scholarly journals Microstructural Variation and a Physical Mechanism Model for a Ti-55511 Alloy during Double-Stage Hot Deformation with Stepped Strain Rates in the β Region

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6371
Author(s):  
Dao-Guang He ◽  
Gang Su ◽  
Yong-Cheng Lin ◽  
Yu-Qiang Jiang ◽  
Zhou Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Physical Mechanism ◽  
Nucleation Mechanism ◽  
Strain Rates ◽  
Mechanism Model ◽  
Flow Features ◽  
Variation Characteristics

The microstructural variation and high-temperature flow features of a Ti-55511 alloy in the β region are studied by utilizing double-stage compression with a stepped strain rate. The results demonstrate that the stresses in the latter stage of hot compression markedly reduce as the strain at the previous stage or the strain rate at the previous/latter stage drops. Moreover, the annihilation/interaction of substructures is promoted, and the distinct refinement of the dynamic recrystallization (DRX) in the β grain can be found. However, the coarsening of the β grain and the consumption of dislocation substructures are accelerated at high temperatures. Furthermore, the principal DRX nucleation mechanism of the Ti-55511 alloy during double-stage compression with a stepped strain rate in the β region is discontinuous DRX. Additionally, by using the microstructural variation characteristics related to the forming parameters, a physical mechanism equation is modeled to forecast the forming features, the DRX fraction, and the size of the β grain in the investigated alloy. The forecasted results are in accordance with the tested results, indicating that the established model can accurately forecast the microstructure variation and flow features of the studied alloy.

scholarly journals Hot Deformation Behavior of a Ni-Based Superalloy with Suppressed Precipitation

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 605
Author(s):  
Franco Lizzi ◽  
Kashyap Pradeep ◽  
Aleksandar Stanojevic ◽  
Silvana Sommadossi ◽  
Maria Cecilia Poletti
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Strain Rates ◽  
Compression Tests ◽  
Deformation Bands ◽  
Stress Softening ◽  
Relative Stress ◽  
The Matrix ◽  
Thermomechanical Processes

Inconel®718 is a well-known nickel-based super-alloy used for high-temperature applications after thermomechanical processes followed by heat treatments. This work describes the evolution of the microstructure and the stresses during hot deformation of a prototype alloy named IN718WP produced by powder metallurgy with similar chemical composition to the matrix of Inconel®718. Compression tests were performed by the thermomechanical simulator Gleeble®3800 in a temperature range from 900 to 1025 °C, and strain rates scaled from 0.001 to 10 s−1. Flow curves of IN718WP showed similar features to those of Inconel®718. The relative stress softening of the IN718WP was comparable to standard alloy Inconel®718 for the highest strain rates. Large stress softening at low strain rates may be related to two phenomena: the fast recrystallization rate, and the coarsening of micropores driven by diffusion. Dynamic recrystallization grade and grain size were quantified using metallography. The recrystallization grade increased as the strain rate decreased, although showed less dependency on the temperature. Dynamic recrystallization occurred after the formation of deformation bands at strain rates above 0.1 s−1 and after the formation of subgrains when deforming at low strain rates. Recrystallized grains had a large number of sigma 3 boundaries, and their percentage increased with strain rate and temperature. The calculated apparent activation energy and strain rate exponent value were similar to those found for Inconel®718 when deforming above the solvus temperature.

Hot Workability of Ultrafine-Grained Aluminum Alloy Produced by Severe Plastic Deformation of Al6063 Powder and Consolidation

2010 ◽  
Vol 667-669 ◽  
pp. 979-984 ◽  
Author(s):  
Hamed Asgharzadeh ◽  
Abdolreza Simchi ◽  
Hyoung Seop Kim
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Grain Structure ◽  
Al Alloy ◽  
Strain Rates ◽  
Hot Workability ◽  
Ultrafine Grained

Al6063 powder was subjected to severe plastic deformation via high-energy mechanical milling to prepare ultrafine-grained (UFG) aluminium alloy. Uniaxial compression test at various temperatures between 300 and 450 °C and strain rates between 0.01 and 1 s-1 was carried out to evaluate hot workability of the material. Microstructural studies were performed by EBSD and TEM. The average activation energy and strain rate sensitivity of the hot deformation process were determined to be 280 kJ mol-1 and 0.05, respectively. The deformation temperature and applied strain rate significantly affected the grain structure of UFG Al alloy. A finer grain structure was obtained at lower temperatures and higher strain rates. The formation of highly misoriented and equiaxed grains also revealed that dynamic recrystallization occurred upon hot deformation. Furthermore, elongated grains with high dislocation density were observed that disclosed partial dynamic recrystallization of the aluminum matrix.

Flow Behavior and Microstructural Evolution of a 7039 Aluminum Alloy during Hot Deformation

2011 ◽  
Vol 239-242 ◽  
pp. 2395-2398 ◽  
Author(s):  
Hui Zhong Li ◽  
Xiao Peng Liang ◽  
Min Song ◽  
Min Zeng
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Microstructural Evolution ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Flow Behavior ◽  
Thermal Simulation ◽  
Strain Rates

The flow behavior of a 7039 aluminum alloy and the corresponding microstructural evolution during hot deformation were studied by Gleeble-1500 thermal simulation tests, EBSD and TEM observations with temperatures ranging from 300 °C to 500 °C under strain rates from 0.01 s-1 to 10 s-1. It has been shown that the flow stress increases with the decrease in the deformation temperature and increase in the strain rate. The degree of dynamic recrystallization (DRX) increases with the increase in the deformation temperature and strain rate in 7039 aluminum alloy. The complete dynamic recrystallization occurs at 500 °C with a strain rate of 10 s-1.

Characterization of Hot Deformation Behavior of Zr-1.0Sn-0.3Nb-0.3Fe-0.1Cr Using Processing Map

2013 ◽  
Author(s):  
B. F. Luan ◽  
R. S. Qiu ◽  
Z. Zhou ◽  
K. L. Murty ◽  
J. Zhou ◽  
...  
Keyword(s):  
Activation Energy ◽  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
True Strain ◽  
Compression Testing ◽  
Strain Rates ◽  
Processing Maps ◽  
Deformation Activation Energy

Hot deformation characteristics of forged and β-quenched Zr-1.0Sn-0.3Nb-0.3Fe-0.1Cr (N18 alloy) in the temperature range 625–950°C and in the strain rate range 0.005–5 s−1 have been studied by uniaxial compression testing of Gleeble 3500. For this study, the approach of processing maps has been adopted and their interpretation done using the Dynamic Materials Model (DMM). Based on a series of true stress-true strain curves on various temperatures and strain rates, the flow stress has been summarized and both the strain rate sensitivity index (m) and deformation activation energy (Q) have been calculated by the constitutive equations that flow stress and the relationship of Z parameter and flow stress have been established subsequently. Furthermore, the efficiency of power dissipation (⬜) given by [2m/(m+1)] and improved by Murty has been plotted as a function of temperature and strain rate to obtain different processing maps at different true strain rates ranging from 0.1–0.7. Subsequently, the microstructures of the specimens after compression testing were characterized by electron channeling contrast (ECC) imaging techniques used an FEI Nova 400 field emission gun scanning electron microscopy (FEG-SEM). The results showed that: (i) The hyperbolic sine constitutive equation can describe the flow stress behavior of zirconium alloy, and the deformation activation energy and flow stress equation were calculated under the different temperature stages which insists that the deformation mechanism is not dynamic recovery. (ii) The hot processing maps and its validation were analyzed, which indicated that the DMM theory was reliable and could be adopted as useful tool for optimizing hot workability of Zr. The optimum parameters for extrusion and hammer forging were revealed on the processing maps of 830–950°C, 0.048–2.141 s−1 and 916–950°C, 2.465–5 s−1. (iii) The microstructure of the ingot exhibits a typical lamellar Widmanstatten structure. Under the different strain rates, the grains formed by dynamic recrystallization existed normally in the central zone of the compression samples while the no uniformity of grain size increased with the increasing of strain rate. Meanwhile, due to the dynamic recrystallization as a thermal activation process, the grains size and uniformity increased with the increasing of temperature. In brief, microstructure analysis showed that continuous dynamic recrystallization and geometric dynamic recrystallization operated concurrently during the isothermal compressive deformation.

Dynamic Recrystallization of Biomedical Co-Cr-W-Ni (L-605) Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 472-477 ◽  
Author(s):  
Julien Favre ◽  
Akihiko Chiba ◽  
Yuichiro Koizumi ◽  
Damien Fabrègue ◽  
Éric Maire
Keyword(s):  
High Temperature ◽  
Dynamic Recrystallization ◽  
High Strain Rate ◽  
Strain Rate ◽  
Grain Boundaries ◽  
High Strain ◽  
Nucleation Mechanism ◽  
Compression Tests ◽  
Annealing Twins ◽  
Low Strain Rate

Compression tests are carried out at high-temperature on Thermec-master Z, followed by gas quench. Microstructures after deformation are evaluated using SEM-EBSD. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T>1100°C, SR<0.1s-1), and at high strain rate (SR~10s-1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging of grain boundaries. However, recrystallization occurs also by rotation of annealing twins. Thereafter the twin boundaries can bulge as well. The modeling of mechanical behavior gives a fair quantification of flow softening due to dynamic recrystallization indicating the progress of dynamic recrystallization with deformation.

The effects of temperature and strain rate on the hot deformation behavior of AISI H10 tool steel

2020 ◽  
Vol 118 (1) ◽  
pp. 107
Author(s):  
Maryam Kamali Ardakani ◽  
Maryam Morakabati
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Tool Steel ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Strain Rates ◽  
Compression Tests ◽  
Hot Deformation Behavior ◽  
Temperature Range

The hot deformation behavior of a H10 hot work tool steel was studied by performing hot compression tests over the temperature range of 900 to 1200 °C and strain rates of 0.001–1 s−1 and total strain of 0.7. At temperatures below 1100 °C, the grain size is fine and below 20 μm. In this temperature range, grain size increase with temperature due to dissolution of carbides. Then by increasing temperature to 1150 and 1200 °C, the grain size is increased significantly due to growth of grains. The study on the effect of strain rate showed that at constant temperature of 1000 °C, the grain size increased from 4.8 to 6 μm with increasing strain rate from 0.001 to 1 s−1. Also, this increase in the strain rate at temperature of 1100 °C lead to increase the grain size from 5.9 to 17 μm, due to the occurrence of dynamic recrystallization. At 1200 °C growth of grains causes to decrease grain size from 112 to 87 μm by increasing strain rate. According to the microstructural investigations, at the temperatures of 1000 and 1100 °C and strain rates of 0.01 and 0.1 s−1 dynamic recrystallization was the main softening mechanism. As a result, the most suitable range for hot deformation was obtained at the temperature range of 1000–1100 °C and strain rates of 0.01–0.1 s−1.

scholarly journals Dynamic Softening and Hardening Behavior and the Micro-Mechanism of a TC31 High Temperature Titanium Alloy Sheet within Hot Deformation

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6515
Author(s):  
Kexin Dang ◽  
Kehuan Wang ◽  
Gang Liu
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Tensile Deformation ◽  
Alloy Sheet ◽  
Dynamic Softening ◽  
Thin Walled

TC31 is a new type of α+β dual phase high temperature titanium alloy, which has a high specific strength and creep resistance at temperatures from 650 °C to 700 °C. It has become one of the competitive candidates for the skin and air inlet components of hypersonic aircraft. However, it is very difficult to obtain the best forming windows for TC31 and to form the corresponding complex thin-walled components. In this paper, high temperature tensile tests were carried out at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.001 s−1 to 0.1 s−1, and the microstructures before and after deformation were characterized by an optical microscope, scanning electron microscope, and electron back-scatter diffraction. The dynamic softening and hardening behaviors and the corresponding micro-mechanisms of a TC31 titanium alloy sheet within hot deformation were systematically studied. The effects of deformation temperature, strain rate, and strain on microstructure evolution were revealed. The results show that the dynamic softening and hardening of the material depended on the deformation temperature and strain rate, and changed dynamically with the strain. Obvious softening occurred during hot tensile deformation at a temperature of 850 °C and a strain rate of 0.001 s−1~0.1 s−1, which was mainly caused by void damage, deformation heat, and dynamic recrystallization. Quasi-steady flowing was observed when it was deformed at a temperature of 950 °C~1000 °C and a strain rate of 0.001 s−1~0.01 s−1 due to the relative balance between the dynamic softening and hardening. Dynamic hardening occurred slightly with a strain rate of 0.001 s−1. Mechanisms of dynamic recrystallization transformed from continuous dynamic recrystallization to discontinuous dynamic recrystallization with the increase in strain when it was deformed at a temperature of 950 °C and a strain rate of 0.01 s−1. The grain size also decreased gradually due to the dynamic recrystallization, which provided an optimal forming condition for manufacturing thin-walled components with the desired microstructure and an excellent performance.

Characteristics of Dynamic Recrystallization during Hot Deformation for High Nitrogen Stainless Steels

2012 ◽  
Vol 715-716 ◽  
pp. 115-121
Author(s):  
Hai Wen Luo ◽  
Xu Dong Fang ◽  
Rui Zhen Wang ◽  
Zhan Yin Diao
Keyword(s):  
Dynamic Recrystallization ◽  
Stainless Steels ◽  
Hot Deformation ◽  
Strain Rates ◽  
Peak Strain ◽  
High Nitrogen ◽  
Flow Curves ◽  
Grain Sizes ◽  
Nitrogen Contents ◽  
High Nitrogen Stainless Steel

Dynamic recrystallization was studied for the stainless steels with nitrogen contents of 0.56% to 1.08% during hot deformation at temperatures of 900~1200 with strain rates ranging from 0.003 to 42 s-1. It was found that flow stress could increase remarkably with increasing nitrogen content. Flow curves during the deformation by 0.1~42/s at temperatures of 900~1200°C show a single peak, indicating the occurrence of dynamic recrystallization during deformation. The peak strain seems to decrease with increasing N content, suggesting that higher content of N facilitates dynamic recrystallization. The quenched microstructures were analyzed by optical microscopy, EBSD and TEM. The recrystallized grain sizes on the quenched specimens were measured and its dependence on temperature and strain rate was analyzed. At high temperature, continuously dynamically recrystallized microstructures were observed; whilst at low temperature, necklace-like partially recrystallized microstructures were found. Key words: High nitrogen stainless steel; dynamic recrystallization; stress-strain curves

Hot working of SP-700 titanium alloy with lamellar α + β starting structure using a processing map

2020 ◽  
Vol 111 (4) ◽  
pp. 297-306
Author(s):  
Amir Hosein Sheikhali ◽  
Maryam Morakkabati
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Hot Deformation ◽  
Processing Map ◽  
Microstructural Analysis ◽  
Shear Bands ◽  
Alpha Phase ◽  
Strain Rates ◽  
Compression Tests ◽  
Temperature Range

Abstract In this study, hot deformation behavior of SP-700 titanium alloy was investigated by hot compression tests in the temperature range of 700-9508C and at strain rates of 0.001, 0.1, and 1 s-1. Final mechanical properties of the alloy (hot compressed at different strain rates and temperatures) were investigated using a shear punch testing method at room temperature. The flow curves of the alloy indicated that the yield point phenomenon occurs in the temperature range of 800- 9508C and strain rates of 0.1 and 1 s-1. The microstructural analysis showed that dynamic globularization of the lamellar α phase starts at 7008C and completes at 8008C. The alpha phase was completely eliminated from b matrix due to deformation- induced transformation at 8508C. The microstructure of specimens compressed at 8508C and strain rates of 0.001 and 0.1 s-1showed the serration of beta grain boundaries, whereas partial dynamic recrystallization caused a necklace structure by increasing strain rate up to 1 s-1. The specimen deformed at 7008C and strain rate of 1 s-1was located in the instability region and localized shear bands formed due to the low thermal conductivity of the alloy. The processing map of the alloy exhibited a peak efficiency domain of 54% in the temperature range of 780-8108C and strain rates of 0.001- 0.008 s-1. The hot deformation activation energy of the alloy in the α/β region (305.5 kJ mol-1) was higher than that in the single-phase β region (165.2 kJ mol-1) due to the dynamic globularization of the lamellar a phase.

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