The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Tadashi Furuhara - One of the best experts on this subject based on the ideXlab platform.
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Microstructure evolution during deformation of a near-α titanium alloy with different Initial structures in the two-phase region
Scripta Materialia, 2009Co-Authors: Behrang Poorganji, Goro Miyamoto, Makoto Yamaguchi, Yoshio Itsumi, Katsushi Matsumoto, Tomofumi Tanaka, Yusuke Asa, Tadashi FuruharaAbstract:The effects of Initial Microstructure on the Microstructure evolution of a Ti–1.5Fe (mass%) alloy during deformation in the (α + β) two-phase region are studied at different deformation temperatures. Refining interlamellar spacing and colony size of the (α + β) lamellar structure by quenching after β solutionizing results in promotion of dynamic recrystallization.
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formation of ultrafine grained ferrite by warm deformation of lath martensite in low alloy steels with different carbon content
Scripta Materialia, 2008Co-Authors: Behrang Poorganji, Goro Miyamoto, T. Maki, Tadashi FuruharaAbstract:Formation of ultrafine grained ferrite by warm deformation of tempered lath martensite was investigated in Fe–2Mn–(0.1–0.8)C (mass%) alloys. Analysis of Initial Microstructure shows that an increase in carbon content leads to a decrease of lath martensite block size. Fine equiaxed (α) grains surrounded by high-angle boundaries are formed by dynamic recrystallization. As carbon content increases, the recrystallized α grain size decreases. It is considered that dynamic recrystallization of tempered lath martensite is a continuous type.
Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.
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effect of Initial Microstructure on ti 6al 4v joint by friction stir welding
Materials & Design, 2015Co-Authors: Sungook Yoon, Rintaro Ueji, Hidetoshi FujiiAbstract:Abstract Ti–6Al–4V alloy plates with three types of Initial Microstructures, which have different densities of the high angle boundaries, were joined by friction stir welding (FSW), and the Microstructure evolution in the stir zone by the FSW was clarified. Concerning the morphology of the Microstructure, all three joints show similar characteristics; the top surface of the SZs exhibited a mixture of the lamellar structure with equiaxed α grains and the area fraction of the equiaxed α grain gradually increased with the increasing distance from the top surface due to the temperature gradient. On the other hand, the mean α grain size of the fully equiaxed α structure area decreased with the increasing Initial density of high angle boundaries. This accelerated grain refinement was discussed based on the effect of the inhomogeneous Microstructure on the recrystallization.
Elisabeth Aeby-gautier - One of the best experts on this subject based on the ideXlab platform.
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Influence of the ageing conditions and the Initial Microstructure on the precipitation of α phase in Ti-17 alloy
Journal of Alloys and Compounds, 2018Co-Authors: Nicolas Maury, Moukrane Dehmas, Benoît Denand, Claude Archambeau-mirguet, Jérôme Delfosse, Elisabeth Aeby-gautierAbstract:The precipitation of α phase during ageing was investigated in the near-β titanium alloy Ti-17 considering either a fully βmetastable Initial Microstructure or a 35% αprimary + 65% βmetastable Initial Microstructure. In-situ electrical resistivity and high energy X-ray diffraction measurements revealed the influence of the Initial Microstructure, with different α morphologies (size and distribution of αprimary), as well as the heating rate on the precipitation sequences and kinetics following the decomposition of the β-metastable phase. Various amounts of metastable phases (ωisothermal and α″isothermal) precipitate in temperature ranges that increase with the heating rate. From temperatures about 500 °C, the orthorhombic α″isothermal structure evolved towards the hexagonal close-packed α as temperature increased. SEM Microstructure characterisations showed that slow heating rates promoted a fine and dense α precipitate distribution through the formation of ωisothermal and/or α″isothermal, leading to higher hardness values. A higher heating rate restricted the precipitation of α″isothermal and shifted to the one of α at a higher temperature, leading to coarser precipitates. Furthermore, precipitation kinetics of α″isothermal/α were quicker considering an Initial intragranular α precipitation as compared to α colonies.
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In situ synchrotron X-ray diffraction and dilatometric study of austenite formation in a multi-component steel: Influence of Initial Microstructure and heating rate
Acta Materialia, 2014Co-Authors: Vladimir A. Esin, B. Denand, Quentin Le Bihan, Moukrane Dehmas, Julien Teixeira, Guillaume Geandier, Sabine Denis, T. Sourmail, Elisabeth Aeby-gautierAbstract:The formation of austenite during both slow and fast heating (0.25–100 °C s−1) was investigated for different Microstructures of a selected low-alloy steel. With the simultaneous use of dilatometry and high-energy X-ray diffraction, it was possible to follow not only the global progress of the austenitization, but also the individual evolutions of each phase (ferrite, cementite and retained austenite if present in the Initial Microstructure). The results confirm earlier published data regarding the ease of austenitization of different Initial Microstructures (ferrite–pearlite, bainite and tempered martensite). More importantly, two stages were clearly identified, corresponding to the simultaneous transformation of ferrite and cementite, followed by the progressive disappearance of the remaining ferrite. While this is well known for ferrite–pearlite Microstructures, it is not yet documented for bainite and tempered martensite. Microstructure evolution calculations based on a diffusion-controlled mechanism helped rationalize the differences observed between the three Initial Microstructures. In addition, they also strongly suggested the existence of a critical carbide size beyond which the second austenitization phase would correspond to carbide dissolution instead of ferrite transformation.
Zhiqiang Jia - One of the best experts on this subject based on the ideXlab platform.
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constitutive model of ti17 titanium alloy with lamellar type Initial Microstructure during hot deformation based on orthogonal analysis
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Jianglin Liu, Weidong Zeng, Yunjin Lai, Zhiqiang JiaAbstract:Abstract Isothermal compression tests of Ti17 titanium alloy with the Initial lamellar-type Microstructure at the deformation temperatures and strain rate ranges of 780–860 °C and 0.001–10.0 s −1 , respectively, were conducted on a Gleeble-1500 thermo-mechanical simulator. The flow stresses of all different conditions were obtained. The typical flow curves presented that softening at all the deformation conditions, even at low strain rate (0.001 s −1 ), which have been considered that the flow softening results from lamellar globularization at low strain rates and adiabatic shear bands at high strain rates. According to orthogonal experiment and variance analysis on the significance of strain, strain rate, deformation temperature as well as interaction between strain rate and deformation temperature to the flow stress, the effect of interaction between strain rate and deformation temperature can be neglected in comparison with other factor. Thus, with consideration of strain, strain rate, and deformation temperature, a multivariate nonlinear regression model was established to predict the flow stress in isothermal compression of Ti17 titanium alloy in this paper. Predicted and experimental results show that the developed constitutive equation enables to predict the flow stress accurately throughout the entire domain of temperature and strain rate, excepting at high strain rate (10 s −1 ), deformation temperature 780 °C for Ti17 titanium alloy.
D L Chen - One of the best experts on this subject based on the ideXlab platform.
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hot deformation behavior of ti 6al 4v alloy effect of Initial Microstructure
Journal of Alloys and Compounds, 2017Co-Authors: Zhen Zhang, A H Feng, J Shen, D L ChenAbstract:Abstract The purpose of this study was to identify plastic flow behavior and microstructural evolution during sub-transus hot deformation of a Ti-6Al-4V alloy with three Initial Microstructures (namely, transformed β Microstructure, bimodal Microstructure, and α′ martensitic Microstructure) through compressive deformation at different strain rates in a Gleeble simulator and via SEM and TEM examinations. When deformed at a temperature of 800 °C and 850 °C (below the beta transus temperature of ∼975 °C), samples with a transformed β Microstructure exhibited globularization of lamellar α phase at a strain rate of 10−3 s−1, while adiabatic shear banding occurred at a strain rate above 10−3 s−1 due to the presence of Initial coarse β grains. Equiaxed grain Microstructures were present after hot deformation in the samples containing a bimodal starting Microstructure mainly at lower strain rates, and in the samples with an α′ martensitic starting Microstructure at all strain rates from 10−3 s−1 to 1 s−1. Especially, a homogenous ultra-fine grained structure with an average grain size of 400 nm was achieved at both deformation temperatures at a strain rate of 1 s−1 in the case of α′ martensitic starting Microstructure. The new ultra-fine grains were formed mainly through the phase transformation of α′/α+β and the subsequent continuous dynamic recrystallization during hot deformation. This opens the door to the development of homogenous ultrafine-grained structure from a fully martensitic Initial Microstructure via hot deformation (e.g., hot rolling, extrusion, forging).