Ultra-Fine Grain Development in an AZ31 Magnesium Alloy during Multi-Directional Forging under Decreasing Temperature Conditions

Xing, Jiadi; Soda, H.; Yang, Xuyue; Miura, Hiromi; Sakai, Taku

doi:10.2320/matertrans.46.1646

Cited by 99 publications

(36 citation statements)

References 10 publications

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“…This process should finally lead to a homogeneous and full development of fine grained structure in a whole volume. 5) The grain size developed in high strain does not change during isothermal MDF at 623 K (Figs. 4 and 7).…”

Section: Grain Refinement In Mg Alloy During Mdfmentioning

confidence: 97%

“…The sample dimension did not change during MDF when Á" was kept at constant. 5) MDF was carried out with decreasing temperature from 623 K to 403 K, or at a constant temperature of 623 K, and then quenched in water in each pass. Deformed samples were cut along planes parallel to the last compression axis, and microstructural observations were carried out by using optical microscopy (OM) and transmission electron microscopy (TEM) under an accelerating voltage of 200 kV.…”

Section: Experiments Proceduresmentioning

confidence: 99%

“…Fine-grained structures were developed in a Mg alloy AZ31 by using multidirectional forging (MDF) under decreasing temperature conditions from pass to pass. 4,5) The process of grain refinement taking place during MDF and the mechanical properties of the products were investigated in detail. The mechanisms of grain refinement and plastic deformation of the fine-grained Mg alloy are analyzed and discussed.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical Properties of Magnesium Alloy AZ31 after Severe Plastic Deformation

Xing

Miura

et al. 2008

Mater. Trans.

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Grain refinement of magnesium alloy AZ31 was studied in multidirectional forging (MDF) under decreasing temperature conditions. MDF was carried out up to large cumulative strains of 5.6 with changing the loading direction during decrease in temperature from pass to pass. MDF can accelerate the uniform development of very fine-grained structures and an increase of the plastic workability at low temperatures. New grain structures with the minimal grain size of 0.23 mm can be developed by continuous dynamic recrystallization at a final processing temperature of 403 K. As a result, the multidirectional-forged alloy showed excellent higher strength as well as moderate ductility at room temperature, and also a superplastic elongation of over 300% at 423 K. The mechanisms of strain-induced and fine-grained structure development and of the excellent plastic deformation are discussed in detail.

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Section: Grain Refinement In Mg Alloy During Mdfmentioning

confidence: 97%

Section: Experiments Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanical Properties of Magnesium Alloy AZ31 after Severe Plastic Deformation

Xing

Miura

et al. 2008

Mater. Trans.

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“…To date, the grain refinement due to DRX during hot deformation has been demonstrated in conventional Mg-Al-Zn alloys. [15][16][17][18][19][20][21][22][23][24][25][26][27][28] It has been reported that dynamically recrystallized grain size (DRX grain size) decreases with an increase of Zener-Hollomon parameter (Z-parameter) 29) in several magnesium alloys. 19,24,27,30,31) Watanabe et al have reported that there is initial grain sizes dependence on DRX grain size in AZ61 magnesium alloy.…”

Section: Introductionmentioning

confidence: 99%

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

et al. 2008

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The effect of initial grain size on dynamically recrystallized grain size (DRX grain size) is examined in AZ31 magnesium alloy with four kinds of initial grain sizes. When the average grain size after the high-temperature compression test is plotted against Zenner-Hollomon parameter (Z-parameter), initial grain size dependence on DRX grain size appears only in the specimen with large initial grain size in the low Z region, but not in the specimen with small grain size or in high Z region. When the grain size measured only in recrystallized region is plotted against Z-parameter, initial grain size dependence on DRX grain size does not appear. From these results, it is concluded that there is no initial grain size dependence on DRX grain size when the DRX proceeds to some degree, because the DRX grain size becomes constant for a given Zvalue. The initial grain size dependence on DRX grain size observed in the low Z region would be related to the rotation of basal plane perpendicular to the compression axis during deformation before the DRX grains have been developed sufficiently.

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“…Следует, однако, отметить [14,15], что как и в других труднодеформируемых материалах [9,16,17], процесс формирования методами ИПД однородной УМЗ / НК структуры в Al-Mg-Sc-x сплавах с содержанием Mg более 3 -4 % связан с рядом трудностей. Например, исследования структурных изменений при равнока-нальном угловом прессовании (РКУП) сплава 1570 (Al-6Mg-0,3Sc) показали, что основной механизм из-мельчения зерен обусловлен развитием непрерывной динамической рекристаллизации [15,18], при которой сетки малоугловых дислокационных границ, форми-рующиеся на ранней стадии деформации, увеличивают свою разориентировку в процессе последующей об-работки и трансформируются в новые высокоугловые границы.…”

Section: Introductionunclassified

Structure of the aluminum alloy 1570C subjected to multidirectional forging with decreasing temperature

Sitdikov¹,

Garipova²,

Avtokratova³

et al. 2017

LoM

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The structure of cast and homogenized aluminium alloy 1570C (Al5Mg0.18Mn0.2Sc0.08Zr, wt. %) was studied after multidirectional isothermal forging (MIF). Repetitive upsetting was carried out with a 25°C decrease of temperature at each pass starting from 450°C, a pass strain of 0.7 and strain rate 10 -2 s -1. The alloy ductility was sufficient for a successful (without cracking) straining of the sample up to е ~ 10.5 at 100°C. In the initial state, the alloy had a coarse-grained structure with a grain size of 25 μm and uniform distribution of the nanoscale aluminides Al 3 (Sc,Zr). MIF resulted in continuously refined (sub) grains and material hardening. At low strains (е ≤ 4.2) and high temperatures (Т > 325°С), new grains were developed mainly in the mantle regions of the initial grains. As a result, a bimodal structure was formed, which persisted up to е ~ 6.3 (250°C). With further MIF, the evolved grain structure became more homogeneous and occupied practically the whole material volume. Electron microscopy showed that a nanocrystalline structure with a crystallite size of 100 -170 nm and a uniform distribution of dispersoids was developed. The deformation structure was characterized by a high dislocation density that is attributed to a decelerating rate of dynamic recovery under decreasing temperature. Note that the structure developed was close in its characteristics to that observed in some fcc or hcp alloys after high pressure torsion at room temperature. However, in the last case, the sample dimensions were significantly smaller than after MIF.Keywords: aluminum alloy, multidirectional forging, microstructural evolution, nanocrystalline structure. Изучали структуру литого и гомогенизированного алюминиевого сплава 1570C (Al5Mg0.18Mn0.2Sc0.08Zr, вес. %) после всесторонней изотермической ковки (ВИК). Ковку проводили со степенью однократной осадки 0,7, скоростью деформации ~10 -2 с -1 и понижением температуры с 450°C в каждом проходе на 25°С. Пластичность сплава в процессе ВИК оказалась достаточной для деформирования заготовки без образования трещин до суммарной степени дефор-мации е ~ 10.5, достигаемой при 100°С. Структурный анализ показал, что в исходном состоянии сплав имел круп-нозернистую структуру с размером зерна ~25 мкм и равномерным распределением наноразмерных алюминидов Al 3 (Sc,Zr). ВИК приводила к непрерывному измельчению зерен и упрочнению материала. При относительно малых степенях (е ≤ 4.2) и высоких температурах деформации (Т > 325°С) новые мелкие зерна зарождались преимуществен-но в области мантии исходных зерен, в результате чего формировалась бимодальная структура, которая сохранялась до е ~ 6.3 (250°С). При дальнейшей ВИК формирующаяся структура становилась более гомогенной и занимала прак-тически весь объем исследованного материала. Электронно-микроскопические исследования показали, что после ВИК была сформирована нанокристаллическая структура с размером кристаллитов ~100 -170 нм и однородным распределением дисперсоидов. Для деформационной структуры была также характерна высокая плотность ...

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Ultra-Fine Grain Development in an AZ31 Magnesium Alloy during Multi-Directional Forging under Decreasing Temperature Conditions

Cited by 99 publications

References 10 publications

Mechanical Properties of Magnesium Alloy AZ31 after Severe Plastic Deformation

Mechanical Properties of Magnesium Alloy AZ31 after Severe Plastic Deformation

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

Structure of the aluminum alloy 1570C subjected to multidirectional forging with decreasing temperature

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