High Efficiency Of Power Dissipation Research Articles

Hot deformation behavior and process parameter optimization of Ti22Al25Nb using processing map

The hot deformation behavior of Ti22Al25Nb was investigated by hot compression test. The flow stress–strain curves can be divided into two types: conventional dynamic recrystallization (DRX) and discontinuous DRX. The different softening mechanism and microstructure observation of conventional DRX and discontinuous DRX were analyzed. The processing map (PM) of Ti22Al25Nb was built to predict the safe deformation region. The optimal low strain rate domain (DOM I) with high power dissipation efficiency indicates the complete DRX. Additionally, in the high strain rate and low-temperature domain (DOM III), the power dissipation efficiency is low and some adiabatic shear bands and glide bands are observed, which are unsafe and should be avoided. Finally, the DRX map was established. In DOM I, it reveals low dislocation density and high DRX content, which is in agreement with PM.

An Investigation into Hot Deformation Characteristics and Processing Maps of High-Strength Armor Steel

The isothermal hot compression tests of high-strength armor steel over wide ranges of strain rates (0.01-10 /s) and deformation temperatures (950-1100 °C) are carried out using Gleeble thermo-simulation machine. The true stress-strain data obtained from the experiments are employed to establish the constitutive equations based on the strain-compensated Arrhenius model. With strain-compensated Arrhenius model, good agreement between the experimental and predicted values is achieved, which represents the highest accuracy in comparison with the other models. The hot deformation activation energy is estimated to be 512 kJ/mol. By employing dynamic material model, the processing maps of high-strength armor steel at various strains are established. A maximum efficiency of about 45% of power dissipation is obtained at high temperature and low strain rate. Due to the high power dissipation efficiency and excellent processing ability in dynamic recrystallization zone for metal material, the optimum processing conditions are selected such that the temperature range is between 1050 and 1100°C and the strain rate range is between 0.01 and 0.1/s. Transmission electron microscopy observations show that the dislocation density is directly associated with the value of processing efficiency.

Hot deformation behavior of in situ nano ZrB2 reinforced 2024Al matrix composite

Abstract The hot deformation behavior of in situ 5 wt.% nano ZrB 2 /2024Al composite was studied at deformation temperatures of 350–450 °C and strain rates of 0.001–10 s −1 . The results show that the flow stress depends strongly on the deformation temperature and strain rate, and especially exhibits a strain hardening at high temperature and high strain rate, related to the introduction of nanoparticles (ZrB 2 : 15–40 nm). The kinetic equation was constituted and indicates that the key deformation mechanism is dynamic recrystallization (DRX), which is in accordance with the deformed microstructures. The processing maps (PMs) exhibit two deterministic domains of domain 1 (380–410 °C/0.018–0.032 s −1 ) and domain 2 (440–460 °C/0.075–0.56 s −1 ), where domain 2 has the higher power dissipation efficiency, higher strain rate, meaning more safety and higher efficiency for the hot processing. At the same time, the deformed specimen exhibits equiaxed and fine grains in domain 2, i.e., a typical DRX structure, thus is suggested as the optimum hot processing window for this nanocomposite.

Hot deformation behavior of extruded Mg–Zn–Y–Zr alloy

The Mg–Zn–Y–Zr alloys, which exhibit high strength and high elongation, have great potential for applications in many fields, such as automotive, aircraft, and aerospace industries. However, plastic deformation behavior under hot compression is still not fully understood. Hot compression tests of extruded Mg–Zn–Y–Zr alloy were performed at temperatures from 250°C to 450°C and strain rates from 0.001s−1 to 1s−1. A constitutive equation and processing map were developed to describe the flow characteristics. In addition, isothermal forging tests were conducted to verify the optimal deformation parameters. The results show that the strain rate and deformation temperature exert remarkable influences on the flow stress. The average activation energy and the stress exponent of deformation were determined as 137.400kJ/mol and 3.707, respectively. The efficiency of power dissipation was high for all deformation conditions compared to the cast Mg–Zn–Y–Zr alloy, and the processing map exhibited four domains with high efficiency of power dissipation. The optimal deformation temperatures and strain rates for extruded Mg–Zn–Y–Zr alloy were 350–400°C and 0.001–0.1s−1, respectively. Components were prepared successfully according to the optimal deformation temperature and strain rate, which exhibited good surface quality and no deformation defect. The component after aging treatment exhibited an ultimate tensile strength of 396MPa, a yield strength of 356MPa and an elongation of 5.2%.

Evaluation of the hot workability corresponding to complex deformation mechanism evolution for Ti–10V–2Fe–3Al alloy in a wide condition range

The hot workability of as-forged Ti–10V–2Fe–3Al alloy was evaluated. Meanwhile, the intrinsic relationships between deformation mechanisms and processing parameters were determined by the processing maps on the basis of dynamic materials model (DMM) with the input stress–strain data collected from a series of isothermal compressions at temperatures of 948–1123K (across β-transus) and strain rates of 0.001–10s−1. At the beginning, at a set of discrete true strains the response maps of strain rate sensitivity exponent (m-value), power dissipation efficiency (η-value) and instability parameter (ξ-value) to temperatures and strain rates were developed respectively. Following that, a processing map corresponding to each true strain was constructed by superimposing an instability map over a power dissipation map. According to m-criterion, η-criterion and ξ-criterion, the stable regions with higher power dissipation efficiency (η>0.3) and unstable regimes with negative strain rate sensitivity exponent and instability parameter (m<0 and ξ<0) were clarified clearly. Moreover, the deformation mechanism map was established, based on which the parameter domains corresponding to different deformation mechanisms were identified. By the criteria of two main stable strain-softening mechanisms, i.e. globularization and dynamic recovery (DRV), the globularization-predominant parameter domain in α+β-phase temperature range and DRV-predominant parameter domain in β-phase temperature range were identified and recommended. In a wide temperature range across β-transus and a large strain rate range, the clarification of stable and unstable parameter regions corresponding to different deformation mechanisms contributes to design in the various hot forming processes of Ti–10V–2Fe–3Al alloy without resorting to time-consuming trial-and-error procedures.

Study on Hot-Working Behavior of High Carbon Steel / Low Carbon Steel Composite Material Using Processing Map

The high carbon steel (HCS)/low carbon steel (LCS) laminated composite made by centrifugal casting technology was subjected to hot compression tests on Gleeble 3500 thermomechanical simulator in a range of temperatures (800-1100 oC) and strain rates (0.02-10 s-1). The hot-working behavior of the laminate was characterised by analysing the flow stress-strain curves and constructing the processing map based on dynamic materials model via superimposing efficiency of power dissipation and flow instability maps. The safe and unsafe processing conditions were identified in the processing map which was validated by microstructural examinations. Banded microstructure and micro-shear cracks occurred in the unsafe domains were responsible for the flow instability, while dynamic recrystallisation in stable domains with high efficiency of power dissipation imparted a good workability to the laminate. The optimum hot-working parameters were determined to be: (i) 800-1050 oC and 0.02-0.04 s-1, (ii) 800-1045 oC and 2.5-10 s-1 and (iii) 1050-1100 oC and 0.02-2.5 s-1.

High Temperature Deformation Behavior of As-Cast Al-3Mg-0.25Sc Alloy

High temperature deformation behavior of as-cast Al-3Mg-0.25Sc alloy was characterized in a wide range of temperatures 573 K to 773 K (300 °C to 500 °C) and strain rates (0.001 to 10 s−1). A threshold stress behavior is observed in the temperature range of 573 K to 673 K (300 °C to 400 °C) due to interaction of dislocations with precipitates. In the temperature range of 573 K to 623 K (300 °C to 350 °C), the dislocations are pinned by precipitates, following Orowan-bowing mechanism. At 673 K (400 °C), the dislocations bypass the particles by climb process. At high temperature and low strain rate of 723 K (450 °C), and 0.001 s−1, respectively, the alloy exhibited high efficiency of power dissipation for optimal hot working process.

Hot deformation behavior and processing map of a γ′-hardened nickel-based superalloy

The hot deformation behavior of a γ′-hardened nickel-based superalloy was investigated by means of isothermal compression tests in the temperature range of 1010–1160°C and strain rate range of 0.001–1s−1. The results show that the hot activation energy of the alloy is about 427.626kJ/mol. On the basis of experimental data, processing maps were developed by utilizing the principles of the dynamic materials model (DMM). The processing maps exhibit one domain with high efficiency of power dissipation. At the strain of 0.6, the domain occurs in the temperature range of 1105–1160°C and strain rate range of 0.02–0.25s−1 with a peak efficiency of about 42.2%. Microstructure observations reveal that full dynamic recrystallization (DRX) occurred in the domain. In the processing maps, the curvature changes of the isoefficiency contours occur in the temperature range of 1080–1090°C, which is at the dissolution temperature of γ′ phase in the alloy. Moreover, it can be found that the strain has an effect on the efficiency of power dissipation. The efficiency value increases with increasing strain in the high strain rate domain (0.1–1s−1), while the efficiency value decreases with increasing strain in the high temperature (1080–1160°C) and low strain rate (0.001–0.01s−1) domain. The flow instability is predicted to occur in the high strain rate domain, which is manifested as adiabatic shear bands.

Quantitative Design Methodology for Flat Ring Rolling Process

For a specific ring rolling, the quantitative design of the rolling billet and feeding strategy is the most important factor to obtain the ideal process. This research focuses on developing the quantitative design methodology for the flat ring rolling in a systematic way. The paper is organized in two parts: billet constraint and feeding interval in the flat ring rolling. In the first part, the constraint conditions for both the piercing process and ring rolling are taken into consideration, deducing the limiting wall thickness and the limiting height of the billet for a specific ring rolling. And for the second part, the expansion of ring outer diameter, the rolling force and rolling temperature, the form error occurrence together with the gripping and penetration condition are included to generate the feeding interval. In the feeding interval created, the response of ring material to the processing parameters must also be considered. So for a specific ring rolling, we established the processing map of the material used. Based on that, a desirable feeding strategy that could obtain a higher efficiency of power dissipation was determined by means of the subroutine VUAMP in ABAQUS. Practical ring rolling experiment was carried out and the microstructure of the finished ring was also observed. The experiment shows that the deformed ring was rolled to the final dimension in a stable manner without macroscopic or microscopic defects, which indicated that the quantitative design of the flat ring rolling process is reasonable.

Deformation behavior in the isothermal compression of Ti–5Al–5Mo–5V–1Cr–1Fe alloy

Isothermal compression of the Ti–5Al–5Mo–5V–1Cr–1Fe alloy was carried out on a Gleeble-1500 hot-simulator at the deformation temperatures ranging from 993K to 1203K, strain rates ranging from 0.01s−1 to 5.0s−1 and height reductions ranging from 40% to 70%. The results show that the deformation temperature affects significantly the extent of dynamic softening in the isothermal compression of Ti–5Al–5Mo–5V–1Cr–1Fe alloy. The apparent activation energy for deformation in the isothermal compression of Ti–5Al–5Mo–5V–1Cr–1Fe alloy is 291.73±50kJmol−1 in α+β two-phase region and 179.93±20kJmol−1 in β single-phase region. The dynamic recovery is the dominant deformation mechanism in β single-phase region of Ti–5Al–5Mo–5V–1Cr–1Fe alloy. Finally, the processing map of isothermally compressed Ti–5Al–5Mo–5V–1Cr–1Fe alloy is exhibited at the strains of 0.3, 0.5 and 0.7, in which two domains with high efficiency of power dissipation and an instable domain are presented, and the main instability mechanism is flow localization.

Identification of optimal deforming parameters from a large range of strain, strain rate and temperature for 3Cr20Ni10W2 heat-resistant alloy

The intrinsic workability of 3Cr20Ni10W2 was investigated using processing maps constructed from the stress–strain data generated by isothermal compression tests with a height reduction of 60% over a temperature range of 1203–1403K and a strain rate range of 0.01–10s−1. As the true strain was −0.3, −0.5, −0.7 and −0.9, the responses of strain rate sensitivity (m-value), power dissipation efficiency (η-value) and instability parameter (ξ-value) to temperatures and strain rates were evaluated respectively. By the superimposition of power dissipation and instability maps, the stable regions with higher power dissipation efficiency (⩾0.3) and unstable regions were clarified clearly. As the true strain was −0.3, −0.5, −0.7 and −0.9, respectively, the area of instability regions decreased with increasing true strain from −0.3 to −0.7, while it increased with increasing true strain from −0.7 to −0.9. In further, in the stable area, on the basis of determination for domains with dynamic recrystallization (DRX) microstructural evolution, the DRX-predominant regions with higher power dissipation efficiency were identified and recommended. Then not only DRX-predominant domains were validated by the stable microstructures refined by DRX, but also the regimes of flow instabilities were validated by the microstructures involving cracks. The identification of optimal deforming parameters from a large range of strain, strain rate and temperature for 3Cr20Ni10W2 heat-resistant alloy contributes to designing reasonable hot deforming processes without resorting to expensive and time-consuming trial-and-error methods.

Feeding strategy design for steel 42CrMo in radial-axial ring rolling using processing map

To reasonably design the feeding strategy for radial-axial ring rolling process with material 42CrMo, the processing map of 42CrMo was constructed. The flow instability regions, ideal hot working domains and optimized deformation path were identified in the processing map. Based on this map, a desirable feeding strategy that could obtain a higher efficiency of power dissipation was determined by means of the subroutine VUAMP in ABAQUS. Moreover, a practical ring rolling experiment with the designed feeding strategy was carried out and the microstructure of the finished ring was also observed. The experiment shows that the deformed ring is rolled to the final dimension in a stable manner without macroscopic or microscopic defects, which indicates that the proposed feeding strategy is reasonable.

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α+β type titanium alloy TC11 (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 °C and the strain rate range of 0.001-10 s−1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in α+β phase field is at the temperature of 950-990 °C and the strain rate of 0.001-0.01s-1, which correspond to a better hot compression process window of α+β phase field. The peak of efficiency of power dissipation in α+β phase field is at 950 °C and 0.001 s-1, which correspond to the best hot compression process parameters of α+β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 °C and the strain rate of 0.001-0.1 s-1, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in β phase field occurs at 1050 °C over the strain rates from 0.001 s-1 to 0.01 s-1, which correspond to the best hot compression process parameters of β phase field. The divergence domain occurs at the strain rates above 0.5 s-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress—strain curves. The deformation mechanisms of the optimized hot compression process windows in α+β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

High-temperature deformation behavior and thermal properties of an Ni30Co17Fe53 alloy

Abstract High temperature deformation behavior of a Ni30Co17Fe53 alloy has been investigated by carrying out hot compression tests at temperatures ranging from 600°C to 1150°C under strain rates between 10−5 and 1 s−1. Both the temperature and strain-rate dependence of the flow stress were found to be described by a hyperbolic sine function. Hot formability of this alloy was also estimated by constructing an empirical processing map based on a dynamic materials model, from which the region with high power dissipation efficiency was exhibited as a feasible combination of processing condition at around 1150°C and 10−2 s−1. Three different thermo-mechanical treatment processes were adopted for hot-forging to investigate its influence on microstructure and subsequent thermal expansion and thermal conductivity.

Flow Behavior and Workability of a Zn-8Cu-0.2Cr Alloy during Hot Deformation

The hot deformation behavior of Zn91.8-Cu8-Cr0.2 (in wt.%) was investigated by means of hot compression tests in the temperature range of 230-380 °C and strain rate range of 0.01 - 10 s-1. The constitutive equation and processing maps were developed. The influence of strain on the flow stress was studied by considering the effect of the strain on material constants. The stress-strain curves obtained by the constitutive equation are in good agreement with experimental results. The proposed constitutive equations can be used for the analysis problem of hot forming processes. The processing maps have exhibited a domain, which is optimum processing window for hot working, in the temperature range of 310 - 380 °C and strain rate range of 0.01-1 s-1 corresponding to the higher efficiency of power dissipation. The large regime of flow instability is observed at high strain rate. The instability regime should be avoided during hot deformation processing.

Characterization of hot deformation behaviors of wrought and P/M oxygen free coppers (OFCs) using processing maps

Wrought and powder sintered (P/M) oxygen free coppers (OFC) were subjected to hot deformation testing over the range of strain rates (0.01–10.0s−1) and temperatures (200–800°C). Processing maps of both materials have exhibited different deterministic domains representing dynamic recrystallization (DRX), which occurs in the following temperature and strain rate ranges: for wrought copper, 400–600°C and 0.01–0.1s−1, 600–800°C and 0.01–10.0s−1; for P/M one, 600–800°C and 0.01–1.0s−1. The domain for wrought copper has higher efficiency of power dissipation with increasing temperature and decreasing strain rate. For P/M OFC, the region at temperature of 600°C and strain rate of 10−2s−1showed peak efficiency. The results on processing maps have well correlated with those obtained from kinetic analysis. The apparent activation energies estimated in the DRX domains are 146.04 and 190.67kJ/mol for wrought and P/M OFCs, respectively, which suggest that dislocation core diffusion and lattice self-diffusion are the rate controlling mechanism each. In all domains, the average grain diameter varies linearly with Zener–Holloman parameter.

Hot Workability of a High Strength Low Alloy Steel for Construction Application

The hot deformation behavior of a high strength low alloy (HSLA) steel for construction application under hot working conditions in the temperature range of 900 to 1100 and strain rate range from 0.1 to 10 s-1 has been studied by performing a series of hot compression tests. The dynamic materials model has been employed for developing the processing maps, which show variation of the efficiency of power dissipation with temperature and strain rate. Also the Kumars model has been used for developing the instability map, which shows variation of the instability for plastic deformation with temperature and strain rate. The efficiency of power dissipation increased with decreasing strain rate and increasing temperature. High efficiency of power dissipation over 20 % was obtained at a finite strain level of 0.3 under the conditions of strain rate lower than 1 s-1 and temperature higher than 1050. Plastic instability was expected in the regime of temperatures lower than 1000°C and strain rate lower than 0.3 s-1.

Fe-Ni-Co 합금의 고온 변형 공정 변수와 미세조직 및 열물리적 특성의 상관 관계

Abstract High temperature deformation behavior of a Ni 30 Fe 53 Co 17 alloy, with its extraordinary low coefficient of thermal expansion less than 10x10 -6 K 1 at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum -forming was deduced to be in the ~1373K, 10 -2 s 1 region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size. Key Words : Ni-Fe-Co Alloy, High Temperature Deformation, Open Die Forging, Coefficient of Thermal Expansion

Investigation on hot workability characteristics of Inconel 625 superalloy using processing maps

Hot compression tests of the commercial Inconel 625 were performed in the temperature range of 950–1200 °C and strain rate range of 0.01–10 s−1. The flow behavior and processing maps were investigated using the corrected flow stress data to eliminate effects of the friction and adiabatic heating. The processing maps have exhibited a domain in the temperature range of 1100–1200 °C and strain rate range of 0.01–10 s−1 corresponding to the higher efficiency of power dissipation. Microstructural observations reveal that the full dynamic recrystallization (DRX) occurs in this domain, which is optimum processing window for hot working to obtain a homogeneous microstructure. DRX grain growth occurs in the temperature range of 1150–1200 °C and strain rate range of 0.01–0.1 s−1. In view of the refined and uniform grains obtained by hot deformation, the finish forming processing should be selected the deformation conditions in which the full DRX occurs without the grain growth. The small regimes of flow instability are noticed at temperature below about 970 °C at the different strains. The material undergoes flow instability manifesting as bands of flow localizations and high density deformation twins. In addition, it is found that the undissolved second-phase particles and carbides can promote the DRX processing and be helpful to restrict the DRX grain growth.

Identification for the optimal working parameters of as-extruded 42CrMo high-strength steel from a large range of strain, strain rate and temperature

Abstract The intrinsic workability of as-extruded 42CrMo high-strength steel was investigated by using processing maps constructed from the stress–strain data generated by hot compression tests with a height reduction of 60% over a range of temperatures 1123–1348 K and strain rates 0.01–10 s −1 . As the true strain was −0.3, −0.5, −0.7, and −0.9, respectively, the responses of strain rate sensitivity ( m -value), power dissipation efficiency ( η -value) and instability parameter ( ξ -value) to temperature and strain rate were evaluated. By the superimposition of power dissipation and instability maps, the stable and unstable regions were clarified clearly, and furthermore in the stable area the regions with higher power dissipation efficiency (≥0.2) were identified and recommended. As the true strain is −0.3, −0.5, −0.7, and −0.9, respectively, three domains were identified at each strain. The whole area of the domains increased with increasing true strain from −0.3 to −0.7, while it decreased with increasing true strain from −0.7 to −0.9. On the basis of determination for domains with dynamic recovery (DRV) or dynamic recrystallization (DRX) microstructural evolution, the full DRX regions were identified in the processing map at true strain −0.5 to −0.9, and the full DRV regions at true strain −0.2 to −0.9. Then not only the domains optimized were validated by DRX refined microstructures without any wedge crack, but also the regimes of flow instabilities were validated by the microstructures involving intercrystalline cavity, dynamic strain aging (DSA), deformation twinning. The optimal working parameters identified by processing maps and validated by microstructure observations contribute to designing the reasonable hot forming process of as-extruded 42CrMo high-strength steel without resorting to expensive and time-consuming trial-and-error methods.