Optimum Deformation Condition Research Articles

Hot deformation mechanism of a rapidly-solidified Al–Zn–Mg–Cu–Zr alloy

This study systematically investigates the flow behavior of 7050 aluminum (Al) alloy produced via spray forming and subjected to a proposed pretreatment through thermal compression tests. The experimental findings reveal that the peak stress increased with decreasing deformation temperature or increasing strain rates. The parameters in the Arrhenius constitutive model were determined and verified by experimental results for spray formed (SFed) 7050 Al alloy. Hot deformation activation energy of the SFed 7050 Al alloy (147.38 kJ/mol) is notably lower than that of cast Al–Zn–Mg–Cu–Zr alloys, which is attributed to factors such as fine grains, low segregation, pores, and dispersed Al3Zr induced by pretreatment. Furthermore, processing maps have been constructed at various strains, revealing optimal stable deformation conditions at 300–450 °C/0.001–0.15s−1 and 425–450 °C/0.2–1s−1. Microstructural analysis of deformed samples highlights the critical role of dynamic recrystallization in influencing the stable and unstable areas of the alloy, which may be activated by high temperature and slow strain rate. The hot deformation mechanism of the SFed Al alloy is governed by interactions among η-Mg(Zn,Al,Cu)2 precipitates, dispersed Al3Zr particles, dislocation structures, and (sub-)grain boundaries.

Microstructural evolution and dynamic recrystallization in Fe50Mn30Co10Cr10 medium entropy alloy under hot compression

This comprehensive study investigates the recrystallization behavior and deformation mechanisms of the Fe50Mn30Co10Cr10 alloy during hot compression conditions. The alloy undergoes discontinuous dynamic recrystallization, evidenced by necklace-like structures at grain boundaries, competing with the initial hexagonal close-packed (HCP) phase and γ→ε reversion. Early deformation is dominated by strain-induced martensite transformation, twinning, with slip with strain partitioning at the end of deformation. The developed Zener-Hollomon equation, validated experimentally, shows a constant activation energy of 126.96 kJ/mol. Stress-strain curves indicate that recrystallization only partially compensates for hardening effects, with no significant peaks observed. The work hardening curve exhibits significant oscillations due to encounters with pre-existing thermal HCP layers, influencing the work hardening rate. Energy efficiency maps based on temperature and strain rate identify optimal deformation conditions at temperatures ranges of 710–750 °C and strain rates of 0.0025–0.0035 s⁻1. This study provides a deeper understanding of the alloy's behavior, offering insights into the interplay between recrystallization, HCP phase formation, and twin generation. These findings contribute to the optimization of the alloy's mechanical properties for industrial applications.

Ti6Al4V-0.72H on the Establishment of Flow Behavior and the Analysis of Hot Processing Maps

Significant columnar grains usually occur in the metallurgical microstructure of laser additive manufacturing, and plastic deformation introduced into additive manufacturing can significantly refine grain size. Due to the high deformation resistance and difficult deformation of titanium alloys, reducing the high-temperature deformation resistance of additive manufacturing titanium alloys is essential to facilitating the implementation of online rolling processes. High-temperature compression of titanium alloys was performed on a Gleeble-3800. It was found that the flow stress of the alloy decreased when the strain of the alloy decreased or the deformation temperature increased. The flow behavior of titanium alloys at high temperatures was investigated with the help of a Z-parameter flow model and multiple linear regression model. A positive correlation was found between the experimental and predicted values of the alloy under the multiple linear regression model, with a correlation coefficient of 0.98 and its error of 13.5%, which could better predict the flow stress values. In addition, hot processing maps were established, and the optimal deformation conditions were determined to provide some theoretical guidance for subsequent experiments.

Formability of the ultra high strength automotive steel docol 1500 bor by using hot processing maps and austenite reconstruction

In this study, the hot processing map was drawn to study the hot formability of high strength automotive steel Docol 1500 Bor. The quenching microstructure of the test steel was observed under optical microscope and EBSD and the deformed PA (parent austenite) was reconstructed under different conditions according to KS (Kurdjumov–Sachs) OR (orientation relationship). The results indicate that the optimal deformation conditions in the stable region are strain rates less than 1s−1 and temperatures higher than 900 °C. Overall, the fine-grained martensite structure with a larger Schmid factor has a better deformation ability for subsequent service. The texture component {011} <100> appears in the PA at the strain rate of 5 s−1 and the temperature of 1000 °C, while the dynamic recrystallization is significantly inhibited. The quenched martensite is found coarse. In the stable region, the recrystallized austenite grains with certain deformation transforms into the martensite grains with low cumulative misorientation values and higher Schmid factors. In the unstable region, the austenite grains are smaller in size, in which severe cumulative misorientation caused by higher strain rates leads to poor plasticity.

Hot deformation behavior and microstructure evolution of a novel nickel-based powder metallurgy superalloy

With the increase in service temperature of aero-engine hot components, the requirements for the high-temperature performance and processability of the powder metallurgy (PM) superalloys used for preparing turbine disks also increase. To overcome the bottlenecks that constrain the preparation and microstructure control of PM superalloys, this work investigates the impacts of hot compression parameters on the hot deformation behavior and microstructure evolution of a novel PM superalloy, FGH4113A. Hot compression tests were conducted on the FGH4113A alloy, which underwent hot isostatic pressing, within a temperature range of 1050 °C–1150 °C and at a consistent true strain rate ranging from 0.001s−1 to 1s−1. The results reveal that the flow stress decreases progressively with the reduction of strain rate and the rise in temperature. Optimal hot deformation conditions are identified at a temperature of 1110 °C with strain rates ranging from 0.1s−1 to 1s−1, and a temperature of 1130 °C with strain rates between 0.01s−1 and 0.1s−1. Within these optimal regimes, grains are uniform, and the average grain size is maintained within10μm. Grain evolution during hot compression involves original grain deformation, followed by recrystallization, subsequent grain coarsening, and then deformation again. Additionally, the γ′ area fraction diminishes with an increase in deformation temperature. Specifically, as the deformation temperature raises from 1050 °C to 1110 °C, and subsequently to 1150 °C, at a rate of 0.001s−1, the primary γ′ area fraction diminishes progressively from 6.2 % to 3.0 % and ultimately to zero. Above 1130 °C, the γ′ area fraction remained largely unaffected by variations in strain rate. These insights are pivotal, offering both experimental data and theoretical perspectives for optimal microstructure control in PM superalloys.

High temperature performance of additively manufactured Al 2024 alloy: Constitutive modelling, dynamic recrystallization evolution and kinetics

The current study investigates the high-temperature deformation behaviour, and microstructural evolution of the laser powder bed fused, Ti modified Al 2024 alloy. The high-temperature performance was evaluated using a hot compression test performed in the temperature range of 200–350 °C and strain rate range of 0.1–10 s−1. The flow behaviour at elevated temperatures at different strain rates can provide us insight into the high temperature application and can also be utilized for optimization of deformation-based post processing technique. The deformation-based post processing method utilizes work hardening to improve the mechanical properties and to reduce the inherent defect of additively manufactured parts, such as pores and lack of fusion. The optimal deformation conditions for these processes can be obtained from the processing map. The flow stress during different deformation conditions (strain, strain rate and temperature) was predicted using different phenomenological models such as Johnson-Cook (JC) model, strain compensated Arrhenius equation, and artificial neural network (ANN). The JC model was observed to be the least suited method in the current investigation, whereas the ANN method was observed to be best suited for predicting flow stress with an average absolute relative error of 0.5% and a correlation coefficient of 0.9998. Different deformation mechanisms such as dynamic recovery (DRV) and dynamic recrystallization (DRX) were investigated for different deformation conditions using empirical models, finite element analysis (FEA) and microstructural characterization using TEM, and EBSD. The primary DRX mechanism in the current study was observed to be continuous dynamic recrystallization or CDRX mechanism.

Processing map and hot deformation behavior of squeeze cast 6082 aluminum alloy

The hot deformation behavior and microstructure evolution of 6082 aluminum alloy fabricated through squeeze casting (SC) under different pressures were studied. The alloy was subjected to hot compression tests and 3D hot processing maps were established. The microstructure evolution was studied by optical microscope (OM), scanning electron microscope (SEM), and electron backscattered diffraction (EBSD). It is found that more dynamic recrystallization (DRX) grains are generated during the deformation of the specimen fabricated under higher SC pressure. At high temperature the effect of SC pressure on microstructure evolution weakens due to the dissolution of second phase particles. In addition, uneven second phase particles in specimens fabricated under higher SC pressure compressed with low temperature and middle strain rate would result in flow localization instability. Finally, the optimum deformation conditions for the 6082 aluminum alloy fabricated by SC were obtained at the temperatures of 430−500 °C and the strain rates of 0.01−1 s−1.

Constitutive Model and Recrystallization Mechanism of Mg-8.7Gd-4.18Y-0.42Zr Magnesium Alloy during Hot Deformation.

The hot deformation behavior of Mg-8.7Gd-4.18Y-0.42Zr alloy was investigated by uniaxial hot compression tests at 300–475 °C with strain rates of 0.002–10 s−1. The average activation energy was calculated as 227.67 KJ/mol and a constitutive relation based on the Arrhenius equation was established in this study. The results show that Mg-8.7Gd-4.18Y-0.42Zr magnesium alloy is a strain rate and temperature-sensitive material. When the temperature is constant, the flow stress increases with the increase of strain rate, while when the strain rate is stable, the flow stress decreases with the increase of temperature. DRX is the main softening mechanism of the alloy, including continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Meanwhile, the DRX grains nucleate preferentially at the twin intersections in the parent grains under the deformation condition below 300 °C and gradually expand outward with the increase of strain. When the compression temperature is above 400 °C, DRX grains nucleate preferentially at the original grain boundary and then gradually expand inward with the increase of strain. The optimum deformation conditions of the studied alloy are performed at 400–450 °C and 0.002–0.02 s−1 by a comprehensive comparison of the hot processing map, microstructure refinement, and formability.

Hot deformation behavior of micro-alloyed steel using processing maps developed with different constitutive equations

The hot workability of microalloyed steel was studied in the deformation temperature range of 850?1200?C and strain rate of 0.001-100s-1. The constitutive relation of flow stress with temperature, strain rate and strain was established to construct processing maps of the microalloyed steel. The processing maps were constructed using conventional power law, integral method, and Arrhenius equations. The developed processing maps were used to predict the optimal hot deformation conditions and were validated with metallurgical examinations. The safe regime for hot working of the experimental steel was found to be in the intermediate temperature-strain rate range (1000-1150?C;0.001-10 s-1), where the deformation process was dominated by dynamic recrystallization and dynamic recovery of the austenitic phase. The processing map constructed using Arrhenius equations increased continuously with an increase in deformation temperature and decrease in strain rate and it did not reveal relevant information of hot workability with respect to deformation temperature and strain rate. The dynamic recrystallization behavior of experimental steel was affected by both deformation temperature and strain rate which was explained in detail through microstructural examination.

Thermal Processing Map and Microstructure Evolution of Inconel 625 Alloy Sheet Based on Plane Strain Compression Deformation.

Plane strain compression tests were used to study the deformation behavior of an Inconel 625 alloy sheet at various temperatures and strain rates. The peak stress was selected to establish the constitutive equation, and the processing maps under different strains were drawn. The results show that the effective stress–strain curve of Inconel 625 has typical dynamic recrystallization (DRX) characteristics. With the increasing deformation temperature and the decreasing strain rate, the softening effect is significantly enhanced. The parameters of the constitutive equation are calculated, and the average error of the constitutive equation is 5.68%. Through the analysis of the processing map, a deformation temperature of 950–960 °C with a strain rate of 0.007–0.05 s−1 were determined as the unstable region, and obvious local plastic-rheological zones were found in the unstable region. The optimum deformation condition was found to be 1020–1060 °C/0.005–0.03 s−1. Through electron backscattered diffraction (EBSD) characterization, it was found that both the increase of temperature and the decrease of strain rate significantly promote the recrystallization process. At a low strain rate, the main recrystallization mechanism is discontinuous dynamic recrystallization (DDRX). It is expected that the above results can provide references for the optimization of the rolling process and microstructure control of an Inconel 625 alloy sheet.

A Comparative Study on the Hot Deformation Behavior of As-Cast and Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Alloy.

The Mg-6.8Y-2.5Zn-0.4Zr (WZ73) alloy exhibits different microstructure characteristic after conventional casting compared to the twin-roll cast (TRC) state. Twin-roll casting results in a finer microstructure, where the LPSO phases are more finely distributed and less strongly connected. A transfer of the hot deformation behavior from the as-cast condition to the TRC condition is only possible to a limited extent due to the microstructural differences. Both states show differences in the recrystallization behavior during hot deformation. In the conventional cast state, dynamic recrystallization (DRX) is assumed to be delayed by the occurrence of coarse blocky LPSO phases. Main DRX mechanisms are continuous dynamic recrystallization (CDRX), particle stimulated nucleation (PSN) and twin induced dynamic recrystallization (TDRX). The deformed TRC sample showed pronounced DRX at almost all deformation conditions. Besides the TDRX and the PSN mechanism, kink induced dynamic recrystallization (KDRX) can be observed. Optimum deformation conditions for both states are temperatures from 500 °C to 520 °C, and strain rates ranging from 0.01 s−1 to 0.1 s−1 for the as-cast material as well as a strain rate of 1 s−1 for the TRC material.

Investigation on hot forging strategy for 5CrNiMoV via high-throughput experiment and machine learning

Hot deformation conditions have important influence on the final properties of 5CrNiMoV steel. Based on the developed high-throughput forging equipment, a combined method of high-throughput simulation and machine learning was put forward to efficiently explore the best deformation conditions for 5CrNiMoV steel. A dataset containing 960 sets of data was established, describing the average grain size, damage, and dynamic recrystallization volume fraction of samples, strain rates and temperatures. The RFR (Random Forest Regression) model was trained and used to predict the optimal hot deformation conditions of 5CrNiMoV steel. Based on the searching space and the screening strategies, the optimal hot deformation conditions of 5CrNiMoV at different strains was successfully achieved. The results show that the designed strategy could be used to improve the research efficiency for better production processes and provide a certain theoretical reference for further experimental verification.

Hot Deformation Behavior and Constitutive Analysis of As-Extruded Mg–6Zn–5Ca–3Ce Alloy Fabricated by Rapid Solidification

The plasticity of Mg–6Zn–5Ca–3Ce alloy fabricated by rapid solidification (RS) at room temperature is poor due to its hexagonal-close-packed (HCP) structure. Therefore, hot deformation of RS Mg–6Zn–5Ca–3Ce alloy at elevated temperature would be a major benefit for manufacturing products with complex shapes. In the present study, hot deformation behavior of as-extruded Mg–6Zn–5Ca–3Ce alloy fabricated by RS was investigated by an isothermal compression test at a temperature (T) of 573–673 K and strain rate (ε˙) of 0.0001–0.01 s−1. Results indicated that the flow stress increases along with the declining temperature and the rising strain rate. The flow stress behavior was then depicted by the hyperbolic sine constitutive equation where the value of activation energy (Q) was calculated to be 186.3 kJ/mol. This issue is mainly attributed to the existence of fine grain and numerous second phases, such as Mg2Ca and Mg–Zn–Ce phase (T’ phase), acting as barriers to restrict dislocation motion effectively. Furthermore, strain compensation was introduced to incorporate the effect of plastic strain on material constants (α,Q,n,lnA) and the predicted flow stresses under various conditions were roughly consistent with the experimental results. Moreover, the processing maps based on the Murty criterion were constructed and visualized to find out the optimal deformation conditions during hot working. The preferential hot deformation windows were identified as follows: T = 590–640 K, ε˙ = 0.0001–0.0003 s−1 and T = 650–670 K, ε˙ = 0.0003–0.004 s−1 for the studied material.

A High-Throughput Forging Technique and Its Application in the Optimization of the Deformation Conditions

Abstract The high-throughput (HT) forging technique is introduced for speeding up the research on the forming property of materials. The core concept of the HT forging technology is to assign two influencing factors to multiple samples simultaneously. By se4tting gradients with different factors in the vertical direction and the horizontal direction, all the samples will be forged at different deformations and HT experimentation will be achieved. HT forging equipment was designed and developed to accomplish the 5 by 6 HT experimentation by establishing a temperature gradient in the vertical direction and a strain or a strain rate gradient in the horizontal direction. A simplified experiment with 5CrNiMoV steel to verify the reliability and efficiency was carried out. Combined with the analysis of microstructure, the relatively excellent deformation condition for the steel was the temperature of 1,000°C and strain rate of 1s−1. For obtaining the optimum deformation condition, more specimens should be forged in the HT equipment. It evidenced that the HT forging technique and the HT equipment would be favorable for analyzing the property and optimize the forming process rapidly.

Investigation of the mechanical behavior of a two-phase Mg-Ni compound during fast compression

The paper presents the results of using a pressing process well known in metallurgy as forging. However, here the Fast Forging process is used as a new way to synthesize materials having e.g. a high hydrogen sorption capacity. Firstly, the method allows delivering a final consolidated product from the initial Mg and Ni powdered elements during pressing. Secondly, it enables a phase transformation, i.e. synthesizing the Mg2Ni binary phase from the initial Mg-Ni mixture of powders, which is a unique result. It is established that the key point in the formation of the binary phase in a sample is the temperature of the Fast Forging. The temperature increase (below the level of the eutectic transition) leads to an almost full consumption of free Ni and the resulting presence of the Mg2Ni phase in the material without melting the work piece. In order to determine the optimal deformation conditions with the goal to obtain a maximum Mg2Ni phase content in the sample, a 2D calculation model of the cell is built with an arbitrary distribution of different-sized Ni particles among the Mg ones. The numerical simulation of the adiabatic compression of the cell up to an average strain of 80-90 % shows that except for preheating the sample chamber, it is necessary to account for the rise of еру sample’s temperature created with the hammer impact during the Fast Forging. It is found that when increasing the initial temperature from 20 °C to 400 °C, the contribution of the additional heat during the intense plastic deformation decreases progressively. The numerical simulation results of the temperature increase within the contact zone of the two types Mg and Ni particles are presented. The deformation fields are determined in the used 2D model cell, which makes it possible to evaluate the system’s mechanical behavior during the Fast Forging process. The calculation results are found in an excellent agreement with the experimental ones.

Hot deformation behavior and dynamic recrystallization mechanism of an Mg-5wt.%Zn alloy with trace SiCp addition

The influence of trace (3 vol%) silicon carbide particle (SiCp) addition on the hot deformation behavior of the Mg-5wt.%Zn (Mg–5Zn) alloy was studied through the hot compression test. The activation energy of the Mg–5Zn alloy is decreased by the addition of trace SiCp, which is due to the high dislocations density in particle deformation zone (PDZ) around SiCp stimulates the pipe diffusion. Moreover, the activation energy of the composite also decreases with the increase of the size of PDZ (dPDZ). Additionally, the optimum deformation condition of 3 vol% 20 μm SiCp/Mg–5Zn composite is 693 K and 0.1–0.01s−1 according to the processing map. The instability region of the processing map at 543 K and 1 s−1 disappears with the increase of strain, which is associated with the inhibitory effect of trace SiCp on {101¯2} extension twins and promoting effect on the dynamic recrystallization (DRX) within {101¯1} contraction twins and {101¯1}-{101¯2} double twins by introducing flow localization. Moreover, the DRX behavior of the 3 vol% 20 μm SiCp/Mg–5Zn composite was analyzed by EBSD technology. The DRX mechanisms of the composite at 543 K and 1 s−1 are continuous dynamic recrystallization (CDRX), particle stimulated nucleation (PSN) and twining dynamic recrystallization (TDRX). With the increase of temperature, the DRX mechanisms are discontinuous dynamic recrystallization (DDRX) and PSN.

Flow characterization of magnesium alloy ZK61 during hot deformation with improved constitutive equations and using activation energy maps

The present study aimed at characterizing the flow characteristics and workability of an as-extruded magnesium alloy ZK61 by isothermal compression tests performed at temperatures of 523–673 K and strain rates of 0.001–1s−1. The flow stress curves were analysed via considering the mechanism of microstructure evolution. Using the obtained flow stress data, both of the conventional and improved Arrhenius constitutive equations were developed to predict the flow characteristics, and the 3D activation energy maps were constructed to propose the optimal deformation conditions and reveal the effects of deformation parameters on microstructure evolution. It can be found that the strain factor plays an important role in determining the shapes of the flow stress curves, which exhibit three types of variation tendencies due to the flow softening and hardening behaviour as the strain increases. The improved constitutive equations resulted in excellent predictability of the peak flow stress within all the deformation conditions. Combining with the activation energy maps, the dominant deformation mechanisms, i.e., dynamic recrystallization and flow localization in different deformation regions were identified, and the optimal processing window of the alloy can be obtained at strain rate and temperature range of 0.001–0.01s−1 and 623 ~ 673 K under a strain of 0.9.

Hot working behavior of near alpha titanium alloy analyzed by mechanical testing and processing map

Abstract The hot deformation characteristics of the Ti−5.7Al−2.1Sn−3.9Zr−2Mo−0.1Si (Ti-6242S) alloy with an acicular starting microstructure were analyzed using processing map. The uniaxial hot compression tests were performed at temperatures ranging from 850 to 1000 °C and at strain rates of 0.001−1 s−1. The developed processing map was used to determine the safe and unsafe deformation conditions of the alloy in association with the microstructural evolution by SEM and OM. It was recognized that the flow stress revealed differences in flow softening behavior by deformation at 1000 °C compared to the lower deformation temperatures, which was attributed to microstructural changes. The processing map developed for typical strain of 0.7 in two-phase field exhibited high efficiency value of power dissipation of about 55% at 950 °C and 0.001 s−1, basically due to extensive globularization. An increase in strain rate and a decrease in temperature resulted in a decrease in globularization of α lamellae, while α lamellar kinking increased. Eventually, the instability domain of flow behavior was identified in the temperature range of 850−900 °C and at the strain rate higher than 0.01 s−1 reflecting the flow localization and adiabatic shear banding. By considering the power efficiency domains and the microstructural observations, the deformation in the temperature range of 950−1000 °C and strain rate range of 0.001−0.01 s−1 was desirable leading to high efficiencies. It was realized that (950 °C, 0.001 s−1) was the optimum deformation condition for the alloy.

Application of an Intermetallic Orthorhombic Titanium Alloy in the Bling Design of the Guide of a High-Pressure Compressor

The results of simulating of a rolling process and selecting the optimal deformation conditions and the QForm software package are used to develop a technology for manufacturing ring workpieces with an outer diameter of 660 mm made of an intermetallic orthorhombic VIT1 titanium alloy. The conditions of heat treatment of the VIT1 alloy ring workpiece are selected. The structure of the ring workpiece in various directions and the mechanical properties of the ring workpiece material are comprehensively studied. The strength characteristics are found to be at a satisfactory level. A sample of the bling guide of a high-pressure compressor is made for the first time from an orthorhombic VIT1 alloy.

Hot Deformation Behavior and Processing Maps of a 9Ni590B Steel

To increase the hot workability and provide proper hot forming parameters of a 9Ni590B steel for the simulation and production, the hot deformation behavior of the 9Ni590B steel is investigated through isothermal compression tests using a Gleeble-3180 thermal–mechanical simulator over a temperature range of 850-1200 °C with strain rates of 0.001-5 s−1. The results indicate that as the deformation temperature increases and the strain rate decreases, the flow stress of the 9Ni590B steel decreases. The deformation–activation energy was calculated to be 364.99 kJ/mol based on the flow stress curve data. The dynamic material model (DMM) was used to establish the process map of the thermal deformation for the 9Ni590B steel. The results show that the optimal deformation conditions for the 9Ni590B steel hot working are with a temperature range of 1100-1200 °C and a strain rate range of 0.001-0.01 s−1. The validity of the calculations was confirmed by observing the microstructure of the 9Ni590B steel sample under the optimal thermal process parameters.