Papers by Keyword: Static Recrystallization

Abstract: The effect of various deformation degree and temperature on static recrystallization of 304 stainless steel during two-passes hot compression deformation with the strain rate of 0.1s-1 was investigated by use of Gleeble-1500D thermo-mechanical simulation. It is indicated that deformation degree is the most obvious factor to static recrystallization. Besides, the grain sizes after deformation were also measured by metallographic method. The results show that the grain sizes decreased dramatically with the conditions of deformation temperature (1050°C), holding time (30s) and total deformation degree (0.35). The result has provides the corresponding scientific basis for the quality forecast of 304 stainless steel during hot thermoplastic deformation.

Abstract: The effect of Al addition on the static softening behavior of C-Mn steels was investigated. The compositions of the steels studied are representative of the recently developed TRIP-assisted steels: a base composition of 0.2%C, 2%Mn, 50ppm N and three different Al levels, 0.03 (base steel), 1 and 2%. Double-hit torsion tests were performed at different deformation temperatures, in the range 950°C to 1100°C, and pass-strains, =0.2 and 0.35. It was found that solute Al produced a significant retardation on static recrystallization kinetics, equivalent to that exerted by 0.026%Nb for the 1%Al steel and to 0.05%Nb for the 2%Al steel. Additionally, at the lowest temperatures (950-1000°C) and 2%Al level, austenite to ferrite phase transformation was found to be concurrent with softening, enhancing retardation in the mechanical softening.

Abstract: The Plane Strain Compression and Static Recrystallisation Textures of BCC Metals Have Been Simulated Using a Coupled 3D Crystal Plasticity Finite Element (CPFE)-Single Phase Field (PF) Model Using an Interstitial-Free (IF) Steel as an Example. the Recrystallisation Nucleation Is Modelled Based on the Orientation Dependent Recovery (ODR) Theory which Assumes that Deformation Texture Components with a Relatively High Number of Slip Systems Activated during the Plane Strain Compression Undergo a Faster Recovery Process during the Subsequent Annealing due to the Cross Slip of Dislocations and as a Result Will Nucleate Earlier than Others. the Growth of Strain-Free Grains Is Simulated Using the Mis-Orientation Angle Dependent Grain Boundary Energy and Interface Mobility. A Linear Interpolation Method Is Adopted to Map the Data between the CPFE Model of Deformation and the Single PF Model of Recrystallisation. Simulated Results Show a Qualitative Agreement with the Typical Rolling and Annealing Textures Measured Experimentally for BCC Metals. Apart from the Texture and Grain Structure Formed during Deformation and Annealing, the Softening Fraction Can Also Be Simulated Using the Developed Model.

Abstract: Avoiding recrystallization of austenite in hot strip rolling of steels is highly important for enhancing mechanical properties of hot rolled products, as well as for the products undergoing cold rolling and annealing or coating. Recrystallization can only be avoided if its incubation time is longer that the time intervals characteristic for a particular hot rolling process. The present work focuses on computation of incubation time t_inc for static recrystallization using laboratory hot deformation data and on extrapolation the results to industrial conditions. The computations are done based on application of critical conditions for initiation of dynamic recrystallization to the static case. No-recrystallization temperature in hot strip rolling is determined by setting t_inc equal to interpass time. Simulations allow for prediction of the onset of austenite static or metadynamic recrystallization after individual rolling passes during industrial hot rolling and evaluation of the effects of strip thickness, rolling speeds, etc.

Abstract: The model of cellular automaton (CA) for simulating the static recrystallization of Nb micro alloyed steel after hot deformation was established. The static precipitation of micro alloyed elements on the impact of static recrystallization was considered in the mode. The microstructure evolution of austenite static recrystallization of Nb micro alloyed steel was simulated dynamically, such as the the volume fraction, kinetics curve of static recrystallization, dislocation density and grain shape, were quantitatively, accurately and visually described. According to the simulation results by cellular automaton, the effects of the deformation temperature, strain rate, and other processing parameters on the microstructure of the austenite static recrystallization of Nb micro alloyed steel were analyzed. The simulation results could provide a theoretical reference for the control of the microstructure and property of Nb micro alloyed steel.

Abstract: The static recrystallization and precipitation behavior of weathering steel were studied using thermal simulation technology. The influence of temperature and interval time was analyzed and the softening percentage of static recrystallization was calculated. The morphology and distribution of precipitates were studied, and the driving force for static recrystallization and pinning force of precipitation were calculated. Results show that the higher the deformation temperature is, the faster static recrystallization proceed. Retardation of recrystallization could occur even in the early stage of precipitation. The precipitation pinning force showed a peak in the intermediate stage, and finally decreased as particles coarsened.

Abstract: Softening behavior of deformed austenite zone of E36 ship plate in hot continuous rolling process was studied with double passes compression experiments, including cases in different deformation temperature and time span. Analyzing the influence of different factors on the softening ratio of static recrystallization. The results show that deformation temperature is the main factor to influence the recrystallization. When the deformation temperature being achieved, static recystallization ratio increases step by step with time span extending. The best time span was got and the softening ratio curve was verified through metallographic analysis, and the activation energy was obtained. Dynamic model of static recystallization was built at the end.

Abstract: An integrated crystal plasticity-phase field model has been developed to simulate the static recrystallisation textures of both Face-Centred Cubic (FCC) and Body-Centred Cubic (BCC) metals. Nucleation sites are determined using the Orientation Dependent Recovery (ODR) theory. Both the interface mobility and the grain boundary energy are set to be dependent on mis-orientation angles in the simulations. A pre-deformed microstructure without a particular texture is generated using a Monte Carlo simulation. Plane strain compression textures before recrystallisation are predicted by a Crystal Plasticity Finite Element (CPFE) model showing a good agreement with the typical experimental rolling textures. It is shown that the typical recrystallisation textures for FCC and BCC metals can be simulated correctly using a Phase Field (PF) method by choosing appropriate critical values for the nucleation criterion. A comparison between the two different nucleation criteria based on the ODR theory or the stored energy is also presented.

Abstract: A multi-state free energy function for deformation alloy with storage energy is proposed to simulate the microstructure evolution of static recrystallization with phase field model. The grain growth and grain size distribution during recrystallization are discussed. The simulation results are in good agreement with other theoretical or experimental results.

Abstract: Two 5Mn-1.5Al TRIP steels with and without Nb microaddition were developed in the present study. The steels contain bainite, martensite, interlath retained austenite and martensite- austenite islands. The paper presents the results of the compression tests carried out at various temperatures using the Gleeble simulator. To analyze the kinetics of static recrystallization in these steels, a softening kinetics were determined in a double-hit compression test. It was found that the dynamic recovery is a main thermally activated process occurring during hot deformation. The Nb microalloyed steel has higher flow stresses and peak strains than the Nb-free steel. A solute drag effect of Nb results in a slower softening kinetics of Nb containing steel. The effects of Mn on the retardation of Nb(C,N) precipitation and hot deformation characteristics are also discussed.