Influence Of Deformation Parameters Research Articles

Hot deformation behavior and microstructure evolution model of 7055 aluminum alloy

Hot compression tests were conducted on 7055 aluminum alloy under different strain rates, temperatures, and reduction ratios. The influence of deformation parameters on microstructure evolution and hot deformation behavior was studied through EBSD and TEM characterization. An Arrhenius constitutive model was established and the recovery and recrystallization characteristics of the alloy under different conditions were analyzed. Results showed that the softening mechanism during the hot compression process of 7055 aluminum alloy was mainly attributed to recovery and partial recrystallization. The Zener-Holloman (Z) parameter was utilized to reveal the combined effects of strain rate and temperature on recrystallization behavior. Under conditions of high LnZ values (20 < LnZ), the alloy exhibited predominantly discontinuous dynamic recrystallization (DDRX) characteristics, while at low LnZ values (14 < LnZ <17), it displayed significant continuous dynamic recrystallization (CDRX) characteristics. The alloy showed a coexistence of CDRX and DDRX phenomena under conditions of moderate LnZ values (17<LnZ <20). In addition, based on the characterization, statistical analysis, and examination of the hot-compressed microstructure of the 7055 aluminum alloy, models for recrystallization fraction, grain size evolution, and deformed grain size were established, and an average grain size model was further developed. Comparison between the finite element simulation results based on the models and experimental results demonstrated good agreement in predicting the average grain size.

The effect of rolling temperature on the microstructure and properties of multi pass rolled 7A04 aluminum alloy

The current research on 7-series aluminum alloys mainly focuses on solid solution and aging treatments, as well as the flow stress during the deformation process. There are limited researches on the influence of thermal deformation temperature on the microstructure and properties of the aluminum alloy during multi-pass hot rolling process. In this study, the as-cast 7A04 aluminum alloy was subjected to homogenization treatment, followed by multi-pass hot rolling. The effects of different deformation parameters on dislocation density were analyzed. Microstructural characterization of the deformed alloy was performed using optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and micro-hardness tester. The optimal microstructure of the deformed alloy was selected based on the size of recrystallization. Subsequently, the Deform–3D finite element simulation software was used to analyze the multi-pass hot rolling process. The influence of deformation parameters on the uniformity of equivalent strain distribution within the samples was investigated. The results showed that at the deformation temperature of 430 °C, a significant amount of recrystallized microstructure appeared in the alloy, resulting in the lowest dislocation density and a significant reduction in the quantity of coarse precipitates. Finite element numerical simulation revealed that the deformation temperature had a certain influence on the uniformity of strain distribution within the alloy. However, this influence was mostly eliminated when the deformation temperature exceeded 380 °C. Meanwhile, the distribution of strain within the alloy was found to be related to the temperature distribution.

Investigation on the fracture mechanism and constitutive relations of a typical Ni-based superalloy

The hot tensile behavior of a typical Ni-based superalloy is elucidated using a microcomputer-controlled electronic universal testing machine at various deformation temperatures (920–1010 °C) and strain rates (0.001–0.01 s−1). Further, the influence of deformation parameters on the fracture characteristics is clarified. The results reveal that the tensile stress speedily rises to a peak level, beyond which it continuously declines until the final rupture. Moreover, numerous dimples exist on the fracture surface, and tenacity nests appear between adjacent dimples, suggesting that micro-void coalescence is the primary failure mechanism. Meanwhile, almost completed dynamic recrystallization (DRX) at elevated deformation temperature and slow strain rate promotes the intergranular fracture of the tested superalloy. Besides, an Arrhenius-type (AT) constitutive model and an artificial neural network (ANN) combined with particle swarm optimization (PSO) algorithms are established and validated. The maximum value of the mean absolute relative error (MARE) for the AT model is 9.74%, while it decreases to 4.20% for the PSO-ANN model. The correlation coefficient (R) increases from 0.9050 for the AT model to 0.9737 for the PSO-ANN model. Overall, it is demonstrated that the established PSO-ANN model has a high prediction performance and is an effective model for reproducing the hot tensile behavior of the tested superalloy.

Research on ultrasonic vibration assisted ploughing-extrusion process in forming μ-scale micro grooves

The surface micro groove structure on metallic components has received extensive attention for its role in improving the heat transfer coefficient. Limited by the size effect, it is difficult to manufacture μ-scale micro groove structure with large depth-to-width ratio through conventional extrusion or rolling processes. A novel UV assisted ploughing-extrusion process was proposed to manufacture μ-scale micro grooves. A series of UV assisted compression tests were conducted to study the acoustic deformation behavior of α-Ti, and a modified Ludwik model were established., The influence of deformation parameters was investigated, and the optimized deformation parameters are the leading angle is 60°, the extruded angle is 40°, and the ultrasonic amplitude is 10.30 μm. The results indicate that the novel ultrasonic vibration assisted ploughing-extrusion is able to continuously form large-sized micro-grooves parts with high quality.

Long-Term Stable Elastocaloric Effect in a Heusler-Type Co51V33Ga16 Polycrystalline Alloy

Cyclic stability is of utmost importance for the long-term work of caloric materials in solid-state refrigeration. Heusler-type shape memory alloys show a large elastocaloric effect under low driving stress, but their intrinsic brittleness always leads to poor cyclic stability. Here, we demonstrate the simultaneously achieved large elastocaloric effect and long-term cyclic stability in a Heusler-type Co51V33Ga16 polycrystalline alloy. Over a wide temperature range of 290–340 K, large adiabatic temperature change (ΔTad) values of −6.0 to −10.9 K can be obtained upon fast unloading. Moreover, by synthetically considering the influences of deformation parameters on the ΔTad values, stress hysteresis, energy dissipation, and temporary residual strain to balance cooling capacity and cyclability, large ΔTad values higher than 6.0 K are maintained for more than 50 000 superelastic cycles performed under the compressive strain of 3.5% and strain rate of 1.1 × 10–2 s–1, showing a very low degradation rate of 2 × 10–5 K per cycle. Such cyclic stability of elastocaloric effect well outperforms those reported in Heusler-type alloys so far.

Influence of deformation parameters on quality of billets and grinding balls during their production from rejects of rail steels

The conducted studies have determined the regularities of influence of rolling parameters of billets and grinding balls in their production from the rejects of K76F rail steel on probability of defects formation during deformation. Modeling of the rolling process of high-grade billets from the rejects of continuously cast ingots of rail steel of the specified grade in DEFORM-2D software package allowed us to establish a significant effect of such parameters as: partial coefficients of drawing along the transfer bar, frequency of rolling edges, and rolling temperature, on the probability of defect formation, characterized by the maximum value of the Cockcroft-Latham criterion in cross section of the rolls. It is shown that an increase in the coefficients of drawing (compression) along the transfer bar, due to intensification of the rolling mode and an increase in frequency of edging, reduces the likelihood of defects forming during rolling by reducing the temperature inhomogeneity along the rolls section. The established effect of temperature increase on reducing the probability of defects formation is due to an increase in plasticity of the considered rail steel. Based on the data obtained, general recommendations are formulated on the directions of improving the rolling modes of billets from the rejects of rail steels and restrictions on their application in practice. Based on the results of modeling the rolling of grinding balls from the rejects of rail steel on a helical rolling mill, a significant effect of an increase in the deformation temperature on reduction of cracking in the balls axial zone, due to an increase in the steel ductility, was established. Therefore, a new mode of rolling grinding balls from the rejects of K76F rail steel was developed, which provides an increase in impact resistance of grinding balls while maintaining high surface hardness. Effectiveness of this mode is confirmed by the results of its pilot testing in conditions of the ball rolling mill at JSC “Guryevskii Metallurgical Plant”.

Hot deformation and microstructure evolution of selective laser melted 718 alloy pre-precipitated with δ phase

In this work, the hot deformation behavior of SLM 718 alloy pre-precipitated with δ phase was studied by uniaxial compression test, and the microstructure evolution of the alloys was analyzed in detail by back-scattered electron contrast (BSE), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the deformation parameters have a significant effect on the flow behavior of the alloys. The influence of deformation parameters on DRX volume fraction and DRX grain has certain difference. Due to the δ phase hindrance, dislocations will accumulate near δ phase during deformation, resulting in fracture and bending of δ phase. The stacking dislocation can be transformed into subgrains and formed the DRX grains by rotation.

Influence of Forging Parameters on Microstructure and Properties of En AW-6082 Alloy

Aluminum alloys are widely used in automotive industry due to their low density and good corrosion resistance. This category includes alloys based on AlSiMg which are suitable for load bearing parts operating under higher temperatures. This paper deals with analysis of influence of deformation parameters and heat treatment on structure and mechanical properties of EN AW-6082 (AlSi1MgMn) alloy manufactured by horizontal cast module technology. Casted rods were used as a billet, which was formed to defined height by hot open-die forging. Subsequently the precipitation hardening was used as heat treatment. Changes in microstructure were evaluated based on the metallographic analyzes performed by light optical microscopy and scanning electron microscopy using an energy dispersive X-ray spectrometry and electron backscatter diffraction. Mechanical properties were determined by uniaxial tensile test and hardness testing. The results showed, that due to the process parameters, no significant structural changes were observed in the surface layer of forging. However, microstructure is significantly inhomogeneous in the core due to the dynamic softening processes. Mechanical properties are increasing which is significantly influenced by the type and distribution of precipitates emerging during the artificial aging.

High-Temperature Deformation Characteristics and Constitutive Model of an Ultrahigh Strength Steel

The high-temperature deformation characteristics of an ultrahigh strength steel is studied by hot compression tests under the deformation temperatures of 920–1160 °C and strain rates of 0.01–10 s−1. By employing the metalloscope and transmission electron microscope, the influences of deformation parameters (deformation temperature and strain rate) upon microstructure evolution are analyzed in detail. Results show that the hot deformation activation energy of the studied steel is estimated as 332.3 kJ/mol. The microstructure presents the typical dynamic recrystallization (DRX) features, and the DRX behaviors are mainly dominated by the discontinuous DRX mechanism under different deformation parameters. Under the low strain rate or the high deformation temperature, the continuous DRX behavior caused by the rotation of subgrains takes place. For forecasting the deformation stress of the studied steel, a physically-based constitutive model is constructed by combining dislocation density theory and DRX kinetics. The reproduced deformation stresses well close to the measured data indicates that the developed physically-based constitutive model enjoys a preferred prediction ability to forecast the high-temperature deformation behaviors for the studied steel.

A modified Johnson-Cook model considering strain softening of A356 alloy

The compression experiments of as-received A356 alloy were conducted at temperatures ranges from 300 to 500 °C with varying strain rates. The influence of deformation parameters on the strain softening of flow stress were researched. The observation of microstructure indicated that high temperature and large strain were favorable for dynamic recrystallization behavior. In order to improve the predictability, a modified Johnson-Cook (JC) model considering strain softening mechanism was proposed. The JC model and modified JC model were calculated according to experimental data. In contrast with the JC model, the new proposed model had the better correlation and the smaller average absolute error (1.46%). Furthermore, thermal compression experiments at constant reduction speed and finite element simulations based on the new model were performed. High consistency of load-displacement curve indicated that new model had good prediction accuracy for the A356 aluminum alloy.

Effects of deformation parameters and stress triaxiality on the fracture behaviors and microstructural evolution of an Al-Zn-Mg-Cu alloy

Abstract Hot tensile tests are performed on an Al-Zn-Mg-Cu alloy at larger temperature and strain rate ranges. The influences of deformation parameters and stress triaxiality on hot tensile fracture characteristics, fracture mechanisms and microstructural evolution are discussed. It is found that the maximum tensile load increases with raising stress triaxiality. The fracture strain rises with increasing strain rate or decreasing stress triaxiality. When the deformation temperature is raised, the fracture strain firstly increases and then decreases. Dynamic recovery (DRV) is the main softening mechanism. At low strain rates or high deformation temperatures, the partial dynamic recrystallization (DRX) behavior occurs, and continuous dynamic recrystallization (CDRX) is the main DRX mode. The dominant fracture mechanism is the coalescence of micro-voids at the tested deformation conditions. Due to the occurrence of DRX, the intergranular fracture also occurs at low strain rates or high deformation temperatures. The low strain rate or high stress triaxiality easily induces the appearance of micro-voids, which accelerate the fracture failure.

A physically-based constitutive model and processing map of as-cast 30Cr2Ni4MoV low-pressure rotor steel

The hot deformation behaviour of as-cast 30Cr2Ni4MoV steel was systematically investigated within a temperature range of 1173–1473 K and strain rate range of 0.001–1 s−1 using uniaxial compression tests with a Gleeble-1500D thermal simulation tester. Flow curves were obtained under these conditions and the influences of deformation parameters on their morphologies are discussed. The characteristic parameters of the flow curves were determined and expressed in the form of simple power-law Zener-Hollomon parameters. A physically-based constitutive model was developed and its predictions of flow stress agree well with experimentally-measured flow stresses. Moreover, in order to optimize the forging parameters, processing maps of as-cast 30Cr2Ni4MoV steel were established at different stains based on a dynamic material model. By analysing the processing maps and microstructure at a strain of 0.7, the optimum forging process parameters for as-cast 30Cr2Ni4MoV steel were determined to comprise temperatures ranging from 1323–1473 K and strain rates of 0.1–1 s−1.

Precipitation behavior of a β-quenched Ti-5Al-5Mo-5V-1Cr-1Fe alloy during high-temperature compression

The precipitation behavior of α phase in a β-quenched Ti-55511 alloy during high-temperature compression is investigated. The influences of deformation parameters on the flow characteristics, microstructural evolution, as well as the precipitation behavior of α phase, are discussed. Results show that the flow stress features and the dominant softening mechanism are sensitive to the deformation parameters. At low strain rates or high deformation temperatures, the main softening mechanism is dynamic recovery. But, the dynamic recrystallization becomes the dominant softening mechanism at high strain rates or low temperatures. At low strain rates, the continuous strengthening, induced by the pinning effect of α precipitates, happens at the late period of deformation. Distribution of α precipitates is not greatly affected by deformation parameters. In the region near β grain boundary, α precipitates are densely distributed with few orientations. While in the central region of β grain, the α precipitates are distributed a bit more sparsely with several scattering orientations. In addition, with increasing deformation temperature, the content, aspect ratio and size of α phases decrease. However, with increasing strain rate, the content, aspect ratio and size first increase and then decrease. Furthermore, the peak value of aspect ratio appears at 0.01 s−1.

High temperature stress–strain curves of MnS and their applications in finite element simulation

Abstract A novel method for testing stress–strain curves of non-metallic materials was presented. The high temperature stress–strain curves of MnS were preliminarily obtained and corrected to account for the influence of friction. Using the finite element method, the influence of deformation parameters on the deformation evolution of MnS inclusions was investigated based on the experimental reference data. The corresponding physical experiment was designed for comparative analysis. The results indicate that the experimental high-temperature deformation data of MnS are highly reliable. In the process of matrix deformation, the shapes of MnS inclusions change from spherical to ellipsoidal and even to lamellar. There are some differences in the morphological deformation of MnS inclusions located at different positions. With the increase in the initial size of MnS inclusions, the risk of failing the inclusion-flaw inspection increases and the forging quality further deteriorates.

Influence of strain rate on dynamic transformation of austenite in an as-cast medium-carbon low-alloy steel

In this work, the effect of strain rate on the dynamic transformation (DT) of austenite to ferrite during high temperature forging of an as-cast medium-carbon low-alloy steel was investigated. Hot deformation experiments were carried out in the 1150 °C to 1200 °C temperature range (400–450 °C above Ae3) and 0.25 s−1 to 2 s−1 strain rate range using a Gleeble 3800® thermomechanical simulator. The critical strains for DT and dynamic recrystallization (DRX) were determined to be in the 0.08 to 0.18 strain range. A microstructural analysis was conducted using optical and electron microscopy. The kernel average misorientation (KAM) technique was applied to electron back-scattered diffraction (EBSD) images to quantify the internal misorientation of grains for the characterization of DT ferrite. Furthermore, it was found that an increase in strain rate decreased the amount of dynamically formed ferrite under the same applied strain and testing temperature. The obtained results were correlated with the influence of deformation parameters on carbon diffusivity and its impact on the growth of dynamically formed ferrite. It was found that an increase in the strain rate decreased the diffusion distance of carbon, which was the responsible mechanism for decreased ferrite formation at higher strain rates.

The Precipitation Behavior and Hot Deformation Characteristics of Electron Beam Smelted Inconel 740 Superalloy

The Inconel 740 superalloy was prepared by the electron beam smelting (EBS) technology, the precipitation behavior and strengthening mechanism were studied, and the hot deformation characteristics of EBS 740 superalloy were investigated. The results indicate that the EBS 740 superalloy is mainly strengthened by the mechanism of weakly coupled dislocation shearing, and the resulting critical shear stress is calculated to be 234.6 MPa. The deformation parameters show a great influence on the flow behavior of EBS 740 superalloy. The strain rate sensitivity exponent increases with the increasing of deformation temperature, and the strain hardening exponent shows a decreasing trend with the increasing of strain. The activation energy of EBS 740 above 800 °C is measured to be 408.43 kJ/mol, which is higher than the 740H superalloy. A hyperbolic-sine-type relationship can be observed between the peak stress and Zener–Hollomon parameter. Nevertheless, the influence of deformation parameters is found to be considerably different at temperatures below and above 800 °C. The size of dynamic recrystallization (DRX) grains decreases with the increasing of strain rate when the strain rate is lower than 1/s, and reverse law can be found at higher strain rate. As a result, a piecewise function is established between the DRX grain size and hot working parameters.

Effect of Deformation Parameters on Microstructure and Properties During DIFT of X70HD Pipeline Steel

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

Influence of Deformation Parameters on Fracture Mechanism of Ti40 Titanium Alloy

An important concern in forming is whether the desired deformation can be accomplished without cracking or fracture of the work material. In this research, based on the cracking specimens obtained from hot compression experiment, the fracture behavior of as-cast highly β stabilized Ti40 alloy was investigated at the deformation temperatures of 1123∼1373 K, strain rates of 0.01∼10 s −1 and height reduction of 70%. The main fracture modes consist of 45° shear fracture and longitudinal cracking occurring on free-surface, as well as inner cracking occurring at the triple boundary junctions. Moreover, the influence of deformation parameters on fracture mechanism was analyzed emphatically in terms of SEM. At low temperature of 1123 K the transgranular cleavage brittle fracture is observed; at 1273 K the ductile fracture occurs; at high temperature of 1373 K a lot of small dimples on the fracture interface are examined. Furthermore, the effect of strain rate on the fracture behavior of as-cast Ti40 alloy is significant. At 0.01 s −1 , the fracture des not occur. At the strain rates of 0.1 and 1 s −1 , the fracture surface is covered with a large amount of dimples indicating that the fracture mode is ductile fracture, while at high strain rate of 10 s −1 , the fracture surface shows a brittle fracture feature. Finally, the damage mechanism and fracture reason were discussed and fracture principle diagram was drawn for the as-cast Ti40 titanium alloy.

Constitutive behavior of Al2O3np/Al7075 composites with a high solid fraction for thixoforming

Abstract The thixotropic compression tests of nano-Al2O3 (Al2O3np)/Al7075 composites with different particle sizes and contents and containing a high fraction of solid, were conducted under conditions of 560–590 °C and 0.01–5 s−1, and the microstructures were observed. A visco-plastic constitutive model of nanoparticle reinforced composites for thixoforming was proposed, considering the coupling effects of strain, strain rate, deformation temperature and liquid fraction and presence of nanoparticles, to describe constitutive behavior of the composites under various deformation conditions. Furthermore, the influence of deformation parameters on thixoforming was investigated. It could be shown that the predictions by the developed model were consistent with experimental results. Fracture analysis of the thixotropic compression samples revealed that high deformation temperature or/and high strain rate could prompt continuous uniform distribution of the liquid phase along the grain boundary, causing the formation of a thin liquid film around an approximately spherical grain, accordingly improving thixoformability of the composites with a high solid fraction. Moreover, deformation mechanisms of the composites during thixotropic compression process were discussed.

Magnetized particle motion around non-Schwarzschild black hole immersed in an external uniform magnetic field

The motion of a magnetized particle orbiting around non-Schwarzschild black hole immersed in an external uniform magnetic field is considered. The influence of deformation parameter $h$ to effective potential of the radial motion of the magnetized particle around non-Schwarzschild black hole using Hamilton-Jacobi formalism is studied. We have obtained numerical values of area $\Delta \rho $ where magnetized particles can move which is expanding (narrowing) due to the effect of the negative (positive) deformation. Finally, we have studied the collision of two particles (magnetized-neutral, magnetized-magnetized, magnetized-charged) in non-Schwarzschild spacetime and got the center-of-mass energy $(E_{c.m})$ for the particles. Moreover, we have found the capture radius ( $r_{cap}$ ) – the distance from the central object to the point where particles collide and fall down to the central compact object. It is shown that non-Schwarzschild black holes could also act as particle accelerators with arbitrarily high center-of-mass energy.