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Search Results: 1 - 10 of 1639 matches for " Static Recrystallization "
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Prediction of the Microstructural Variations of Cold-Worked Pure Aluminum during Annealing Process  [PDF]
Hamid Reza Rezaei Ashtiani, Peyman Karami
Modeling and Numerical Simulation of Material Science (MNSMS) , 2015, DOI: 10.4236/mnsms.2015.51001
Abstract: The mechanical properties such as hardness and ultimate tensile strength of metals depend on the grain size, which have to be properly controlled and optimized to ensure the better economy and desirable mechanical characteristics of the metals. In order to study the microstructure evolution of AA1070, many experimental tests were conducted at different cold working and annealing conditions. Utilizing the experimental results, the static recrystallization and grain growth behavior of AA1070 have been investigated and the developed equations that can be used to the FEM of the annealing process have been obtained. The agreement between numerical modeling and experimental results is reasonably good for this material. The results showed that the recrystallization and grain growth behavior of AA1070 was evidently affected by both the annealing temperature and plastic strain.
A Phase-field Model to Simulate Recrystallization in an AZ31 Mg Alloy in Comparison of Experimental Data

Mingtao WANG BYZong Gang WANG School of Materials,Metallurgy,Northeastern University,Shenyang,China,

材料科学技术学报 , 2008,
Abstract: A model has been established to simulate the realistic spatio-temporal microstructure evolution in recrystal-lization of a magnesium alloy using the phase field approach.A set of rules have been proposed to decide the real physical value of all parameters in the model.The thermodynamic software THERMOCALC is applied to determine the local chemical free energy and strain energy,which is added to the free energy density of grains before recrystallization.The Arrhenius formula is used to describe boundary mobility and the activity energy is suggested with a value of zinc segregation energy at the boundary.However,the mobility constant in the formula was found out by fitting to a group of grain size measurements during recrystallization of the alloy.The boundary range is suggested to decide the gradient parameters in addition of fitting to the experimental boundary energy value.These parameter values can be regarded as a database for other similar simulations and the fitting rules can also be applied to build up databases for any other alloy systems.The simulated results show a good agreement with reported experimental measurement of the alloy at the temperatures from 300 to 400℃ for up to 100 min but not at 250℃.This implies a mechanism variation in activity energy of the boundary mobility in the alloy at low temperature.
Effects of Nb, Ti and V on recrystallization kinetics of austenite in microalloyed steels
M. Opiela,W. Ozgowicz
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The work presents research results of impact of Nb, Ti and V microadditions on flow stress, recrystallization kinetics and microstructure of newly elaborated steels assigned for production of forged machine parts, using the method of thermo-mechanical treatment.Design/methodology/approach: The study was performed with the use of Gleeble 3800 simulator. Stressstrain curves were determined during continuous compression test in a temperature range from 900 to 1100°C and at a strain rate of 1, 10 and 50 s-1. In order to determine recrystallization kinetics of plastically deformed austenite, discontinuous compression tests of specimens were done with a given strain at the rate of 10 s-1, in a temperature range from 900 to 1100°C, with isothermal holding of samples between successive stages of deformation for 2 to 100 s. Recrystallization kinetics of plastically deformed austenite was described using the Johnson-Mehl-Avrami equation. The observations of microstructures of thin foils were done using JEOL JEM 3010 transmission electron microscope.Findings: Basing on the analysis of the form and the course of curves obtained in the compression test, it was found that in the studied range of parameters of hot plastic deformation, the decrease of strain hardening of studied steels is caused by the process of continuous dynamic recrystallization. This is also confirmed by calculation results of activation energy of plastic deformation process. Performed two-stages compression tests revealed that microadditions introduced into steel considerably influence the kinetics of static recrystallization.Research limitations/implications: It was found that the time necessary for a total course of recrystallization of austenite is too long to be accepted in the production process of forgings.Practical implications: Executed hot compression tests will contribute to establishing conditions of forging with the method of thermo-mechanical treatment.Originality/value: Strain-stress curves and recrystallization kinetics curves of newly elaborated microalloyed steels have been determined.
Hot deformation and recrystallization of advanced high-manganese austenitic TWIP steels
L.A. Dobrzański,W. Borek
Journal of Achievements in Materials and Manufacturing Engineering , 2011,
Abstract: Purpose: The aim of the paper is to determine the influence of hot-rolling conditions on structure of new-developed high-manganese austenitic steels.Design/methodology/approach: Flow stresses during continuous and multi-stage compression tests were measured using the Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steels were compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in different stages of hot-rolling was determined in metallographic investigations using light microscopy as well as X-ray diffraction.Findings: The steels are characterized by different microstructure in the initial state. Steel with higher Al concentration has stable microstructure of austenite with annealing twins, while steel with higher Si concentration consists of certain portion of ε martensite in form of plates. The flow stresses are in the range of 200-430 MPa for the applied conditions of hot-working and are up to 40 MPa lower compared to continuous compressions. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery. On the basis of analysis of thermo-mechanical treatment carried out in continuous axisymetrical compression test and multi-stage compression test using the Gleeble 3800 simulator allowed to work out a schedule of three different variants of hot-rolling for each of investigated steels 26Mn-3Si-3Al-Nb-Ti and 27Mn-4Si-2Al-Nb-Ti.Research limitations/implications: To fully describe the hot-rolling behaviour of the new-developed steels, further investigations in wider temperature and strain rate ranges are required.Practical implications: Various conditions of hot-rolling for advanced high-manganese austenitic steels can be useful to determine influence of microstructure on mechanical properties obtained in static and dynamic tensile test.Originality/value: Microstructure evolution in various conditions of hot-rolling for advanced high-manganese austenitic steels were investigated.
Hot-working of advanced high-manganese austenitic steels
L.A. Dobrzański,W. Borek
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range of 850 to 1100°C using the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observations of the specimens compresses to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction.Findings: The investigated steels are characterized by high values of flow stresses from 230 to 450 MPa. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steels and slightly higher compared to Fe-(15-25)Mn alloys. Increase of flow stress along with decrease of compression temperature is accompanied by translation of εmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization. The steel 27Mn-4Si-2Al-Nb-Ti has austenite microstructure with annealing twins and some fraction of ε martensite plates in the initial state. After the grain refinement due to recrystallization, the steel is characterized by uniform structure of γ phase without ε martensite plates.Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates.Practical implications: The obtained microstructure – hot-working relationships can be useful in the determination of power-force parameters of hot-rolling and to design a rolling schedule for high-manganese steel sheets with fine-grained austenitic structures.Originality/value: The hot-deformation resistance and microstructure evolution in various conditions of hot-working for the new-developed high-manganese austenitic steels were investigated.
Processes forming the microstructure evolution of high-manganese austenitic steel in hot-working conditions
L.A. Dobrzański,W. Borek
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The aim of the paper is to characterise the microstructure evolution of new-developed 27Mn-4Si-2Al-Nb-Ti high-manganese steel in various conditions of hot-working.Design/methodology/approach: Flow stresses during the multistage compression test were measured usingthe Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steelwas compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction.Findings: The steel has austenite microstructure with annealing twins and some fraction of ε martensite plates in the initial state. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steelsand slightly higher compared to Fe-(15-25) Mn alloys. The flow stresses are in the range of 200-400 MPafor the applied conditions of hot-working. Making use of dynamic and metadynamic recrystallization,it is possible to refine the microstructure and to decrease the flow stress to 350 MPa during the last deformation at 850°C. Applying the true strains of 0.23 and 0.19 requires the microstructure refinementby static recrystallization. After the grain refinement due to recrystallization, the steel is characterisedby uniform structure of γ phase without ε martensite plates.Research limitations/implications: To fully describe the hot-working behaviour of the new-developed steel, further investigations in wider temperature and strain rate ranges are required.Originality/value: The hot-deformation resistance and microstructure evolution in various conditionsof hot-working for the new-developed high-manganese 27Mn-4Si-2Al-Nb-Ti austenitic steel were investigated.
Structural and mechanical behaviour of TRIP-type microalloyed steel in hot-working conditions
A. Grajcar
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The aim of the paper is to investigate the influence of various deformation conditions on microstructure evolution and flow curves of TRIP-type steel.Design/methodology/approach: In order to determine the influence of MX-type interstitial phases on limiting the grain growth of primary austenite, samples were quenched in water from a temperature range, from 900 to 1200°C. Determination of processes controlling strain hardening was carried out in compression test using Gleeble 3800 simulator. The σ-ε curves were defined in a temperature range from 850 to 1150°C, for 0.1, 1 and 10s-1 of strain rate. To determine the progress of recrystallization samples were isothermally held for up to 60 s at 900 and 1000°C.Findings: Profitable impact of TiN and NbC particles on austenite grain growth limitation is present up to 1050°C. The values of flow stress are equal from 120 to 270 MPa. The steel is characterized by quite high values of deformation, εmax=0.4-0.65, corresponding to maximum stress on σ-ε curves. Beneficial grain refinement of primary austenite microstructure can be obtained due to static recrystallization. In temperature of 1000°C, t0.5 is equal 35 s and elongates to 43 s after decreasing deformation temperature to 900°C. The σ-ε curves obtained during multi-stage compression tests confirmed that a process controlling the strain hardening is a dynamical recovery.Research limitations/implications: To design hot-rolling conditions, the analysis of the primary austenite microstructure evolution during successive deformation cycles should be carried out.Practical implications: The obtained precipitation kinetics of MX-type phases and σ-ε curves are useful in determining hot-rolling conditions ensuring the fine-grained microstructure of primary austenite.Originality/value: The determined true stress–true strain curves were obtained for the TRIP-type microalloyed steel containing decreased Si concentration.
Hot-working behaviour of high-manganese austenitic steels
L.A. Dobrzański,A. Grajcar,W. Borek
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator.Findings: It was found that they have austenite microstructure with numerous annealing twins in the initial state. Continuous compression tests realized in the temperature range from 850 to 1050°C with the strain rate of 10s-1 enabled determination of yield stress values and values of εmax deformations – corresponding to maximum flow stress. It was found that initiation of dynamic recrystallization requires true strain equal at least 0.29. Holding of steel after plastic deformation allowed determining the progress of recrystallization in the function of isothermal holding time. Determined half-times of recrystallization at 900°C after deformation with 25% of reduction are equal 32 and 17s for 27Mn-4Si-2Al-Nb-Ti and 26Mn-3Si-3Al-Nb-Ti steel, respectively. Several-stage compression tests with true strain of 0.29 permit to use dynamic recrystallization for shaping fine-grained microstructure of steel in the whole range of deformation temperature. Decreasing true strain to 0.23 limits the course of dynamic recrystallization to two first deformation cycles. In two final cycles of deformation, as well as in the whole range of hot-working realized with true strain of 0.19 – dynamic recovery is the process controlling strain hardening.Practical implications: The obtained microstructure – hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures.Originality/value: The hot-working behaviour and microstructure evolution in various conditions of plastic deformation for new-developed high-manganese austenitic steels with Nb and Ti microadditions were investigated.
Microstructural evolution of a superaustenitic stainless steel during a two-step deformation process
N. Bayat,G. R. Ebrahimi,A. Momeni,H. R. Ezatpour
- , 2018, DOI: https://doi.org/10.1007/s12613-018-1561-3
Abstract: Single- and two-step hot compression experiments were carried out on 16Cr25Ni6Mo superaustenitic stainless steel in the temperature range from 950 to 1150°C and at a strain rate of 0.1 s-1. In the two-step tests, the first pass was interrupted at a strain of 0.2; after an interpass time of 5, 20, 40, 60, or 80 s, the test was resumed. The progress of dynamic recrystallization at the interruption strain was less than 10%. The static softening in the interpass period increased with increasing deformation temperature and increasing interpass time. The static recrystallization was found to be responsible for fast static softening in the temperature range from 950 to 1050°C. However, the gentle static softening at 1100 and 1150°C was attributed to the combination of static and metadynamic recrystallizations. The correlation between calculated fractional softening and microstructural observations showed that approximately 30% of interpass softening could be attributed to the static recovery. The microstructural observations illustrated the formation of fine recrystallized grains at the grain boundaries at longer interpass time. The Avrami kinetics equation was used to establish a relationship between the fractional softening and the interpass period. The activation energy for static softening was determined as 276 kJ/mol.
Microstructure evolution of high-manganese steel during the thermomechanical processing
L.A. Dobrzański,A. Grajcar,W. Borek
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution of new-developed high-manganese austenitic steel.Design/methodology/approach: The hot-working behaviour was determined in continuous and multi-stage compression tests performed in a temperature range of 850 to 1100°C by the use of the Gleeble 3800 thermomechanical simulator. The processes controlling work hardening and removing it were identified by microstructure evolution observations in successive stages of compression with the amount of true strain 4x0.29, 4x0.23 or 4x0.19.Findings: The investigated steel is characterized by high values of flow stresses from 250 to 450 MPa. Increase of flow stress along with decrease of compression temperature is accompanied by translation of εmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization.Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates.Practical implications: The obtained σ-ε curves can be useful in determination of power-force parameters of hot-rolling and to design a rolling schedule ensuring a fine-grained microstructure of high-manganese steel products.Originality/value: The microstructure evolution in various conditions of hot-working for the new-developed high-manganese Mn-Si-Al-Nb steel was determined.
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