scholarly journals Determining a Flow Stress Model for High Temperature Deformation of Ti-6Al-4V

2015 ◽  
Vol 828-829 ◽  
pp. 441-446 ◽  
Author(s):  
E. Calvert ◽  
J. Pollard ◽  
M. Jackson ◽  
B. Wynne ◽  
Richard Thackray
Keyword(s):  
Flow Stress ◽  
Hot Deformation ◽  
True Strain ◽  
Extrusion Process ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Stress Model ◽  
Specific Flow ◽  
Flow Stress Model

In some commercial titanium extrusion practices, twisting of the extrudate can occur, which can result in the need to crop the back and front end of the extruded material, thereby reducing yield and increasing material losses. Understanding more about the behaviour of material during the extrusion process, and investigating the cause of defects such as twisting by use of finite element (FE) modelling techniques could help to reduce these losses, improve the productivity of the extrusion process, and the overall quality of the material produced. One of the most important components of FE techniques for hot deformation is the type of flow stress model that is used in the simulations. In this investigation isothermal uniaxial compression testing was performed on cylindrical specimens of Ti-6Al-4V at temperatures ranging from 950 °C to 1200°C and strain rates of 0.1 s-1 to 50 s-1, to produce true stress against true strain and load against die travel curves which were subsequently used to develop a new specific flow stress model for use in hot deformation above the beta transus, which can ultimately be applied to the hot extrusion of Ti-6Al-4V. From analysis of this data it was concluded that flow softening and work hardening do not occur during deformation, and that low friction conditions exist between the material and the tooling. The activation energy for deformation was found to be 193178 J.mol-1, and the flow stress model was shown to give a good fit to the raw data at low strain rates, but this relationship broke down at higher strain rates. Finally the importance of generating a flow stress model specific to a particular operation, and set of experimental data, rather than relying on existing data available in the literature is demonstrated.

A Constitutive Equation Coupling the Grain Size during the High Temperature Deformation of Ti-6.62Al-5.14Sn-1.82Zr Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 155-158 ◽  
Author(s):  
Jiao Luo ◽  
Miao Quan Li ◽  
Y.Q. Hu
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Flow Stress ◽  
Constitutive Equation ◽  
Steady Flow ◽  
Maximum Error ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Stress Model ◽  
Flow Stress Model

A constitutive equation has been established to describe the effect of grain size on the deformation behavior of Ti-6.62Al-5.14Sn-1.82Zr alloy during the high temperature. In this paper, firstly a steady flow stress model is proposed, and a function relating to the grain size is introduced to modify the steady flow stress model. Meanwhile, a microstructure model established by the fuzzy neural network method is applied to calculate the grain size of prior α phase during the high temperature deformation of Ti-6.62Al-5.14Sn-1.82Zr alloy. The calculated flow stress using the present constitutive equation shows a good agreement with the experimental flow stress of the Ti-6.62Al-5.14Sn-1.82Zr alloy. The relative maximum error was not more than 15%.

High Temperature Deformation Behavior of Ti-7333 Titanium Alloy and its Flow Stress Model

2012 ◽  
Vol 538-541 ◽  
pp. 945-950 ◽  
Author(s):  
Jiang Kun Fan ◽  
Hong Chao Kou ◽  
Min Jie Lai ◽  
Bin Tang ◽  
Hui Chang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Stress Model ◽  
Compression Tests ◽  
Flow Stress Model

The effects of processing parameters on deformation behavior of a new near β titanium alloy were investigated by using compression tests. The experiments were carried out in the Gleeble-3800 thermal and mechanical simulator in the temperature range of 770-970°C and strain rate range of 10-3-10s-1, and height direction reduction of 70%. The results show that the flow stress of Ti-7333 titanium alloy increases obviously with the strain and reaches a peak, then decreases to a steady value. The steady and peak stress significantly decreases with the increase of deformation temperature and decrease of strain rate. The flow stress model of Ti-7333 titanium alloy during high temperature deformation was established by using the regression method. The average relative difference between the calculated and experimental flow stress is 6.33%. The flow stress model can efficiently predict the deformation behavior of Ti-7333 titanium alloy during high temperature deformation.

Mechanical Aspects of Plastic Deformation of Nickel Based Superalloy

2013 ◽  
Vol 592-593 ◽  
pp. 724-727
Author(s):  
Andrzej Nowotnik ◽  
Paweł Rokicki ◽  
Paweł Pędrak ◽  
Slawomir Kotowski ◽  
Jan Sieniawski ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Flow Stress ◽  
Strain Rate ◽  
Deformation Process ◽  
True Strain ◽  
True Stress ◽  
Effect Of Temperature ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Nickel Based Superalloy

Variations of a true stress vs. true strain illustrate behaviour of materials during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests. Results of these tests provide crucial information pertaining to the stress values which are necessary to run deformation process at specified temperature and cooling rate. Uniaxial compression tests at temperatures below the γ solvus were conducted on nickel based superalloy CMSX-4, to study the effect of temperature and strain rate on its flow stress. On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (σpl -T i σpl - ἐ) and compression data were used to determine material constants. These constants allow to derive a formula that describes the relationship between strain rate, deformation temperature and true stress.

High-Temperature Deformation Behavior of the γ Alloy Ti-48Ai-2Cr-2Nb

1990 ◽  
Vol 213 ◽  
Author(s):  
Donald S. Shih ◽  
Gary K. Scarr
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
True Strain ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Compression Tests ◽  
Uniform Deformation ◽  
Good Workability ◽  
Low Strain Rate

ABSTRACTThe hot-workability of a two-phase (γ+α2) alloy, Ti-48A1-2Cr-2Nb, has been studied by conducting isothermal compression tests to 0.8 true strain over the temperature range of 975–1200°C at strain rates between 1×l0−1 and 3×10−3s−1. A deformation map showing temperature, strain rate, soundness of deformation, and isostress contours was constructed. Good workability is found from the low temperature/low strain rate regime to combinations of high temperature and either high or low strain rate. The upper-limit flow stress for good workability is between 450 and 500 MPa. Deformation induced softening occurs at all conditions. SEM and TEM examinations of the deformed specimens reveal that non-uniform deformation takes place at all strain rates, but cracking occurs mostly at high strain rates (e.g. 1×10−1s−1), especially combined with low temperatures. The cracking appears to progress primarily along γ/α2interfaces. It is thought that non-uniform deformation develops channels of shear bands, which in turn promote localized recrystallization, thus accommodating higher strains.

Dynamic Deformation Response of G33 Steel under High Temperature

2015 ◽  
Vol 782 ◽  
pp. 61-70
Author(s):  
You Jing Zhang ◽  
Hong Nian Cai ◽  
Xing Wang Cheng ◽  
Shuang Zan Zhao
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Shear Bands ◽  
Shear Zones ◽  
Adiabatic Shear ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Adiabatic Shear Bands

The high temperature deformation and fracture behavior of ultra-high strength G33 steel under high strain rate compression are investigated by means of a split Hopkinson p ressure bar. Impact tests are performed at strain rates of 1000/s and 2200/s and at temperatures ranging from 25°C to 700°C. The SEM and TEM techniques are also used to analyze the microstructure evolution of the adiabatic shear band (ASB) and fracture characteristics of the deformed specimens at high temperature. The experimental results indicate that the flow stress of G33 steel is significantly dependent on temperatures and strain rates. The flow stress of G33 steel increases with the increase of strain rates, but decreases with the increase of temperatures. The strain rate sensitivity is more pronounced at the low temperature of 25°C. In addition, G33 steel is more liable to fracture at high temperatures than at 25°C. Observations of microstructure show two well-developed symmetric parabolic adiabatic shear bands on the longitudinal cross-section of the cylindrical specimen deformed at the temperature of 700°C and at the strain rate of 2200/s. Within the ASB, the width of the fine equiaxed grain structure is about 7μm. The size of those equiaxed grains is approximately 100nm. The fracture analysis results indicate that the ASBs are the predominant deformation and the specimens fracture along adiabatic shear bands. The fracture surfaces of the deformed G33 steel specimens are characterized by two alternating zones: rough dimple zone and relatively smooth shear zone. Further observations reveal that smooth shear zones consist of severely sheared dimples.

High-Temperature Deformation of Yba2Cu307-8 With Ag Additions

1989 ◽  
Vol 169 ◽  
Author(s):  
J.L. Routbort ◽  
K.C. Goretta ◽  
J.P. Singh
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
Flow Stress ◽  
Compressive Strain ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Steady State Flow ◽  
Ag Additions

AbstractThe steady‐state flow stress of YBa2Cu3O7‐δ containing 15 to 30 vol.% Ag has been measured in air at nearly constant compressive strain rates between 5 x 10‐6 and 1 x 10‐4 s‐1 from 830 to 900°C. Addition of Ag dramatically decreases the flow stress compared to that of the pure superconductor, but the stress exponents and the activation energy for deformation remain unchanged.

Hot Deformation Behavior of 2519 Al Alloy during Isothermal Compression

2007 ◽  
Vol 546-549 ◽  
pp. 749-754 ◽  
Author(s):  
Hui Zhong Li ◽  
Xin Ming Zhang ◽  
Min Gan Chen ◽  
Ying Liu ◽  
Hui Gao
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Deformation Temperature ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Al Alloy ◽  
Strain Rates ◽  
Isothermal Compression

The deformation behavior of 2519 aluminum alloy was studied by isothermal compression by Gleeble-1500 simulator in the temperature range from 300 to 450°C under the strain rates of 0.01~10s-1. The results showed that the flow stress was controlled by strain rate and deformation temperature. The flow stress increased with strain rate and decreased with deformation temperature. The flow stress of 2519 aluminum alloy increased with strain and to the constant values at three strain rates of 0.01 s-1,0.1 s-1and1 s-1, indicating the dynamic recovery to occur. The flow stress decreased after a peak value with increase of strain at strain rate 10s-1 and deformation temperature higher than 350°C, showing partly dynamic recrystallization. The flow stress of 2519 aluminum alloy during high temperature deformation can be represented by Zener-Hollomon parameter.

scholarly journals A Comparative Study on Modified Johnson–Cook and Arrhenius-Type Constitutive Models to Predict the Hot Deformation Behaviour of Molybdenum-Hafnium-Carbide Alloy

2021 ◽  
Author(s):  
Athar Safari ◽  
Muhammad Imran ◽  
Sabine Weiss
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Constitutive Equations ◽  
Hot Deformation ◽  
Deformation Behaviour ◽  
Experimental Results ◽  
Temperature Deformation ◽  
Computational Time ◽  
Strain Rates ◽  
Material Constants

AbstractMolybdenum alloys are commonly used as tool material for high-temperature deformation processes like forming or forging. For these types of application, the material has to withstand static load at elevated temperatures. To investigate the high-temperature performance of the material, uniaxial hot tensile tests were performed on a Mo-1.2% Hf-0.1% C alloy (MHC) over the temperature range of 1173-1473 K with intervals of 100 K and strain rates of 0.001, 0.01 and 0.1 s−1 up to the fracture of the specimen. The flow stress decreases with increase in temperature and the reduction in strain rate. This behaviour could be related to the increasing rate of restoration mechanisms, i.e. dynamic recrystallization or recovery as well as to the decrease in the strain hardening rate. Microstructure of the two most critical hot deformation conditions were shown and compared. Based on modified Johnson–Cook and strain-compensated Arrhenius-type models, constitutive equations were established to predict the high-temperature flow stress of the respective MHC alloy. The accuracy of both models was evaluated by comparing the predicted stress values and the values obtained from experiments. Correlation coefficient, average absolute relative error, the number of material constants involved and the computational time required for evaluating the constants were calculated to quantify and compare the precision of both models. The flow stress values predicted by the constitutive equations are in good agreement with the experimental results. At lower strain rates (0.001 and 0.01 s−1), distinct deviation from the experimental results can be observed for the modified Johnson–Cook model. Despite the longer evaluation time and the larger number of material constants, the deformation behaviour, tracked by the Arrhenius-type model is more accurate throughout the entire deformation process.

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