Papers by Keyword: Zener-Hollomon Parameter

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Authors: Auchariya Aungsusiripong, Surasak Suranuntchai, Vitoon Uthaisangsuk
Abstract: In this work, plastic flow behavior of an as-cast manganese aluminum bronze was investigated under various compressive deformation conditions. The forming temperatures of 1023, 1073, 1123 and 1173 K and strain rates of 0.01, 0.1, 1.0 and 10 s-1 were considered. It was found that all obtained stress-strain responses of manganese aluminum bronze showed a single peak stress that afterwards approached a steady flow stress. Additionally, constitutive equations based on the Arrhenius model were applied for describing the determined flow stresses, in which Zener-Hollomon parameter in a hyperbolic-sine function was taken into account. By the flow stress modeling, the activation energy of about 194 kJ/mol was calculated for the examined manganese aluminum bronze.
442
Authors: S.V.S. Narayana Murty, Shiro Torizuka, Kotobu Nagai
Abstract: During large strain deformation of materials, the width of the initial high angle grain boundaries approaches the order of mean diffusion distances encountered during elevated temperature deformation. Since the evolution of ultrafine grains is attributed to thermally activated processes, the role of interfaces in determining the grain size is significant. In order to investigate into this role, microstructure development in low carbon steel (0.15% C) subjected to large strain deformation was studied with specific reference to the controlling mechanism of ferrite grain size evolution. Plane strain compression tests have been conducted in the temperature range of 773-923K at strain rates of 0.01 s -1 and 1 s-1 and the specimens were deformed to 25% of the original thickness and the Microstructural evolution is studied. Based on the results obtained, diffusion along grain boundaries was found to be the mechanism controlling ferrite grain size in this material processed through large strain deformation.
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Authors: Chao Bei Hu, Bao Feng Guo, Yongtao Zhang, Miao Jin, Guan Qiang Yang, Ming Fang Ma
Abstract: Calculation of the critical condition for the initiation of DRX is of considerable interest for the modeling of industrial processes but it strongly depends on the chemical composition of the material, the grain size prior to deformation, and the deformation conditions ( T and ε ). This paper was therefore to show an approach that allows for accurate but convenient identification of the occurrence of DRX. For a Fe-Cr-Ni super stainless steel, the results show that there is a linear relationship between σc and lnZ ( σc=457.26-12.52lnZ). In addition, within the entire range of temperature and strain rate studied, it can be found that the values of both σc and σp or εc and εp keep similar variation trends, respectively. Finally, it was found that the critical ratios of both σc/σp and εc/εp remain fairly constant (≈0.92 and ≈0.47, respectively).
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Authors: Tamás Mikó, Peter Barkoczy
Abstract: This paper presents an investigation about the occurrence of the dynamic recrystallization (DRX) during hot forming. Two 7075 aluminum alloy samples in different initial states were examined by compression tests at temperatures between 573 K and 723 K and constant strain rates ranging from 0.002 to 2 (s-1) with the maximum strain of 0.5 mm/mm. The activation energies of the examined aluminium were calculated, being 137.7 kJ/mol and 142.4 kJ/mol. The critical stresses and strains for the initiation of the dynamic recrystallization were determined using a numerical method based on the changes of the work hardening rate (θ) as a function of the flow stress (σ) or a strain (ε), respectively. Based on the micrographs taken after the deformations it was revealed that in some cases only dinamyc recovery (DRV) whereas in others DRX occurred under the applied examination conditions. The critical stress which belongs to the onset of the DRX or the DRV depend on the temperature, the strain rate, and the initial grain size. The critical and maximal stresses and the corresponding strain values at different conditions were determined. In the examined range of deformation, temperature and strain rate, the critical rations are σ_c/σ_p= (0.93-0.99) and εc/ εp = (0.3-0.74), respectively.
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Authors: M. Honda, Tokuteru Uesugi, Yorinobu Takigawa, Hiroshi Mabuchi, Kenji Higashi
Abstract: Dynamic recrystallization behavior that occurs during the hot extrusion was examined in two commercial Mg alloys, AZ31 and AZ80 alloys. The initial grain size, d0, and the dynamically recrystallized grain size, drec, after the extrusion was investigated using optical microscopy. The dynamically recrystallized grain size decreased with an increasing the Zener-Hollomon parameter.
449
Authors: T. Noro, Tokuteru Uesugi, Yorinobu Takigawa, Masato Tsujikawa, Hiroshi Mabuchi, Kenji Higashi
Abstract: Dynamic recrystallization behavior of Mg-3.1wt.%Al-0.1wt.%Y alloy was investigated. During extrusion, dynamic recrystallization occurred and very fine microstructure was obtained. We compared the relationship between Zener-Hollomon parameter, Z, and the dynamically recrystallized grain size, drec, and between the normalized recrystallized grain size, drec/d0, where d0 is the initial grain size, and Z for Mg-3.1wt. %Al-0.1wt.%Y with commercial Mg-3Al-0.5Zn alloy. As the result, the dynamically recrystallized grain size of Mg-3Al-0.1Y was finer than that of Mg-3Al-0.5Zn alloy under the equivalent Z, while the initial grain size of Mg-3Al-0.1Y was coarser than Mg-3Al-0.5Zn alloy. The normalized grain size for Mg-3Al-0.1Y alloy was much smaller than that of Mg-3Al-0.5Zn alloy under the equivalent Z. We conclude that small addition of Y to Mg-Al alloys is effective for grain refinement by dynamic recrystallization.
433
Authors: Suk Bong Kang, H.S. Ko, Hyoung Wook Kim, S.T. Lee
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Authors: Tokuteru Uesugi, Hideaki Iwami, Yorinobu Takigawa, Kenji Higashi
Abstract: Friction stir processing (FSP) is one of the severe plastic deformation (SPD) processes. It has been reported that SPD-processed Al with various purities attained a minimum grain size when Zener-Hollomon parameter is larger than 1016 s-1. The minimum grain size is different by purity level and alloying elements. We investigated the influence of Fe solute atoms on grain refinement of high-purity Al on the condition that Zener-Hollomon parameter was larger than 1016 s-1. FSP was conducted on Al-0.01%Fe, which was fabricated by using 5N Al (99.999% purity). FSP-ed Al-0.01%Fe exhibits the minimum grain size of 1.4 μm, although high-purity aluminums with more than 99.998% exhibits much larger minimum grain sizes of 30-40 μm. Only 101 at.ppm Fe played a critical role in the grain refinement of pure aluminums.
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Authors: Yi Zhang, Bao Hong Tian, Ping Liu
Abstract: The hot deformation behavior of Cu-Ni-Si-P alloy have been investigated by means of isothermal compression tests on a Gleeble-1500D thermal mechanical simulator in the temperature ranges of 873-1073 K and strain rate ranges of 0.01-5s-1. The results show that the dynamic recryatallization occurs in Cu-Ni-Si-P alloy during hot deformation. The peak stress during hot deformation can be described by the hyperbolic sine function. The influence of deformation temperature and strain rate on the peak stress can be represented using the Zener-Hollomon parameter. Moreover, the activation energy for hot deformation of Cu-Ni-Si-P alloy is determined to be 485.6 kJ / mol within the investigated ranges of deformation temperature and strain rate. The constitutive equation of the Cu-Ni-Si-P alloy is also established. Keywords: Cu-Ni-Si-P alloy; Hot deformation; Dynamic recrystallization; Zener-Hollomon parameter.
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