scholarly journals Superplasticity of Ti-6Al-4V Titanium Alloy: Microstructure Evolution and Constitutive Modelling

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1756 ◽  
Author(s):  
Ahmed O. Mosleh ◽  
Anastasia V. Mikhaylovskaya ◽  
Anton D. Kotov ◽  
James S. Kwame ◽  
Sergey A. Aksenov
Keyword(s):  
Strain Rate ◽  
Microstructural Evolution ◽  
Deformation Temperature ◽  
Superplastic Deformation ◽  
Deformation Behaviour ◽  
Strain Rate Range ◽  
Grain Structure ◽  
Rate Range ◽  
Temperature Range ◽  
Elongation To Failure

Determining a desirable strain rate-temperature range for superplasticity and elongation-to-failure are critical concerns during the prediction of superplastic forming processes in α + β titanium-based alloys. This paper studies the superplastic deformation behaviour and related microstructural evolution of conventionally processed sheets of Ti-6Al-4V alloy in a strain rate range of 10–5–10–2 s–1 and a temperature range of 750–900 °C. Thermo-Calc calculation and microstructural analysis of the as-annealed samples were done in order to determine the α/β ratio and the grain size of the phases prior to the superplastic deformation. The strain rate ranges, which corresponds to the superplastic behaviour with strain rate sensitivity index m ˃ 0.3, are identified by step-by-step decreasing strain rate tests for various temperatures. Results of the uniaxial isothermal tensile tests at a constant strain rate range of 3 × 10−4–3 × 10−3 s−1 and a temperature range of 800–900 °C are presented and discussed. The experimental stress-strain data are utilized to construct constitutive models, with the purpose of predicting the flow stress behaviour of this alloy. The cross-validation approach is used to examine the predictability of the constructed models. The models exhibit excellent approximation and predictability of the flow behaviour of the studied alloy. Strain-induced changes in the grain structure are investigated by scanning electron microscopy and electron backscattered diffraction. Particular attention is paid to the comparison between the deformation behaviour and the microstructural evolution at 825 °C and 875 °C. Maximum elongation-to-failure of 635% and low residual cavitation were observed after a strain of 1.8 at 1 × 10−3 s−1 and 825 °C. This temperature provides 23 ± 4% β phase and a highly stable grain structure of both phases. The optimum deformation temperature obtained for the studied alloy is 825 °C, which is considered a comparatively low deformation temperature for the studied Ti-6Al-4V alloy.

scholarly journals Hot Deformation Characteristics—Constitutive Equation and Processing Maps—of 21-4N Heat-Resistant Steel

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 89 ◽  
Author(s):  
Yiming Li ◽  
Hongchao Ji ◽  
Wangda Li ◽  
Yaogang Li ◽  
Weichi Pei ◽  
...  
Keyword(s):  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Strain Rate Range ◽  
Processing Maps ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Rate Range ◽  
Temperature Range ◽  
Heat Resistant

Abstract: The hot deformation behavior of 21-4N heat-resistant steel was studied by hot compression test in a deformation temperature range of 1000–1180 °C, a strain rate range of 0.01–10 s−1 and a deformation degree of 60%, and the stress-strain curves were obtained. The functional relationship between flow stress and process parameters (deformation degree, deformation temperature, strain rate, etc.) of 21-4N heat-resistant steel during hot deformation was explored, the constitutive equation of peak stress was established, and its accuracy was verified. Based on the dynamic material model, the energy dissipation maps and destabilization maps of 21-4N heat-resistant steel were established at strains of 0.2, 0.4 and 0.6, and processing maps were obtained by their superposition. Within the deformation temperature range of 1060~1120°C and a strain rate range of 0.01–0.1 s−1, there is a stable domain with the peak efficiency of about 0.5. The best hot working parameters (strain rate and deformation temperature) of 21-4N heat-resistant steel are determined by the stable and instable domain in the processing maps, which are in the deformation temperature range of 1120–1180 °C and the strain rate range of 0.01–10 s−1.

The Phenomenon of Superplasticity in Feal-Ti Alloy with Large Grains

1994 ◽  
Vol 364 ◽  
Author(s):  
Dingqiang Li ◽  
Aidang Shan ◽  
Yi Liu ◽  
Dongliang Lin
Keyword(s):  
Strain Rate ◽  
Superplastic Deformation ◽  
Dynamic Recovery ◽  
Rate Sensitivity ◽  
Strain Rate Range ◽  
Ti Alloy ◽  
Maximum Elongation ◽  
Rate Range ◽  
First Time ◽  
Range Of Values

AbstractThe phenomenon of superplasticity in an ordered FeAl based alloy is reported in this paper for the first time. The behavior of superplastic deformation for the FeAl based alloy (Fe-36.5at.%-2at.%Ti) with large grains of above 300 μm has been examined at 1000°C in a strain rate range from 1.39×10− 4 /s to 2.78×l0−2 /s. The maximum elongation of 208% for the FeAl based alloy with large grains has been obtained and the index of strain rate sensitivity, the m value, has a range of values from 0.25 to 0.42. The reason for the large elongation is ascribed to the dynamic recovery and recrystallization during deformation in this large grained alloy at high temperatures.

The Constitutive Relationship and Processing Map of Hot Deformation in A100 steel

2016 ◽  
Vol 35 (4) ◽  
pp. 399-405 ◽  
Author(s):  
Yongkang Liu ◽  
Zongmei Yin ◽  
Junting Luo ◽  
Zhang Chunxiang ◽  
Yanshu Zhang
Keyword(s):  
Strain Rate ◽  
Type Equation ◽  
Strain Rate Range ◽  
Constitutive Relationship ◽  
Compression Tests ◽  
Rate Range ◽  
Temperature Range ◽  
Average Grain Size ◽  
Strain Data ◽  
Different Strains

AbstractIsothermal compression tests were conducted on A100 steel using a Gleeble 1500 thermal simulator at a temperature range of 900–1,200°C and strain rate range of 0.001–3 s−1. Results show that the A100 steel has higher strength than the Aermet 100 steel at high temperatures. Constant values, such as A, α, and n, and activate energy Q were obtained through the regression processing of the stress–strain data curves under different strains. A set of constitutive equations for A100 steel was proposed by using an Arrhenius-type equation. The optimum processing craft ranges for A100 steel based on the analysis of the hot working diagram and deformation mechanism are as follows: temperature range of 1,000–1,100°C and strain rate range of 0.01–0.1 s−1. The average grain size within this working range is 7–22.5 μm.

Characterization of Hot Deformation Behavior of Zr-4 Alloy in Material Application Area

2012 ◽  
Vol 578 ◽  
pp. 202-205
Author(s):  
Guo Qing Lin
Keyword(s):  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Flow Behavior ◽  
Strain Rate Range ◽  
Processing Maps ◽  
Peak Efficiency ◽  
Hot Deformation Behavior ◽  
Rate Range ◽  
Temperature Range

The hot deformation behavior of Zr-4 alloy was studied in the temperature range 650-900°C and strain rate range 0.005-50s-1 using processing maps. The processing maps revealed three domains: the first occurs in the temperature range 780-820°C and strain rate range 0.005-0.05s-1, and has a peak efficiency of 45% at 790°C and 0.005s-1; the mechanism is the dynamic recrystallization. The second occurs in the temperature range greater than 900°C and strain rate range 0.05-0.8s-1, and has a peak efficiency of 40% at 900°C and 0.5s-1, which are the domains of dynamic recovery. In addition, the instability zones of flow behavior can also be recognized by the maps in the temperature range 650-780°C and strain rate range 0.01-0.1s-1, which should be strictly avoided in the processing of the material. Zr-4 alloy is the material for pressure tube applications in nuclear reactors and has better strength and a lower rate of hydrogen uptake compared to other materials under similar service conditions.

scholarly journals Determination of Constitutive Equation and Thermo–Mechanical Processing Map for Pure Iridium

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1087
Author(s):  
Mi Zhou ◽  
Rui Hu ◽  
Jieren Yang ◽  
Chuanjun Wang ◽  
Ming Wen
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Processing Map ◽  
Frictional Coefficient ◽  
Strain Curve ◽  
Strain Rate Range ◽  
Forming Process ◽  
Thermal Compression ◽  
Rate Range ◽  
Temperature Range

Deformation behavior of pure iridium has been studied during thermal compression testing with the help of Gleeble-1500D in the temperature range of 1200 °C~1500 °C and strain rate range of 10−1 s−1~10−2 s−1. Resistance to deformation, microstructural evolution and hot workability of pure iridium have been used to analyze in detail. Frictional coefficient has been used to modify the experimental stress–strain curve of thermal compression test, and it has been found effective in reducing the influence of friction during thermo–mechanical testing. The hyperbolic sine constitutive equation of pure iridium has been established to give a material processing model for numerical simulation. A very high value of activation energy for iridium, 573 KJ/mol, clearly indicates that it is very hard to deform this material. The deformation mechanism of pure iridium is dependent upon temperature as well as strain rate. At low temperature and strain rate (temperature range of 1200 °C~1300 °C and strain rate range of 10−1 s−1~10−2 s−1), dynamic recovery is active while dynamic recrystallization becomes operative as temperature and stain rate are increased. On further increase in temperature and decrease in strain rate (temperature range of 1400 °C~1500 °C and strain rates of 10−2 s−1~10−3 s−1), abnormal grain growth takes place. On the basis of a constitutive model and processing map, suitable forming process parameters (temperature range of 1400 °C~1500 °C and strain rate range of 0.1 s−1~0.05 s−1) for pure iridium have been worked out.

A Study at the Workability of Ultra-High Strength Steel Sheet by Processing Maps on the Basis of DMM

2017 ◽  
Vol 36 (7) ◽  
pp. 657-667 ◽  
Author(s):  
Yu Feng Xia ◽  
Shuai Long ◽  
Tian-Yu Wang ◽  
Jia Zhao
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
High Strength Steel ◽  
High Strength ◽  
Strain Rate Range ◽  
Diffusion Activation Energy ◽  
Processing Maps ◽  
Rate Range ◽  
Temperature Range ◽  
Ultra High Strength Steel

AbstractThe hot workability of the ultra-high strength steel BR1500HS has been investigated by processing maps. A series of hot deformation tensile tests were carried out on a Gleeble-3500 thermal simulator in the deformation temperature range of 773–1,223 K and strain rate range of 0.01–10 s–1. The obtained flow stress curves reveal that the peak stress increases with the rising of strain rate and decreases with the rising of temperature. Based on dynamic materials model (DMM), the processing maps at the strains of 0.05, 0.10 and 0.15 were developed, and the optimum hot working conditions were recommended as the temperature range of 1,200–1,223 K and the strain rate range of 0.01–0.1 s–1, where the peak power dissipation efficiency is about 37 % revealing the occurrence of typical dynamic recrystallization (DRX). The main instability defects are deformation twinning and micro-crack occurring mainly at the temperature range of 773–873 K with the strain rate higher than 1 s–1. In order to deeply understand the microstructure mechanisms, the Zener–Hollomon parameter is solved, and then the self-diffusion activation energy is compared with the apparent activation energy Q at different deformation temperatures and strain rates.

Hot Deformation Behavior and Processing Map of a New High-Temperature Titanium Alloy

2017 ◽  
Vol 898 ◽  
pp. 566-573
Author(s):  
Shao Hui Shi ◽  
Li Hua Chai ◽  
Tao Li ◽  
Yong Shuang Cui ◽  
Guo Dong Shi ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Constant Strain Rate ◽  
Strain Rate Range ◽  
Instability Criterion ◽  
Engineering Strain ◽  
Rate Range ◽  
Temperature Range

Isothermal constant strain rate compression testing of a new as-cast high-temperature titanium alloy Ti-6.5Al-11.5(Sn,Zr)-2.5(Mo,W,Nb)-0.25Si-0.1Er was carried out at the deformation temperatures range from 900°C to 1100°C, strain rate range from 0.001 to 1 s-1 and 60% of engineering strain. The deformation behavior of this high-temperature titanium alloy was analyzed based on the stress-strain result, and the constitutive equation based on the hyperbolic sine model and the parameters of Zener–Hollomon was established, showing a close accordance with the experimental value. The hot processing maps based on the dynamic material model and the Prasad’s instability criterion were constructed at strains of 0.3 and 0.6. The maps exhibit two stable deformation domains in the temperature range of 940~960°C and strain rate range of 0.001~0.002s-1, and in the temperature range of 1030~1070°C and strain rate range of 0.02~0.06s-1 with the power dissipation efficiency of 58.5% and 54.5%, respectively.

Processing Maps for TC18 Titanium Alloy Deformed in α+β Region

2012 ◽  
Vol 490-495 ◽  
pp. 3423-3426 ◽  
Author(s):  
Xin Zhao ◽  
Hong Zhao ◽  
Rui Zhang
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Power Dissipation ◽  
Strain Rate Range ◽  
Hot Working ◽  
Maximum Efficiency ◽  
Processing Maps ◽  
Compression Tests ◽  
Rate Range ◽  
Temperature Range

The hot deformation characteristics of TC18 titanium alloy were studied in the temperature range 750-850°C and strain rate range 0.001-1 s-1 by using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate. The results reveal that the flow stress of TC18 is sensitive to strain rate. Processing map at stain of 0.6 reveals two domains: one is centered at 750°C and 0.001s-1; another is centered at 850°C and 0.001s-1. The maximum efficiency is more than 60%. According to the maps, the zone with the temperature range of 750-850°C and strain rate range of 0.01-0.001s-1 may be suitable for hot working

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