Influence Of Deformation Conditions Research Articles

Hot deformation and dynamic recrystallization of Mg-Gd-Y-Zn-Zr alloy containing high volume fraction 18R-LPSO phase

The deformation behavior including flow behavior, hot workability and dynamic recrystallization (DRX) mechanism of as-cast Mg-9Gd-3Y-3.75Zn-0.6Zr alloy containing 26.5 % volume fraction 18R long-period stacking ordered (LPSO) phase distributed in continuous network morphology were studied by hot compression experiments at deformation condition of 350 ℃-500 ℃, 0.01–1 s−1 strain rate and 0.75 true strain. The influence of deformation conditions on the microstructural evolution was analyzed by using optical microscopy (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). Results display that stress exponent and deformation activation energy are 5.58 and 241.39 kJ·mol−1 correspondingly, which suggested that dislocation climb is the principal deformation mechanism. The Arrhenius type constitutive equation is established as ε̇=4.09×1016sinh(9.922×10−3σ)5.58exp(−241394RT). Microstructure evolution can be characterized by Zener-Holomon parameter (Z) which reflects the combining effect of temperature and strain rate on microstructure. At low lnZ (lnZ<36), the 18R-LPSO phase dissolves from continuous network to blocks and high DRX volume (>50 %) is realized by particle-stimulated nucleation and discontinuous dynamic recrystallization. At moderate lnZ (36≤lnZ<40), a fine and coarse grains bimodal structure is formed at the original grain boundary by continuous dynamic recrystallization resulting in a DRX volume between 10 % and 50 %. At high lnZ (lnZ≥40), layered 14H‐LPSO phase precipitates and inhibits DRX (DRX volume＜10 %) by absorbing dislocations. With combination of dissipation coefficient, instability factor and microstructure analysis, 400 ℃/0.01–0.05 s−1 and 450 ℃/0.01 s−1 are confirmed as optimal hot working domains for the as-cast alloy, under which conditions bimodal microstructure and equiaxed grains microstructure (average grain size 10.3 μm) can be formed correspondingly.

Hot Deformation Behavior and Processing Maps of ZnSnO3/Cu Composites.

In this work, we designed ternary ZnSnO3 particle-reinforced Cu matrix composites and evaluated the hot deformation behavior of ZnSnO3/Cu composites. The hot deformation characteristics of typical dynamic recrystallization were probed by the resulting true stress–strain curves of ZnSnO3/Cu composites. The influences of deformation conditions, including temperatures (650–850 °C) and strain rates (0.01–5 s−1), on the flow stress of the designed composites were investigated. This revealed that the peak stress increased with the increasing of strain rate and decreasing of temperature. Additionally, the activation energy was calculated to be 237.05 kJ/mol and followed by yielding a constitutive equation for low-stress ZnSnO3/Cu composites. The processing maps established by dynamic materials model theory indicated that the designed composites possessed excellent hot workability, and then the processing parameters (790–850 °C and 0.01–0.04 s−1) of the ZnSnO3/Cu composites were determined for practical industrial production. Our work discloses the deformation behavior of ZnSnO3/Cu matrix composites and extends the rational process design for ternary ceramic/metal materials with excellent hot workability.

An efficient grain remapping algorithm for phase-field modeling of dynamic recrystallization

A phase-field (PF) model of dynamic recrystallization was built to predict the microstructure evolution and mechanical responses of maraging stainless steel during hot deformation. Given that the traditional techniques for solving the phase-field model are usually computationally demanding, especially when a large number of grains are present for DRX simulating, an efficient grain remapping algorithm was incorporated into the PF model. Taking advantage of the similarity between order parameters and images, some well-established image processing methods were employed in the algorithm. The algorithm adopted a reduced set of order parameters instead of a one-to-one assignment of order parameters for each grain, but still tracked individual grains for the involvement of unique grain properties and remapped coming-to-contact ones to different order parameters. First, in terms of the PF model, a set of isothermal compression tests were performed to derive necessary model parameters and provide experimental data regarding microstructural and mechanical characteristics for verification purposes. The simulation results, including grain structure and flow stress responses, showed good agreement with experimental observations under various deformation conditions, which indicated the reliability of the established PF model. The influences of deformation conditions on the microstructure evolution and mechanical responses were investigated. Next, a comparative analysis of fidelity and efficiency between the current model and the unmodified model was carried out. Results suggested that the algorithm yielded faithful results of the original model, and significantly reduced the computational memory and time.

The influence of deformation conditions of titanium alloys on the surface quality of the feather of compressor blades

Purpose of work. Improving the quality of manufacturing of blanks of compressor blades from titanium alloys by precision stamping.&#x0D; Research methods and equipment. The research was carried out by precise stamping of blade blanks from the VT8 titanium alloy of the compressor of the D-436 aircraft engine at various temperatures of deformation.&#x0D; Precise stamping of parts was carried out in one tool stroke from a preliminary blank obtained by extrusion from a rod with a diameter of 30 mm.&#x0D; The research of the surface of the workpiece was carried out after processing by X-ray spectral analysis on a JSM6360LA scanning electron microscope.&#x0D; Microhardness was measured on a PMT-3 device at a load of 50 g.&#x0D; Investigations by precision stamping were also carried out on blades made of the OTCh-1 alloy of the input guide vane of the HPC of the D-136 helicopter engine and on the rotor blades of the compressor of the D-36 aircraft engine made of VT3-1 titanium alloy.&#x0D; The obtained results. It is shown that the conditions of deformation of a titanium alloy blade blank by precise stamping have a significant effect on the quality of its surface (macrostructure and microstructure). The deformation temperature of the metal affects the macrostructure and microstructure of the surface during precision stamping of blades from titanium alloys.&#x0D; Scientific novelty. It has been established that during precise stamping of blade blanks from titanium alloys, the deformation temperature has a significant effect on the quality of their surface. The values of the deformation temperature are determined, which provide a significant level of quality of the surface of the airfoil of the blades with precise stamping.&#x0D; Practical value. The results obtained made it possible to develop multi-pass stamping of blade blanks from titanium alloys, when fractional deformation in one pass is applied, not exceeding 30%.&#x0D; The heating temperature of the intermediate billet for deformation should be as close as possible to Тm within ± 10 °С.

Deformed and stressed states of materials at the rolling of three layer stacks, dislocation structure of inner layer – nickel foil

The deformed and stressed states during rolling of a three-layer stack from various materials with a nickel foil inner layer are considered. The technique of determining the density of dislocations is described. The data about the influence of deformation conditions on the distribution and density of dislocations during rolling of nickel foil in various stacks are presented, including the registration or determination of the dislocation structure of nickel foil before deformation and at various degrees of deformation. It is shown that the mechanical scheme of deformation of the inner layer of the stack, namely, the deformation of the nickel foil by non-uniform compression with shear, has a decisive influence on the development of the dislocation structure and properties. It is established that the dislocation density is determined not only by the degree of deformation, but also by a scheme of the deformed and stressed state of matter, and for the case of shear deformation with increasing degree of deformation the dislocation density increases more rapidly than in the case of tensile strain or compression without shear; the result of shear deformation is a significant refinement of the structure of materials: with increasing degree of plastic deformation of the material a three-dimensional cellular network of dislocation is formed, wherein the borders of cells are formed by tangles of dislocations. With increasing degree of deformation, the density of dislocations at the cell boundaries increases, and the size of the cells decreases; in this case, the areas inside the cells of the dislocation network are always free of dislocations. The obtained results allow recommending the schemes with shear deformation for new promising processes of production of materials with unique properties.

Design of a hot deformation processing map for a Ni-free, N-bearing austenitic stainless steel

The hot deformation characteristics of a FeCrMnN austenitic stainless steel containing 0.28 wt.% nitrogen (N) was investigated by hot compression tests using a Gleeble simulator in the temperature range of 800−1200 °C and at constant true strain rates of 0.01–10 s−1 with all specimens deformed to ∼0.9 true strain. The influence of deformation conditions on microstructural mechanisms and phase transformations was characterized. A processing map based on dynamic materials modelling (DMM) was designed and interpreted for predicting the domain of stable flow for safe, defect-free hot deformation. The results revealed the occurrence of dynamic recrystallization (DRX) in a domain extending over the temperature and strain rate ranges of 1100−1200 °C and 0.1–1 s−1, respectively, with the efficiency of power dissipation (η) of 45–55 %. Decreasing temperature and increasing strain rate led to a reduction in DRX grain size following microstructural reconstitution. Another small deterministic domain of 820−1000 °C and 0.01−0.05 s−1 was identified showing occurrence of partial DRX in shear bands leading to formation of a mixed microstructure. The instability criteria delineated the regime of unstable flow covering a large part of the processing map extending over low temperatures (800−950 °C) and high strain rates (0.1–10 s−1) that must be avoided during processing.

Influence of Deformation Conditions on the Power Regimes of the Process of Cold Crimping of a Pipe Billet in a Conical Die

An engineering technique has been developed that makes it possible to determine the power regimes of the process of crimping a tubular billet in a conical die, taking into account the effect of deformation conditions. The influence of the geometric parameters of the workpiece and tool, the crimping coefficient and non-contact deformation on the axial stress of the crimping process is studied. The main factors influencing the limiting values ​​of the workpiece crimping factor are established. Calculations are performed for the crimping process performed on an open circuit (without stop block), taking into account the friction and hardening of the material. The obtained results are in good agreement with the known experimental data and can be used in the development of the processes of crimping of pipe billets.

Quantitative Assessment of Dynamic Recovery Kinetics in Sn-5Sb Lead-Free Solder Alloy During Hot Working

The deformation behavior of Sn-5Sb alloys was investigated using isothermal hot compression at 300 K, 330 K, 360 K and 400 K and strain rates of 0.01 s−1, 0.005 s−1, 0.001 s−1 and 0.0005 s−1. The recorded true stress–strain curves were obtained from load–stroke data and their quantitative characteristics were analyzed. Relationships between the flow stress, temperature and strain rate were expressed in terms of the conventional hyperbolic sine equation. By performing regression, 54 kJ/mol was determined as the average activation energy of deformation. Based on σ (dσ/de) versus σ curves, the coefficient of dynamic recovery (DRV) rate (r), saturated stress (σRV) and yield strength (σ0) under different thermomechanical conditions were computed. For the volume fractions of DRV, the modified Avrami type equation was derived as a function of the Zener–Hollomon parameter (Z) and the influence of deformation conditions on the kinetics of DRV was investigated in detail.

Hot deformation characterization of a novel Al-Zn-Mg-Cu aluminum alloy through processing map and microstructure evolution

The isothermal compression experiments of a novel 7A36 aluminum alloy were performed on Gleeble3500 thermal simulation equipment at temperature range of 350 °C ∼ 450 °C with an interval of 25 °C and strain rates of 0.01 s−1 ∼ 10 s−1. The influence of deformation conditions on flow stress, microstructure and thermal process performance were investigated. The constitutive equation and processing map were established. The optical microscopy (OM), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the microstructure evolution. The results indicate that 7A36 aluminum alloy has steady rheological characteristics and a trend to dynamic softening. The alloy has positive strain sensitivity, the flow stress decreases with increasing of deformation temperature and decreasing of strain rate. The estimated activation energy in constitutive model is 153.703 kJ mol−1 which is close to that self diffusion in pure aluminum. The constitutive equation and microstructure evolution during isothermal compression process confirmed that dynamic recrystallization (DRX) should be the soften mechanism. The processing map exists two safe regions of domain 1 (380 ∼ 450 °C, 1 ∼ 10 s−1) and domain 2 (350 ∼ 450 °C, 0.01 ∼ 1 s−1). The specimens deformed at 450 °C/0.01 s−1 in domain 2 is proposed to be the optimum hot-working condition.

Influence of deformation conditions on the inhomogeneity of plastic flow of structurally graded bimetal systems

Bimetals produced by explosive welding and subjected to surface mechanical attrition treatment (SMAT) were investigated. It is expected that the way of manufacturing and the morphology of nano- crystalline and multilayered materials obtained by the "top down" group of methods such as severe plastic deformation (SPD) has significant influence on the deformation mechanisms. The basic materials investigated in the paper were microalloyed steel and Nickel super-alloy. Bimetals were subsequently subjected to the deformation by compression test under dynamic and quasi-static conditions. Microstructural study based on light microscopy and scanning electron microscopy was performed focused presumably on the plastic flow of the deformed metallic laminate.

Influence of Deformation Conditions on the Critical Damage Factor of AZ31 Magnesium Alloy

The influence of deformation conditions on the critical damage factor of AZ31 magnesium alloy was analyzed in this paper. Physical experiments and numerical simulation were used to study the critical damage factor. Compression test was carried out using a Gleeble 1500 device at temperatures between 250°C and 400°C, as well as strain rates from 0.01 s−1 to 1 s−1. True stress‐strain curves of samples were obtained. Based on experimental data, an Arrhenius constitutive model was constructed. Material performance parameters and constitutive model were inputted into the finite element program DEFORM. Simulation results show that the maximum damage appears on the outer edge of the upsetting drum, and damage softening behavior is more sensitive to strain rate. According to the concept of damage sensitive rate, its values were computed. The intersection of line fitted and horizontal axis was obtained in the fracture step, and its relative maximum damage value was as the critical damage factor. The distribution of the critical damage value shows that it is not a constant but fluctuates within the range of 0.1445–0.3759, and it is more sensitive to strain rate compared with temperature.

The influence of deformation conditions on the structure and hardening of cast iron surface layer in machining with combined carbide broaches

The behavior of the metal matrix and graphite inclusions during the cold plastic deformation of the surface layer during the cold plastic deformation of graphite-containing cast iron specimens by carbide tools is studied using testing and metallographic equipment as well as a modern electron scanning microscope.

Influence of deformation conditions on the development of heterogeneous recrystallization microstructures in experimentally deformed Carrara marble

Abstract Recrystallized grains are potentially useful as indicators of palaeostress in naturally deformed rocks, providing that well-calibrated relationships (palaeopiezometers) exist between the recrystallized grain size and stress. Rocks can exhibit microstructures that are heterogeneous, that is, containing recrystallized as well as deformed grains, and showing subgrains within grains that differ in size and character from the grain core to the mantle. Previous studies on palaeopiezometers only rarely took into account such heterogeneous microstructure. We used electron backscattered diffraction (EBSD) to accurately quantify the heterogeneous microstructures in experimentally deformed Carrara marble (flow stress 15–85 MPa, temperature 700–990 °C and natural strain 0.15–0.90). The sizes of bulges, recrystallized grains and deformed grains have been measured. We found that the overall character of the microstructures varies as a function of deformation conditions. In heterogeneous samples showing core-mantle microstructures, the sizes of the bulges and recrystallized grains are independent of strain and show an inverse dependency on stress. The recrystallized grains have been found to nucleate at grain boundary bulges. Our study illustrates that very different microstructures may develop in relation to the complexity of the recrystallization mechanisms. We therefore suggest that piezometers should be calibrated and applied for a single type of overall microstructure.

The influence of deformation conditions in solid-state aluminium welding processes on the resulting weld strength

Solid bonding of aluminium is an important joining technology with applications in fabrication, forming and new low-carbon recycling routes. The influence of deformation conditions on the strength of the resulting weld has yet to be fully assessed, preventing optimization of current processes and development of new ones.In this work, an extensive literature review identifies the deformation parameters important to weld strength: interface strain, strain rate, normal contact stress, temperature and shear. The film theory of bonding is used to derive a model that quantifies the relevance of these parameters to the weld strength. This model is then evaluated using an experiment in which the interface strain and normal contact stress are decoupled, and the friction hills between both the tooling and the samples and between the samples themselves minimized. Neither the model nor the experiments deal with samples that have undergone mechanical surface preparation (for example, scratch brushing) prior to bonding.The experiments show that a minimum strain is required for bonding. Increasing the temperature, normal contact stress or shear stress can reduce this minimum strain. A normal contact stress above the materials’ uniaxial yield stress is necessary to produce a strong bond. Increasing the strain rate has little affect on the weld strength for bonds created at low temperatures, but can significantly reduce the strength of bonds created at higher temperatures.The proposed model correctly predicts these trends; however, for higher temperatures it underestimates bond strengths and the influence of strain rate, suggesting that diffusion mechanisms increase the strength of bonds created at higher temperatures.

Constitutive modeling for the dynamic recrystallization kinetics of as-extruded 3Cr20Ni10W2 heat-resistant alloy based on stress–strain data

In order to improve the understanding of the dynamic recrystallization (DRX) behaviors of as-extruded 3Cr20Ni10W2 heat-resistant alloy, a series of isothermal upsetting experiments with a fixed height reduction of 60% were performed at the temperatures of 1203K, 1253K, 1303K, 1353K and 1403K, and the strain rates of 0.01s−1, 0.1s−1, 1s−1 and 10s−1 on a Gleeble1500 thermo-mechanical simulator. By the regression analysis for conventional hyperbolic sine equation, the activation energy of DRX was determined as Q=892.3511kJmol−1. According to the conventional strain hardening rate curves (dσ/dɛ versus σ) and their derived results, three characteristic points including the critical strain for DRX initiation (ɛc), the strain for peak stress (ɛp), and the strain for maximum softening rate (ε∗) were identified. In order to characterize the evolution of DRX volume fraction, the modified Avrami type equation including ɛc and ε∗ as a function of the dimensionless parameter controlling the stored energy, Z/A, was evaluated, and the influence of deformation conditions was described in details. Finally, the theoretical prediction results of DRX volume fraction were shown to be in agreement with experimental observations.

Effect of hot deformation conditions on grain structure and properties of 7085 aluminum alloy

The influences of deformation conditions on grain structure and properties of 7085 aluminum alloy were investigated by optical microscopy and transmission electron microscopy in combination with tensile and fracture toughness tests. The results show that the volume fraction of dynamic recrystallization increased with the decrease of Zener-Hollomon (Z) parameter, and the volume fraction of static recrystallization increased with the increasing of Z parameter. The strength and fracture toughness of the alloy after solution and aging treatment first increased and then decreased with the increase of Z parameter. The microstructure map was established on the basis of microstructure evolution during deformation and solution heat treatment. The optimization deformation conditions were acquired under Z parameters of 1.2 × 1010−9.1 × 1012.

Stressed state of chemically active polymeric systems under shear, elongation, and oscillating deformations

The stressed state of chemically active polymeric systems under the conditions of shear, elongation, and oscillating deformations has been investigated. From the viewpoint of locally nonequilibrium thermodynamics and statistical physics for systems with a complex internal structure, the moment characteristics of the locally nonequilibrium transfer process and the related components of their stress tensor deviator have been established. The influence of deformation conditions on the amount and character of the change in the stressed state of chemically active polymeric systems has been analyzed.

Deformation Microstructures and Textures of Cast Mg-3Sn-2Ca Alloy under Uniaxial Hot Compression

The influence of deformation conditions on the microstructure and texture evolution during hot compression of Mg-3Sn-2Ca (TX32) has been studied. Cylindrical samples were compressed uniaxially at different combinations of temperatures and strain rates in the ranges 300-500 oC and 0.0003-10 s-1. The crystallographic orientation information of the as-cast and deformed specimens was obtained by EBSD micro-texture analysis. Activation of different slip systems was investigated using Schmid factor analysis and the results reinforce the importance of non-basal slip for deformation at high temperatures. Samples deformed at 500 oC/0.1 s-1 resulted in a fully recrystallized microstructure with near random crystallographic texture.

Texture and microstructure development during hot deformation of ME20 magnesium alloy: Experiments and simulations

Abstract The influence of deformation conditions and starting texture on the microstructure and texture evolution during hot deformation of a commercial rare earth (RE)-containing magnesium alloy sheet ME20 was investigated and compared with a conventional Mg sheet alloy AZ31. For all the investigated conditions, the two alloys revealed obvious distinctions in the flow behavior and the development of texture and microstructure, which was primarily attributed to the different chemistry of the two alloys. The presence of precipitates in the fine microstructure of the ME20 sheet considerably increased the recrystallization temperature and suppressed tensile twinning. This gave rise to an uncommon Mg texture development during deformation. Texture simulation using an advanced cluster-type Taylor approach with consideration of grain interaction was employed to correlate the unique texture development in the ME20 alloy with the activation scenarios of different deformation modes.

The Influence of Deformation Conditions on Structure of Fe-Al Intermetallic Phase ‒ Based Alloys

The major problem restricting universal employment of intermetallic phase base alloy is their low plasticity which leads to hampering their development as construction materials. The following work concentrates on the analysis of microstructure and plasticity of ordered Fe3Al (D03) and FeAl (B2) during hot plastic deformation process.. The microstructure analyses applying optical electron microscopy and EBSD method have revealed the structure reconstruction processes occurring in Fe3Al and FeAl alloys. It has been shown that different mechanisms of the structural changes ensue from the thermal plastic strain in the investigated alloys, which influences their technological plasticity.