Papers by Keyword: Isothermal Deformation

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Authors: Shamil Kh. Mukhtarov, Vener Valitov, M.F.X. Gigliotti, P.R. Subramanian, J.S. Marte, Nadya Dudova
Abstract: The influence of severe thermomechanical treatment via multiple forging on the formation of a nanocrystalline (NC) structure in bulk samples of Alloy 718 and ATI 718Plus has been investigated. It was observed that a step-wise decrease of processing temperature from 950 down to 575°C allowed the refinement of the initial coarse grain structure to a NC state. Investigations of structural changes in the deformed samples have shown that extending the temperature interval of dynamic recrystallization to low homologous temperatures resulted in the formation of a fine-grained recrystallized structure. The temperature of NC structure formation in ATI Alloy 718Plus was 50-100°С higher than that required for alloy 718. This was due to the presence of the additional γ′-phase, which increased the recrystallization temperature. This decreased the total strain required to produce NC structure, as compared with Alloy 718. It was observed that increasing the total strain and decreasing temperatures step-wise during deformation via multiple forging resulted in a uniform structure across the cross-section of the samples. The room temperature mechanical properties of the investigated alloys with various grain sizes are also compared.
Authors: Xu Bin Li, Zhi Min Zhang
Abstract: In this paper, rigid plastic finite element method simulation of AZ31 wrought magnesium alloy radiator isothermal extrusion is studied according to the stress - strain data of magnesium alloy obtained from isothermal compression experiments and the mathematical model of warm forming by the regression. And the paper focuses on the AZ31 magnesium alloy during isothermal extrusion, the deformation force and metal flowing law. The simulated stress field, strain field, velocity field, load changes and so on from simulation can predict the defect in deformation, and offer the reliable reference basis for such parts processing in isothermal extrusion.
Authors: Shuang Fang, Min Cong Zhang, Yun Peng Dong, Shu Yun Wang
Abstract: The samples with a length of 50mm and cross section area of 20mm2 were machined from extruded P/M Nickel-base superalloy billet and the isothermal deformation tests were carried out at constant strain rate in a vacuum environment using the Thermecmastor. All the samples were deformed to a true strain of 1.04 at deformation temperature 1070°C and 1100°C and strain rate 0.001s-1~1s-1 respectively. The result is the deformation strain rate determine the position and the deformation temperature determine the severity of abnormal grain growth (AGG). The initial grain size and dislocation density is not the only reason to AGG. The AGG is related the recrystallization nucleation process is inhibited in the heat treatment. The AGG region usually has more low energy and low migration rate boundary than other regions.
Authors: Yong Wei Wang, Lu Yi Yang, Wei You, Bing Zhe Bai
Abstract: The influence of temperature, strain rate, strain on mechanical parameters and microstructure evolution in isothermal deformation of GH4169 alloy were investigated. Lower resistance is obtained under higher temperature and or lower strain rate. However, coarser microstructure also is gained under such condition. The tensile property at room temperature and elevated temperature, permanent properties at elevated temperature of the GH4169 alloy with the treatment of “direct aging after isothermal deformation” are better than those of the same alloy with the treatment of solid-solution+direct aging after isothermal deformation. Isothermal forming was undertaken for a 1/4 size simulated part of a kind of turbo disk of an aviation engine. Its external is fine and the microstructure of the material was fine and homogeneous for both straightly after forming and after direct aging.
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