Recrystallization Kinetics and Microstructure Evolution of Annealed Cold-Drawn Low-Carbon Steel (original) (raw)
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STORED ENERGY EFFECT ON KINETICS OF RECRYSTALLIZATION OF ANNEALED 0.12WT. % C STEEL
IMEETMCon 2016 P068:
Cold deformation in metals influences the mechanical properties of the metal as a result of changes in its microstructure which stores energy due to strain hardening. The strains in the deformed metal could be relieved by annealing which results in the reformation of the microstructure grains of the metal. The influence of cold drawn deformation on the recrystallization kinetics of the grains has been examined in cold-drawn 0.12wt %C steel. The as-received low carbon steel was cold drawn to 20%, 25%, 40% and 55% degree and the specimens were annealed at temperature range of 500 o C-650 o C for soaking time between 10 and 60 minutes. The stored energy of each cold -drawn specimen was estimated using the Stibitz procedure. The recrystallization kinetics for the temperature range of drawn steel was analyzed by hardness measurement. The rate of recrystallization was found to increase with increasing degree of cold drawn deformation. The increase in rate of recrystallization is found to be due to the rapid loss of stored energy during the annealing process. Recrystallization is found to commence at annealing temperature of 550 o C-600 o C during which the rate at which energy is lost decreases drastically. The rate at which energy is lost due to annealing determines the rate of recrystallization of the 25%, 40% and 55% cold drawn steel. The 20% cold drawn steel only experiences recovery due to low grain slip interaction within the steel structure. The rate of energy loss due to annealing temperature is shown to affect the kinetics of recrystallization and can be used as foundation study for improving the mechanical properties of cold drawn steel.
Phase Field Simulation for Recrystallization Kinetics of 0.12wt.% C Steel in Full Annealing
The importance of recrystallization kinetics in metal process cannot be over emphasized in providing information as to the control of microstructure of materials for purpose of improving or impacting desired mechanical properties in processed materials. In this study, 0.12wt% C steel cold drawn between 20% -55% were graduallyheateduptoatemperatureof900°C followed bysoakingtreatment between 600 seconds and 3600 seconds in a Gallenkomp® mufflefurnace model SVL-1009 with voltage regulation of 220 V, 50 Hz of temperature range 300°C -1000°C. The influence of the annealing process on the strength and impact toughness properties of the annealed steel were evaluated from tensile and charpy-impact testsconductedontheannealedsteel.A phase field method is used to describe the recrystallization kinetics of the annealed cold drawn 0.12wt%C steel for the different degrees of cold drawn deformation.The experimental data obtained from the tensile and charpy-impact test were used as input data for the phase field simulation of the recrystallization process. The results show that the yield strength of the annealed cold drawn 0.12wt% C steel increases with increasing soaking time within the range of 600 sec.-3600 sec. for the 20% cold drawn steel, between 600 sec.-2400 sec. for the 25% and between 600 sec.-1800 sec. for the 40% and 55% cold drawn steel. The treatment increased the impact toughness of the steel for the 20%-40% cold drawn deformation but loses its toughness for the 55% cold drawn steel. The tensile strength however reduces for all the cold drawn steel irrespective of the degree of deformation.The simulation results show that reformation of grains in cold drawn 0.12wt%C steel depends on the degree of cold drawn deformation and the soaking time of annealing. The response of the mechanical properties of the annealed cold drawn 0.12wt% C steel therefore depends on the degree of cold deformation and soaking time of annealing.
This work studied the effect of grain size evolution of cold drawn 0.12wt% C steel subjected to process annealing on tensile behavior. 20%, 25%, 40% and 55% cold drawn 0.12wt% C steel were subjected to annealing comprising of slow heating-up to various temperature ranging from 500oC to 700oC at interval of 50oC followed by soaking treatment for 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes under each of the temperature in a muffle furnace. These samples were submitted tooptical microscopy analysis and to tensile test. After annealing at 650oC and soaked for 10 minutes, the dislocation defects were annihilated in the 25% cold drawn samples. Grain coarsening is observed for the annealed steel at soaking time of 20 minutes to 30 minutes after which grain growth commenced at annealing temperature above 650oC at soaking time of 40 minutes for the 25%, 40% and 55% cold drawn samples. Fine grains of the microstructure were observed for all the annealed samples between the temperature range 500 o C-650 o C.The yield strength of the annealed samples increases compared to the non-treated samples thus improving the ductility of the steel. A better improvement of the yield strength is observed for the annealing temperature of 500 o C and 550 o C at soaking time of 10 minutes and 30 minutes for all the cold drawn samples except for the annealed 25% cold drawn steel whose yield strength is below the yield strength of the non-treated samples.
Acta Materialia, 2011
The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 600˚C and 650˚C was investigated. Hardness tests were used to characterize the recrystallization kinetics. The micrographs of the steel were obtained using optical microscopy (OM) to characterize the grain microstructure of the non-treated and the annealed steel samples. Annihilation of dislocation defects occur within the soaking time of 5-10 minutes for all the deformed steel after annealing at 650˚C. Specifically at 5 minutes soaking time the grains elongation is still observed indicating that reformation of grains is not taking place but recovery of the deformed grains. At the 10 minutes annealing time, new grains are observed to begin and full recrystallization is achieved at 15 minutes annealing time. At annealing time between 20-25 minutes, grains coarsening are observed indicating the onset of grain growth. The hardness of the material reduces with increasing annealing temperature for all the degree of cold drawn deformation. On the basis of the experimentally obtained hardness values, recrystallization increases with increasing degree of cold drawn deformation for the annealed steel. Recovery process was found to prolong in the 20% cold drawn steel as compared to the 55% cold drawn steel. The prolong recovery process is due to reduction in the driving force. Full recrystallization of the annealed steel is achieved at different soaking time depending on the degree of the cold drawn steel.
The Deformation Microstructure and Recrystallization Behavior of Warm Rolled Steels
ISIJ International, 2002
The deformation microstructure of various warm (ferritic) rolled steels was characterized and its influence upon the subsequent annealing behavior determined. The materials investigated included three interstitialfree (IF) steels (stabilized with either titanium or niobium), an extra low carbon (ELC) steel, and four experimental low carbon chromium steels with varying levels of boron, nitrogen and phosphorus. Single pass rolling experiments were conducted in a pilot mill at temperatures between 440 and 850°C and the asrolled microstructures were examined using optical microscopy. Particular attention was paid to the nature and intensity of the in-grain shear bands produced. Partial annealing was conducted to examine the nucleation of recrystallization in the deformed microstructure. Shear bands of moderate intensity were usually formed in the IF steels, which tended to be insensitive to rolling temperature. For the ELC steel, intense shear bands were formed at low rolling temperatures, but at higher temperatures this intensity was found to be drastically reduced. The development of shear bands at the higher rolling temperatures was significantly enhanced by alloying with chromium. The differences in shear band frequency and intensity are explained in terms of the dynamic strain aging behaviors of the various materials. Recrystallized grains were found to nucleate preferentially on the shear bands during annealing, regardless of their morphology or intensity.
ISIJ International, 2005
The early stages of recovery and recrystallisation were studied using transmission electron microscopy in four warm rolled low carbon steels. Three of these contained additions of chromium and of the latter, one was phosphorus and a second boron modified. Addition of the alloying elements led to the formation of both shear and microbands within some of the grains. The progress of recovery in these areas differed from that applicable to the grains containing only microbands. Two types of carbides were present after warm rolling in the steels containing the alloying additions: (i) coarse carbides; and (ii) fine strain-induced particles. The coarse carbides underwent spheroidization and coarsening during annealing. They, on the one hand, accelerated recrystallisation as the particles stimulated nucleation; on the other hand, they retarded it by pinning both the high and low angle grain boundaries. These carbides also influenced the morphology of the recrystallised grains by restraining their growth.
Kinetics of Austenite Recrystallization during the Annealing of Cold-rolled Fe-Mn-Al-C Steel
2020
In the current study, the recrystallization behavior of 75% cold-rolled Fe-22Mn-10Al-1.4C steel during annealing at 750, 770, 790, 810, and 830°C was studied. X-ray diffraction patterns and optical microscopy were used to characterize microstructures. The Vickers Micro-hardness test was used to characterize recrystallization kinetics during annealing. Johnson-Mehl-Avrami-Kolmogorov (JMAK) model was used to evaluate the experimental data. The as-homogenized microstructure illustrated only austenite with a high fraction of annealing twins, and austenite to martensite phase transformation was not observed after quenching at a high temperature and also until high thickness reduction. Avrami exponent was decreased from 0.76 to 0.42, with increasing the annealing temperature from 750 to 830°C. The activation energy value was determined to be ~175 kJ/mol, which was slightly higher than the diffusion activation energy of carbon in austenite.
Acta Materialia, 2011
The detailed evolution of microstructure and microtexture during the annealing of warm-rolled (WR) and cold-rolled (CR) 0.78 wt.% Cr extra-low-carbon steels was studied via electron back-scattering diffraction (EBSD). The partially recrystallized maps were deconstructed into deformed, recovered, newly nucleated and growing grain fractions using a newly developed procedure. In the early stages of recrystallization, the WR samples contained a mixture of discontinuously recrystallized {1 1 1}h1 1 2i newly nucleated grains and previously recovered {1 1 1}h1 1 0i growing grains. During the later stages of annealing, continuous recrystallization was the predominant mechanism with the strengthening orientations confined mostly to the a-fibre at $ ð1 1 2Þ½1 1 0. Conversely, during the annealing of the CR samples, discontinuous recrystallization took place, with the newly nucleated and growing grain fractions consisting mostly of {1 1 1}h1 1 2i orientations.
Recrystallization kinetics of microalloyed steels deformed in the intercritical region
Metallurgical Transactions A, 1992
A plain carbon and two microalloyed steels were tested under interrupted loading conditions. The base steel contained 0.06 pct C and 1.31 pct Mn, and the other alloys contained single additions of 0.29 pct Mo and 0.04 pct Nb. Double-hit compression tests were performed on cylindrical specimens of the three steels at 820 ~ 780 ~ and 740 ~ within the a + y field. A'softening curve was determined at each temperature by the offset method. In parallel, the progress of ferrite recrystallization was followed on quenched specimens of the three steels by means of quantitative metallography. It was observed that, in the base steel, a recrystallizes more slowly than % The addition of Mo retards recrystallization and has a greater influence on Y than on a recrystallization. This effect is in agreement with calculations based on the Cahn theory of solute drag. Niobium addition has an even greater effect on the recrystallization of the two phases. In this steel, the recrystallization of ferrite was incomplete at the three intercritical temperatures. Furthermore, the austenite remained completely unrecrystallized up to the maximum time involved in the experiments (1 hour). The metallographic results indicate that the nucleation of recrystallization occurs heterogeneously in the microstructure, the interface between ferrite and austenite being the preferred site for nucleation.