Search

Tungsten wire with high strength and toughness for silicon wafer cutting in photovoltaic industry is a new hot research content. In order to improve the strength and processing performance of tungsten wire, tungsten alloy containing 0.5 wt%La2O3 was prepared by powder metallurgy method. The hot deformation behavior and microstructure evolution of tungsten lanthanum alloy were studied. Studies have shown that the alloy is extruded to grow fine grains, and its texture structure mainly presents two directions. The grain size of the instability zone is too large, and there are obvious cracks. With the decrease of strain rate and the increase of temperature, the recrystallization ratio of the alloy increases gradually, showing a partial equiaxed grain structure. The recrystallization ratio reaches the maximum at 1600 °C/0.01s−1, but it is still not completely recrystallized. Lanthanum oxide gradually aggregates to the grain boundary during the hot deformation process, which improves the thermal deformation activation energy of tungsten. The Q value is about 410.018 kJ/mol, which improves the high temperature strength of tungsten alloy. The compressive strength of tungsten alloy at high temperature is about 10% higher than that of pure tungsten. Combined with the hot processing map, the optimum process parameters of tungsten alloy were determined to be 1400 °C–1600 °C, 0.01–0.05s−1. The φ35.5 μm ultra-fine tungsten wire was prepared according to this parameter. The microstructure of tungsten wire is uniform and dense, and there are no cracks and defects. The tensile strength of tungsten wire is extremely high, reaching 5723 MPa.

To explore the thermoformability of Mn–Cr–Ni–Co steel for ball mill liner, isothermal compression tests were performed on Mn–Cr–Ni–Co steel using a Gleeble-3800 thermal compressive testing machine. Flow stress curves at 900 °C–1200 °C and 0.01s−1∼10s−1 were obtained. Results show Mn–Cr–Ni–Co steel has obvious positive strain rate sensitivity, with peak stress decreasing with increasing temperature. A constitutive equation for Mn–Cr–Ni–Co steel was established using the Arrhenius model based on strain compensation, and fitted values were compared to experimental values. A hot working map for Mn–Cr–Ni–Co steel was established and analyzed. Hot working process parameters are: deformation temperature of 980∼1200 °C, strain rate of 0.04–1.78s−1, providing a basis for selecting the hot forging process of the ball mill liner. Forging and forming experiments of the ball mill liner were carried out using the optimal parameters of Mn–Cr–Ni–Co steel from the hot working map. The ball mill liner has good forming quality with a relatively uniform martensitic structure inside. Tensile and impact tests were performed on the ball mill liner. Compared to the mechanical properties of traditional cast Mn13 ball mill liners, results show the tensile strength increased by 159.75%, elongation by 18.8%, and impact capacity by about 16.7%.

Fe40Mn20Cr20Ni20 medium-entropy alloy (MEA) has a single-phase crystal structure with high strength and good ductility at room temperature. It is important to study the hot deformation behavior for this alloy at a partially recrystallized state for possible high-temperature applications. In this investigation, the tensile tests were conducted on sheet materials treated via cold rolling combined with annealing at strain rates of 1 × 10−3–1 × 10−1 s−1 and deformation temperatures of 573–873 K. And the hyperbolic sine model was used to study the relationship between the peak stress, deformation energy storage and Zener–Hollomon parameter (Z parameter) of Fe40Mn20Cr20Ni20 medium-entropy alloys under high-temperature tension. According to the Arrhenius-type model, the constitutive equation of the alloys based on the flow stress was constructed, and the deformation activation energy and material parameters under different strain conditions were obtained. Based on the power dissipation theory and the instability criterion of the dynamic material model, the power dissipation diagram and the instability diagram were constructed, and the hot working map with a strain of 0.1 was obtained. The results show that the hyperbolic sine relation between the peak stress and Zener–Hollomon parameters can be well satisfied, and the deformation activation energy Q is 242.51 KJ/mol. Finally, the excellent thermo-mechanical processing range is calculated based on the hot working map. The flow instability region is 620–700 K and the strain rate is 2 × 10−3–4 × 10−3 s−1, as well as in the range of 787–873 K and 2 × 10−3–2.73 × 10−2 s−1. The optimum thermo-mechanical window is 850–873 K, ε ˙ = 1 × 10−3–2 × 10−3 s−1. [ABSTRACT FROM AUTHOR]

Fe40Mn20Cr20Ni20 medium-entropy alloy (MEA) has a single-phase crystal structure with high strength and good ductility at room temperature. It is important to study the hot deformation behavior for this alloy at a partially recrystallized state for possible high-temperature applications. In this investigation, the tensile tests were conducted on sheet materials treated via cold rolling combined with annealing at strain rates of 1 × 10−3–1 × 10−1 s−1 and deformation temperatures of 573–873 K. And the hyperbolic sine model was used to study the relationship between the peak stress, deformation energy storage and Zener–Hollomon parameter (Z parameter) of Fe40Mn20Cr20Ni20 medium-entropy alloys under high-temperature tension. According to the Arrhenius-type model, the constitutive equation of the alloys based on the flow stress was constructed, and the deformation activation energy and material parameters under different strain conditions were obtained. Based on the power dissipation theory and the instability criterion of the dynamic material model, the power dissipation diagram and the instability diagram were constructed, and the hot working map with a strain of 0.1 was obtained. The results show that the hyperbolic sine relation between the peak stress and Zener–Hollomon parameters can be well satisfied, and the deformation activation energy Q is 242.51 KJ/mol. Finally, the excellent thermo-mechanical processing range is calculated based on the hot working map. The flow instability region is 620–700 K and the strain rate is 2 × 10−3–4 × 10−3 s−1, as well as in the range of 787–873 K and 2 × 10−3–2.73 × 10−2 s−1. The optimum thermo-mechanical window is 850–873 K, ε˙ = 1 × 10−3–2 × 10−3 s−1.

The high nitrogen austenitic stainless steel is widely used as power generation and geological exploration equipment materials because of its excellent strength, corrosion resistance and non-magnetic. In this paper, the mechanical behavior and microstructure evolution of P550 steel in the range of 900 °C–1200 °C and 0.001–10 s ^−1 deformation conditions were studied by physical and heat treatment simulations, metallographic observations and thermal processing maps. The results showed that the flow curves quickly reach the peak and then soften to a steady state, which indicates dynamic recrystallization (DRX) behavior. DRX is easy to occur when the deformation temperature is above 1080 °C. The activation energy of the forged P550 stainless steel was calculated as 519 kJ mol ^−1 . There is a positive correlation between the peak stress, DRX critical stress, strain and Z value of the tested steel. The instability of the tested steel is easy to produce in the high strain rate region and low temperature region during hot working. Crack germinates and expands preferentially at the ‘necklace structure’ of inadequate dynamic recrystallization. Under the deformation state of 0.001 s ^−1 , coarse crystals and mixed crystals are easily emerged during subsequent heat treatment. Combining the hot working map, the maximum deformation resistance and the grain evolution behavior during hot working and heat treatment, the suggested working window is T = 1020 °C–1200 °C and έ = 0.01–1 s ^−1 .

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The new hot isostatically pressed (HIP) superalloy has demonstrated remarkable superplastic characteristics, as evidenced by studying the compression and tensile deformation behavior. To identify the superplastic deformation zone, the instability regions at various strain variables were overlaid onto the strain rate sensitivity index (m) distribution map at a strain of 0.6, resulting in the acquisition of a new hot working map. The tensile test results showed that under the conditions of 1080 °C-10−2.5 s−1 (0.35 < m < 0.43) and 1030 °C-10−3 s−1 (0.66 < m < 0.74) which located in the superplastic deformation zone in the new hot working map, the new HIPed superalloy exhibited superplasticity, and the elongation was 395 % and 410 %, respectively. Considering the hot working map and the microstructure evolution, the suitable hot working window was further optimized to be 1030–1080 °C and 0.001–0.005 s−1. At high strain rate and low temperature conditions, continuous dynamic recrystallization (CDRX) was the primary mechanism for dynamic recrystallization (DRX), while with the gradual decrease of strain rate, discontinuous dynamic recrystallization (DDRX) tended to occur and dominate the process. DDRX dominated under high temperature deformation condition. [Display omitted] • Constitutive equation and a new hot working map were gained by friction-temperature correction. • The superplastic deformation zone was obtained based on the new hot working map. • The new HIPed P/M superalloy achieved superplasticity in the superplastic deformation zone. • A suitable hot working window was further optimized to be 1030–1080 °C and 0.001–0.005 s−1. • Different DRX mechanisms dominated in different deformation conditions. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of TZM-1.0 wt% ZrO 2 alloy in the temperature range of 1000–1600 °C and strain rate range of 0.005–1 s−1 was studied by hot compression method. The constitutive equation and hot working diagram were established, and the microstructure evolution was emphatically analyzed by SEM and EBSD. The results indicate that the flow stress decreases with the increase of temperature and the decrease of strain rate, and ZrO 2 particles can improve the stability of TZM alloy in rate-control during hot deformation. The constitutive equation accurately predicted the correlation coefficient as high as 0.9685, calculated the average activation energy Q = 426 kJ mol−1, and obtained the best process parameters of 1150 °C–1250 °C /0.01–0.05 s−1 under 0.7 strain. The unstable zone was mainly composed of a small number of coarse grains and a large number of fine grains. The main reason for flow instability was the disharmonious deformation between coarse and fine grains during compression. The optimum hot working zone consists of more uniform equiaxed grains. However, EBSD observed that at a strain rate of 1 s−1, the recrystallization fraction at 1600 °C was lower than 1200 °C, and the dynamic recrystallization (DRX) and texture evolution trends at 1200 °C and 1600 °C were completely different. The abnormal changes in recrystallization fraction and texture evolution at 1600 °C were due to the competition between deformed grain growth and DRX on energy storage consumption, and the effect of deformed grain growth on energy storage consumption was greater than that of DRX. At 1600 °C/1 s−1, the growth of deformed grains was dominant, exhibiting strong texture components in the [001] direction, with〈100〉fibers as the main component and the highest peak texture strength. As the strain rate decreases, DRX dominates and weakens the texture strength, resulting in a significant decrease in<100>fibers. • C-ZrO 2 has a good binding interface with Mo matrix, and there is a 2 nm wide binding layer. • The process parameters of actual production were optimized by using the hot working diagram. • The competition between grain growth and dynamic recrystallization for energy storage consumption leads to opposite microstructure evolution at low and high temperatures. [ABSTRACT FROM AUTHOR]

The deformation behavior and grain size models of hot extruded (HEXed) FGH4096 superalloy at the temperature of 1040–1130 ℃ and the strain rate of 0.001–1 s−1 were investigated by hot compression. On the basis of the corrected flow stress curves, the constitutive equation considering the strain variable and hot working maps were established. The dynamic recrystallization (DRX) behaviors and microstructure evolution in different regions in hot working map superimposing the hot working instability maps were also analyzed. Discontinuous dynamic recrystallization (DDRX) occurs simultaneously with continuous dynamic recrystallization (CDRX) in the HEXed FGH4096 superalloy at low temperature, while only DDRX is activated at high deformation temperature. The wedge cracks, voids, and intergranular cracks are the main causes of flow instability. An optimal hot working window of deformation temperature = 1102–1130 ℃ and strain rate = 10−1.26–10−0 s−1 was obtained by combining the hot working maps and microstructure evolution. An established new grain size model by extending the Z parameter can predict the average grain size more accurately. • Constitutive equation and hot working maps are gained by friction-temperature corrected stresses. • An optimal working window is gained by combining hot working maps and microstructure. • Different DRX mechanisms dominate in different hot working regions. • A new grain size model is established by extending the Z parameter. [ABSTRACT FROM AUTHOR]