Substructure evolution of Zircaloy-4 during creep and implications for the Modified Jogged-Screw model

Morrow, Benjamin M.; Kozar, R.W.; Anderson, Ken R.; Mills, Michael J.

doi:10.1016/j.msea.2016.04.016

Cited by 10 publications

(4 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This scenario has also been proposed to explain the O hardening in Ti [30]. In the case of Zr alloys, it agrees with the analysis of the critical resolved shear stresses and activation volumes measured for various O contents [7,9,12,[40][41][42][43].…”

Section: Oxygen Hardeningsupporting

confidence: 84%

“…The height of the superjogs estimated from the experimental data is between 1 and 2 atomic distances, consistent with the double cross-slip between adjacent prismatic planes observed here. We note that Ardell [40] and Mills et al [41][42][43] also proposed that creep in zirconium alloys is controlled by the motion of jogged screw dislocations through vacancy diffusion [45].…”

Section: Oxygen Hardeningmentioning

confidence: 75%

See 1 more Smart Citation

Oxygen - Dislocation interaction in zirconium from first principles

2017

View full text Add to dashboard Cite

Plasticity in zirconium alloys is mainly controlled by the interaction of 1/3 1210 screw dislocations with oxygen atoms in interstitial octahedral sites of the hexagonal close-packed lattice. This process is studied here using ab initio calculations based on the density functional theory. The atomic simulations show that a strong repulsion exists only when the O atoms lie in the dislocation core and belong to the prismatic dislocation habit plane. This is a consequence of the destruction of the octahedral sites by the stacking fault arising from the dislocation dissociation. Because of the repulsion, the dislocation partially cross-slips to an adjacent prismatic plane, in agreement with experiments where the lattice friction on screw dislocations in Zr-O alloys has been attributed to the presence of jogs on the dislocations due to local cross-slip.

show abstract

Section: Oxygen Hardeningsupporting

confidence: 84%

Section: Oxygen Hardeningmentioning

confidence: 75%

Oxygen - Dislocation interaction in zirconium from first principles

2017

View full text Add to dashboard Cite

show abstract

“…5(a), where straight dislocation arrays 15) were observed. Moon et al 10) and Morrow et al 11,16) found a homogeneous distribution of dislocations with no cell structure, even at ¾ < 0.09. These results mean that the first steady state results from individual dislocation motions without interactions between dislocations.…”

Section: Resultsmentioning

confidence: 97%

Double Steady-State Creep Behavior in Solid-Solute-Strengthened Zircaloy-4

et al. 2022

View full text Add to dashboard Cite

Long-term creep tests on the solid-solute-strengthened zirconium alloy, i.e., Zircaloy-4, revealed the presence of double steady-state creep behavior at 623673 K. The first steady state manifested as a faster creep strain rate at a strain (¾) of ³0.05, and the second appeared with a slower creep strain rate at ¾ > 0.1. Several electron microscopy revealed a change in the dislocation structure during creep from the motion of individual dislocations to the generation of cell structure. Along with this change, the stress exponent differed in each steady state, increasing from 6.7 in the first steady state to 10 in the second steady state. The temperature dependency also changed because the apparent activation energies were 201 and 298 kJ/mol for the first and second steady states, respectively. These results show that pipe diffusion and self-diffusion are the rate-controlling processes in the first and second steady state, respectively. Because such changes in the deformation mechanism during one creep curve are highly unusual, the double steady state is a characteristic feature of high-temperature deformation in Zircaloy-4. For engineering, observation of the second steady state is necessary in estimating the time-to-rupture by means of the MonkmanGrant relationship because creep strain rates at the first steady state deviate from the relationship.

show abstract

“…In the Zr alloy used for comparison, the initial dislocation density is reported to be low (of order 10 12 m -2 ), and most of the dislocations are on the prismatic slip plane (Caillard et al, 2015;Murty, 2015a, 2015b;Moon et al, 2006;Morrow et al, 2016Morrow et al, , 2013. To comply with this observation, the initial dislocation density is set to be 2.4• 10 11 m -2 for each prismatic slip system and 0.14• 10 11 m -2 for each basal, pyramidal <a> and pyramidal <c+a> system.…”

Section: Parameter Calibrationmentioning

confidence: 99%

Mechanism-based modeling of solute strengthening: Application to thermal creep in Zr alloy

Wen

Capolungo

Tomé

2018

International Journal of Plasticity

View full text Add to dashboard Cite

In this work, a crystallographic thermal creep model is proposed for Zr alloys that accounts for the hardening contribution of solutes via their time-dependent pinning effect on dislocations. The core-diffusion model proposed by Soare and Curtin (2008a) is coupled with a recently proposed constitutive modeling framework (Wang et al., 2017, 2016) accounting for the heterogeneous distribution of internal stresses within grains. The Coble creep mechanism is also included. This model is, in turn, embedded in the effective medium crystallographic VPSC framework and used to predict creep strain evolution of polycrystals under different temperature and stress conditions. The simulation results reproduce the experimental creep data for Zircaloy-4 and the transition between the low (n~1), intermediate (n~4) and high (n~9) power law creep regimes. This is achieved through the dependence on local aging time of the solute-dislocation binding energy. The anomalies in strain rate sensitivity (SRS) are discussed in terms of core-diffusion effects on dislocation junction strength. The mechanism-based model captures the primary and secondary creep regimes results reported by Kombaiah and Murty (2015a, 2015b) for a comprehensive set of testing conditions covering the 500 to 600 o C interval, stresses spanning 14 to 156 MPa, and steady state creep rates varying between 1.5• 10-9 s-1 to 2• 10-3 s-1. There are two major advantages to this model with respect to more empirical ones used as constitutive laws for describing thermal creep of cladding: 1) specific dependences on the nature of solutes and their concentrations are explicitly accounted for; 2) accident conditions in reactors, such as RIA and LOCA, usually take place in short times, and deformation takes place in the primary, not the steady-state creep stage. As a consequence, a model that accounts for the evolution with time of microstructure is more reliable for this kind of simulation.

show abstract

Substructure evolution of Zircaloy-4 during creep and implications for the Modified Jogged-Screw model

Cited by 10 publications

References 16 publications

Oxygen - Dislocation interaction in zirconium from first principles

Oxygen - Dislocation interaction in zirconium from first principles

Double Steady-State Creep Behavior in Solid-Solute-Strengthened Zircaloy-4

Mechanism-based modeling of solute strengthening: Application to thermal creep in Zr alloy

Contact Info

Product

Resources

About