Creep Exponent Research Articles

Hourly three-minute creep testing of an LC3 paste at early ages: Advanced test evaluation and the effects of the pozzolanic reaction on shrinkage, elastic stiffness, and creep

In this study, hourly three-minute creep testing is used to elucidate the evolution of the viscoelastic behavior of cement pastes produced with ordinary Portland cement (OPC), limestone Portland cement (LPC), and limestone calcined clay cement (LC3), from 1 to 7 days after production. An innovative test evaluation protocol, accounting for shrinkage, is used to identify values of the elastic modulus, the creep modulus, and the creep exponent, without making assumptions. The S-shaped shrinkage evolution of the LC3 paste is explained by Portlandite dissolution and the associated redistribution of chemical shrinkage-induced compressive stresses to the remaining solid skeleton. The evolution of the elastic stiffness of the LC3 paste is explained by space filling by C-A-S-H phases. The small creep compliance of the LC3 paste is explained by C-A-S-H which creeps less than C-S-H, and by AFm phases which precipitate in nanoscopic slit pores between C-S-H structures, gluing viscous interfaces.

The influence of microstructural heterogeneities on high-temperature mechanical properties of additively manufactured γ'-forming Ni-based alloys

AbstractAdditive manufacturing (AM) of metallic materials yields distinctive hierarchical and heterogeneous microstructures owing to the complex thermal conditions during the build-up process. Consequently, the knowledge gained from creep properties of conventionally manufactured (CM) Ni-based alloys cannot be directly applied to AM-processed alloys. Furthermore, insufficient creep life has posed a significant challenge in the development of Ni-based superalloys fabricated by laser powder bed fusion (LPBF), one of the most important AM techniques. Nevertheless, limited research has been conducted to understand their creep behavior due to the time-consuming nature of creep testing and extended research cycles. This study delves into investigating the creep behavior of an additively manufactured, precipitation-strengthened Ni-based alloy (NiCrAl) in comparison to its CM counterpart, focusing on the structure-property relationships. Constant-load creep tests were conducted at temperatures of 750 °C and 950 °C up to a maximum duration of nearly 1500 h. Although both the AM and CM states demonstrated high creep activation energy and creep exponents, indicative of a dislocation climb mechanism, the AM state demonstrated inferior creep life and ductility compared to the CM state for creep times below 500 h. To gain deeper insights into the underlying mechanisms, multi-scale microstructural characterization was performed to understand the effect of the AM-inherent microstructure. Overall, this study provides a comprehensive understanding of the creep behavior of Alloy 699XA after AM and CM processes, emphasizing the significance of AM-specific microstructural heterogeneities.

Microstructure and constitutive modeling of an ultrafine-grained refractory high-entropy alloy fabricated by powder metallurgy

In the present study, a novel AlCr0.3FeMoNbTiV2 alloy was prepared by means of mechanical alloying and subsequent spark plasma sintering, resulting in an ultrafine-grained (UFG) microstructure consisting of a bcc matrix phase with an average grain size of 0.32 μm accompanied by Ti carbide, Laves phases, and minor contents of Al2O3. Excellent thermal stability was exhibited by the alloy, since no considerable phase transformations were observed after a heat treatment at 1350 °C for 16 h, beyond microstructural coarsening, as can be appreciated from the increase of the average bcc grain size up to 1.50 μm. Compression tests were performed at elevated temperatures (950–1100 °C) at strain rates ranging 0.0005–0.01 s−1. According to the constitutive analysis of the peak stress using the hyperbolic sine law, an experimental creep exponent of 2.17 was obtained, which indicates that deformation is mainly controlled by grain boundary sliding, as typically observed in UFG materials, with a large apparent activation energy of 527.7 kJ mol−1, superior to that of other RHEAs reported in literature.

Formation and persistence of glaciovolcanic voids explored with analytical and numerical models

Abstract One fifth of Earth's volcanoes are covered by snow or ice and many have active geothermal systems that interact with the overlying ice. These glaciovolcanic interactions can melt voids into glaciers, and are subject to controls exerted by ice dynamics and geothermal heat output. Glaciovolcanic voids have been observed to form prior to volcanic eruptions, which raised concerns when such features were discovered within Job Glacier on Qw̓elqw̓elústen (Mount Meager Volcanic Complex), British Columbia, Canada. In this study we model the formation, evolution, and steady-state morphology of glaciovolcanic voids using analytical and numerical models. Analytical steady-state void geometries show cave height limited to one quarter of the ice thickness, while numerical model results suggest the void height h scales with ice thickness H and geothermal heat flux $\dot {Q}$ as $h/H = a H^b \dot {Q}^c$ , with exponents b = −n/2 and c = 1/2 where n is the creep exponent. Applying this scaling to the glaciovolcanic voids within Job Glacier suggests the potential for total geothermal heat flux in excess of 10 MW. Our results show that relative changes in ice thickness are more influential in glaciovolcanic void formation and evolution than relative changes in geothermal heat flux.

Microstructural effects on the ambient temperature indentation creep behavior of metastable β Ti-5Al-5V-5Mo-3Cr alloy

Ti-5553 alloy is considered as a potential candidate for heavy structural components such as landing gears in aerospace industries, that operate particularly at room temperature. For achieving the targeted performance, microstructural modification and corresponding improvement in mechanical properties, particularly room temperature creep behavior of Ti-5553 alloy is of significant concern. In this regard, an optimized thermomechanical processing (TMP) schedule is employed to tailor the microstructure of as-cast Ti-5553 alloy. Typical bimodal microstructure containing both α and β phases is noted to evolve upon TMPing, as compared to its as-cast counterpart, having sole β phase. The size and volume fraction of αp are noted to be 0.85 ± 0.39 µm and 11.7 ± 0.5%, respectively. Such pronounced variation in the microstructural features is expected to alter the localized mechanical properties significantly. To assess that, room temperature small-scale creep behavior of as-cast and TMPed Ti-5553 alloys is investigated using nanoindentation technique. The effect of maximum load on different creep parameters are analyzed and correlated with the corresponding microstructures. It is noted that at any particular applied load level, creep deformation of TMPed Ti-5553 alloy is ∼ 20–64% lower than that for the as-cast one. This is reflected in significant reduction in the minimum creep strain rate from 10−4 s−1 for as-cast to 10−5 s−1 for TMPed Ti-5553 alloy. Dislocation creep mechanism is found to be active for both the alloys since creep exponent for both the as-cast and TMPed Ti-5553 alloys exceed the value of 2. Discontinuous semi-circular micro-shear bands are noted to form around the indents for the as-cast Ti5553 alloy. The kernel average misorientation map for this alloy reveals a lower degree of misorientation and a more homogeneous distribution of plastic strain. In contrary, the TMPed Ti-5553 alloy exhibits higher misorientation around the indent impression, thereby indicating towards the restriction of dislocation movement against α/β laths and hence positively influencing the creep behavior. Overall, the study highlights the important role of TMP in enhancing the creep resistance of Ti-5553 alloy for industrial applications.

Hot deformation behaviour of sintered cobalt

Hot deformation of sintered cobalt during hot compression testing was investigated in the temperature range of 700–1000 °C and at strain rates ranging from 0.0005 to 0.1 s−1. Cobalt underwent considerable dynamic recrystallization (DRX) during hot deformation, with stress-strain flow curves exhibiting one or several peaks followed by significant flow softening and leading to a steady-state stress. Constitutive equations were used to derive the flow stress behaviour. A physically based model to describe the strain rate as a function of stress was suggested for temperatures ranging between 775 and 1000 °C. In this case, a creep exponent (n) of 5 indicated that the deformation mechanism was controlled by the glide and climb of dislocations. The activation energy coinciding with the one for self-diffusion of ferromagnetic cubic cobalt implied a diffusion-controlled mechanism and the presence of face-centered cubic (FCC) cobalt during deformation. Interestingly, the results at 700 °C could not be perfectly fitted to this model and exhibited a higher resistance to deformation. This revealed that the glide and climb deformation mode was close to the transition where glide mode was dominant, and thus mostly glide occurred at 700 °C, especially for the largest strain rates.

Vortex Dynamics and Pinning in CaKFe4As4 Single Crystals from DC Magnetization Relaxation and AC Susceptibility

Among various “families” of iron-based superconductors, the quite recently discovered AeAFe4As4 (where Ae is an alkali-earth metal and A is an alkali metal) has high critical current density, a very high upper critical field, and a low anisotropy, and has recently received much interest for the possibility of high magnetic field applications at the liquid hydrogen temperature. We have performed DC magnetization relaxation and frequency-dependent AC susceptibility measurements on high-quality single crystals of CaKFe4As4 with the aim of determining the pinning potential U*. The temperature dependence of U* displays a clear crossover between elastic creep and plastic creep. At temperatures around 27–28 K, U* has a very high value, up to 1200 K, resulting in an infinitesimally small probability of thermally activated flux jumps. From the dependence of the normalized pinning potential on irreversible magnetization, we have determined the creep exponents in the two creep regimes, which are in complete agreement with theoretical models. The estimation of the pinning potential from multifrequency AC susceptibility measurements was possible only near the critical temperature due to equipment limitations, and the resulting value is very close to the one that resulted from the magnetization relaxation data. Magnetic hysteresis loops revealed a second magnetization peak and very high values of the critical current density.

Ferroelectric Size Effects on Statics and Dynamics of Domain Wall.

Domain walls separating differently oriented polarization regions of ferroelectric materials are known to greatly impact nanoscale materials and device functionalities. Though the understanding of size effects in ferroelectric nanostructures has progressed, the effect of thickness downsizing on domain wall scaling behavior has remained unexplored. Using piezoresponse force microscopy, epitaxial BaTiO3 film thickness size (2-90nm) effects on the critical scaling universality of the domain wall dynamical creep and static roughness exponents including dimensionality is demonstrated. Independently estimated static roughness exponents ranging between 0.34 and 0.28 and dynamical creep exponents transition from 0.54 to 0.22 elucidate the domain wall dimensionality transition from two- to quasi-one-dimension in the thickness range of 10-25nm, which is later validated by evaluating effective dimensionality within the paradigm of random-bond universality. The observed interdimensional transition is further credenced to the compressive strain and long-range strain-dipolar interactions, as revealed by the structural analyses and additional measurements with modified substrate-induced strain. These results provide new insights into the understanding of size effects in nanoscale ferroelectricity, paving the way toward future nanodevices.

Anisotropic microstructure, nanomechanical and corrosion behavior of direct energy deposited Ti–13Nb–13Zr biomedical alloy

The present study investigates the anisotropic microstructure, nanomechanical and corrosion behavior of Ti–13Nb–13Zr biomedical alloys, which were fabricated using the direct energy deposition (DED) method. The microstructure of the as-deposited material was studied using a field-emission scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). We found anisotropic mechanical behavior using nanoindentation from strain rate sensitivity and creep tests. For the maximum load of 50 mN, the x-y plane (normal to the building direction) shows better indentation hardness and lower strain rate sensitivity value (0.014) compared to the x-z plane (0.022) (parallel to the building direction). The difference in the indentation hardness was mainly attributed to the smaller equiaxed prior-β grains and finer α’ martensitic laths on the x-y plane. In terms of creep behavior, the x-y planes show better creep strength than the x-z plane. Meanwhile, both planes show a very high creep exponent, which signifies a similar creep mechanism, i.e., dislocation based. Moreover, we further found the anisotropic corrosion behavior using electrochemical tests. Corrosion results reveal that the x-y plane is more corrosion-resistant than the x-z plane. In summary, the x-y plane of the direct energy deposited Ti–13Nb–13Zr alloy possesses better strength and corrosion resistance due to its finer microstructure.

The long-term creep behavior and damage mechanism of RAFM steel for fusion reactors

The reduced-activation ferritic-martensitic (RAFM) steel serves as the structural material for the blanket of the International Thermonuclear Experimental Reactor (ITER) and future fusion reactors. In order to achieve a design lifetime of 2–3 years for the blanket in the fusion reactor, it is imperative to thoroughly understand the long-term (>20,000 h) creep behavior of RAFM steel. In this regard, the present study investigated the long-term creep damage mechanism of RAFM steel under creep periods greater than 20 000 h. The results indicated that the creep exponent decreases as the creep rupture time increases from several thousand hours to more than 20,000 h. The microstructure analysis revealed that dislocation slip was effectively pinned by the precipitates in the long-term creep process. Additionally, the M23C6 and Laves phase played a critical role in inhibiting interfacial slip and preventing lath coarsening. However, a few micron-scale M23C6 and Laves phases led to the formation of cavities in the boundary. These cavities subsequently polymerized and aggravated into cracks, ultimately becoming the primary mechanism for the long-term creep fracture.

Mechanical Properties and Creep Behavior of Undoped and Mg-Doped GaN Thin Films Grown by Metal–Organic Chemical Vapor Deposition

This paper investigates the mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown on sapphire substrates using metal–organic chemical vapor deposition (MOCVD) with trimethylgallium (TMG) and bis(cyclopentadienyl)magnesium (Cp2Mg) as the precursors for Ga and Mg, respectively. The Mg-doped GaN layer, with a [Mg]/[TMG] ratio of 0.33, was systematically analyzed to compare its mechanical properties and creep behavior to those of the undoped GaN thin film, marking the first investigation into the creep behavior of both GaN and Mg-doped GaN thin films. The results show that the incorporated [Mg]/[TMG] ratio was sufficient for the transition from n-type to p-type conductivity with higher hole concentration around 4.6×1017 cm−3. Additionally, it was observed that Mg doping impacted the hardness and Young’s modulus, leading to an approximately 20% increase in these mechanical properties. The creep exponent is also affected due to the introduction of Mg atoms. This, in turn, contributes to an increase in pre-existing dislocation density from 2 × 108 cm−2 for undoped GaN to 5 × 109 cm−2 for the Mg-doped GaN layer. The assessment of the creep behavior of GaN and Mg-doped GaN thin films reveals an inherent creep mechanism governed by dislocation glides and climbs, highlighting the significance of Mg doping concentration in GaN thin films and its potential impact on various technological applications.

Comparative Study of Creep and Stress Relaxation Behaviour during Ageing of 7050 Aluminum Alloy

This work focuses on quantitatively investigating the relationship between creep and stress relaxation of 7050 aluminum alloy at ageing temperatures. The creep strain rates, creep exponent, n, and activation energy were extracted from both the creep and stress relaxation curves to explore the creep mechanisms. Results showed that higher applied stress promotes the creep and stress relaxation extents. The calculated creep strain rates from creep and stress relaxation curves located in similar ranges and share similar n values (n = 3.7 for creep and n = 3.5 for stress relaxation), indicating that both tests are dominated by the dislocation slip mechanism. Additionally, the n value for creep tests is a constant throughout the tests, indicating that the dominant creep mechanism is unchanged. However, the activation energy changes from 123 kJ/mol to 139 kJ/mol, possibly due to evolved dislocations. Such a new finding could provide a supporting mechanism for building constitutive equations depending on the evolved A value. Furthermore, compared to the single-stage creep ageing, no primary creep was observed in T74 multi-stage creep ageing while similar amount of total creep strains was achieved. This suggests an alternative loading sequence for creep age forming of 7050 aluminum alloy, i.e., loading at the second stage to avoid prolonged exposure to high temperatures, extend the tool life, and achieve similar amounts of inelastic deformations. Based on all the above studies, creep and stress relaxation have a certain relationship. This paper provides a theoretical basis for future research on creep ageing forming of 7050 aluminum alloy.

Hypo-eutectic microstructure formation and nanomechanical response in Sn-3.0Ag-0.5Cu solder balls: Effects of undercooling

The microstructure control and refinement in length scale are pursued in the development of next generations of Pb-free solder alloys with high reliability in harsh environments. In the present work, the influences of nucleation undercooling, as brought by solder ball size, over the microstructure evolution and nanomechanical behavior in Sn-3.0Ag-0.5Cu (wt%) Pb-free solder alloys, have been quantitively investigated using Differential Scanning Calorimeter (DSC), Scanning Electron Microscopy (SEM) and nanoindentation. The results reveal that undercooling increases with the decrease of solder ball size. The frequency of interlaced grain microstructure was significantly increased in 200 μm balls, with a further increase of undercooling by ~10 K. The volume fraction of primary β-Sn increased with larger undercooling, leading to microstructure refinement with a finer spacing of both β-Sn dendrite and eutectic Ag3Sn. The length scale of refinement is on the order of ~2, as the solder ball size reduced from 650 μm to 200 μm. Nano-hardness and creep resistance increase with smaller ball size and larger undercooling. Nano-hardness values are relatively higher as more eutectic regions being measured due to the strengthening effect of finer and denser eutectic Ag3Sn, and also the refinement of interlaced β-Sn grains. The creep exponent is insensitive to the loading force or solder ball size. The variation of nanomechanical deformation behavior was reduced in the 200 μm balls, due to the substantial microstructure refinement, while the dominant creep mechanism stays as the dislocation climb for various solder ball sizes.

Study on Hot Flow Behaviors and Deformation/Diffusion Mechanisms of V and V–Ti Microalloyed Steels by Physical Constitutive Modeling

The hot compression tests of medium carbon V and V–Ti microalloyed steels are carried out at the temperature of 900–1100 °C and strain rate of 0.01–10 s−1. Three physical constitutive models based on creep theory are studied, the prediction accuracy is compared and analyzed by employing the correlation coefficient (R) and average absolute relative error (AARE), and the deformation/diffusion mechanisms are discussed. The results show that Ti has obvious hardening effect in V microalloyed steel and retards the onset of dynamic recrystallization. The physical constitutive model containing the theoretical value of creep exponent 5 can accurately describe the hot flow behavior of both steels, the prediction accuracy of which is comparable to that of the model containing exponent n, reflecting that the dominant deformation mechanism of both steels is dislocation climbing. Furthermore, a modified physical constitutive model combining diffusion mechanisms of lattice diffusion and grain boundary diffusion shows higher accuracy (R = 0.996, AARE = 3.81% of V steel and R = 0.994, AARE = 4.52% of V–Ti steel), indicating that the diffusion mechanism is controlled not only by lattice diffusion but also by grain boundary diffusion.

Internal nitridation of Alloy 690 during creep deformation at 1100 °C

This study reports internal nitridation of alloy 690 during creep deformation at 1100 °C. A series of creep tests were conducted at stresses ranging from 7 to 18 MPa, which corresponded to 0.3–0.7 of the alloy's yield stress at 1100 °C. The alloy exhibited normal creep response at 15 and 18 MPa whereas at 7 and 12 MPa, oscillatory creep were observed. The alloy exhibited creep exponent of about 8 and failed by cavitation at all the stresses studied. A higher value of the creep exponent was attributed to the cavitation dominant failure mechanism. Needle shaped nitride precipitates were observed near cracks, which were identified to be of trigonal Cr2N phase. The Cr2N particles formed near cracks which extended to the free surface. These precipitates formed as a result of internal nitridation of the freshly exposed crack surface. The phase stability analysis of the nitride phases in Ni–Cr–10Fe alloys in equilibrium with nitrogen using the Thermo-Calc software supported the formation of the Cr2N phase at a N2 fugacity of 0.79 bar. Atmospheric nitrogen permeated through the creep cracks linked to the outer sample surface. However, the precipitation of nitride particles appeared to have little effect on creep life of the alloy as the precipitation occurred towards the end of tertiary creep regime. The creep fracture at the lowest stress was dominant by transgranular cleavage of stable crack propagation, but tended to be erratic crack propagation at higher stresses.

Interaction behavior for multiple embedded cracks subjected to bending load in creep regimes

Abstract Multiple cracks growing from pre-existing defects during the manufacturing/installation process or from small cracks initiated are primary concerns in evaluating the structural integrity. In this study, the interaction behavior for coplanar multiple embedded cracks subjected to bending load in creep regimes was studied using numerical simulation approach. Influences of crack configurations (crack shape, crack depth, and crack distance) and creep properties on creep interaction factor and C* distribution along the embedded cracks were evaluated based on the three-dimensional finite element solutions. Due to the interaction among the multiple cracks, the C* distribution was asymmetric along the crack front and the C* values were pronounced as the cracks approached each other. Moreover, crack depth, crack distance, and creep exponent significantly affected the creep interaction factor and crack shape had limited influence. However, the maximum creep interaction factor did not coincide with the maximum C* values occurring along the crack front. The creep interaction factor determined by the average C* values along the crack front was employed to represent the intensity effect of multiple embedded cracks on the crack growth behavior. Finally, an empirical relation was proposed for estimating crack creep interaction factors of embedded cracks.

Pinning potential in highly performant CaKFe4As4 superconductor from DC magnetic relaxation and AC multi-frequency susceptibility studies

We have investigated the pinning potential of high-quality single crystals of superconducting material CaKFe4As4 having high critical current density and very high upper critical field using both magnetization relaxation measurements and frequency-dependent AC susceptibility. Preliminary studies of the superconducting transition and of the isothermal magnetization loops confirmed the high quality of the samples, while temperature dependence of the AC susceptibility in high magnetic fields show absolutely no dependence on the cooling conditions, hence, no magnetic history. From magnetization relaxation measurements were extracted the values of the normalized pinning potential U*, which reveals a clear crossover between elastic creep and plastic creep. The extremely high values of U*, up to 1200 K around the temperature of 20 K lead to a nearly zero value of the probability of thermally-activated flux jumps at temperatures of interest for high-field applications. The values of the creep exponents in the two creep regimes resulted from the analysis of the magnetization relaxation data are in complete agreement with theoretical models. Pinning potentials were also estimated, near the critical temperature, from AC susceptibility measurements, their values being close to those resulted (at the same temperature and DC field) from the magnetization relaxation data.

Displacive-Diffusive plasticity in nanoporous gold nanowires under tensile creep

While creep deformation of nanoporous gold (NPG) was argued to be mainly dislocation mediated, we show using molecular dynamics simulations of tensile creep of NPG nanowires that diffusion plays a significant role. Lower creep stress regimes are influenced by dominant atomic diffusion with negligible dislocation accumulation, while the interplay between surface diffusion and dislocation slips governs the deformation at higher creep stresses. The deformation mechanisms manifest themselves in the calculated activation volumes and creep stress exponents, which are of the same orders of those calculated from indentation creep experiments despite the different length and time scales. The contribution from the dislocation events decreases with increase in the ligament diameter, which is expressed as change in the creep exponents at the higher creep stresses. We suggest that this displacive-diffusion plasticity mechanism is essential to capture creep deformation of NPG structures.

Microstructure evaluation and thermal deformation behaviours of wrought magnesium alloys

Due to the large orientation gradient, the dynamic recrystallisation of Mg–Zn–Nd–Zr wrought alloy occurred first around grain boundaries. The Nd-rich second phase promoted the nucleation of recrystallisation. With the increasing strain, more non-basal plane slip occurred near the grain boundary, which caused the adjacent subgrain boundary merging into a high angle grain boundary. In addition, some twin intersecting regions gathered high-density dislocation, leading to twin dynamic recrystallisation. By deducing the stress–strain constitutive relation during thermal deformation and analysing the relation between the apparent value of constant creep exponent (n) and the corresponding deformation mechanism, the dominant mechanism of dislocation sliding and climbing during dynamic recrystallisation was deduced backwards.

Impression creep behavior of different zones in friction stir welded ZE41 magnesium-rare earth alloy

The ability of the impression tests to obtain localized creep data is exploited to study the creep behavior of the friction stir welded (FSWelded) joints made on 15 mm thick plates of ZE41 magnesium alloy. The three zones of the FSWelded joint, Nugget zone (NZ), Thermo-Mechanically Affected Zone (TMAZ), and Heat Affected Zone (HAZ), were divided into ten different parts and their local steady-state creep behavior was studied. Impression tests were carried out at stresses of 350, 400, and 450 MPa and temperatures of 513 K, 533 K, and 553 K. Optical and SEM micrographs were used to study the microstructure of various zones of the FSWelded joint both before and after the impression test. Power law was used to obtain the creep exponent (n) and activation energy (Q) for different parts of the weld and the weld zones as a whole. The creep exponent was found to vary from 3.6 to 10.45 and the activation energy from ∼81 kJ/mol to ∼226 kJ/mol. The creep rate was found to vary between the upper and lower surfaces of the weld zones and also among the advancing and retreating sides. The weak zone was found to be temperature-dependent and varied when the temperature or stress changes. Within the parameters studied, the lower part of the TMAZ on the AS showed poor creep resistance at a lower temperature, while the lower part of TMAZ on the RS showed poor creep resistance at higher temperatures. The upper part of the TMAZ on the RS showed better creep resistance throughout the range of temperatures studied. To rationalize the high n and Q values, the threshold stress approach and the Eyring relationship were adopted. Using the threshold approach, creep exponents of 4.87 and 5.17 were obtained for TMAZ and HAZ, respectively. Using Eyring hyperbolic sine relationship, single activation energies of 143.5 kJ/mol and 261.5 kJ/mol were obtained for TMAZ and HAZ, respectively. Based on the obtained n and Q values, it is proposed that two mechanisms, namely climb and cross-slip of dislocations, are operative in the creep of the ZE41 FS weld joint. However, the dominant/rate controlling mechanism could not be arrived at conclusively.