A physical-based unified constitutive model of AA7075 for a novel hot forming condition with pre-cooling

A constitutive model is proposed for simulations of hot forming processes. Dominant mechanisms in hot forming including inter-granular deformation, grain boundary sliding and grain boundary diffusion are considered in the constitutive model. A Taylor type polycrystalline model is used to predict inter-granular deformation. Previous works on grain boundary sliding and grain boundary diffusion are extended to drive three dimensional macro stress-strain rate relationships for each mechanism. In these relationships, the effect of grain size is also taken into account. It is shown that for grain boundary diffusion, stress-strain rate relationship obeys the Prandtl-Reuss flow rule. The proposed model is used to simulate step strain rate tests and the results are compared with experimental data. It is concluded that the model can be used to predict flow stress for various grain sizes and strain rates. The proposed model can be directly used in simulation of hot forming processes and as an example the bulge forming process is simulated and the results are compared with experimental data.

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Research on the High-Temperature Hot Compressive Deformation Behavior of Ni-Based Superalloy GH3128

Journal of Pressure Vessel Technology ◽

10.1115/1.4034147 ◽

2016 ◽

Vol 139 (2) ◽

Cited By ~ 1

Author(s):

Xi Zhao ◽

Kun Yuan ◽

Yu Zhou ◽

Fu Li

Keyword(s):

High Temperature ◽

Strain Rate ◽

Dominant Role ◽

Reactor Core ◽

Hot Forming ◽

High Temperature Strength ◽

High Stack Fault Energy ◽

Hot Workability ◽

Compression Tests ◽

Forming Condition

Intermediate heat exchanger (IHX), which transfers the heat generated in the reactor core to the secondary loop, is one of the key structural components of the very high-temperature gas-cooled reactor (VHTR). The Ni-based superalloy GH3128 has good high-temperature strength and so is a promising main structural material for the IHX. In this paper, the flow stress behaviors and the deformation microstructure of superalloy GH3128 were investigated by high-temperature compression tests conducted at various temperatures (950–1150 °C) and strain rates (0.001–10 s−1), and the processing maps were analyzed in order to establish the hot deformation constitutive model and obtain the optimum hot forming condition. The results show that (1) both flow stresses and peak flow stresses increase along with the increase of strain rate or decrease of temperature, (2) GH3128 has excellent hot workability, (3) the dynamic recovery (DRV) plays the dominant role during the dynamic softening process due to the high stack fault energy, and (4) the optimum hot forming condition of GH3128 should be defined in the temperature of 1150 °C and strain rate range of 0.01–0.056 s−1. This work contributes to the application of GH3128 alloy on IHX structure.

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Formability of 7000 aluminum alloys in warm and hot forming condition

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/418/1/012027 ◽

2018 ◽

Vol 418 ◽

pp. 012027

Author(s):

B-A Behrens ◽

S Hübner ◽

H Vogt

Keyword(s):

Aluminum Alloys ◽

Hot Forming ◽

Forming Condition

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Research on Deformation Behavior of 2024 H18 Aluminum Alloy at Elevated Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.770.329 ◽

2013 ◽

Vol 770 ◽

pp. 329-334 ◽

Cited By ~ 1

Author(s):

Guo Liang Chen ◽

Ning Wang ◽

Ming He Chen

Keyword(s):

Aluminum Alloy ◽

Elevated Temperature ◽

Constitutive Model ◽

Strain Rate ◽

Deformation Behavior ◽

Tensile Deformation ◽

Tensile Elongation ◽

Linear Regression Analysis ◽

Hot Forming ◽

Uniaxial Tensile

Uniaxial tensile deformation behavior of 2024 H18 aluminum sheet alloys was studied in the hot forming process with synchronous cooling temperature range of 300°C~475°C and in the strain rate range of 0.0005/s~0.1/s. The effects of temperature and strain rate on stress, elongation to facture were analyzed. And a constitutive model was proposed to describe the relationship of true stress-true stain by multiple linear regression analysis. It was found that the forming temperature and strain rate have great effect on the hot forming behavior of the alloys. The max stress reduced greatly with the increasing of temperature or reducing of strain rate, while the tensile elongation tended to rise first and then fall with the increasing of temperature and strain rate. The forming of 2024 H18 aluminum alloy at elevated temperature occurred with the strain hardening and dynamic softening. The constitutive model of 2024 H18 aluminum alloy agrees well with the experimental data.

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