Temperature Increase during Isothermal Forging of Ti-5Al-2Sn-2Zr-4Cr-4Mo Alloy Using a 1500-Ton Forging Press

2021 ◽  
Vol 1016 ◽  
pp. 702-707
Author(s):  
Tomonori Kitashima ◽  
Yoshinori Yoshida ◽  
Ryo Matsumoto

In this study, the temperature increase of the Ti-17 alloy (Ti–5Al–2Sn–2Zr–4Cr–4Mo, wt.%) during isothermal forging in the (α + β) dual-phase region was investigated using large-size workpieces forged between hot dies in a 1500-ton forging press. The temperature increase was predicted using finite element analysis (FEA). The tip of a thermocouple was inserted into the center of the workpiece (diameter: 100 mm; height: 50 mm). The forging temperatures were 1023 K (750 °C) and 1073 K (800 °C) in the (α + β) dual-phase region. The strain rate was 0.05 s−1 and 0.5 s−1 at each temperature. Meanwhile, the compression percentage was 75%. The true stress–true strain curves were inversely obtained by fitting the load–stroke curves using the FEA. The predicted temperature was in a good agreement with that in the experimental results when the value of 1.0 was used as the conversion factor for plastic deformation energy to heat energy in the FEA under the current forging conditions. At the strain rate of 0.5 s−1, the temperature instantly increased to a β-transus temperature in 3 s at 1073 K (800 °C). In contrast, the temperature logarithmically increased at both 1023 K (750 °C) and 1073 K (800 °C) at 0.05 s−1 in 28 s (e.g., 42 K at 1023 K (750 °C)). The obtained true stress–true strain curves indicate that flow softening occurred during the forgings, which is attributed to dynamic recrystallization and/or dynamic recovery. The temperature increase in the Ti-17 alloy was smaller than that in the Ti–6Al–4V alloy under the same forging condition.

Author(s):  
Sijia Zhong ◽  
Jianfeng Shi ◽  
Jinyang Zheng

Polyethylene (PE) pipes have been applied in transportation of key energy medium such as natural gas in the past decades. The mechanical property of PE is of great importance for better design and safer application of PE pipeline system. The large deformation behavior is a key character of PE, not only for its significant strain rate sensitivity, but also for localized necking process after yielding. In this paper, a new constitutive modeling method was proposed to charaterize the rate-denpendent large deformation behavior of PE, in which the true stress is regarded as a function of true stain and true strain rate alone. Uniaxial tensile tests of PE were conducted under various cross-head speeds, and a digital camera was used to record the real-time deformation of specimens. By separating the composite effect into respective effect of local true strain and strain rate on the local true stress in the necking region, a phenomenological model for describing the rate-dependent deformation behavior under uniaxial tension was ealstablished. Model results were validated and found in good agreement with experimental data.


Author(s):  
James M. Fragomeni ◽  
Giridhar Venugopal

Many systems that work on the processing of energy can be modeled in terms of that energy. The energy that is given to the system may be stored or dissipated in the form of heat. It was proposed to extend this concept to attainment of critical level of stored energy and/or dissipated energy for occurrence of buckling of a metal column under compressive loading. The fact that Energy Factor Parameter (E.F.P.) computed from the experimental true stress-true strain values, suddenly decreased and approached value close to zero indicated either buckling and/or softening, but deviated with the E.F.P. computed from the theoretical true stress and true strain values. The 7050-T7451 (Al-Zn-Mg-Cu-Zr) and Al-Li-Cu aluminum alloys in longitudinal and transverse grain orientations were compression tested for mechanical properties of yield strength, buckling strength, strength coefficient, strain hardening exponent. Correlation between ratio of buckling strength and yield strength with aging time for preaged ASTM compression specimens was established. The compression deformation of aluminum alloy 7050 was modeled using finite element analysis, with the experimental testing parameters and the database in the software package.


2013 ◽  
Vol 592-593 ◽  
pp. 724-727
Author(s):  
Andrzej Nowotnik ◽  
Paweł Rokicki ◽  
Paweł Pędrak ◽  
Slawomir Kotowski ◽  
Jan Sieniawski ◽  
...  

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.


2013 ◽  
Vol 747-748 ◽  
pp. 703-708 ◽  
Author(s):  
Tao Wang ◽  
Shu Hong Fu ◽  
Zhao Li ◽  
Yong Zhang ◽  
Yu Xin Zhao ◽  
...  

Hot compressive deformation of Udimet720Li alloy was carried out on Gleeble-3500 thermal mechanical simulator. The flow stress behavior of Udimet720Li alloy during hot compression was studied in the temperature range of 1100-1160 and at a strain rate of 0.001-1s -1. The results showed that the flow stress was controlled by both strain rate and deforming temperature. The flow stress decreased with the increase of deforming temperature, while increased with the increase of strain rate. The change of flow stress with deformation thermal parameters was revealed from true stress-true strain curves, and constitutive relationship of Udimet720Li alloy was obtained on the base of Arrhenius equations and the deformation activation energy was calculated.


Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1502
Author(s):  
Xiao Li ◽  
Lifeng Hou ◽  
Yinghui Wei ◽  
Zhengyan Wei

The hot deformation behavior of a nitrogen-bearing martensitic stainless steel was researched by the isothermal compression test in the temperature range of 950–1150 °C and strain rate range of 0.01–10 s−1 with a Gleeble-3800 thermal-mechanical simulating tester. A strain compensated sine-hyperbolic Arrhenius-type constitutive equation was developed to describe the relationship between true stress and deformation parameters such as temperature, strain rate and true strain. The hot deformation activation energy is calculated to be from 407 to 487 KJ mol−1. It is validated by the standard statistical parameters that the established constitutive equation can accurately predict the true stress. The processing maps at different true strains were constructed based on the dynamic material model (DMM) and the true stress data obtained from the hot compression tests. Two unstable regions which should be avoided during hot working were observed from the processing map. In addition, the optimum hot working parameters are located in the domain of 1000–1150 °C/0.1–1 s−1 with the peak power dissipation efficiency of 39.9%, in which complete dynamic recrystallization (DRX) occurs.


2011 ◽  
Vol 704-705 ◽  
pp. 124-128
Author(s):  
Xin Zhang ◽  
Yi Xiong

Using thermal simulator (Gleeble 1500D), the thermal deformation behavior of Cu-P weathering steel containing Cr, Ni, Mo under the conditions of various deformation temperatures and strain rates was studied. The true stress-true strain curves at various thermal deformation conditions were got, and the thermal deformation equation was established. Then the microstructure features of the steel under various deformation temperatures and strain rates were analyzed when the true strains were same. The results show that with the same strains and strain rates, the higher the deformation temperature, the easier the recrystallization occurs, and the greater the size of the recrystal grains. And with the same strains and deformation temperatures, the lower the strain rate, the easier the recrystallization occurs, and the greater the proportion and size of the recrystal grains. Keywords:Weathering steel, Deformation temperature, Strain rate, Thermal deformation equation, Recrystallization


1945 ◽  
Vol 12 (4) ◽  
pp. A217-A227
Author(s):  
C. W. MacGregor ◽  
J. C. Fisher

Abstract Tension tests of the true stress-strain type are reported for which the true strain rate is maintained constant throughout each test. Several metals are investigated under testing temperatures ranging from −183 C to 665 C. The influence of temperature and strain velocity on the true stress-strain properties is described. A single variable called the velocity-modified temperature is used to represent the combined influences of true strain rate and testing temperature.


2012 ◽  
Vol 426 ◽  
pp. 101-105
Author(s):  
Hui Yang ◽  
Wen Tong Tian

The microstructure and stress variation of semisolid 7A04 alloy have been studied through unconstrictive isothermal compressing test. The results show that the relationships between true stress and true strain at different deformation temperatures and strain rates are the same, and the peak stress in the curve of true stress and true strain mainly depends on deformation temperature and strain rate. Analysis on the microstructure of compressive specimen demonstrates that segregation of liquid-solid phase is mainly affected by strain rate and deformation temperature. There are mainly two kinds of flow in liquid phase: either from the region with relatively large hydrostatic compressive stress to the region with relatively small hydrostatic compressive stress or from the grain boundaries perpendicular to the compressive axis to the grain boundaries with a certain directional angle to the compressive direction. Based on the above results, the microstructure and stress variation mainly depend on deformation temperature, strain rate and stress state.


2011 ◽  
Vol 194-196 ◽  
pp. 175-178
Author(s):  
Xin Zhang ◽  
Yi Xiong

The effects of temperature and strain rate on the thermal deformation-behavior of Cu-P weathering steel were studied by using thermal simulator. And the true stress-true strain curves at different thermal deformation conditions were got. Then the features of the microstructure of the steel under different temperatures and strain rates were analyzed. The results show that with the same deformation dimensions and strain rates, when the deformation temperatures were higher, the recrystallization would proceed much easier, and the size of the recrystal grains could be also larger. And with the same deformation dimensions and temperatures, when the strain rates were lower, the recrystallization could also occur easier, and the proportion and size of the recrystal grains were larger.


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