The Experts below are selected from a list of 366 Experts worldwide ranked by ideXlab platform
Xiang Zhao - One of the best experts on this subject based on the ideXlab platform.
-
DIFFUSION-CONTROLLED PHASE TRANSFORMATION UNDER HIGH MAGNETIC FIELD IN MEDIUM AND HIGH CARBON SteelS
2016Co-Authors: Y. D. Zhang, Claude Esling, Xiang Zhao, L. ZuoAbstract:grain elongation Abstract. The new phase equilibrium of Fe-C diagram under magnetic field has been theoretically calculated. Results show that the magnetic field mainly shifts the γ⁄α+γ equilibrium line and the eutectoid point to the high carbon and high temperature sides. Based on this result, an experimental setup has been launched to investigate the effect of magnetic field on austenite decomposition in medium carbon and high carbon Steels. The thermodynamic and kinetic effects of the high magnetic field on proeutectoid transformation at different cooling rates have been studied. It was found that for medium carbon Steels, the magnetic field increases the amount of proeutectoid ferrite and accelerates the diffusional decomposition of austenite at medium and relatively fast cooling rates (10°C/min and 46°C/min). But there is no special grain growth along the field direction. The results led to a proposal of a new rapid annealing under a high magnetic field. However, when cooling is slow (2°C/min), the magnetic field shows a strong tendency to promote the proeutectoid ferrite grains to grow along the field direction through the magnetic dipolar interaction, which leads to the formation of an elongated grain structure. Moreover, the magnetic field also exhibits influence on the austenite decomposition in Hypereutectoid Steel by changing the amount of secondary cementite and lamellar spacing of pearlite
-
Microstructural features induced by a high magnetic field in a Hypereutectoid Steel during austenitic decomposition
Scripta Materialia, 2006Co-Authors: Yikun Zhang, M L Gong, G. Vincent, Claude Esling, Xiang ZhaoAbstract:Abstract A 12-T magnetic field was introduced during the austenitic decomposition of a high carbon Steel at various cooling rates. It was found that the magnetic field applied can reduce the amount of proeutectoid cementite, increase the lamellar spacing of pearlite and decrease the frequencies of low angle misorientations in ferrite. The experimental results of this work prove the shift of the eutectoid point to high carbon side and high temperature side by the application of a magnetic field.
Yongning Liu - One of the best experts on this subject based on the ideXlab platform.
-
ultrafine grain effect on pearlitic transformation in Hypereutectoid Steel
Journal of Materials Research, 2013Co-Authors: Fuliang Lian, Hong Ji Liu, Jun Jie Sun, Xue Jiao Sun, Sheng Wu Guo, Yongning LiuAbstract:Pearlitic transformation in an ultrafine-grained (UFG) Hypereutectoid Steel was investigated. The Steel was a plain carbon Steel containing 1.0 wt% C and very few other elements. The UFG samples were prepared by thermomechanical treatment, and an average grain size of approximately 1 μm was achieved. The pearlitic transformation was conducted by heating the UFG samples at 1023 K for different times and then cooling in air. A new pearlitic transformation phenomenon was observed: traditional lamellar pearlite can be observed only when the grain size increases to a dimension larger than approximately 4 μm, which is a critical value. When grain size is smaller than this value, the pearlitic transformation occurs in the form of divorced eutectoid, and the microstructure is the ferrite matrix with granular cementite. This research indicates that grain size has a great influence on pearlitic transformation by shortening the diffusion distance and increasing the diffusion rate of carbon atoms in the UFG Steel.
-
Pearlitic Transformations in an Ultrafine-Grained Hypereutectoid Steel
Metallurgical and Materials Transactions A, 2011Co-Authors: Yongning Liu, Guangjin Peng, Fuliang LianAbstract:Common Steels of both hypo- and Hypereutectoid compositions form pearlitic or martensitic constituents when cooled from austenite temperature in air or in water. Here, we provide evidence that this is not the case in an ultrafine-grained Hypereutectoid Steel. In this system, when the grain size was reduced to a scale of 2 to 4 μm, normal pearlite could not be obtained when the Steel was cooled in air; instead, nanometer-sized granular cementite and ferrite were formed in the eutectoid transformation. When the cooling rate was increased by quenching in saltwater, martensite was no longer formed; instead, fine lamellar pearlite was formed. This research indicates that these abnormal phase transformations were related to the rapid diffusion present in the ultrafine-grained Steel, which changed the diffusive transformations.
M Benito - One of the best experts on this subject based on the ideXlab platform.
-
high hardness and retained austenite stability in si bearing Hypereutectoid Steel through new heat treatment design principles
Materials & Design, 2018Co-Authors: Thomas Sourmail, F G Caballero, F Moudian, David De Castro, M BenitoAbstract:Abstract Austempering, and quenching and tempering heat treatments of high Si hyper-eutectoid Steels are investigated using both dilatometry and salt-bath heat treatments. Changes in retained austenite content are measured using X-ray diffraction. Results are compared to the prevailing theory for bainite formation and published data. From the understanding of retained austenite evolution during tempering, a novel heat treatment is designed which is technologically identical to quenching and tempering with the exception that the principles guiding the selection of tempering temperature and duration are different. This heat treatment is shown to lead to a combination of hardness, retained austenite content and thermal stability entirely unprecedented for this category of alloys. In addition, this result is achieved for heat treatment durations that can be considered standard. In comparison, low temperature austempering is shown to require considerably longer holding durations to achieve somewhat lower combinations of hardness and retained austenite content.
Wei Liu - One of the best experts on this subject based on the ideXlab platform.
-
Effects of high magnetic field on isothermal pearlite transformation and microstructure in a Hypereutectoid Steel
Journal of Magnetism and Magnetic Materials, 2014Co-Authors: Wei LiuAbstract:Abstract A high magnetic field was applied during the isothermal pearlite transformation of a Hypereutectoid carbon Steel at three different temperatures. It was found that the magnetic field applied can increase the transformation rate and the pearlite nodule growth rate, decrease the interlamellar spacing of pearlite and the amount of low angle boundary in ferrite lamella. The magnetic field effects are more obvious at high temperature. The mechanism of field-effect was discussed by analyzing the influences of high magnetic field on the eutectoid temperature, diffusion activation energy in austenite, Gibbs free energy of ferrite and dislocation mobility.
Pietro Mario Lugarà - One of the best experts on this subject based on the ideXlab platform.
-
Discrete spot laser hardening and remelting with a high-brilliance source for surface structuring of a Hypereutectoid Steel
Materials and Design, 2017Co-Authors: Luca Tricarico, Donato Sorgente, Antonio Ancona, Roberto Spina, Gaetano Palumbo, Pietro Mario LugaràAbstract:In this work the single-pulse laser irradiation of a Hypereutectoid Steel was investigated using a fiber laser source, in a range of process parameters enabling surface hardening and remelting. Effects of laser power, pulse energy and defocusing distance were investigated using a numerical/experimental approach. Laser surface treatments were conducted on uncoated samples without any gas shielding, changing both the laser power and the pulse energy, and exploring a wide range of defocusing distances. Numerical simulations were conducted using a finite element model calibrated by means of an optimization procedure based on a specific calculation algorithm and using a subset of experimental data producing surface melting. Using both simulations and experiments, the process operating windows of the discrete spot laser treatment were determined: it was found that, when varying the laser power between 250 W and 750 W, melt-free hardened zones are produced with a maximum extension between 0.7 mm and 1.0 mm; on the contrary, in case of more tightly beam focusing conditions, surface melting occurred with a size of the re-melted areas ranging between 1.0 mm and 1.4 mm. Results further showed that a small change (generally 2–3 mm) of the defocusing distance suddenly brings the material from melting to a non-hardening condition.