A Critical Assessment of Three Usual Equations for Strain Hardening and Dynamic Recovery

Montheillet, F.; Piot, David; Matougui, N.; Fares, Mohamed Lamine

doi:10.1007/s11661-014-2388-9

Cited by 24 publications

(18 citation statements)

References 16 publications

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“…The coalescence of dimples is likely to benefit the formation and propagation of large cracks during the tensile deformation process [ 1 ]. This phenomena also accords with the grain boundary mediated mechanisms resulting in higher ductility of rolled specimens with finer microstructure [ 30 , 31 , 32 , 33 ]. Tm is the melting temperature of alloy, and at temperatures above 0.5 Tm , ( Tm = 475 °C), deformation led by grain boundary sliding and diffusion creep can result in a fine-grain-sized alloy, which is weaker than its counterpart at relatively low temperature with a large grain size [ 10 ].…”

Section: Resultssupporting

confidence: 81%

Effects of Temperature and Strain Rate on the Fracture Behaviors of an Al-Zn-Mg-Cu Alloy

et al. 2018

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Effects of temperature and strain rate on the fracture behaviors of an Al-Zn-Mg-Cu alloy are investigated by isothermal uniaxial tensile experiments at a wide range of temperatures and strain rates, from room temperature (RT) to 400 °C and from 10−4 s−1 to 10−1 s–1, respectively. Generally, the elevation of temperature leads to the increasing of elongation to fracture and the reduction of peak stress, while higher strain rate results in the decreasing of elongation to fracture and the increasing of peak stress. Interestingly, we found that the coefficient of strain rate sensitivity (m-value) considerably rises at 200 °C and work of fracture (Wf) fluctuates drastically with the increase of strain rate at RT and 100 °C, both of which signify a non-uniform and unstable deformation state below 200 °C. A competition of work hardening (WH) and dynamic recrystallization (DRX) exists at 200 °C, making it serve as a transitional temperature. Below 200 °C, WH is the main deformation mechanism of flow stress, and DRX dominates the flow stress above 200 °C. It has been found that from RT to 200 °C, the main feature of microstructure is the generation of dimples and microvoids. Above 200 °C, the coalescence of dimples and microvoids mainly leads to the failure of specimen, while the phenomenon of typically equiaxed dimples and nucleation appear at 400 °C. The observations of microstructure are perfectly consistent with the related macroscopic results. The present work is able to provide a comprehensive understanding of flow stress of an Al-Zn-Mg-Cu alloy at a wide range of temperatures and strain rates, which will offer valuable information to the optimization of the hot forming process and structural design of the studied alloy.

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Section: Resultssupporting

confidence: 81%

Effects of Temperature and Strain Rate on the Fracture Behaviors of an Al-Zn-Mg-Cu Alloy

et al. 2018

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“…With the temperature increased, the yield strength of powders declines and the powder starts to deform which introduces accumulated dislocations in powders [ 17 ]. Generally, to initial RX, critical dislocation density should be satisfied, and the dislocation density in the bulk ρ under isothermal deformation is related with RV and working hardening before recrystallization as described by Equations (2) and (3) [ 29 , 30 ]:

wherein, t is the time, ε represents equivalent strain. The right two positive terms of above equations correspond to work hardening and RV respectively.…”

Section: Discussionmentioning

confidence: 99%

Effects of Temperature and Pressure of Hot Isostatic Pressing on the Grain Structure of Powder Metallurgy Superalloy

Tan

Liu

et al. 2018

Materials

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The microstructure with homogeneously distributed grains and less prior particle boundary (PPB) precipitates is always desired for powder metallurgy superalloys after hot isostatic pressing (HIPping). In this work, we studied the effects of HIPping parameters, temperature and pressure on the grain structure in PM superalloy FGH96, by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM) and Time-of-flight secondary ion spectrometry (ToF-SIMS). It was found that temperature and pressure played different roles in controlling PPB precipitation and grain structure during HIPping, the tendency of grain coarsening under high temperature could be inhibited by increasing HIPping pressure which facilitates the recrystallization. In general, relatively high temperature and pressure of HIPping were preferred to obtain an as-HIPped superalloy FGH96 with diminished PPB precipitation and homogeneously refined grains.

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“…On the one hand, the hot deformation behaviors are significantly influenced by the thermo-mechanical parameters, such as strain rate, deformation temperature, and strain ( Ref 3,4). On the other hand, different metallurgical phenomena, including the work hardening (WH) ( Ref 5,6), dynamic recovery (DRV) ( Ref 7,8), and dynamic recrystallization (DRX) (Ref 9, 10), often occur in metals or alloys with low stacking fault energy during hot deformation. Additionally, for the multi-stage rolling or forging processes, the metadynamic recrystallization (MDRX) ( Ref 11,12) and static recrystallization (SRX) ( Ref 13,14) often appear.…”

Section: Introductionmentioning

confidence: 99%

New Constitutive Model for Hot Deformation Behaviors of Ni-Based Superalloy Considering the Effects of Initial δ Phase

Lin

Zhou

et al. 2015

J. of Materi Eng and Perform

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The hot deformation behaviors of a typical Ni-based superalloy are investigated by uniaxial tensile tests over wide ranges of strain rate and deformation temperature. The experimental results show that the flow stress is sensitive to strain, strain rate, and deformation temperature. Especially, initial d phase (Ni 3 Nb) has a special effect on the flow stress. The initial d phase can enhance the work-hardening behavior and result in the increased peak stress at relatively small strains. With the further straining, the initial d phase can stimulate the dynamic recrystallization and promote the dynamic-softening behaviors. Considering the synthetical effects of deformation temperature, strain, strain rate, and initial d phase on the hot deformation behaviors, a new phenomenological constitutive model is proposed. In the proposed model, the peak stress and material constant are expressed as functions of Zener-Hollomon parameter and the initial content of d phase. A good agreement between the predicted and measured results shows that the proposed model can give an accurate and precise estimate of the hot deformation behaviors for the studied Ni-based superalloy.

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A Critical Assessment of Three Usual Equations for Strain Hardening and Dynamic Recovery

Cited by 24 publications

References 16 publications

Effects of Temperature and Strain Rate on the Fracture Behaviors of an Al-Zn-Mg-Cu Alloy

Effects of Temperature and Strain Rate on the Fracture Behaviors of an Al-Zn-Mg-Cu Alloy

Effects of Temperature and Pressure of Hot Isostatic Pressing on the Grain Structure of Powder Metallurgy Superalloy

New Constitutive Model for Hot Deformation Behaviors of Ni-Based Superalloy Considering the Effects of Initial δ Phase

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