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.

Prediction of High Temperature Flow Stress of Alloy 2618-Ti during Hot Deformation

2014 ◽  
Vol 0 (0) ◽  
Author(s):  
Ya Liu ◽  
Jing Li ◽  
Yuanfeng Song ◽  
Tao Li ◽  
Xuping Su ◽  
...  
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Constitutive Equations ◽  
Hot Deformation ◽  
Compressive Deformation ◽  
Strain Rates ◽  
Material Parameters ◽  
Deformation Behaviors

AbstractIn order to find material parameters of established Zener-Hollomon constitutive equations and predict high-temperature flow stress of alloy 2618-Ti, the hot compressive deformation behaviors of the alloy were investigated at temperatures ranging from 300 to 500 °C at intervals of 50 °C and at constant strain rates of 0.001, 0.01, 0.1 and 1 s

scholarly journals High-Temperature Flow Behaviour and Constitutive Equations for a TC17 Titanium Alloy

2019 ◽  
Vol 38 (2019) ◽  
pp. 168-177 ◽  
Author(s):  
Liu Shi-feng ◽  
Shi Jia-min ◽  
Yang Xiao-kang ◽  
Cai Jun ◽  
Wang Qing-juan
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Constitutive Equation ◽  
Constitutive Equations ◽  
Deformation Behaviour ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Compression Tests ◽  
Average Absolute Relative Error ◽  
Wide Range

AbstractIn this study, the high-temperature deformation behaviour of a TC17 titanium alloy was investigated by isothermal hot compression tests in a wide range of temperatures (973–1223 K) and strain rates (0.001–10 s−1). Then, the constitutive equations of different phase regimes (α + β and single β phases) were developed on the basis of experimental stress-strain data. The influence of the strain has been incorporated in the constitutive equation by considering its effect on different material constants for the TC17 titanium alloy. Furthermore, the predictability of the developed constitutive equation was verified by the correlation coefficient and average absolute relative error. The results indicated that the obtained constitutive equations could predict the high-temperature flow stress of a TC17 titanium alloy with good correlation and generalization.

High Temperature Deformation Behaviour and Processing Maps of AZ81 Magnesium Alloy

2011 ◽  
Vol 686 ◽  
pp. 168-175 ◽  
Author(s):  
Hui Min Liao ◽  
Ming Zeng ◽  
Si Yuan Long ◽  
Han Xue Cao
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Magnesium Alloy ◽  
Strain Rate ◽  
Hot Deformation ◽  
Flow Instability ◽  
Temperature Deformation ◽  
Stable Phase ◽  
Processing Temperature ◽  
Processing Maps

The hot compression deformation behavior of AZ81 magnesium alloy was studied with Gleeble-1500 thermal simulation machine at the strain rate of 0.003 ~ 3.0s-1 and temperature of 340 ~ 430 °C. The results show that, the flow stress decreases when the deformation temperature increases and strain rate decreases; the peak stress increases with decrease of the temperature and the increase of the strain rate; the critical strain that comes into stable phase increases obviously. It is that the high temperature flow stress model of AZ81 magnesium alloy is constructed by introduceing Zener-Hollomon parameters, its average deformation activation energy is 169.48 kJ / mol. Processing maps of AZ81 magnesium alloy is also calculated and analyzed by the dynamic model of the material. Useing hot deformation processing maps, the flow instability zone is determined and the best process parameters access to the test parameters during hot deformation are as follow: thermal processing temperature range of 380 °C ~ 420 °C, strain rate range of 0.01 ~ 0.03 S-1.

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.

Prediction of FV520B Steel Flow Stresses at High Temperature and Strain Rates

2015 ◽  
Vol 34 (6) ◽  
Author(s):  
Xiaolan Han ◽  
Shengdun Zhao ◽  
Chenyang Zhang ◽  
Shuqin Fan ◽  
Fan Xu
Keyword(s):  
High Temperature ◽  
Constitutive Equations ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Strain Rates ◽  
Isothermal Compression ◽  
Compression Tests ◽  
Hot Deformation Behavior ◽  
Wide Range ◽  
Steel Flow

AbstractIn order to develop reliable constitutive equations for the simulation, the hot deformation behavior of FV520B steel was investigated through isothermal compression tests in a wide range of temperatures from 900 °C to 1100 °C at an interval of 50 °C and strain rate from 0.01 to 10 s

Deformation Mechanism Maps for Al-Cu-Mg Alloys Micro-Alloyed with Tin

2011 ◽  
Vol 410 ◽  
pp. 283-286
Author(s):  
P.S. Robi ◽  
Sanjib Banerjee ◽  
A. Srinivasan
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Base Alloy ◽  
Mg Alloy ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Microstructural Investigation

High temperature deformation behavior of Al–5.9%Cu–0.5%Mg alloy and Al–5.9%Cu–0.5%Mg alloy containing 0.06 wt.% of Sn was studied by hot compression tests at various temperatures and strain rates. Addition of trace amounts of Sn into the Al–Cu–Mg alloy system resulted in a significant increase of flow stress for all conditions of temperature and strain rate. 100% and 89% of the flow stress values during hot deformation could be predicted within ± 10% deviation values for the aluminum alloys with and without Sn content, respectively, by artificial neural network (ANN) modeling. From the deformation mechanism maps and microstructural investigation, the safe process regimes for hot working of the base alloy was identified to be at (i) very low strain rate (< 0.003 s−1) at temperature < 450 °C, and (ii) high temperature (> 400 °C) with strain rate > 0.02 s−1. For the micro-alloyed alloy, it was at low strain rates (< 0.01 s-1) for the entire temperature range studied. Flow softening for both alloys was observed to be at low strain rates and was identified to be due to dynamic recrystallization (DRX). The metallurgical instability during deformation was identified due to shear band formation and/or inter-crystalline cracking.

Hot Deformation Behavior and Constitutive Equation of Mg-4Al-3Ca -1.5Zn-1Nd-0.2Mn Magnesium Alloy As-Extruded

2014 ◽  
Vol 900 ◽  
pp. 588-591
Author(s):  
Gang Chen ◽  
Wei Chen ◽  
Guo Wei Zhang ◽  
Jing Zhai ◽  
Li Ma ◽  
...  
Keyword(s):  
Activation Energy ◽  
Flow Stress ◽  
Magnesium Alloy ◽  
Constitutive Equation ◽  
Constitutive Equations ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Strain Rates ◽  
Compression Tests ◽  
Hot Deformation Behavior

The deformation behavior and constitutive equation of Mg-4Al-3Ca-1.5Zn-1Nd-0.2Mn alloy were investigated using hot compression tests at the temperatures range of 200, 250, 300, and 350°C with the constant strain rates of 0.001, 0.01, 0.1 And1 s-1. The influence of strain was also incorporated in the constitutive equation by considering the effects of strain on material constants which are consist of A, α, β, n and activation energy Q. The predicted flow stress curves using the proposed constitutive equations well agree with the experimental results of the flow stress for experimental Alloy.

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.

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