Magnitude Of Plastic Strain Research Articles

Influence of water on crystallographic preferred orientation patterns in a naturally deformed quartzite

Abstract. Laboratory experiments demonstrate that intragranular water exerts an important control on deformation within quartz, causing weakening and promoting plasticity. The role of water in natural quartz deformation, however, remains unclear, as recent studies find an inverse relationship between water content and the magnitude of plastic strain. Furthermore, little work has investigated the effects, if any, of water on the relative activity of various slip systems in quartz. We focus on a naturally strained quartzite from the Antietam Formation of the Blue Ridge in Virginia, USA. Quartz water content ranges from < 50 to > 2000 ppm H2O. Water content and crystallographic data were correlated for 968 grains, enabling us to explore the relationship between water content and quartz crystallographic preferred orientation (CPO) patterns. “Dry” (< 150 ppm H2O) and “wet” (> 500 ppm H2O) subsets show distinct CPOs; c axes of dry grains define a cross girdle oriented perpendicular to the extension direction (x), whereas c axes of wet grains are concentrated along the perimeter of the pole figure. All water content subsets show grains clustered near the direction of maximum shortening (z), consistent with activity of the basal 〈a〉 slip system. The cross girdle in the driest grains suggests activity of prism 〈a〉 and possibly rhomb 〈a〉, whereas the orientation of the wettest grains implies a contribution from prism [c] slip. These slip system interpretations are supported by analyses of intragranular misorientations. These results indicate that water content impacts the relative activity of various slip systems in natural quartz, potentially affecting application of the quartz opening angle thermometer.

A Study on the Influence of Double Tunnel Excavations on the Settlement Deformation of Flood Control Dikes

This article combines numerical simulation and field monitoring methods to study the stability of the overlying Liuyang River embankment in the tunnel crossing between Huaqiao Station and Rice Museum Station of Changsha Metro’s Line 6. Using AutoCAD, 3Dmine, and COMSOL Multiphysics, a calculation model of the entire subway tunnel section crossing the flood control embankment under the coupling of fluids and solids was established. The process of tunnel-crossing the embankment and the variation in spatial displacement and plastic strain in different geological layers were analyzed from the perspective of time evolution and spatial distribution. The research results show that during the process of crossing the embankment, the deformation of the east bank is greater than that of the west bank, and crossing the west bank is the relatively riskier stage of the entire project. Moreover, during the process of crossing the embankment, the overlying soil layer will produce a plastic strain zone, and only a small amount of plastic strain is generated in the surrounding sandstone layer of the tunnel walls. In terms of the magnitude of plastic strain, the plastic strain area produced by the leading tunnel’s surrounding rocks is larger than that of the following tunnel. As the excavation progresses, a funnel-shaped settlement displacement gradually forms during the passage of the leading tunnel, and this settlement funnel gradually expands during the passage of the following tunnel, with the maximum settlement point transitioning from directly above the leading tunnel to the middle position between the two tunnels. Using the jitter filter algorithm and the adjacent average method to process the field monitoring data, the results show that the monitored deformation results well match the simulated settlement results.

Burst of Internally Pressurized Steel Torispheres

Abstract The paper begins with derivation of true stress–true strain data, including postnecking section. Available results of past uni-axial tests on round 10 mm diameter and 200 mm long mild steel samples are the basis of the conversion. The steel in question was used to manufacture ten torispherical domes that were in the past tested for burst. Hence, the relevance of matching material model is necessary for the finite elements (FE), analyses. In the past, plastic instability and constraints on the magnitude of plastic strains were postulated as criteria for the burst of internally pressurized torispheres. These criteria for burst pressure are being examined and benchmarked against the tests. The current paper, using the FE analyses, shows that modification of constraints on plastic strains has only marginal effect on the burst which still remains on the unsafe side of test data by a sizeable margin. The same is found to be true for plastic instability criterion. Subsequent computations moved back to the use of engineering stress–strain. Then, two types of computing are carried out here, based on multisegment and bilinear modeling of material. Computed results of burst pressure follow the test data to within (−6%, +10%). These results are far better than all the previous.

Numerical prediction of warm pre-stressing effects for a steam turbine steel

In warm pre-stressing (WPS), the fracture resistance of cracked steel components is raised when subjected to certain temperature-load histories. WPS’s beneficial effects enhance safety margins and potentially prolong fatigue life. However, understanding and predicting the WPS effects is crucial for employing such benefits. This study utilised pre-cracked compact tension specimens made from steam turbine steel for WPS and baseline fracture toughness testing. Two typical WPS cycles were investigated (L-C-F and L-U-C-F), and an increase in fracture resistance was observed for both cycles. The WPS tests were simulated using finite element analysis to understand its effects and predict the increase in fracture resistance. A local approach was followed based on accumulative plastic strain magnitude ahead of the crack tip. Since cleavage fracture is triggered by active plasticity, the WPS fracture is assumed when accumulated plasticity exceeds the residual plastic zone formed at the crack tip due to the initial pre-load.

The elastic threshold for strain-gradient plasticity, and comparison of theoretical results with experiments

This work continues an earlier study, aimed at determining the threshold of elastic behaviour for specimens at the microscale. Given the size-dependent nature of the response the theory makes use of a model of rate-independent strain-gradient plasticity to establish conditions for lower and upper bounds to the threshold. The model is based on a family of yield or dissipation functions. In the earlier work bounds were established for one member of the family, in which the dissipation depends on the root mean square of the magnitude of plastic strain and its gradient. In this work bounds are derived based on a second alternative, in which the dependence is linear. These two alternatives are most relevant in determining length scales through fits to experimental results. The second aim of this work is to carry out comparisons between the bounds obtained theoretically, with experimental data on initial yielding for torsion tests. The correlations are in some cases reasonable, while in others there are discrepancies. Generally they illustrate the complexities – for example in accurate experimental determination of the elastic threshold, and of the length scale – in predicting aspects of behaviour at the microscale.

Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation.

This paper develops a hybrid experimental/simulation method for the first time to assess the thermal stresses generated during electron beam melting (EBM) at high temperatures. The bending and rupture of trusses supporting Inconel 625 alloy panels at ~1050 °C are experimentally measured for various scanning strategies. The generated thermal stresses and strains are thereafter simulated using the Finite-Element Method (FEM). It is shown that the thermal stresses on the trusses may reach the material UTS without causing failure. Failure is only reached after the part experiences a certain magnitude of plastic strain (~0.33 ± 0.01 here). As the most influential factor, the plastic strain increases with the scanning length. In addition, it is shown that continuous scanning is necessary since the interrupted chessboard strategy induces cracking at the overlapping regions. Therefore, the associated thermal deformation is to be minimized using a proper layer rotation according to the part length. Although this is similar to the literature reported for selective laser melting (SLM), the effect of scanning pattern is found to differ, as no significant difference in thermal stresses/strains is observed between bidirectional and unidirectional patterns from EBM.

Micromechanical aspects of the effect of temperature and local plastic strain magnitude on the fracture toughness of ferrite steels

The paper shows that the influence of plastic strain and temperature on the rate of crack nuclei (CN) formation is a crucial factor controlling the shape of the temperature dependence of fracture toughness and its scatter limits. Within the framework of the microscopic model described, it is explained that the dependence of the incompatibility of microplastic deformation at grain boundaries or interfaces on the value of plastic strain and temperature is the reason for the effect of these factors on the rate of CN formation. The dependencies of the CN bulk density on temperature and plastic strain are given. In the latter case, a non-monotonic change in CN density is observed. The maximum intensity of CN formation is observed when the critical value of plastic strain is reached. For ferritic structural steels, this strain is about 2%. Using reactor pressure vessel steel and cast manganese steel as examples, it is shown that not taking these effects into account in the local fracture approach leads to considerable errors in the prediction of the temperature dependence of the fracture toughness and its scatter limits.

Superior fracture toughness with high yield strength in a high-Mn steel induced by heterogeneous grain structure

Heterogeneous grain structures were designed in a high Mn steel (Fe28Mn10Al1.00C), and the tensile properties and fracture toughness were investigated and compared with those for homogeneous structures. The heterogeneous grain structures display larger tensile ductility, stronger strain hardening and higher fracture toughness at the similar yield strength level. Hetero-deformation-induced hardening is found to play an important role in the heterogeneous grain structures, resulting in better mechanical properties. The size of plastic zone and the strain hardening capacity around the crack tip for the heterogeneous grain structures are found to be much larger/higher than those for the homogeneous grain structures at the same level of yield strength, resulting in better fracture toughness. High density of geometrically necessary dislocations and grain refinement are induced at the adjacent area of the main crack path, and numerous microvoids are also observed besides the main crack for the heterogeneous grain structures, resulting in more energy dissipation for higher fracture toughness. The deformation mechanisms around the crack tip are highly dependent on the magnitude of plastic strain and the grain size. The observed higher fracture toughness in the heterogeneous grain structures can be partly attributed to the formation of microbands.

Surgically-induced deformation in biodegradable orthopaedic implant devices

The biocompatibility and mechanical performance of biodegradable metals (e.g. magnesium, iron, and zinc-based alloys) in orthopaedic-targeted applications are contingent on limiting the rate of corrosion in vivo throughout the bone healing. Concurrently, the surgical procedure for the implantation of internal bone fixation devices may impart plastic deformation to the device, potentially altering the corrosion rate of the device. However, the potential effect of the surgical implantation procedure on the mechanochemical performance of metallic degradable orthopaedic devices in vivo remains largely unresolved. The objective of the present study is to develop a robust technique that permits the quantification of the strain introduced due to surgical implantation of degradable orthopaedic devices. Specifically, a novel combined experimental-modelling approach based on 3D laser scanning in situ and the finite element method is utilised to quantify the plastic strain introduced to a bone fixation plate following surgical implantation in a cadaveric porcine model where the plate is based on a ternary magnesium-zinc-calcium alloy (ZX10). The magnitude of plastic strains determined by the above approach for the Mg craniofacial miniplate confirms that the surgical procedure itself has the potential to enhance the corrosion rate of the Mg alloy in an accelerated and potentially localised manner. Statement of SignificanceBiodegradable metallic orthopaedic implant devices have emerged as a potential alternative to permanent implants, although successful adoption is contingent on achieving an acceptable degradation profile. Plastic strain that is introduced to the device during surgical implantation may influence the resulting degradation behaviour of the implant. In the present work, 3D laser scanning is combined with computer simulation to estimate the level and distribution of surgically-induced plastic strain in a magnesium alloy (ZX10). Subsequently, clinically-relevant pre-strain is shown to influence the rate of corrosion of ZX10 in vitro, indicating the value of such an approach in the design of biodegradable metallic devices under multiaxial loading.

Examining the pathways for deformation band formation at the mesoscale

At the macroscopic scale, strain accumulation is known to form parallel to the plane of maximum shear stress. In this work, plastic strain accumulation is tracked across four mesoscale areas of interests. Each representing a different configuration of tension-torsion loading. The local deviations in the deformation pathways were investigated relative to the plane of maximum shear stress. The deviations in the deformation pathways were observed to be a function of the local plastic strain magnitude and the microstructural features. From these results, a representative volume element was created based on the macroscopic and micromechanical deformations as well as the spatial statistics of the deformation bands.

Folding Responses of Origami-Inspired Structures Connected by Groove Compliant Joints

Abstract The compliant mechanism can effectively reduce friction and eliminate the joint gap during the motion. The performances of compliant joints directly determine the overall behavior of mechanisms. In this paper, a new type of compliant joint is designed based on weakened creases and elastic–plastic materials. Parametric analysis is carried out to investigate the influence of compliant joint details on its structural performances by combining finite element methods and experiments. The compliant joints are evaluated and optimized regarding the rotational stiffness and plastic strain magnitude of the slot region. In addition, the optimized compliant joint is introduced to the Miura unit. The configuration analysis is performed for the folding, unfolding, and releasing processes, which are further extended to the discussion on the cyclic performance of the compliant joint. It can be found that the origami-inspired structures can maintain a high residual stiffness after the release process. Finally, the methodology is applied to the Miura origami array embedded with the designed compliant joint. The results of dimensional errors and stress distributions can show that the design of the compliant joints can effectively control the configuration of the Miura origami array. The principle in this paper can open a new avenue to design and utilize the compliant in the deployable or morphing structures.

A bayesian optimisation methodology for the inverse derivation of viscoplasticity model constants in high strain-rate simulations

We present an inverse methodology for deriving viscoplasticity constitutive model parameters for use in explicit finite element simulations of dynamic processes using functional experiments, i.e., those which provide value beyond that of constitutive model development. The developed methodology utilises Bayesian optimisation to minimise the error between experimental measurements and numerical simulations performed in LS-DYNA. We demonstrate the optimisation methodology using high hardness armour steels across three types of experiments that induce a wide range of loading conditions: ballistic penetration, rod-on-anvil, and near-field blast deformation. By utilising such a broad range of conditions for the optimisation, the resulting constitutive model parameters are generalised, i.e., applicable across the range of loading conditions encompassed the by those experiments (e.g., stress states, plastic strain magnitudes, strain rates, etc.). Model constants identified using this methodology are demonstrated to provide a generalisable model with superior predictive accuracy than those derived from conventional mechanical characterisation experiments or optimised from a single experimental condition.

Localization of Plastic Deformation in Ti-6Al-4V Alloy

This article investigated the mechanical behavior of Ti-6Al-4V alloy (VT6, an analog to Ti Grade 5) in the range of strain rates from 0.1 to 103 s−1. Tensile tests with various notch geometries were performed using the Instron VHS 40/50-20 servo hydraulic testing machine. The Digital Image Correlation (DIC) analysis was employed to investigate the local strain fields in the gauge section of the specimen. The Keyence VHX-600D digital microscope was used to characterize full-scale fracture surfaces in terms of fractal dimension. At high strain rates, the analysis of the local strain fields revealed the presence of stationary localized shear bands at the initial stages of strain hardening. The magnitude of plastic strain within the localization bands was significantly higher than those averaged over the gauge section. It was found that the ultimate strain to fracture in the zone of strain localization tended to increase with the strain rate. At the same time, the Ti-6Al-4V alloy demonstrated a tendency to embrittlement at high stress triaxialities.

Surrogate modeling of elasto-plastic problems via long short-term memory neural networks and proper orthogonal decomposition

Because of its nonlinearity and path-dependency, analysis of the elasto-plastic behavior of the finite element (FE) model is computationally expensive. By directly learning sequential data, modeling plasticity via deep learning has shown successful performance in immediately predicting the path-dependent response. However, large-scale elasto-plastic FE models still have challenges in that they require numerous degrees of freedom and are accompanied by high-dimensional data. This study proposes a practical framework for the surrogate modeling of a large-scale elasto-plastic FE model by combining long short-term memory (LSTM) neural networks with proper orthogonal decomposition (POD). First, displacement, plastic strain magnitude, and von Mises stress are generated using commercial FE analysis software, and then, the high-dimensional data are reduced to low-dimensional POD coefficient data before being used for training. With the drastically reduced data, a neural network architecture can be introduced in the form of individual and ensemble structures to achieve accurate and robust prediction. As the proposed POD-LSTM surrogate model operates on the structural level, POD-LSTM surrogate models are constructed and implemented for each of the three large-scale elasto-plastic FE models. In all three examples, the proposed POD-LSTM surrogate models were found to be efficient and accurate for predicting elasto-plastic responses.

Influence of tack operation on metallographic and angular distortion in electron beam welding of Ti-6l-4V alloy

Electron beam welding process is one such advanced fusion welding technique that fabricates structural parts with high dimensional precision and induces minimum thermal stresses and distortion. However, with incorporation of tack procedure prior to full pass electron beam welding process the effect of distortion and stresses in welded parts is lowered significantly. In the present work, an attempt has been made to investigate the effect of incorporation and elimination of tack operation prior to full pass electron beam welding process in 5 mm thick butt-jointed Ti6Al4V alloy plates. The influence of electron beam current is analyzed for tack and full pass electron beam welding procedures with an aim to produce full penetrated defect free weld joint. The characteristics difference in terms of macro and microstructural properties, microhardness distribution and welding induced angular deformation is evaluated for electron beam welded specimens. It is found that the weld width, undercut defect, and angular deformation was reduced by 7.6%, 4.2%, and 22%, respectively due to incorporation of tack procedure prior to full pass welding operation. The refined martensitic phases were observed in the fusion zone of tack welded specimens due to solidification process which enhanced the hardness of the joints. Moreover, finite element results revealed that induced thermal stresses are highly localized and longitudinal stress is more prominent across the weld joint. The angular deflection and plastic strain magnitude is estimated to be lower in specimens that are joined initially with tack operation. Moreover, the numerically computed angular deflection magnitude validates well with the experimentally measured deflection values.

Roles of Hydrogen and Plastic Strain Distribution on Delayed Crack Growth in Single-crystalline Fe–Si alloy

Abstract Effects of hydrogen on macroscopic and microscopic features of crack growth in thin specimens were investigated using a thin sheet of single-crystal Fe-3wt%Si alloy. Center-cracked specimens were tested under a sustained load in a hydrogen environment, and under continuous stretching in an air environment. The fracture features were compared to elucidate the role of hydrogen in hydrogen-induced delayed crack growth. In both air and hydrogen environments, the crack growth mode of the thin specimens was the same as that of the thick specimens, despite the significantly reduced thickness. Surprisingly, the crack grew discontinuously, and left striations on the fracture surface, in which shorter striation spacing was observed in hydrogen. In addition, there was a similarity in the deformation microstructures beneath the fracture surface, that is, both microstructures were composed of three distinct layers characterized by different plastic strain gradients and dislocation densities. In the hydrogen environment, the hydrogen-enhanced localized plasticity (HELP) mechanism is believed to be relevant to the crack growth process. Also, HELP was supposed to cause different characteristics (the magnitude of plastic strain, the plastic strain gradient, and dislocation structure) of the three layers in the hydrogen compared to those in the air. Reverse plastic deformation occurred in the regions behind the crack front during crack growth, which is speculated to contribute not only to enlarge the crack tip opening angle (CTOA) but also to blunt the crack tip.

Dynamic flow stress of pure polycrystalline aluminum: Pressure-shear plate impact experiments and extension of dislocation-based modeling to large strains

The dynamic thermo-mechanical behavior of pure aluminum has attracted renewed interest lately due to experimental observations of an anomalous increase in Hugoniot Elastic Limit (HEL) at incipient plasticity and elevated temperatures in polycrystalline pure metals. In context of current dislocation-mediated plasticity models for metals, this increase in dynamic strength is indicative of a transition in the rate controlling mechanism for dislocation glide from being thermally assisted to phonon-drag restricted due to increase in phonon viscosity at elevated temperatures. Though these studies have helped to shed light on these important mechanisms operative in FCC metals at incipient plasticity, the extent to which they contribute to flow stress, particularly at larger strains, remains unclear. In the present study, we address these questions through a combined experimental and modeling effort focused on investigating the evolution of dynamic flow stress in polycrystalline aluminum using experimental data gathered from a series of combined pressure-and-shear plate impact (PSPI) experiments designed to reveal the flow stress of pure aluminum at strain rates ~ 105/s, plastic strains of up to 40% and temperatures ranging from room to 866 K. In all cases, the flow stress of aluminum, as inferred from the measured transverse particle velocity histories at the free surface of an elastic tungsten carbide target plate, reveals saturation with increasing plastic strains at stress levels that decrease with increasing test temperatures. Numerical simulations are performed to correlate the experimentally observed temperature and strain rate dependence of flow stress at small and large plastic strains using the Austin-McDowell dislocation-mediated plasticity model parametrized to normal plate impact experiments conducted in an earlier study by Zaretsky and Kanel (2012). Extensions to the model are made to better represent dynamic behavior of pure aluminum at larger plastic strains as observed in elevated temperature split Hopkinson Pressure bar (SPHB) experiments of Samanta (1971) and Lindholm and Yeakly (1965), and the combined pressure-and-shear plate-impact experiments conducted in the present study. The main theoretical extension to the Austin-McDowell model made in this paper is the introduction of a new rate- and temperature- dependent dynamic recovery function, which can potentially allow for an effective reduction in the rate of accumulation of dislocations at large plastic strains. The numerical predictions of the revised and re-calibrated plasticity model are brought into agreement with the experimental observations, correlating sufficiently well with dynamic yield stress at incipient plasticity and the flow stress levels at larger plastic strains, plastic strain rates in the range 103 – 106 /s, and elevated temperatures up to near melt. The model, in concert with the experimental measurements, suggests that at incipient plasticity the rate governing mechanism for plastic flow is phonon-drag restricted dislocation glide, whereas, at higher magnitudes of plastic strain, it transitions to stress-assisted thermally activated glide. The transition between these two rate governing mechanisms is controlled by the evolution of dislocations throughout the deformation process.

Effect of strain rate on mechanical behavior of Sn0.3Ag0.7Cu solder at macro- and micro-scales

At present, there have been many researches on the effect of trace elements on the mechanical properties of Sn–Ag–Cu solder, and the methods used are mainly shear test or nanoindentation test. However, the size of structural solder joints in electronic packaging has reached the order of micrometers, and the mechanical behavior characteristics related to the strain rate of solder at the micro-scale are obviously more needed for the application of small-scale structural solder joints. For this reason, this paper selects Sn0.3Ag0.7Cu solder with superior comprehensive properties such as ductility and shear strength and low cost, and uses universal testing machine and Split Hopkinson Pressure Bar to perform quasi-static and dynamic compression tests on it. After fitting the Johnson–Cook constitutive model parameters of Sn0.3Ag0.7Cu, the dynamic indentation process at the micro-scale was simulated by ABAQUS, and the effect of strain rate on the mechanical behavior of the material at the macro-scale and micro-scale was analyzed, respectively. Our macro test results show that the yield strength of Sn0.3Ag0.7Cu solder is about 28.74 MPa. Under quasi-static load, the rate of increase of the stress value in the strain hardening stage will increase with the increase of the strain rate; while under dynamic load, the stress value corresponding to different strain rates does not increase significantly, and the main difference lies in the magnitude of plastic strain. In our numerical simulation of dynamic indentation, the result shows that when Sn0.3Ag0.7Cu solder is subjected to a high strain rate load at the micro-scale, a certain degree of hardening occurs in the middle and late stages of indentation propagation. At the same time, the calculated load–displacement curves indicate that the plastic flow ability of Sn0.3Ag0.7Cu solder in the micro-scale increases with the increase of the indentation expansion rate.

Effect of strain on degradation behaviors of WE43, Fe and Zn wires

The biodegradable metallic devices undergo stress/strain-induced corrosion when they are used for load-bearing applications. The stress/strain induced-corrosion behavior causes differences in corrosion rate, corrosion morphology, strain distribution and mechanical performance of the devices. One representative example is the biodegradable stent. Biodegradable stents undergo complex inhomogeneous deformation that can cause dramatic non-uniform stent degradation, resulting in stress concentration and stents failure. The degradation of biodegradable devices requires special attention to the mutual effect between the applied strain and degradation.The quantitative relationship between strain and corrosion of the sample alloys (WE43, Fe and Zn), selected from three typical biodegradable metals, is firstly investigated and compared in this study. The in vitro degradation and the strength retention of WE43, Fe and Zn wires were investigated under different elastic and plastic strain levels ranging from 0.1% to 30%. The results indicated that the applied strain could bring down the corrosion potential, increase corrosion current and accelerate the degradation of three biodegradable metals. Specifically, remarkable enhanced localized corrosion was observed for plastic strained WE43 compared with those with elastic strains. This localized corrosion morphology significantly accelerated the strength decline at first, while the differences diminished with longer immersion period. Fe and Zn exhibited increased degradation with plastic strain applications than those under elastic strains. However, the degradation was not further increased with the increasing magnitude of plastic strains. Moreover, the bended wires were subcutaneously implanted in the dorsal aspect of the rats and the effect of bending deformation on in vitro and in vivo degradation of three metallic wires were also compared. The U-bended WE43 wires suffered more severe in vitro degradation at the stress concentrated region. Surprisingly, the early fracture of the undeformed regions was observed in the in vivo test. In conclusion, the corrosion rate, corrosion morphology and mechanical properties of WE43, Fe and Zn was sensitive to magnitude of the applied strains. The quantification results provided new insights into understanding the strain-dependent corrosion of three biodegradable metals both in vitro and in vivo. Statement of SignificanceBiodegradable implants are subjected to various mechanical environment during the deployment and subsequent physiological activity. It is necessary to have a clear understanding of the effects of the applied stress on degradation. This study addresses the quantitative effects of applied strain/stress on the in vitro and in vivo degradation of three typical biodegradable metals (Mg, Fe and Zn). These quantification results provide new insights into understanding the strain-induced corrosion of three metals.

Investigation on the tensile deformation mechanisms in a new Ni–Fe-base superalloy HT700T at 750 °C

After a standard heat treatment and subsequent isothermal aging at 750 °C for 8,220 h, the tensile deformation behavior of a novel precipitation-hardened Ni–Fe-base superalloy HT700T containing around 23 vol% of γ′ precipitates is studied at 750 °C. It is found that the work-hardening rate decreases monotonously with plastic strain. Transmission electron microscopy observations on the specimens stretched to various magnitudes of plastic strain reveal that Orowan looping prevails at the very beginning of plastic deformation. Whereas, as plastic deformation proceeds, more and more isolated superlattice stacking faults are produced within the γ′ precipitates although numerous dislocation loops have surrounded the same γ′ precipitates, suggesting shearing of γ′ precipitates by {111} <112> slip systems plays a more and more important role in the plastic deformation with strain. Based on the experimental observations, the relationship between the operative deformation mechanisms and the work-hardening rate of HT700T is discussed.