Microstructural-mechanism relationship in the zinc/ aluminium eutectoid superplastic alloy

Naziri, H.; Pearce, R.; Brown, Matthew L.; Hale, K. F.

doi:10.1016/0001-6160(75)90088-7

Cited by 70 publications

(17 citation statements)

References 14 publications

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“…In the previous reports, the average grain sizes in Zn-22Al alloys processed by only quenching were about 0.6-0.8 mm. [24][25][26] The grain refinement during ECAE at room temperature was verified in the present investigation. The diffraction spots corresponding to Al and Zn were also observed as shown in Fig.…”

Section: Methodssupporting

confidence: 75%

“…2, which includes the results of earlier reports, 7,20,[24][25][26] as well. The strain rate sensitivity exponent (m-value) is defined in the equation (d ln =d ln _ " ") where is the flow stress and _ " " is the strain rate.…”

Section: Resultsmentioning

confidence: 99%

“…In order to compare the present data with other high temperature superplastic behaviors, 7,18,19,[24][25][26][32][33][34][35][36] normalized strain rate, _ " "ðkT=D gb GbÞðd=bÞ 2 , as a function of normalized stress, ð À 0 Þ=G, is plotted in Fig. 6, where Q ¼ 60:5 kJ/mol.…”

Section: Resultsmentioning

confidence: 99%

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Superplasticity at Room Temperature in Zn-22Al Alloy Processed by Equal-Channel-Angular Extrusion

Tanaka

Higashi

2004

Mater. Trans.

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Equal-Channel-Angular extrusion (ECAE) has been conducted at room temperature in order to develop an ultrafine-grained structure in a Zn-22 mass% Al eutectoid alloy. The microstructures had an equiaxed and homogeneously distributed Al-rich and Zn-rich duplex-phase and its average grain size was about 0.35 mm. This alloy exhibited a large elongation of 240% albeit at room temperature and a high strain rate of 10 À2 s À1 . A grain-size-dependent phenomenon was also observed at lower strain rates. The activation energy was close to that for grain boundary diffusion. It was apparent that the deformation behavior at room temperature is consistent with that observed in conventional superplasticity. From the results, it was concluded that the dominant deformation mechanism was grain boundary sliding accommodated by dislocation movement controlled by grain boundary diffusion.

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Section: Methodssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

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Superplasticity at Room Temperature in Zn-22Al Alloy Processed by Equal-Channel-Angular Extrusion

Tanaka

Higashi

2004

Mater. Trans.

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“…It has been reported that an ultrafine-grained Zn-Al system alloy exhibited significant elongation at room temperature. [16][17][18][19][20][21][22][23][24][25] Very recently, in order to produce large and bulky materials to serve as damping substances in buildings, Makii et al 26) developed a new technique using thermomechanical controlling process (TMCP) technology, and reported that the material had Zn particles 50 nm in diameter and exhibited large uniform elongation even at room temperature. Though SePD processes are efficient for obtaining equiaxed and ultrafinegrained materials, the techniques are not suitable to produce materials large enough for service as seismic dampers.…”

Section: Introductionmentioning

confidence: 99%

Room Temperature Deformation Behavior of Zn-22 mass%Al Alloy with Nanocrystalline Structure

et al. 2002

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The deformation behavior near room temperature in Zn-22 mass%Al alloy including nanocrystalline structure produced with Thermo Mechanical Controlling Process (TMCP) technology has been characterized over a wide range of strain rates from 10 −6 to 10 −1 s −1 at temperatures from 273 to 473 K. The microstructure of TMCP produced Zn-22 mass%Al alloy had both a random distribution of equiaxed Al-rich and Zn-rich phases with grain size of 1.3 µm and many nanocrystalline Zn particles in Al-rich phases. Since the flow stress in the deformation near room temperature was much larger than that in superplastic deformation and a maximum m value is only 0.3 (n = 3) at low strain rates below 10 −5 s −1 , the pure superplastic behavior may not be observed near room temperature. However it is noted that the large elongation of ∼ 200% was observed at 10 −5 s −1 . From microstructural observations of the specimens tested in the condition with the m value of 0.3 near room temperature, furthermore, it is considered that grain boundary sliding (GBS) is the dominant deformation process, and the specimen may be fractured by cavitation as well as the conventional superplastic materials. Therefore, it seems that the various factors contribute to the deformation flow at room temperature.

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“…However, considering the superplastic deformation at RT chemical composition of the phase boundaries becomes more important than microstructural stability in Zn-Al alloys due to the low deformation temperature. It is known that GBS as the dominant deformation mechanism occurs mainly at the η / η and η / α phase boundaries and the α / α phase (or grain) boundaries do not slide easily in the Zn-Al alloys [31][32][33][34]. Decreasing the Al content in the ZnAl alloys decreases the possibility of α / α phase boundary formation.…”

Section: Effects Of Grain Size and Chemical Composition On Rt Superplmentioning

confidence: 99%

Effect of chemical composition and grain size on RT superplasticity of Zn-Al alloys processed by ECAP

Demirtas¹,

Pürçek²,

Yanar³

et al. 2015

LoM

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Dilute Zn-0.3Al, eutectic Zn-5Al and eutectoid Zn-22Al alloys were processed by multi-pass equal channel angular pressing (ECAP) in order to achieve fine grained (FG) or ultrafine-grained (UFG) microstructure and room temperature (RT) superplasticity. ECAP refined the microstructure of Zn-0.3Al and resulted in a FG Zn-rich η-matrix with an average grain size of 2 µm and homogeneously distributed nano-sized Al-rich α-particles with the grain sizes in the range of 50-200 nm. A bi-modal microstructure was achieved in Zn-5Al alloy with UFG Al-rich α-and FG Zn-rich η-phases having mean grain sizes of 110 nm and 540 nm, respectively. ECAP brought about an agglomerate-free UFG microstructure in Zn-22Al alloy with an average grain size of 200 nm which is the lowest one obtained so far for this alloy after ECAP processing. The maximum RT superplastic elongations of 1000%, 520% and 400% were achieved for Zn-0.3Al, Zn-5Al and Zn-22Al alloys, respectively. Considering the RT superplasticity in Zn-Al alloys, it was found that lower Al content results in higher superplastic elongations even if the alloy has relatively larger grain size. Grain boundary sliding (GBS) was found to be the main deformation mechanism in region-II as the optimum superplastic region during RT deformation for all three Zn-Al alloys with the strain rate sensitivity factor ranging between 0.25-0.31.Keywords: Zn-Al alloys, room temperature superplasticity, ultrafine-grained materials, equal channel angular pressing Влияние химического состава и размера зерен на сверхпластичность при комнатной температуре сплавов Zn-Al, подвергнутых РКУП Низколегированный сплав Zn-0.3Al, эвтектик Zn-5Al и эвтектоидный сплав Zn-22Al были подвергнуты многопро-ходному равноканальному угловому прессованию (РКУП) с целью получения мелкозернистой (МЗ) или ультрамел-козернистой (УМЗ) структуры и достижения сверхпластичности при комнатной температуре. РКУП привело к из-мельчению микроструктуры Zn-0.3Al и формированию МЗ обогащенной Zn η-матрицы со средним размером зерен 2 мкм и однородно распределенных наноразмерных богатых Al α-частиц с размером в интервале 50-200 нм. В сплаве Zn-5Al была получена бимодальная структура с УМЗ богатой Al α-фазой и МЗ богатой Zn η-фазой, имеющими соответственно размеры зерен 110 нм и 540 нм. В сплаве Zn-22Al РКУП привело к формированию не агломериро-ванной УМЗ микроструктуры со средним размером зерен 200 нм, что представляет собой минимальное достигнутое к настоящему времени значение размера зерен, полученное РКУП на данном сплаве. Для сплавов Zn-0.3Al, Zn-5Al и Zn-22Al были получены максимальные сверхпластические удлинения при комнатной температуре, равные соот-ветственно 1000%, 520% и 400%. По отношению к сверхпластичности сплавов Zn-Al показано, что более низкое содержание Al приводит к более высоким сверхпластическим удлинениям, даже если сплав имеет больший размер зерен. Показано, что зернограничное проскальзывание (ЗГП) является основным механизмом деформации в обла-сти II, являющейся оптимальной областью сверхпластической деформации при комн...

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Microstructural-mechanism relationship in the zinc/ aluminium eutectoid superplastic alloy

Cited by 70 publications

References 14 publications

Superplasticity at Room Temperature in Zn-22Al Alloy Processed by Equal-Channel-Angular Extrusion

Superplasticity at Room Temperature in Zn-22Al Alloy Processed by Equal-Channel-Angular Extrusion

Room Temperature Deformation Behavior of Zn-22 mass%Al Alloy with Nanocrystalline Structure

Effect of chemical composition and grain size on RT superplasticity of Zn-Al alloys processed by ECAP

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