Optimum Processing Domain Research Articles

Intermediate temperature tensile behavior and processing map of a spray formed 7075 aluminum alloy

The intermediate temperature deformation behavior and microstructural evolution of a spray formed 7075 Al alloy were performed at temperatures 60–120 °C with strain rates 0.00001–0.1 s−1. The results reveal that the softening mechanism of the intermediate temperature deformation is dynamic recovery (DRV), which can be quantitated by Zener-Hollomon (Z) parameter. The constitutive equation can reasonably predict the stress-strain behavior of the alloy at intermediate temperatures. The activation energy is related to the deformation process and the interactions of the substructure, the average value is 140.1 kJ/mol. The higher efficiency of power dissipation in the processing map is related to the DRV at lower deformation temperatures. The optimum processing domain is located at the temperature of 90–120 °C and strain rate of 0.006–0.1 s−1 with a power dissipation efficiency range of 20%–40%. The processing parameters of the intermediate temperature deformation should be strictly controlled according to the strain. The uniform microstructure of 7075 alloys obtained by spray forming is crucial to overcome the disadvantage of poor deformability. The inferior coordinated deformation facilitates crack propagation at low strain rates. The high-density dislocation provides adequate nucleation sites for dynamic precipitation. The level of dynamic restoration facilitates the transformation from low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs). The dislocations move to the grain/sub-grain boundary to form dislocation walls at low temperatures. The contribution to the stress from grain boundary (13.2–17.7 MPa), nanoscale precipitates (65.7–191.5 MPa), and dislocation (5.9–23.4 MPa) increases the difficulty of deformation. The deformation process at higher temperatures (105–120 °C) can be facilitated by the dissolution and coarsening of the nanoscale precipitates, and dislocation motion at the grain boundary.

Integrated experimental and modeling approach for hot deformation behavior of Co–Cr–Fe–Ni–V high entropy alloy

The study aims to investigate the hot deformation behavior of Co–Cr–Fe–Ni–V high entropy alloy (HEA) at temperatures ranging from 1073 K to 1373 K and strain rates of 0.001, 0.01, 1, and 10 s−1, and to generate processing maps using dynamic materials modeling (DMM) to identify the optimum processing domain for industrial applications. The material's hardening and softening characteristics are also explored under various hot working conditions. Deformation twinning is observed in materials deformed at 0.1 s−1 at 1273 K and 1373 K, contributing to their observed hardening. The mean free path of dislocation defines the material's strength, and the transition point from dynamic recovery to dislocation-dislocation or dislocation-solute interaction occurs when the mean free path of dislocation reaches its lowest value. The inhomogeneity in the deformed sample is correlated with the strain field distribution using an integrated approach using finite element method (FEM) modeling and electron backscattered diffraction (EBSD) results. EBSD characterization reveals the presence of deformation bands and annealing twins at low and high temperatures, respectively. Additionally, an artificial neural network (ANN) model is proposed to predict the hot deformation behavior of Co–Cr–Fe–Ni–V HEA, with promising results, as evidenced by a correlation coefficient (R) of 0.9983 and an average absolute relative error (AARE) of 2.71% on the test dataset.

Compressive response and microstructural evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite

The hot forming behavior, failure mechanism, and microstructure evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300–450 °C and strain rates of 0.001-1 s−1. The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate, and dimple rupture of the matrix at high temperature and low strain rate. Full dynamic recrystallization, which improves the composite formability, occurs under conditions of high temperature (450 °C) and low strain rate (0.001 s−1); the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite. Based on the flow stress curves, a constitutive model describing the relationship of the flow stress, true strain, strain rate and temperature was proposed. Furthermore, the processing maps based on both the dynamic material modeling (DMM) and modified DMM (MDMM) were established to analyze flow instability domain of the composite and optimize hot forming processing parameters. The optimum processing domain was determined at temperatures of 425-450 °C and strain rates of 0.001-0.01 s−1, in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.

Influence of Temperature and Strain Rate on Microstructural Evolution During Hot Compression of Ti-45Al-xNb-0.2C-0.2B Titanium Aluminide Alloys

The hot deformation response of third-generation titanium aluminides with compositions Ti-45Al-5Nb-0.2B-0.2C and Ti-45Al-10Nb-0.2B-0.2C (hereafter referred to as Ti-45-5 and Ti-45-10, respectively) has been investigated through isothermal compression tests. The tests have been carried out in the $$ (\alpha_{2} + \gamma ) $$ and $$ (\alpha + \gamma ) $$ phase regions for both alloys. The flow response, kinetics and microstructural evolution during hot deformation have been analysed in detail, and the outcome of the investigation has been used to predict the processing window for the two alloys. The optimum processing domain for the Ti-45-10 alloy is situated 50°C higher than that of the Ti-45-5 alloy. The post-mortem analyses of the microstructures revealed that deformation in the $$ (\alpha_{2} + \gamma ) $$ phase field leads to dynamic recrystallisation of all the phases resulting in a distribution of very fine grains. Microstructural features of both alloys depict kinking and breaking of the lamellae for the equivalent temperatures. The higher strength of the Ti-45-10 alloy has been attributed to shifting of the order-disorder transition toward the higher temperature side. In the $$ (\alpha + \gamma ) $$ region, the fraction of $$ \alpha $$ phase increases more for the Ti-45-10 alloy compared with the Ti-45-5 alloy.

Hot deformation behavior and microstructural evolution of as-quenched 7055 Al alloy fabricated by powder hot extrusion

Isothermal compression tests of powder hot-extruded 7055 Al alloy were carried out on a Gleeble-3180 thermo-simulator at temperatures of 330–450 °C and strain rates of 0.001–1 s−1. A processing map was established by superimposing the power dissipation map over the instability map at a true strain of 0.7. The results show that the instability domain tends to occur at high strain rates and low temperatures, and an optimum processing domain (360–420 °C, 0.001–0.013 s−1) is recommended. The softening mechanism of instability domain is manifested as dislocation accumulation and dynamic recovery (DRV), while that of the recommended domain is mainly coexistence of DRV and partial dynamic recrystallization (DRX). As the temperature increases and the strain rate decreases further, the dominant softening mechanism changes from dynamic recovery (DRV) to continuous dynamic recrystallization (CDRX). Strain-compensated Arrhenius model and artificial neuron network (ANN) model are constructed to predict the flow behavior of the alloy. Compared with the Strain-compensated Arrhenius model, the ANN model shows a better predictability with a lower average absolute relative error of 2.24%, a lower root mean square error of 1.21 MPa, and a higher correlation coefficient of 0.9987.

Hot deformation behavior of a spark plasma sintered Fe-25Al-1.5Ta alloy with strengthening Laves phase

Intermetallic iron aluminide alloys show various advantages such as low material cost and a good creep resistance that is superior to the P92 martensitic-ferritic steel at 650 °C, nominating them as potential candidates for steam turbine applications. However, cast preforms for hot forging show a rather coarse microstructure and limited workability. Recent research thus introduced Fe-25Al-Ta alloys, where tantalum prevents excessive grain growth during solidification. This paper, for the first time, investigates the possibility of producing the Fe-25Al-1.5Ta (at.%) alloy by spark plasma sintering (SPS) from pre-alloyed powder particles and investigates its deformation behavior under compression in the temperature range of 900–1100 °C using the concept of processing maps. SPS is mainly used to analyze the possibility of inheriting the size of the initial powder particles into the sintered material.The SPSed specimen at room temperature reveals a homogeneous equiaxed microstructure consisting of fine A2-phase grains with an average size of 7 μm surrounded by the ternary (Fe, Al)2Ta, C14, Laves phase particles. Laves phase particles are precipitated predominantly on grain boundaries of the Fe-Al matrix grains. Several particles are also dispersed inside the grains.The presence of a fine-grained equiaxed microstructure at hot working temperature seems to improve workability and leads to a wide processing window. The optimum processing domain for the studied Fe-25Al-1.5Ta alloy locates at 1050–1100 °C/0.0013–0.01 s−1 with a power efficiency of 40–50%, where the material undergoes dynamic recrystallization. At low temperature and high strain rates, dynamic recovery is the major softening mechanism observed for the samples, where the efficiency of power dissipation reaches around 40%.The current study offers a possibility to produce a homogeneous fine-grained Fe-25Al-1.5Ta alloy strengthened by dispersed Laves phase particles using SPS compared to the coarse and columnar microstructure commonly obtained by casting. Such a refined microstructure leads to a good hot forgeability.

EBSD Study on Processing Domain Parameters of Oxide Dispersion Strengthened 18Cr Ferritic Steel

This paper presents the results of an experimental study aimed to identify hot working domains in oxide dispersion strengthened (ODS) 18Cr ferritic steel over a wide range of temperatures (1323-1473 K) and strain rates (0.01-10 s−1). The experimental data were obtained by uniaxial compression test using the Gleeble-1500D simulator in this range of temperature and strain rate. An inverse relationship with temperature and positive strain rate sensitivity associated with dynamic recovery and recrystallization, which is influenced by temperature and strain rate, was derived from the flow stress. Based on the processing map generated at 0.5 true strain, using rate dynamic material model (DMM) approach and the calculated instability parameter $$\left( {\xi \left( \acute{\epsilon} \right)} \right) > 0$$ , the optimum processing domain has been determined for this steel. The most favorable processing parameters are found in the temperature ranges of 1350-1450 K with a strain rate of 0.01 s−1 and 1473 K with a strain rate 0.1 s−1 with peak efficiency of 30 and 35%, respectively. The material flow behavior was studied using scanning electron microscopy (SEM)-based EBSD microstructural characterization. The steel subjected to 1323 K at high strain rate 10 s−1 in the low-efficiency workability region showed low aspect ratio as compared to the elongated bamboo-like initial microstructure; however, minimum strain rate (0.01 s−1) showing that localized slip/shearing is the key mechanism and fiber texture studied from the intensity distribution of inverse pole figure showed the presence of significant amount of θ-fibers. In contrast, dynamic recrystallization dominated at higher efficiency region in the safe domain of processing map and γ-fiber texture was evident in the specimen deformed at 1373 and 1473 K with strain rate of 0.01 and 0.1 s−1, respectively, which is responsible for the change in the initial 〈1 1 0〉//ED α-fiber texture.

Flow characteristics and hot workability studies of a Ni-containing Fe‑Mn‑Al‑C lightweight duplex steel

The high temperature deformation behavior of Fe‑9Al‑10Mn‑4Ni‑0.7C duplex steel has been investigated in the range of temperatures 1223–1423 K and strain rates 0.001–10 s−1. The multistage work hardening behaviors are analysed using Kocks-Mecking model and the correlations among various characteristic parameters of dynamic softening (viz. peak stress, recovery stress, steady-state stress and critical stress/strain) are evaluated. The processing and activation energy maps are constructed to identify the optimum processing domains. The microstructural responses towards various processing parameters are considered to correlate the dynamic softening phenomena and high efficiency domain of the processing map. The optimum hot working domain is obtained as 1223–1350 K and 0.001–0.01 s−1 which is identified by low apparent activation energy value and dominant continuous dynamic recrystallization mechanism in where typical transition of low-angle to high-angle boundary is observed. At lower temperature (<1373 K) and higher strain rate (≥1 s−1) unstable domain, material exhibits micro-bands and cracks along the austenite/ferrite interphase boundaries. Furthermore, at lower strain rate (0.001 s−1) and higher temperature (≥1373 K) unstable domain, wedge crack at the triple junction is revealed as the sign of deformation instability.

Hot deformation and processing maps of as-sintered CNT/Al-Cu composites fabricated by flake powder metallurgy

Abstract The deformation behaviors of as-sintered CNT/Al-Cu composites were investigated by isothermal compression tests performed in the temperature range of 300−550 °C and strain rate range of 0.001−10 s−1 with Gleeble 3500 thermal simulator system. Processing maps based on dynamic material model (DMM) were established at strains of 0.1−0.6, and microstructures before and after hot deformation were characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and high-resolution transmission electron microscopy (HRTEM). The results show that the strain has a significant influence on the processing maps, and the optimum processing domains are at temperatures of 375−425 °C with strain rates of 0.4−10 s−1 and at 525−550 °C with 0.02−10 s−1 when the strain is 0.6. An inhomogeneous distribution of large particles, as well as a high density of tangled dislocations, dislocation walls, and some sub-grains appears at low deformation temperatures and strain rates, which correspond to the instability domain. A homogeneous distribution of fine particles and dynamic recrystallization generates when the composites are deformed at 400 and 550 °C under a strain rate of 10 s−1, which correspond to the stability domains.

A New Method for Optimizing Hot Processing Parameters of Mg-6.0Zn-0.5Mn-0.5Er Alloy Based on Kinetic Model of Dynamic Recrystallization and Processing Map

Hot deformation behavior of the cast-homogenized Mg-6.0Zn-0.5Mn-0.5Er alloy was studied using dynamic recrystallization (DRX) kinetic model and processing map. The compressing tests were conducted in the temperature range of 250-450 °C and strain rates of 0.001-1 s−1. According to the evolution of microstructures, under lower strain rates, the main DRX mechanism of Mg-6.0Zn-0.5Mn-0.5Er alloy is continuous DRX (CDRX); twinning induced DRX (TDRX) and CDRX both become the main DRX mechanism under higher strain rates. The DRX kinetics model of Mg-6.0Zn-0.5Mn-0.5Er alloy is calculated as $$X_{\text{DRX}} = 1 - \exp \left[ { - 1.9463\left( {\frac{{\varepsilon - \varepsilon_{\text{c}} }}{{\varepsilon^{*} }}} \right)^{1.4608} } \right]$$ , which is corresponding to the microstructure evolutions of DRX under different deformation conditions. The contour map of DRX was proposed based on the calculation results of DRX kinetics model. The processing maps are constructed to predict processing parameters of the alloy, and the predictability was evaluated combining with the contour map of DRX and dynamic materials model (DMM) processing map. It is deduced from the microstructures evolution and processing map that the optimum processing domain is mainly at 380-450 °C and 0.01-0.001 s−1, and 410-420 °C and 0.01-1 s−1.

Flow curve correction and processing map of 2050 Al–Li alloy

Abstract Hot compression tests of 2050 Al–Li alloy were performed in the deformation temperature range of 340–500 °C and strain rate range of 0.001–10 s–1 to investigate the hot deformation behavior of the alloy. The effects of friction and temperature difference on flow stress were analyzed and the flow curves were corrected. Based on the dynamic material model, processing map at a strain of 0.5 was established. The grain structure of the compressed samples was observed using optical microscopy. The results show that friction and temperature variation during the hot compression have significant influences on flow stress. The optimum processing domains are in the temperature range from 370 to 430 °C with the strain rate range from 0.01 to 0.001 s–1, and in the temperature range from 440 to 500 °C with the strain rate range from 0.3 to 0.01 s–1; the flow instable region is located at high strain rates (3–10 s–1) in the entire temperature range. Dynamic recovery (DRV) and dynamic recrystallization (DRX) are the main deformation mechanisms of the 2050 alloy in the stable domains, whereas the alloy exhibits flow localization in the instable region.

Hot workability of PM 8009Al/Al2O3 particle-reinforced composite characterized using processing maps

High-temperature compression testing of powder metallurgy (PM) 8009Al alloy reinforced with 15 vol% Al2O3 particles was performed at temperatures of 400–550 °C and strain rates of 0.001–1 s−1. Its constitutive behavior and processing maps were investigated, and the related microstructural evolutions were characterized by scanning and transmission electron microscopy. The results showed that the stress peak decreased with increasing deformation temperature and decreasing strain rate, which could be described by the Zener-Hollomon parameter Z of the hyperbolic sine relation. The processing map constructed at a strain of 0.5 exhibited two safe processing domains: 500–530 °C at 0.001–0.003 s−1 and 530–550 °C at 0.001–0.01 s−1. After taking into account the processing map, efficiency of power dissipation and microstructural observations, the optimum processing domain corresponding to 530–550 °C/0.001–0.01 s−1 was determined. As increasing deformation temperature and decreasing strain rate, the composite substructures with high density of dislocations were transformed into subgrains with distinct shapes and the fine dispersed Al12(Fe,V)3Si phase coarsened inside the matrix, which exhibited typical dynamic recovery (DRV) characteristics. In addition, the interaction of the dislocation-dispersed phase-Al2O3 particle and its effect on the hot deformation behavior of the 8009Al/Al2O3 composite were discussed.

Constitutive Relationship and Hot Processing Maps of Mg-Gd-Y-Nb-Zr Alloy

The hot working behavior of Mg-Gd-Y-Nb-Zr alloy was investigated using constitutive model and hot processing maps in this work. Isothermal compression tests were conducted with temperature and strain rate range of 703–773 K and 0.01–5 s −1 , respectively. Improved Arrhenius-type equation incorporated with strain compensations was used to predict flow behavior of the alloy, and the predictability was evaluated using correlation coefficient, root mean square error and absolute relative error. Processing maps were constructed at different strains for Mg-Gd-Y-Nb-Zr alloy based on dynamic materials model. The processing maps are divided into three domains and the corresponding microstructure evolutions are referred to the forming of straight grain boundaries, twinning, dynamic recrystallization and grain growth. Instability occurred mainly at the strain rate range of 0.3s −1 –0.5s −1 . The optimum processing domain is mainly at the temperature range of 703–765 K with the strain rate range of 0.01–0.1 s −1 .

Hot deformation characteristics and processing map of a phosphorous modified super austenitic stainless steel

Hot deformation behavior of a phosphorous-modified super austenitic stainless steel was studied in the temperature range of 1173–1423K and strain rate range of 0.001–10s−1 employing thermomechanical simulator. The apparent activation energy for deformation in the above processing regime was estimated to be 482kJmol−1. The deformation parameters were modeled using Arrhenius equation and Zener–Hollomon parameter (Z). Peak stress, critical stress for dynamic recrystallization, stress at which flow softening is maximum as well as steady state stress was found to exhibit a linear relationship with ln(Z/A). Strains corresponding to these stresses were also found to exhibit the relation ε=CZAp. Processing maps were developed at different plastic strains employing dynamic materials modeling. Microstructures corresponding to the different processing conditions were characterized employing electron back scatter diffraction. Based on the analysis of microstructure and processing map, the optimum processing domain for hot deformation is identified as strain rate range of 0.01–0.1s−1 and temperature range of 1300–1350K. Although a significant recrystallization was observed following hot deformation in the strain rate ranges of 1–10s−1 and temperature ranges 1373–1423K, this domain was marked as unstable in the processing map.

Optimum Deformation Criteria and Flow Behavior Description of Boron-Alloyed Steel through Numerical Approach

The capability of a phenomenological, a physical-based, and a restoration-based model in flow behavior description has been evaluated comparatively to determine the optimum high-temperature deformation condition for a boron-alloyed steel. For this purpose, the hot compression tests are performed over wide ranges of strain rate and temperature. The modified Zerilli–Armstrong model is found to be simple and handy for flow modeling since it employs less material constants compared to the other models. The strain-compensated Arrhenius constitutive equation is accurate and can be used to predict the flow behavior of similar alloys over a wide range of deformation temperatures. The restoration-based constitutive analysis is the most accurate approach for flow modeling because it takes different stages of deformation into account separately. Finally yet importantly, the experimental data are used to develop the efficiency maps and the optimum processing domains are determined.

Deformation behaviors and processing maps of CNTs/Al alloy composite fabricated by flake powder metallurgy

Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300–550 °C and strain rate range of 0.001– 10 s−1 with Gleeble–3500 thermal simulator system. Processing maps of the CNTs/Al alloy at different strains were calculated to study the optimum processing domain. Microstructures before and after hot compressions were characterized by electron backscattered diffraction (EBSD) method. Stress–strain curves indicate that the flow stress increases with the increase of strain rate and the decrease of temperature. The processing maps of the CNTs/Al alloy at different strains show that the optimum processing domain is 500–550 °C, 10 s−1 for hot working. EBSD analysis demonstrates that fully dynamic recrystallization occurs in the optimum processing domain (high strainrate 10 s−1), whereas the main soften mechanism is dynamic recovery at low strain rate (0.001 s −1).

Hot deformation and processing maps of Al2O3/Al composites fabricated by flake powder metallurgy

The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300–450 °C and strain rates of 0.001–1.0 s−1 with Gleeble–1500D thermal simulator system. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The hyperbolic sine constitutive equation can describe the flow stress behavior of Al2O3/Al composites, and the deformation activation energy and constitutive equations were calculated. The processing maps of Al2O3/Al-2 μm and Al2O3/Al-1 μm composites at strain of 0.6 were obtained and the optimum processing domains are in ranges of 300–330 °C, 0.007–0.03 s−1 and 335–360 °C, 0.015–0.06 s−1 for hot working, respectively. The instability zones of flow behavior can also be recognized by the maps.

Hot deformation behavior and processing map of a 9Cr ferritic/martensitic ODS steel

The hot deformation behavior of 9Cr oxide-dispersion-strengthened (ODS) steel fabricated through the process of mechanical alloying and hot isostatic pressing (HIP) as investigated through hot compression deformation tests on the Gleeble-1500D simulator in the temperature range of 1050–1200°C and strain rate range of 0.001s−1–1s−1. The relationship between the rheological stress and the strain rate was also studied. The activation energy and the stress and material parameters of the hyperbolic-sine equation were resolved according to the data obtained. The processing map was also proposed. The results show that the flow stress decreases as the temperature increases, and that decreasing of the strain rate of the 9Cr ODS steel results in a positive strain rate sensitivity. It is clear that dynamic recrystallization is influenced by both temperature and strain rate. The results of this study may provide a good reference for the selection of hot working parameters for 9Cr ODS steel. The optimum processing domains are at 1200°C with a strain rate of 1s−1 and in the range of 1080–1100°C with a strain rate between 0.018s−1 and 0.05s−1.