical rolling

Cited by 217 publications

References 11 publications

Achieving Low Temperature Superplasticity from Ca‐Containing Magnesium Alloy Sheets

Achieving Low Temperature Superplasticity from Ca‐Containing Magnesium Alloy Sheets

Accelerated Formation of an Ultrafine-Grained Microstructure in Closed-Cell Aluminum Foam after Extrusion and Differential Speed Rolling

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

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