Deformation kinetics and constitutive relation analyses of bifurcation in work-hardening of face-centred cubic metals at cryogenic temperatures

Saimoto, S.

doi:10.1016/j.actamat.2019.05.029

Cited by 14 publications

(13 citation statements)

References 40 publications

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Section: Theoretical Basis Of Thermodynamic Strain Rate Sensitivitysupporting

confidence: 86%

“…As previously reported for Al [10], the normalized activation work (τ ν/k) was constant up to T C = 69 K and then started to increase according to 1/S = {442.2/(T − 45)} × 10 −5 K −1 } −1 [11]. For Al, the activation energy for constriction (E C ) was derived to be 0.58 eV [10] at T C and below it and in Figure 7 from that study [10] suggested that the increase in τν with temperature could be correlated with energy required for the formation of vacancies. It was deduced that as the thermal energy increased, vacancies formed in the lattice of the dislocation core to offset the compressive energy and only repulsive intersections can give rise to this observation indicating that it is the rate controlling process.…”

Section: Theoretical Basis Of Thermodynamic Strain Rate Sensitivitysupporting

confidence: 86%

“…Hence, the controlling forest dislocation are those resulting in repulsive intersection such that S rep ≡ S for . As previously deduced for Al [10], S rep can be assigned as that at 69 K, that is k/S for = 0.58 eV, the constriction energy, E C . Hence, it was conjectured that the increase in 1/S above T C is due to number of vacancies created, N V , at each activation site and can be estimated by {k/S up − 0.58} eV divided by the formation energy of a vacancy, E v f = 0.65 eV.…”

Section: Experimental Methodsmentioning

confidence: 68%

“…Additionally, ∆G 0 = {N k (T-T C ) + τν} in accord with experimental data of Figure 7 in ref. [10]. If such is the case, {E C + (T − T C ) ∆S * }/T = k/(ST) = k/m which is constant at constant T and strain rate, and independent of strain.…”

Section: Modus Operandimentioning

confidence: 96%

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Rate-Controlling Microplastic Processes during Plastic Flow in FCC Metals: Origin of the Variation of Strain Rate Sensitivity in Aluminum from 78 to 300 K

2022

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The thermodynamic response of dislocation intersections with forest dislocations and other deformation products is recorded using the Eyring rate relation wherein the application of shear stress increases the probability of activation at a given strain rate and temperature. The inverse activation volume, 1/ν, can be directly determined by instantaneous strain-rate change and its dependence on flow stress, τ, defines the strain-rate sensitivity, S, through the Haasen plot slope. A linear slope over a large strain interval is observed even for a heterogeneous distribution of obstacles that could be of more than one type of obstacles encountered by the gliding dislocation. It was deduced that ν and τ at each activation site are coordinated by the internal stress resulting in constant activation work (k/S). The stress changes from down-rate changes become larger than that from up-rate changes due to the formation of weaker obstacles, resulting in a composite S, whereas only forest dislocations are detected by the up-change. The additivity of 1/ν was used to separate obstacle species in specially prepared AA1100 and super-pure aluminum from 78 to 300 K. The deduction that repulsive intersection is the rate-controlling process and creates vacancies at each intersection site depending on temperature was validated by observing the pinning and depinning of dislocations via pipe diffusion above 125 K. A new method to separate S for dislocation-dislocation intersections from the intersections with other obstacles and their temperature dependence is presented and validated.

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Section: Theoretical Basis Of Thermodynamic Strain Rate Sensitivitysupporting

confidence: 86%

Section: Theoretical Basis Of Thermodynamic Strain Rate Sensitivitysupporting

confidence: 86%

Section: Experimental Methodsmentioning

confidence: 68%

Section: Modus Operandimentioning

confidence: 96%

See 2 more Smart Citations

Rate-Controlling Microplastic Processes during Plastic Flow in FCC Metals: Origin of the Variation of Strain Rate Sensitivity in Aluminum from 78 to 300 K

2022

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“…Recent studies show the advantages of deformation at sub-zero temperatures [16][17][18][19][20][21][22][23][24]. Schneider et al [18] described an increase in uniform elongation of 75% for the Al-Mg alloy EN AW 5182 when the temperature is lowered to 77 K. In a multiaxial stress state, realized by limiting dome height experiments, a significant improvement was also achieved.…”

Section: Introductionmentioning

confidence: 99%

Room Temperature Recovery of Cryogenically Deformed Aluminium Alloys

Gruber

Grabner

Falkinger³

et al. 2020

SSRN Journal

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Increased formability of aluminium alloys has been demonstrated via cryogenic deformation. In previous studies, the microstructures of samples deformed at low temperatures were analysed after reheating to room temperature (RT) and storage. However, after heating the dislocation structure and density of the deformed material do not reflect the cryogenic situation. In this work, we investigate the evolution of flow stress during recovery in Al-Mg and Al-Mg-Si alloys. We examine the RT recovery behaviour of samples pre-strained at 77 K to different strain levels, and evaluate the structural stability upon subsequent deformation. We also study microstructural evolution via in-situ synchrotron X-ray diffraction, starting from initial conditions at cryogenic temperatures to long-term RT-recovery. Recovery of cryogenically deformed samples at RT results in reduction of the flow stress, in dependence on RT storage. The recovery process can be divided into three distinct sections, each based on a different mechanism characterized by either the arranging or the annihilation of dislocations. Subsequent further straining at room temperature after cryogenic forming also generates plastic instabilities and premature fracture due to unfavourable hardening and recovery assisted softening interplay.

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Forensic analyses of microstructure evolution of stage II & III: New assimilated model for work-hardening in FCC metals

et al. 2020

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Deformation kinetics and constitutive relation analyses of bifurcation in work-hardening of face-centred cubic metals at cryogenic temperatures

Cited by 14 publications

References 40 publications

Rate-Controlling Microplastic Processes during Plastic Flow in FCC Metals: Origin of the Variation of Strain Rate Sensitivity in Aluminum from 78 to 300 K

Rate-Controlling Microplastic Processes during Plastic Flow in FCC Metals: Origin of the Variation of Strain Rate Sensitivity in Aluminum from 78 to 300 K

Room Temperature Recovery of Cryogenically Deformed Aluminium Alloys

Forensic analyses of microstructure evolution of stage II & III: New assimilated model for work-hardening in FCC metals

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