Decrease In Stacking Fault Energy Research Articles

Composition design study of strong and ductile Mo-alloyed CoCrNi medium-entropy alloys

The assistance of alloying elements provides enormous opportunities for the discovery of high-performance face-centered cubic (FCC) medium-entropy alloys (MEAs). In this work, the influence of alloying element Mo on the phase stability, stacking fault energy (SFE), deformation mechanisms, lattice distortion, and mechanical properties of (CoCrNi)100–xMox (0 ≤ x ≤ 10) MEAs was synthetically explored with the first-principles calculations. It indicates that the FCC phase remains metastable at 0 K, and its stability degenerates with increasing Mo content. The monotonous decrease of SFE is revealed with the rise of Mo content, which promotes the activation of stacking faults, deformation twinning, or martensitic transformation. Raising Mo content also causes the aggravation of lattice distortion and thus triggers intense solid solution strengthening. Significantly, the essential criterion for the composition design of FCC (CoCrNi)100–xMo MEAs with superior strength-ductility combination was established based on the synergistic effects between multiple deformation mechanisms and solid solution strengthening. According to the criterion, the optimal composition is predetermined as (CoCrNi)93Mo7 MEA. The criterion is proved to be effective, and it can provide valuable inspiration for the development of alloying-element reinforced FCC multi-principal element alloys.

Optimizing strength-ductility of laser powder bed fusion-fabricated Ti–6Al–4V via twinning and phase transformation dominated interface engineering

Titanium alloys produced by laser powder bed fusion (LPBF) are known to possess fine microstructures and multi-scale interfaces. Here, we introduce a high density of α'/β, α/β phase interfaces, {10 1‾1} twin boundaries, and basal stacking faults (BSFs) in a Ti–6Al–4V alloy through LPBF and annealing. The LPBF-fabricated alloy consists of fine acicular α′ martensite with numerous {10 1‾1} twins and BSFs, which results in ultrahigh strength (>1300 MPa), but very low ductility (<5%) due to the massive interface strengthening. Subsequent annealing treatments decrease the strength while increasing the ductility, as the α′ martensite partially or fully decomposes into a lamellar (α+β) structure. The 955 °C-annealed alloy possesses a good strength-ductility combination (yield strength of 1000 MPa, tensile strength of 1078 MPa, and total elongation of 20%). During the stages of uniform plastic strain (up to ∼12%), deformation occurs by dislocation slips, leading to significant dislocation accumulations around the α/β interfaces. At later stages (∼20% strain), when necking occurs, a high density of fcc-γ bands is observed in the hcp-α phase, indicating the onset of deformation-induced martensitic transformation (DIMT) from hcp-α to fcc-γ. The occurrence of DIMT may be attributed to the decreased stacking fault energy and the cohesive energy difference between the hcp and fcc phases, due to the segregation of Al elements in the hcp-α phase. Low-loss electron energy loss spectroscopy reveals that the deformation-induced fcc phase is not Ti-hydride, but a new allotrope of Ti.

Comparative study on the formability and microstructure evolution of different tempered Al–Cu–Li alloy sheets during room and cryogenic temperature forming process

High strength aluminum alloy sheets with excellent formability are necessary for the successful fabrication of complex-shaped components in order to prevent cracking during the forming process. To address this issue, this study investigated the formability of annealed (O) and water-quenched (WQ) Al–Cu–Li alloys at both room and cryogenic temperatures. Our results reveal a significant increase in the forming limit curve, with a 40% enhancement observed as the forming temperature decreased from 298 K to 113 K. Additionally, a 30% increase in formability was observed when transitioning from the O temper to the WQ temper. Thickness measurements reveal that WQ pre-treatment and cryogenic forming promoted continuous work hardening, thus improving deformation homogeneity. The mechanism responsible for the higher work hardening ability was elucidated by examining the microstructure evolution in different regions of the components. The results show that coarse particles in the O tempered alloys accelerated cross slip, resulting in the formation of recovered microstructures (i.e., dislocation cells and Cube texture) while simultaneously hindering dislocation movement and inducing local stress concentration. Conversely, for the WQ tempered alloy deformed at cryogenic temperature, the dissolution of particles and decreased stacking fault energy at low temperature suppressed cross slip and resulted in well-arranged dislocations within the slip system. Consequently, the combination of WQ pre-treatment and cryogenic forming demonstrates enhanced formability in high strength aluminum alloys, offering a novel method for manufacturing complex-shaped components.

The role of austenite grain size on martensite start temperature and phase transformation path in SUS321 stainless steel

The change in Ms and transformation path of γ→α′ transformation with austenite grain size (AGS) has been investigated by a thermodynamic model of martensitic transformation and the stacking fault energy (SFE) in SUS321 stainless steel. With increasing AGS, the Ms increases and the SFE decreases. A good linear relationship is established between the Ms and the SFE. This result suggests that the martensitic transformation path changes as the AGS decreases, and the γ→ε→α′ sequence is gradually suppressed when the AGS is smaller than 3.5 μm.

Hydrogen embrittlement behavior in FeCCrNiBSi TRIP steel

The effect of plastic deformations on the hydrogen embrittlement (HE) of transformation-induced plasticity (TRIP) steel was studied. In situ tensile tests showed that with increasing hydrogen current density, total elongation loss was raised to 36.8% as compared to an uncharged specimen. The electron backscatter diffraction (EBSD) observation indicated that hydrogen charging decreased stacking fault energy (SFE), resulting in the formation of more α′- martensite by both indirect and direct transformation. The α′- martensite volume fraction at the same degree of deformation in uncharged and charged samples was 31% and 39%, respectively. With plastic deformation, reversible trap sites were raised because of the increased dislocation density and the formation of α′- martensite, which was obtained from EBSD characterization and had a good correlation with the results of the thermal desorption spectroscopy (TDS) analysis.

Effects of stacking fault energy and temperature on grain boundary strengthening, intrinsic lattice strength and deformation mechanisms in CrMnFeCoNi high-entropy alloys with different Cr/Ni ratios

Tensile properties and deformation mechanisms at 293 and 77 K of single-phase face-centered-cubic (FCC) CrxMn20Fe20Co20Ni40-x (0 ≤ x ≤ 26 at.%) high-entropy alloys (HEAs) with grain sizes (d) in the range [6–283 µm] were studied. A specificity of these alloys is that their stacking fault energy (SFE) strongly decreases with increasing the Cr/Ni ratio while all the other characteristics affecting strength (elastic moduli and solute misfit volumes) remain approximately constant. Therefore, these alloys allow to investigate how the SFE affects the tensile behavior and deformation mechanisms of FCC HEAs. Grain boundary strengthening is found to be nearly independent of SFE, composition, and temperature. While the intrinsic lattice strength (σ0 ≈ 136 MPa) remains approximately constant at 293 K, it strongly increases with increasing Cr/Ni ratio and thus decreasing SFE at 77 K, presumably due to a reduction of dislocation line tension. Deformation twinning occurs at 293 K when x ≥ 20 at.% (SFE ≤ 35 mJ/m2) and in all alloys at 77 K. The strength-ductility combination is found to increase with decreasing SFE only when 14 ≤ x ≤ 24 at.% at 77 K because twinning must be triggered at relatively low plastic strains to yield a significant dynamic Hall-Petch effect, allowing to sustain a high work hardening rate and postpone necking instability. In addition to twinning, an FCC-to-HCP (hexagonal close-packed) martensitic transformation was observed at 77 K in the Cr26Mn20Fe20Co20Ni14 HEA, which induced early rupture when d = 212 µm.

Achieving ultra-high yield strength in austenitic low-density steel via drastic VC precipitation

In this study, the precipitation behavior of V in austenitic low-density steel (LDS) and its influence on microstructure and mechanical properties were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, electron backscatter diffraction, physicochemical phase analysis and tensile testing in an attempt of enhancing the yield strength. Forging samples of novel Fe–25Mn–10Al-1.1C-(0,0.5)V (wt.%) austenitic LDSs were annealed at 900 °C followed by water quenching. Results showed that a drastic VC precipitation could be achieved in the austenitic matrix, which is mainly attributed to the decreased solid solubility products of VC and the reduction of the nucleation barrier due to the 10 wt% Al addition as well as the high C content. Thus, an extremely high yield strength of 1120 MPa, an increase of 260 MPa compared with that of the V-free steel, was obtained due to the precipitation strengthening and dislocation strengthening effect. Moreover, the addition of V inhibited the precipitation of κ-carbide and increased the ferrite content. Dispersedly distributed VC precipitates enhanced the initial work hardening rate and delayed the recrystallization of the V-containing steel. The V-containing steel exhibited primary planar slip but deformation twins were also observed in some austenite grains due to its decreased stacking fault energy. This study thus offers a potential strategy to significantly improve the yield strength of low-density steels through a suitable addition of V and corresponding simple annealing treatment.

Anomalous high-temperature quasi-linear superelasticity of Ni-Fe-Ga-Co shape memory alloy

The superelasticity of shape memory alloys is associated with the martensitic transformation which has been widely used in engineering applications. Here, we clarify quasi-linear superelasticity in Ni-Fe-Ga-Co shape memory alloy exhibiting a recovery strain of 3.58% at 573 K, which is far above the martensitic transformation temperature. Real-time in-situ neutron diffraction measurement was used to explore the underlying quasi-linear superelasticity mechanism via tracing the structural evolution during cyclic compression loading. Neutron diffraction observation showed that the superelasticity is correlated with stress-induced continuous variation of lattice parameter. The in-situ neutron diffraction provides the direct evidence on the anomalous diffraction peak width broadening, which mainly stems from the spatial heterogeneity in strain. The excessive Co doping is responsible for the decrease in stacking-fault energy leading to an increase in stacking faults, which suppresses the martensitic transformation and triggers the nucleation of the weak first-order phase under the external stress. The study provides insights into the interplay between superelasticity and structural transformation in shape memory alloys, and it is also instructive for understanding the anomalous high-temperature quasi-linear superelasticity in functional materials. • The quasi-linear superelasticy of Ni-Fe-Ga-Co shape memory alloy is caused by the weak first-order transformation. • The quasi-linear superelasticity of Ni-Fe-Ga-Co exhibits a recovery strain of ~3.58% at 573 K, which is rarely reported. • The excessive Co is account for trigger the nucleation of the weak first-order phase under the external stress.

TEM study of the dislocation structure at the transition from discontinuous to viscous glide in Cu–Al and Cu–Mn alloys at elevated temperatures

Abstract The dislocation structures developed during plastic deformation in the regimes of discontinuous glide (Portevin – Le-Chatelier effect, PLC) as well as viscous glide at elevated temperatures (600 – 800 K) have been studied by transmission electron microscopy in polycrystals of Cu-5Al, Cu-10Al, Cu-15Al and Cu-4.1Mn alloys (at.%). Discontinuous glide is characterized by correlated dislocation movement in few active slip planes due to breakaway of aged and rapid multiplication of fresh dislocations, while beyond the transition, when solute diffusion is fast enough to continuously reconstitute the solute cloud during dislocation motion, a homogeneous distribution of smoothly moving dislocations is observed in all alloys. Owing to the decrease of stacking-fault energy and increase of short-range order in the Cu–Al alloys a change from cell structure (Cu-5Al) to planar slip (Cu-10Al and Cu-15Al) occurs in the discontinuous glide regime; in the Cu-4.1Mn alloy with a stacking-fault energy like Cu and negligible short-range order, development of cells prevails also during discontinuous glide. The observations are discussed in terms of current views on deformation in the PLC regime.

Counter-balancing effects of Si on C partitioning and stacking fault energy of austenite in 10Mn quenching and partitioning steel

• Si addition delayed carbide formation and promoted c partitioning into austenite. • Si addition decreased stacking fault energy of austenite. • Austenite stability in Si-added steel was appropriate to fully exploit TRIP. • Si-added steel achieved higher yield and tensile strengths than Si-free steel. Silicon is an essential alloying element in quenching and partitioning (Q&P) steels, because it is known to suppress carbide precipitation during partitioning step and promote carbon partitioning to stabilize austenite. When 2 wt% Si was added to 10Mn-2Al-0.2C steel, the size and fraction of the carbides formed during partitioning became smaller than in the Si-free counterpart. Moreover, the suppression of carbide formation promoted C partitioning into austenite as expected. However, austenite stability was always lower with Si under the equivalent partitioning condition because Si effectively decreased the stacking fault energy of austenite. As partitioning progressed, the both yield and tensile strengths of the Si-added steel exceeded that of the Si-free steel with the similar ductility level. This was because Si was an effective solid solution strengthener, and the austenite in the Si-added steel exhibited the appropriate stability to gradually transform into martensite throughout the deformation. The resulting strengthening effect compensated for the softening caused by martensite recovery. Consequently, strain hardening rate decreased continuously throughout deformation, which resulted in high tensile strength and ductility.

Dynamic tensile mechanisms and constitutive relationship in CrFeNi medium entropy alloys at room and cryogenic temperatures

Harsh service conditions in aerospace, defense and military, and other fields are calling for materials with excellent mechanical properties to undergo extreme deformation (such as elevated and cryogenic temperatures and high strain rates) without sustaining damage while retaining high strength. Outstanding mechanical properties of high or medium entropy alloys (MEAs) render them potential candidates. In this paper, as the temperature decreases, a breakthrough of the strength-ductility tradeoff is achieved in a CrFeNi MEA with partially recrystallized face-centered cubic phases, together with body-centered cubic (BCC) precipitates. At a strain rate of $3000\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, the yield strength (YS) is increased from 920 MPa at 298 K to 1320 MPa at 77 K, while the uniform elongation (UE) increases by 28.5%. This phenomenon also occurs at quasistatic tension. Under low-temperature loading, nanotwins are popularly activated due to the decreased stacking fault energy with decreasing temperatures. A positive strain-rate dependent YS arises owing to the contributions from the short-range dislocation obstacles, BCC phases, and refined grains. High-density dislocations and BCC phases result in the degeneration of UE, especially with the increase of strain rates. Strain-rate- and temperature-dependent constitutive models were successfully established to predict the deformation behaviors of CrFeNi MEAs under such a wide range of strain rates at room and cryogenic temperatures.

Elimination of oxygen sensitivity in \u03b1-titanium by substitutional alloying with Al

Individually, increasing the concentration of either oxygen or aluminum has a deleterious effect on the ductility of titanium alloys. For example, extremely small amounts of interstitial oxygen can severely deteriorate the tensile ductility of titanium, particularly at cryogenic temperatures. Likewise, substitutional aluminum will decrease the ductility of titanium at low-oxygen concentrations. Here, we demonstrate that, counter-intuitively, significant additions of both Al and O substantially improves both strength and ductility, with a 6-fold increase in ductility for a Ti-6Al-0.3 O alloy as compared to a Ti-0.3 O alloy. The Al and O solutes act together to increase and sustain a high strain-hardening rate by modifying the planar slip that predominates into a delocalized, three-dimensional dislocation pattern. The mechanism can be attributed to decreasing stacking fault energy by Al, modification of the “shuffle” mechanism of oxygen-dislocation interaction by the repulsive Al-O interaction in Ti, and micro-segregation of Al and O by the same cause.

Phase transformation and deformation behavior of a TiAl–Nb composite under quasi-static and dynamic loadings

To improve the high-temperature deformability of TiAl intermetallics, a TiAl–Nb intermetallic matrix composite was prepared by powder metallurgy to try to introduce the deformable β phase. The microstructure and deformation behavior of the TiAl–Nb intermetallic matrix composite under quasi-static and dynamic conditions were systematically investigated. It is found that the microstructure of the composite is composed of a near-gamma TiAl matrix and Nb-rich regions. In the Nb-rich regions a coexistence of βo, ωo and γ phases was identified where ωo and γ phases were supposed to directly precipitate in the βo matrix. The ultimate tensile strength of the composite exhibits different temperature-dependent behaviors under quasi-static and dynamic loading conditions. It increases with temperatures up to 650 °C and then declines with temperature under quasi-static loading, while it does not decrease from 650 to 850 °C under the dynamic loading. In the deformed microstructures, the Nb-rich regions at all conditions are still composed of βo, ωo and γ phases, indicating that the solvus temperature of the ωo phase could be above 850 °C. Additionally, the TiAl matrix appears to not significantly contribute to the plastic deformation of the composite, where the propensity of dislocations and mechanical twins do not significantly change when varying loading conditions. However, the γ particles formed in Nb-rich regions contain substantial mechanical twins and dislocations under both quasi-static and dynamic loading conditions. Thus, the γ particles directly transformed from the βo phase exhibit better deformability than the γ phase in the matrix. This could be probably explained by a decreased stacking fault energy for the newly formed γ phase due to a decrease in Al fraction and a significant increase in Nb fraction. Meanwhile, twin intersections occurred in the γ particles, and the induced stress concentration in the intersection regions was relieved by lattice distortion and detwinning processes. This twin intersection behavior could be beneficial for improving the composite strength without sacrificing much ductility.

Influence of Mg content in Al alloys on processing characteristics and dynamically recrystallized microstructure of friction surfacing deposits

Friction Surfacing (FS) coatings are deposited by severe plastic deformation at elevated temperatures (≈0.8*Tliquidus), requiring different process parameters for alloys of even small composition variations. For Al alloys it is known that with increasing Mg content the thermal softening rate decreases, i.e. the material retains higher flow strength under thermomechanical processing. Further, the stacking fault energy (SFE) decreases with increasing Mg content, which influences gliding characteristics of dislocations, and also deformation and recrystallization behavior. To elucidate the influence of such known properties on FS process parameters and resulting coatings, three Al alloys differing only in Mg content (0.27, 2 and 3.5 wt.%) were processed by FS in this study.Pronounced shear flow localization was observed for increasing Mg content, yielding thin and narrow coatings and requiring a reduction of process speeds. Further, the decrease in SFE with increasing Mg content resulted in lower recrystallized grain size and higher grain orientation differences, due to a lower tendency for dislocation annihilation by recovery.

Temperature dependent deformation behavior and stacking fault energy of Fe40Mn40Co10Cr10 alloy

The variation in stacking fault energy (SFE) with the change in temperature has been evaluated experimentally for Fe40Mn40Co10Cr10 high entropy alloy. The distance between partial dislocations was measured using transmission electron microscopy (TEM) based weak-beam dark field (WBDF) technique. SFE of the system was found to be 37.7 (±7) mJ/m2 and 19.5 (±5) mJ/m2 at room temperature (RT) and -100°C, respectively. Owing to the decrease in SFE, a transition in the deformation behavior occurred from limited twin formation and slip dominance at RT to mixed-mode consisting of FCC→HCP transformation and twinning at -100°C. Simultaneous occurrence of twins and deformation-induced martensitic transformation led to superior strength-ductility combination in the specimen deformed at -100°C. SFE of the studied alloy at RT was 42% higher than that of the equiatomic FeMnCoCrNi alloy. This increase in SFE, despite removal of Ni can be understood by considering the effect of the alloy chemistry re-adjustment on ΔGγ→ε.

Sluggish hydrogen diffusion and hydrogen decreasing stacking fault energy in a high-entropy alloy

Hydrogen diffusion and its interaction with dislocations play an important role in hydrogen embrittlement, however, such a process in multiple-principal high entropy alloys (HEAs) is still elusive. Here, first-principles calculations were performed to investigate the solution and diffusion of hydrogen and its effect on the stacking fault energy of FeCoNiCrMn. It is shown that the unique lattice distortion in HEAs causes a wide distribution of local hydrogen solution energy, and the trapping of hydrogen in low energy sites increases diffusion barriers. The zigzag path and asymmetry of forward and backward diffusion result in the sluggish diffusion of hydrogen. Furthermore, hydrogen reduces unstable and stable stacking fault energies, originated from the transfer of electron between hydrogen and metal atoms, which promotes formation of deformation twins. This provides a theoretical guidance for designing novel engineering materials with optimal combination of their mechanical properties and hydrogen embrittlement resistance.

Effects of Yb concentration on recrystallization, texture and tensile properties of extruded ZK60 magnesium alloys

Microstructures and mechanical properties of as-extruded ZK60 alloys with different Yb concentrations (0, 1.0 and 2.0 wt%) were investigated. The results showed that Yb addition effectively refined the recrystallized grains and resulted in dense Mg–Zn–Yb nano-precipitates. With increasing Yb concentration, sufficient boundary drag was provided by solute clustering and high-density precipitates, inhibiting the grain boundary bulging. Meanwhile, the decreased stacking fault energy retarded dynamic recovery and led to an increased population of shear bands, extension twins and dislocations, promoting the formation and rotation of sub-grains. These facilitated the transition of the dominant nucleation mechanism from discontinuous dynamic recrystallization (DRX) to continuous DRX. Moreover, Yb addition disrupted the tendency for developing an intense basal texture during extrusion and the “Rare-Earth” (RE) texture was generated in the ZK60–2wt% Yb (ZYbK620) extrudate. It demonstrated that with Yb solute, the comprehensive effects including nucleation along extension twin boundaries preserving an initial “Rare-Earth” orientation, preferential grain growth along the non-basal planes and the opposite lattice rotation triggered by increased activity of pyramidal <c + a> slip contributed to the c-axis rotation of DRX grains to the extrusion direction. Favored by the grain refinement, nano-precipitates dispersion and RE texture, the tensile properties of extruded ZYbK620 alloy were considerably improved in comparison with the Yb-free counterpart, achieving a good strength-ductility balance with the ultimate tensile strength of 378 ± 1.5 MPa, tensile yield strength of 237 ± 2.3 MPa and elongation to failure of 17.6 ± 2.0%, respectively.

Effect of Stacking Fault Energy on the Grain Structure Evolution of FCC Metals During Friction Stir Welding

The effect of stacking fault energy (SFE) on the grain structure evolution of face-centered cubic metals during friction stir welding was investigated by using pure aluminum, pure copper and Cu–30Zn alloy as experiment materials. Tool “stop action” and rapid cooling were employed to “freeze” the microstructure of the flowing materials around the tool. Marker materials were used to show the streamline of the material flow. The microstructures of the three materials at different welding stages were contrastively studied by the electron backscatter diffraction technique. The results show that at the material flow stage, as the SFE decreases, the grain structure evolution changes from the continuous dynamic recrystallization to discontinuous dynamic recrystallization, and further to the dynamic equilibrium between the annealing twinning due to thermally activated grain boundary migration and the twin destruction during the plastic deformation. Owing to different grain structure evolution mechanisms, the grain structure at the end of the material flow is greatly different. Especially in copper, a lot of dislocations remain, which gives rise to the static recrystallization occurring during the subsequent cooling stage.

Joint contribution of transformation and twinning to the high strength-ductility combination of a FeMnCoCr high entropy alloy at cryogenic temperatures

The microstructure-mechanical property relationships of a non-equiatomic FeMnCoCr high entropy alloy (HEA), which shows a single face-centered cubic (fcc) structure in the undeformed state, have been systematically investigated at room and cryogenic temperatures. Both strength and ductility increase significantly when reducing the probing temperature from 293 K to 77 K. During tensile deformation at 293 K, dislocation slip and mechanical twinning prevail. At 173 K deformation-driven athermal transformation from the fcc phase to the hexagonal close-packed (hcp) martensite is the dominant mechanism while mechanical twinning occurs in grains with high Schmid factors. At 77 K athermal martensitic transformation continues to prevail in addition to dislocation slip and twinning. The reduction in the mean free path for dislocation slip through the fine martensite bundles and deformation twins leads to the further increased strength. The joint activation of transformation and twinning under cryogenic conditions is attributed to the decreased stacking fault energy and the enhanced flow stress of the fcc matrix with decreasing temperature. These mechanisms lead to an elevated strain hardening capacity and an enhanced strength-ductility combination. The temperature-dependent synergy effects of martensite formation, twinning and dislocation plasticity originate from the metastability alloy design concept. This is realized by relaxing the equiatomic HEA constraints towards reduced Ni and increased Mn contents, enabling a non-equiatomic material with low stacking fault energy. These insights are important for designing strong and ductile Ni-saving alloys for cryogenic applications.

Atomistic simulations for the effects of stacking fault energy on defect formations by displacement cascades in FCC metals under Poisson’s deformation

We performed molecular dynamics simulations of displacement cascades in FCC metals under Poisson’s deformation using interatomic potentials differing in stacking fault energy (SFE), in order to investigate the effect of tensile strain on the SFE dependence of defect formation processes. There was no clear SFE dependence of the number of residual defects and the size distribution of defect clusters under both no strain and the applied strain, while the strain enhanced the defect formation to a certain extent. We also observed that the strain affected the formations of self-interstitial atom (SIA) clusters depending on their size and the Burgers vector. These results were consistent with the analysis based on the defect formation energies. Meanwhile, the number of SIA perfect loops was higher at lower SFE under both no strain and the applied strain, leading to an increase in the ratio of glissile SIA clusters with a decrease in SFE. Further, the absolute number of SIA perfect loops was increased by the applied strain, while the SFE dependence of the number of SIA perfect loops was not affected. These findings were associated with the difference in formation energy between an SIA perfect loop and an SIA Frank loop. The insights extracted from this study significantly contribute to the modeling of microstructural evolution in nuclear materials under irradiation, especially for low SFE metals such as austenitic stainless steels.