Gleeble Simulator Research Articles

Deformation Mechanism and Constitutive Consideration for Ti-5Al-5Mo-5V-3Cr-1Zr Alloy Compressed at Elevated Temperatures

To investigate hot deformation behavior of a Ti55531 alloy, a series of isothermal compression tests were performed on a Gleeble-3500 simulator at the temperature range of 1033–1153 K and constant strain rates of 0.001–1 s−1. Based on the experimental flow stress data, processing map and grain morphology, the deformation mechanism map was summarized. In this study, the dominant microstructural mechanism processed near or above β-transus temperature was considered to be deformation characteristic of β phase, where dynamic recovery was in dominant and at mediate strain rate dynamic recrystallization was also observed. Superplasticity was found at 1003–1033 K and 0.001 s−1, correlating with dislocation glide and grain boundary slide (GBS). Undesirable plastic flow such as flow localization and flow rotation was found at high strain rate of 0.1-1 s−1 and at the entire test temperature range. The optimum working window of this alloy was finally obtained at 1003–1063 K and 1093–1153 K and at 0.001–0.1 s−1.

Understanding Hot Workability and Flow Stress Prediction through Processing Map with Microstructural Correlation for HY85 Steel

Abstract In this study, the hot compression tests of HY85 steel have been experimented by using thermomechanical simulator Gleeble 3800 in hot compression temperature range of 750°C–1,100°C under strain rates between 0.001–10 s−1 up to true strain 0.7. It is worth noticing from the results that the flow stresses are dependent on the combination of temperature and strain rate. Adiabatic heating corrections of experimental flow stress data were carried out and were used to model stress-strain curves. The predictability of these stress-strain curves was confirmed from experimental results. True stress-true strain curves show the peak stresses followed by softening probability because of the existence of dynamic recrystallization (DRX). The apparent activation energy is calculated to be 360 KJ/mol using the sinh type constitutive equation, and it is observed that its value decreases with increasing strain. Hot compression of HY85 steel is controlled by dislocation climb and glide (n = 6.3). The processing maps are plotted based on different dynamic materials modeled with strain rate versus temperatures. The flow localization is one of the primary factors with resulting instability, which is revealed from the microstructure. Moreover, the partial DRX was noticed besides the grain boundaries and compression bands. Workability regions were identified using processing maps in the domain of strain rate and temperature and verified with microstructures.

Microstructure Evolution in Cu-Ni-Co-Si-Cr Alloy During Hot Compression by Ce Addition.

Cu-Ni-Si alloys are widely used in lead frames and vacuum devices due to their high electrical conductivity and strength. In this paper, a Cu-Ni-Co-Si-Cr-(Ce) alloy was prepared by vacuum induction melting. Hot compression tests of the Cu-Ni-Co-Si-Cr and Cu-Ni-Co-Si-Cr-Ce alloys were carried out using a Gleeble-1500 simulator at 500–900 °C deformation temperatures and 0.001–10 s−1 strain rates. The texture change was analyzed by electron backscatter diffraction. The <110> fiber component dominated the texture after compression, and the texture intensity was reduced during recrystallization. Moreover, the average misorientation angle φ for Cu-Ni-Co-Si-Cr-Ce (11°) was lower than that of Cu-Ni-Co-Si-Cr (16°) under the same conditions. Processing maps were developed to determine the optimal processing window. The microstructure and precipitates of the Cu-Ni-Co-Si-Cr and Cu-Ni-Co-Si-Cr-Ce alloys were also analyzed. The average grain size of the Cu-Ni-Co-Si-Cr-Ce alloy (48 μm) was finer than that of the Cu-Ni-Co-Si-Cr alloy (80 μm). The average size of precipitates in the Cu-Ni-Co-Si-Cr alloy was 73 nm, while that of the Cu-Ni-Co-Si-Cr-Ce alloy was 27 nm. The addition of Ce delayed the occurrence of dynamic recrystallization.

Microstructure evolution of Cu-1.0Co-0.65Si-0.1Ti alloy during hot deformation

The Cu-1.0Co-0.65Si-0.1Ti alloy was obtained by vacuum melting, and then the hot deformation experiment was carried out by using the Gleeble-1500 simulator at 0.001–10 s−1 strain rates and 500–900 °C deformation temperatures. The microstructure evolution of Cu-1.0Co-0.65Si-0.1Ti alloy was discussed. The micro texture of Cu-1.0Co-0.65Si-0.1Ti alloy was analyzed by EBSD. With the deformation temperature increasing from 700 to 800 °C, the dynamic recrystallization was promoted and the texture of Cu-1.0Co-0.65Si-0.1Ti alloy transformed from the {011} <100> Goss texture to the {112} <111> copper texture. The HAGBs and geometrically necessary dislocation (GND) density were calculated, respectively, which can also indicate that the increasing of temperature promoted the dynamic recrystallization. The critical strain for the initiation of dynamic recrystallization in Cu-Co-Si-Ti alloy deformed at 0.01 s−1,800 °C and 0.001 s−1,800 °C was 0.089 and 0.035, respectively. And it can be inferred that the increasing of deformation temperature or decreasing of strain rate can reduce the critical strain and promote the dynamic recrystallization. Finally, the precipitate was determined to be Co2Si.

Optimisation of parameters for the production of perforated armour panels made of nanobainitic steel using dynamic hardness measurement methodology

The study is a continuation of the development of material characteristics in order to expand the range of products for the production of which nanostructured bainitic steels can be used. The tests included measurement of dynamic properties important in the material qualification process for firing tests and for other applications requiring dynamic wear resistance. The novelty of the implemented development of the innovative grade of nanostructured steel and the technology of manufacturing products – including armour systems containing perforated panels made of this grade of steel, consisted in developing the basics of dynamic hardness measurement methods and dynamic indentation tests using a Gleeble simulator.

The hot deformation behavior, microstructure evolution and texture types of as-cast Mg–Li alloy

Abstract In this study, aiming to systematically investigate the hot deformation mechanism, microstructure evolution and texture types of Mg–5Li–3Al–2Zn (LAZ532) alloy, and confirm the optimum constitutive model and hot working conditions of LAZ532 alloy. The hot compression test of LAZ532 alloy was performed on Gleeble-3500 simulator at deformation temperatures and strain rates in the range of 200 °C –350 °C and 0.001 s−1–1 s−1, respectively. The experimental results showed that the established optimum constitutive model could accurately predict the hot deformation behavior of LAZ532 alloy, and the stable hot-deformation zones with peak efficiency of power dissipation were concentrated in the zones range of 300 °C , 1 s−1, 0.001 s−1–0.01 s−1 and 350 °C , 0.01 s−1–0.1 s−1, respectively. By observing the microstructure of the alloy showed that the dynamic recrystallization (DRX) mechanism could be considered to be discontinuous dynamic recrystallization (DDRX), and the recrystallization degree increases with the increasing of deformation temperatures or decreasing of strain rates. Moreover, based on EBSD analysis, it was found that both the deformed microstructure and recrystallization microstructure in the alloy had a //CD texture, and a few {10 1 ¯ 2} extension twins were observed in the coarse deformed grains.

Effect of Post-Weld Heat Treatment Temperature on the Mechanical Properties and Microstructure of Weld Heat-Affected Zone of Low-Alloy Steel for Nuclear Reactor Pressure Vessel

The effect of post-weld heat treatment (PWHT) temperature on the mechanical properties of the heat-affected zone (HAZ) of P-No. 3 low-alloy steel was investigated by taking into account the changes in microstructure. SA-508 Gr. 3 Cl. 1 forged steel was employed, and the specimens taken from the steel were thermally cycled using a Gleeble simulator to simulate coarse-grained HAZ (CGHAZ), fine-grained HAZ (FGHAZ), intercritical HAZ (ICHAZ), and subcritical HAZ (SCHAZ). The respective base metal and simulated HAZ specimens were heat treated in a furnace at 610, 650, 690, and 730°C for 8 hours. Before the heat treatment, the ICHAZ, FGHAZ and CGHAZ exhibited high hardness and poor impact toughness. However, when the PWHT was applied, the hardness decreased and the impact toughness improved; the impact toughness was highly dependent on the PWHT temperature. The impact toughness of the ICHAZ and FGHAZ increased significantly when the PWHT temperature was 650°C or below, while that of CGHAZ improved significantly when the PWHT temperature was 650°C or higher. The microstructural changes due to the PWHT were observed by scanning electron microscopy and correlated with the mechanical properties.r composed of iron-based composition system had similar characteristics to the material to be repaired. Key words: Low-alloy steel, Heat-affected zone, Post-weld heat treatment, Impact toughness

Structure of Fe-Mn-Al-C Steels after Gleeble Simulations and Hot-Rolling.

In this paper, analytical results are compared for the newly developed steels, Fe-Mn-Al-C (X105) and Fe-Mn-Al-Nb-Ti-C (X98), after being hot-rolled and also after undergoing thermomechanical treatment in a Gleeble simulator. These steels have a relatively low density (~6.68 g/cm3) and a content of approx. 11% aluminum. The multistage compression of axisymmetric samples constituting a simulation of the real technological process and hot-rolling performed on a semi-industrial line were carried out using three cooling variants: in water, in air, and after isothermal heating and cooling in water. The temperature at the end of the thermomechanical treatment for all variants was 850 °C. On the basis of detailed structural studies, it was found that the main mechanism for removing the effects of the strain hardening that occurred during the four-stage compression involved the dynamic recrystallization occurring in the first and second stages, the hot formability and dynamic recovery in successive stages of deformation, and the static and/or metadynamic recrystallization that occurred at intervals between individual deformations, as well as after the last deformation during isothermal heating. Analysis of the phase composition and structure allowed us to conclude that the tested steels have an austenitic-ferritic structure with carbide precipitates. Research using scanning and transmission electron microscopy identified κ-(Fe, Mn)3AlC and M7C3 carbides in both the analyzed steels. In addition, complex carbides based on Nb and Ti were identified in X98 steel; (Ti, Nb)C carbides occurred in the entire volume of the material. Slow cooling after thermomechanical treatment influenced the formation of larger κ-carbides at the border of the austenite and ferrite grains than in the case of rapid cooling. The size and morphology of the carbides found in the examined steels was varied. Back-scattered electron diffraction studies showed that wide-angle boundaries dominated in these steels.

Constitutive flow behaviour of austenite at low temperatures and its influence on bainite transformation characteristics of ausformed medium-carbon steel

In order to impart superior mechanical properties to medium carbon carbide-free bainitic steels, an innovative approach has been adopted to extensively refine the bainitic ferrite plate thickness. Unlike controlled deformation in the no-recrystallization regime above the Ar3 temperature, an attempt has been made in this study to carry out low temperature ausforming in the bay between ferrite and bainite C-curves at 500 °C in order to impart high dislocation densities in the austenite prior to phase transformation. Two experimental high-silicon, medium carbon steels were suitably designed and processed for this study, with one steel containing small additions of 0.3Mo and 0.03Nb. Flow stress measurements were made using single-hit compression tests in the temperature range 300–900 °C in steps of 100 °C at different strain rates in the range 0.1–10 s−1 on a Gleeble simulator. Samples ausformed at 500 °C were isothermally held for 1 h at different transformation temperatures in the range of 300–400 °C to complete the bainitic transformation. Influence of strain induced bainite transformation on flow stress was obvious at 0.01 s-1, particularly at 300 and 400 °C. Despite enhanced nucleation in fine-grained steel B containing Nb + Mo, growth of bainite sheaves was much slower. Dilatation behaviour was comparable for the two steels at <350 °C, but at higher temperatures, the effect of Nb + Mo on slower transformation kinetics was obvious. The microstructure of both steels showed extremely fine bainitic ferrite below 325 °C, but at higher temperatures, coarse bainite with M/A constituents and extensive martensite formed in steels without or with Nb + Mo constituents. A correlation between hardness data and retained austenite contents has been established in both the steels. The paper presents the first account of the flow stress and transformation behaviour including the influence of Nb + Mo alloying and the details concerning the carbon-enriched austenite retained at room temperature and hardness variation as a function of isothermal holding temperature.

Simulation of the Hot Deformation and Fracture Behavior of Reduced Activation Ferritic/Martensitic 13CrMoNbV Steel

This study describes deformation behavior and fracture during compression and tension at high temperatures of ferritic/martensitic 13CrMoNbV steel. Hot compression and tensile tests were carried out in the temperature range of 1100–1275 °C with a thermomechanical simulator Gleeble 3800. The true stress and ultimate tensile strength decrease with an increase in the deformation temperature. The modified Arrhenius-type constitutive model was built for 13CrMoNbV ferritic/martensitic steel using the experimental stress–strain compression data. The modified Rice and Tracy ductile fracture criteria were calculated using finite element simulation of the tensile test at different temperatures. The comparison between experimental and computed force vs. displacement curves shows high predictability of the deformation and fracture models for ferritic/martensitic 13CrMoNbV steel.

Modeling &amp; Study of Micro structural Evolution of IN 718

Super alloy IN 718 is used in jet engine application, due to its creep properties and the structural stability at high temperatures. The mechanical properties are affected by the grain size. Control of grain size is the key issue that governs the mechanical properties. The dynamic recrystallization & grain size of IN 718 Cylindrical billet of 10 x 70 mm during Equal channel angular pressing (ECAP) is simulated and analyzed. Cellular Automata (CA) & Mehl-Johnson-Avrami models are used to predict recrystallization and grain growth behaviour, considering the two distinct regimes of dynamic and static recrystallization. Metal forming code DEFORM 3D has been used for numerical modelling that establishes the thermo mechanical history. The material parameters were found using thermo mechanical simulator Gleeble 3800 and also were collected from literature. The experimental results of ECAP processing the IN 718, at 1050 °C, Die & punch is kept at 450 °C, to avoid die chilling, is correlated to the simulated results. The initial average grain size is taken as 28 µm for CA & Avrami models. The IN 718 sample average initial grain size is 29 µm at room temperature.(The average Avrami grain size of IN 718 at 1050 °C, is 56 µm as per numerical simulations) The final Average grain size after ECAP process simulation is 23.3 µm & 22.9 µm by CA & Avrami models respectively. The experimental (after ECAP) average grain size obtained is 22.8 µm. The grains that are less than 10 µm are increased from 12 % initially to 40 % after ECAP.

Effect of Ce addition on microstructure evolution and precipitation in Cu-Co-Si-Ti alloy during hot deformation

Abstract Hot compression behavior of the Cu–Co–Si and Cu–Co–Si–Ti alloys was studied using the Gleeble-1500 simulator at 0.001–10 s−1 strain rate and 500–900 °C deformation temperature. Ti addition increased the flow stress of the Cu–Co–Si–Ti alloy compared with the Cu–Co–Si alloy at the same deformation conditions. With the deformation temperature increased from 700 °C to 900 °C, the Cu–Co–Si alloy texture transformed from the copper texture to the R texture. Due to the addition of Ti, the copper texture and R texture were substituted by the Goss texture and the copper texture, respectively. The constitutive models of the Cu–Co–Si and Cu–Co–Si–Ti alloys hot deformation behavior were obtained. The activation energy of the Cu–Co–Si alloy was 411.648 kJ/mol, and the activation energy of the Cu–Co–Si–Ti alloy was 500.794 kJ/mol, which is 27% higher. The precipitated Co2Si phase was found in both Cu–Co–Si and Cu–Co–Si–Ti alloys deformed at 700 °C and 0.001 s−1. In addition, the CoSi and Cu4Ti phases were found in the Cu–Co–Si and Cu–Co–Si–Ti alloys, respectively. The strengthening mechanisms, including dispersion strengthening, twinning and grain refinement strengthening, control the Cu–Co–Si–Ti alloy hot deformation, and lead to increased flow stress and activation energy, and inhibit dynamic recrystallization of the Cu–Co–Si–Ti alloy.

Hot Deformation Characteristics of 9Cr-1.5Mo-1.25Co-VNb Ferritic-Martensitic Steel

The hot workability of 9Cr-1.5Mo-1.25Co-VNb ferritic-martensitic steel was investigated through hot compression tests using Gleeble simulator over a temperature range of 1223 K (950 °C) to 1573 K (1300 °C) and strain rates of 0.001 to 0.5 per second. Through an analysis of the stress(σ)–strain(e) curves obtained during the hot compression tests, a processing map was developed to predict the hot workability, based on a dynamic material model (DMM). The processing map indicated that the hot workability deteriorates with an increase in the strain rate and a decrease in the temperature. During hot compression tests at temperatures exceeding 1473 K (1200 °C), δ-ferrite was formed along austenite grain boundaries and fine austenite grains then nucleated at the austenite/δ-ferrite interphase due to dynamic recrystallization (DRX), which was beneficial to the hot workability. At a temperature below 1223 K (950 °C), intergranular cracking occurred, after which a transmission electron microscopy (TEM) analysis revealed that this intergranular cracking resulted from the precipitation of intergranular M23C6 particles.

Investigation of Influence of Microstructure on FH32 Steel Corrosion Properties using Gleeble Simulation of Heat-Affected Zone and Electrochemical Methods

Investigation of Influence of Microstructure on FH32 Steel Corrosion Properties using Gleeble Simulation of Heat-Affected Zone and Electrochemical Methods

Workability of High-Strength Automobile Steel at High Temperatures Using Hot Processing Maps and Electron Backscatter Diffraction

Hot deformation behavior of a high-strength steel Docol 1500 Bor was investigated by compression tests on a thermal–mechanical simulator Gleeble 3500. The workability of tested steel was analyzed by building processing maps at three strains based on the test results of flow stresses. The essential deformation mechanism was further studied based on the deformation texture analysis on a scanning electronic microscope with a TSL-OIM™EBSD system. It was found that that strain can affect the workability of the tested steel remarkably. At the engineering strain of 0.6, obvious textures in martensite mainly include recrystallization textures //ND and other texture components //RD and {001} , etc. Dynamic recrystallization and recrystallization texture component //ND in deformed austenite can contribute to increasing the workability of a steel Docol 1500 Bor. Finally, the optimized deformation conditions of the tested steel were obtained.

Continuous dynamic recrystallization during hot torsion of an aluminum alloy.

Most commercial aluminum alloys are characterized by dynamic recrystallization at very large deformations in a continuous manner. The present study deals with the characterization and modeling of the evolution of the microstructure of an aluminum wrought alloy at large plastic deformations. Hot torsion tests of the AA6082 aluminum alloy are carried out using the thermomechanical simulator Gleeble®3800 in a wide range of temperatures and strain rates. The use of water quenching immediately after deformation avoids any static restoration during cooling. Microstructural investigations are carried out by means of electron back scattered diffraction using a scanning electron microscope to determine the grain and subgrain structures, as well as the misorientation distributions. In-situ synchrotron radiation tests during hot torsion are used to confirm the continuous dynamic recrystallization (CDRX) by the evidence of the conversion of low angle boundaries (LAGBs) into high-angle boundaries (HAGBs) and the formation of new texture. Experimental investigations show that CDRX starts with the formation of LAGBs at low strains (center of the sample). By subsequent straining (close to the surface of the sample), the accumulation of dislocations at the LAGBs causes an increase in their misorientation until a critical value is reached and LAGBs transforms into HAGBs. The developed model consists of a microstructural model, equation rates and constitutive equations. The microstructure is described by three internal variables. Their rates are evaluated using the Kocks-Mecking model. The modelled and experimental flow stresses show softening due to the consumption of dislocations and the continuous formation of new HAGBs.

Determination of the static, dynamic and cyclic properties of the heat affected zone for different steel grades

AbstractThe material properties of the heat affected zone (HAZ) in welds can significantly differ from the material properties of the base material (BM) due to recrystallization effects during heating and cooling. In this work, the microstructure of the heat affected zones of the low- and high strength steels S355J2, S690QL and S960QL was physically simulated by a Gleeble simulator. The temperature profiles for heating and cooling were taken from in-situ temperature measurements of a MAG welding process. The static and dynamic yield strengths of the simulated HAZ were determined by tensile tests under variable strain rates. The cyclic material properties according to Coffin, Manson and Morrow were determined for the HAZ and for the BM of each steel by strain- and stress controlled fatigue tests. Furthermore, the cyclic stress-strain curve of each HAZ was determined according to Ramberg and Osgood. Due to the lack of data for comparison, two approximation methods were used for the determination of the cyclic material properties and were compared to the investigated ones.

Determination of Grain Growth Kinetics and Assessment of Welding Effect on Properties of S700MC Steel in the HAZ of Welded Joints

The welding of fine-grained steels is a very specific technology because of the requirement for the heat input limit value. Applying temperature cycles results in an intense grain growth in a high-temperature heat-affected zone (HAZ). This has a significant effect on the changing of strength properties and impact values. The intensity of grain coarsening in the HAZ can be predicted based on the experimentally determined activation energy and material constant, both of which define grain growth kinetics. These quantities, together with real measured welding cycles, can be subsequently used during experiments to determine mechanical properties in a high-temperature HAZ. This paper shows a methodical procedure leading to the obtainment of the material quantities mentioned above that define the grain growth, both at fast and slow temperature cycles. These data were used to define the exposure temperature and the soaking time in a vacuum furnace to prepare test samples with grain sizes corresponding to the high-temperature HAZ of welded joints for the testing procedures. Simultaneously, by means of the thermo-mechanical simulator Gleeble 3500, testing samples were prepared which, due to a temperature gradient, created conditions comparable to those in the HAZ. The experiments were both carried out with the possibility of free sample dilatation and under a condition of zero dilation, which happens when the thermal expansion of a material is compensated by plastic deformation. It has been found that shape of the temperature cycle, maximal achieved cycle temperature, cooling rate, and, particularly, the time in which the sample is in the austenite region have significant effects on the resulting change of properties.

Characterization of Microstructures and Fatigue Properties for Dual-Phase Pipeline Steels by Gleeble Simulation of Heat-Affected Zone.

To increase transmission efficiency and reduce operation cost, dual-phase (DP) steels have been considered for pipeline applications. Welding has to be involved in such applications, which would cause a localized alteration of materials and cause many potential fatigue issues to arise under cyclic loading. In this work, the fatigue crack propagation and fatigue life of simulated heat-affected zone (HAZ) were examined. Results indicate that when the maximum stress is at the same magnitude, the fatigue life at a peak temperature of 1050 °C is very close to that of a peak temperature of 850 °C, and both of them are higher than that of a peak temperature of 1350 °C. The changes in da/dN with ΔK for HAZ subregions are attributed to the variation of crack path and fracture mode during the crack propagation. The fatigue cracks may propagate along the bainite lath preferentially in coarse-grained HAZ (CGHAZ), and the prior austenite grain boundaries can change the crack growth direction. A considerable amount of highly misoriented grain boundaries in fine-grained HAZ (FGHAZ) and intercritical-grained HAZ (ICHAZ) increase the crack growth resistance. The difference of fatigue crack propagation behavior in HAZ subregions between actual and simulated welded joints was also discussed.

Recent advances in the understanding of the role of vanadium carbonitride precipitation to improve surface edge cracking on continuous casting of blooms

This study aims in combining the material properties and numerical modelling techniques through practical application to provide understanding of surface edge cracking caused by V(C, N) precipitation to enhance the yield of the continuous bloom caster at ArcelorMittal Duisburg. The investigation for this work is carried out on three different micro-alloyed steel grades; one of them being the most crack sensitive 20MnV6. A process model is used which calculates the solidification process of the strand to design an optimum cooling strategy. Therefore, two cooling patterns are employed for the steel grade 20MnV6. Reduction of area values of the steel grades 20MnV6, 27MnSiVS6 and 38MnSiVS5 evaluated from hot tensile tests using a Gleeble simulator have been used as an indication in assessing steel’s cracking behaviour. Further precipitates have been analysed by SEM at ArcelorMittal. These laboratory results suggest that precipitation kinetics of V(C, N) influences the crack sensitivity of the micro-alloyed steel. The software MatCalc® is used to simulate precipitation for process parameters of continuously cast blooms at Arcelor Mittal Duisburg as well as the parameters of the Gleeble experiments. From these simulations the Zener pinning force (ZPF), resulting from V(C, N) particles on grain boundaries, is evaluated which can be used as a measure for the crack sensitivity. Using the values of the ZPF it is possible to identify the set of casting parameters of the steel grade 20MnV6 which lead to the minimum crack intensity on the surface of the blooms. Moreover it is possible to make a ranking list with respect to the ductility drop occurring in the Gleeble experiments for the analysed steel grades. The proposed statement is an issue for a continuing investigation of precipitation modelling.