Twin-related Domains Research Articles

New insights into ductility improvement of a nickel-based superalloy through grain boundary engineering

Grain boundary engineering (GBE) provides an effective approach for tailoring the properties of metallic materials by optimizing the grain boundary character distribution (GBCD). Using electron backscatter diffraction analysis and uniaxial tensile testing at room temperature, this study systematically investigated the impact of GBE-type thermomechanical processing (TMP) on the ductility of an Incoloy 925 nickel-based superalloy (Alloy 925). The results showed that at 5 % strain, increasing the annealing temperature results in larger twin-related domains through strain-induced boundary migration. The GBE-type TMP can significantly enhance the ductility of Alloy 925, namely, the elongation increases from 64.22 % to 95.86 % as the annealing temperature increases from 1050 °C to 1100 °C. The evolved GBCD introduces more coherent twin boundaries with lower average residual Burgers vectors, enabling efficient dislocation transmission. In addition, extensive twinning can widely generate some soft orientations and simultaneously reduce the average Taylor factor within the twin clusters, leading to easy dislocation activation during plastic deformation. The synergistic effect of the optimized grain boundary network and twin cluster anisotropy promotes uniform plastic flow and effective strain accommodation, thereby enhancing the ductility of Alloy 925. Overall, this work provides novel and valuable insights into ductility optimization through GBE in a nickel-based superalloy.

Novel role of thermomechanical grain boundary engineering in the microstructure evolution of austenitic stainless steel

The effect of special grain boundary development via the grain boundary engineering process (GBE) was explored in a bimodal microstructured 316L austenitic stainless steel with an average grain size of 1.92 μm. The GBE process was carried out by the rolling-annealing method via two routes of low and medium applied strain, followed by a short annealing period in a single-step and iterative manner. The grain boundary character distribution was obtained by Electron Backscatter Diffraction (EBSD) analysis, and the intergranular corrosion resistance and the tensile behavior of the samples were examined. Microstructural characterization showed that applying low strain repetitively increased the coincidence site lattice (CSL) and Σ3 boundaries percentage and created large twin-related domains (TRD). The reduced sensitization was attributed to a high proportion of CSLs and large-sized TRDs by applying a low-strain route. In the early stages of the low-strain route, the grain boundary character distribution showed a high number of primary twin nuclei in coarse grains and a continuous network of single twin nuclei in smaller grains, creating a high percentage of Σ3-grain boundaries. The low applied strain and the absence of the necessary driving force for the recrystallization and GBs migration led to the formation of twin nuclei, which would assist with the reduction of microstructure energy. A high percentage of Σ3 boundaries and an increase in the percentage of triple points consisting of low energy boundaries were found to be influential factors in increasing elongation.

Evolution of Grain Boundary Character Distribution in B10 Alloy from Friction Stir Processing to Annealing Treatment.

In this study, the grain boundary character distribution (GBCD) of a B10 alloy was optimized, employing thermomechanical processing consisting of friction stirring processing (FSP) and annealing treatment. Using electron backscatter diffraction, the effects of rotational speed of FSP and annealing time on the evolution of GBCD were systematically investigated. The GBCD evolution was analyzed concerning various parameters, such as the fraction of low-Σ coincidence site lattice (CSL) boundaries, the average number of grains per twin-related domain (TRD), the length of longest chain (LLC), and the triple junction distribution. The experimental results revealed that the processing of a 1400 rpm rotational speed of FSP followed by annealing at 750 °C for 60 min resulted in the optimum grain boundary engineering (GBE) microstructure with the highest fraction of low-Σ CSL boundaries being 82.50% and a significantly fragmented random boundary network, as corroborated by the highest average number of grains per TRD (14.73) with the maximum LLC (2.14) as well as the highest J2/(1 - J3) value (12.76%). As the rotational speed of FSP increased from 600 rpm to 1400 rpm, the fraction of low-Σ CSL boundaries monotonously increased. The fraction of low-Σ CSL boundaries first increased and then decreased with an increase in annealing time. The key to achieving GBE lies in inhibiting the recrystallization phenomenon while stimulating abundant multiple twinning events through strain-induced boundary migration.

Cryogenic deformation tailors the dislocation accumulation mode to modify grain boundary character distribution of Incoloy 925

Cryogenic deformation was introduced in thermomechanical processing to restrict dislocation mobility and tailor the initial dislocation distribution at the deformation stage, subsequently followed by annealing treatment to alter the grain boundary characteristic distribution with a view to the feasibility of grain boundary engineering in Incoloy 925. The microstructural evolution deformed at cryogenic (77 K) and room temperature (298 K) under various rolling reductions and annealing conditions was systematically studied to optimize the grain boundary network, which is evaluated using multi-source quantitative statistics of the twin related domains. The results showed that cryogenic deformation can adjust the dislocation accumulation mode and plastic deformation mechanism. Geometrically dislocation distributions, reconstructed by HR-EBSD device, with fishbone-like, ribbon-like or lamellar characteristics can be observed for the deformed specimens. During the subsequent annealing, the samples with 5% and 15% pre-strain are incapable of producing the ideal twin related domains, while the sample annealed at 1075°C with 10% pre-strain show the optimization of GBCD with the highest Σ3n (n = 1, 2, and 3) boundary fraction being 69.67%. Compared with the room temperature pre-deformation, cryogenic deformation can effectively reduce the critical temperature of GBE, and also leads to the Σ3n grain boundaries proportion increasing from 31.47% to 67.46% in 10%/1050°C sample. Meanwhile, with the appropriate strain, cryogenic deformation is more conducive to optimizing the GBCD than room-temperature deformation.

Optimization of Grain Boundary Character Distribution of Fe-19Cr-10Mn-1Ni-0.53N High Nitrogen Austenitic Stainless Steel

High nitrogen austenitic stainless steel (HNASS) has outstanding mechanical properties, but in its hot working, welding, and high-temperature use, there will be a precipitation phase, especially nitride precipitation that reduces its intergranular corrosion, stress corrosion, corrosion fatigue, and other grain boundary-related properties. At present, the traditional methods of suppressing precipitation phase precipitation, such as solution treatment and alloying, have drawbacks. Grain boundary character distribution (GBCD) optimization of Fe-19Cr-10Mn-1Ni-0.53N HNASS was characterized by electron backscatter diffraction (EBSD) in this work. This study reveals that after grain boundary engineering (GBE) treatment, the percentage of low Σ coincidence site lattice (CSL) boundaries of the solid solution treated sample rises from 53.94% to 82.41%, because the sample was cold-rolled (CR) by 5%, followed by annealing at 1423 K for 10 min, and the twin related domains (TRD) size increases from 23.99 μm to 169.82 μm and ν (the ratio of TRD size to grain size) raises from 1.74 to 7.52. The connectivity of the random high-angle grain boundary (RHAGB) web is interrupted and the GBCD of the experimental steel is remarkably optimized.

Revealing hot deformation behavior of inconel X-750 superalloy: A novel hot processing map coupled with grain boundary engineering

In this work, a series of isothermal hot compression tests were performed at the temperature of 900–1150 °C with the strain rate ranging from 0.01 to 10s−1 in Inconel X-750 alloy (referred as Alloy X-750). Based on the flow stress data, the back-propagation artificial neural network model was utilized to accurately predict the flow stress at elevated temperatures. Subsequently, by constructing a modified hot processing map coupled with the variation of Σ3n (n = 1, 2, and 3) twin boundaries fraction, the optimal processing parameters were determined to be in the range of 1100–1150 °C and 1-10s−1 for Alloy X-750. Moreover, the possibility of grain boundary engineering via hot deformation were also evaluated by using some critical quantification descriptors of twin related domains (TRDs), such as the number of grains in the TRDs, the lengths of the longest chain, and the average TRDs size. All the results can further verify the validity of modified hot processing map. Finally, the high-temperature flow behavior combined with the relevant microstructure characterization showed that discontinuous dynamic recrystallization is considered as the predominant softening mechanism, while the continuous dynamic recrystallization and particle-stimulated nucleation also additionally contribute to the recrystallization nucleation during the hot deformation of Alloy X-750.

Roles of the grain-boundary characteristics and distributions on hydrogen embrittlement in face-centered cubic medium-entropy VxCr1-xCoNi alloys

The issue of hydrogen embrittlement (HE) in face-centered (FCC) structured alloys is significant for H storage and transportation application due to unanticipated damage beyond its predicted service life. This unpredictable situation may harm human life and limit hydrogen to a reliable source of renewable energy in industrial fields. Recent research has suggested that multi-principal element alloys possess high resistance to HE. However, there has been limited exploration of how their unique properties affect the HE mechanisms. In this study, using simple model VCrCoNi alloys with analogous grain sizes, the reduction rate of ductility by hydrogen uptake was measured through a slow strain rate tensile test following electro-chemical H charging. Further, the origin of HE resistance was investigated by analyzing various factors such as hydrogen contents, fracture and deformation behaviors, and grain boundary properties using thermal desorption spectroscopy, scanning electron microscope, and electron backscatter diffraction. Despite the consistent trends of the H content, stacking fault energy, and stress with increasing V content, the resistance to HE is the highest for the alloy with an intermediate ratio of V and Cr, namely, for the V0.7Cr0.3CoNi alloy. Through the analysis of grain boundary characteristics, the high resistance is attributed to large fractions of special boundaries and special triple junctions and large twin-related domain size, which suppresses crack growth and interlinkage. The favorable grain boundary characteristics result from mechanical dynamic recovery, achieved by the competitive effects of solid-solution strengthening and stacking fault energy. Thus, the present study provides novel insights into enhancing HE resistance in FCC-structured alloys.

Twin-Related Grain Boundary Engineering and Its Influence on Mechanical Properties of Face-Centered Cubic Metals: A Review

On the basis of reiterating the concept of grain boundary engineering (GBE), the recent progress in the theoretical models and mechanisms of twin-related GBE optimization and its effect on the mechanical properties is systematically summarized in this review. First, several important GBE-quantifying parameters are introduced, e.g., the fraction of special grain boundaries (GBs), the distribution of triple-junctions, and the ratio of twin-related domain size to grain size. Subsequently, some theoretical models for the GBE optimization in face-centered cubic (FCC) metals are sketched, with a focus on the model of “twin cluster growth” by summarizing the in-situ and quasi-in-situ observations on the evolution of grain boundary character distribution during the thermal-mechanical process. Finally, some case studies are presented on the applications of twin-related GBE in improving the various mechanical properties of FCC metals, involving room-temperature tensile ductility, high-temperature strength-ductility match, creep resistance, and fatigue properties. It has been well recognized that the mechanical properties of FCC materials could be obviously improved by a GBE treatment, especially at high temperatures or under high cyclic loads; under these circumstances, the materials are prone to intergranular cracking. In short, GBE has tremendous potential for improving the mechanical properties of FCC metallic materials, and it is a feasible method for designing high-performance metallic materials.

Effect of Heat Treatment Process on the Optimization of Grain Boundary Character Distribution in Heavy Gage Austenitic Stainless Steel

The optimization of grain boundary character distribution (GBCD) is of great significance to improve the GB-related properties for heavy-gauge austenitic stainless steels worked in harsh environments such as reactors of nuclear power, which can usually be realized by regulating the thermomechanical process. In this paper, special solution annealing processes for a hot-rolled nuclear grade 316H plate were designed to introduce different character distribution of Σ3n boundaries (1 ≤ n ≤ 3) and random high-angle GBs (RHAGBs), and the regulation principle among them were clarified. It was worked out that the optimized GBCD by characterization of large twin related domains, abundant interconnected Σ3n boundaries and interrupted topology network of RHAGBs could be effectively facilitated through solution annealing with a long time period at lower temperature or short time period at higher temperature, in which the recrystallization, grain growth and GB migration during heat treatment process played key roles. Moreover, the length fraction of Σ3n boundaries were found to be hardly changed when they reached about 77%, but their character distribution could be continuously optimized.

Effect of Short-Range Ordering on the Grain Boundary Character Distribution Optimization of FCC Metals with High Stacking Fault Energy: A Case Study on Ni-Cr Alloys

The critical roles of short-range ordering (SRO) in the grain boundary character distribution (GBCD) optimization of Ni-Cr alloys with high stacking fault energies were experimentally studied by thermomechanical treatments. It is found that, with the enhancement of the SRO degree (or the increase in Cr content), the dislocation slip mode changes from wavy slip to planar slip, and even deformation twins (DTs) appear in the cold-rolled Ni-40at.%Cr alloy. Within the lower level of Cr content (≤20 at.%), the optimized result of GBCD is conspicuous with the increase in Cr content. As the Cr content is higher than 20 at.%, the GBCD optimization of Ni-Cr alloys cannot be further enhanced, since the cold rolling induced DTs would hinder the growth of twin related domains during subsequent annealing.

The effect of thermomechanical treatment on the evolution of the grain boundary character distribution in a Cr0.8MnFeNi high-entropy alloy

We have employed thermomechanical processing to optimize the grain boundary character distribution (GBCD) of a grain boundary engineered (GBE) microstructure in a face-centered cubic Cr0.8MnFeNi high-entropy alloy (HEA). The influence of the annealing time and the degree of tensile deformation on the GBCD were investigated through electron backscatter diffraction (EBSD). The results show that a 5% tensile deformation followed by annealing at 1000 °C for 40 min led to the formation of a high fraction of low Σ (Σ ≤ 29) coincident site lattice (CSL) boundaries (81.9%), a high (Σ9 + Σ27)/Σ3 ratio (0.17), and a high twin-related domain size to grain size ratio (4.49), demonstrating that the optimization of the GBCD had been achieved. Extending the annealing time further led to a slight decrease in the fraction of low-ΣCSL boundaries. The degree of tensile deformation employed before annealing at 1000 °C/40 min also had a significant influence on the GBCD. As the degree of deformation was increased from 3% to 20%, the low-ΣCSL (Σ ≤ 29) boundaries fraction first increased and then decreased. Any strain-induced boundary migration (SIBM) occurred mainly within low deformation (≤10%) specimens, while any extensive recrystallization occurred within high deformation (20%) specimens. Thus, the optimization of the GBCD could be attributed to sufficient SIBM rather than to significant recrystallization in Cr0.8MnFeNi HEA.

Challenges related to tomographic reconstruction of 3D intragranular orientation fields in the presence of orientation relationships

X-ray diffraction contrast tomography (DCT) is a near-field diffraction imaging technique to characterize the 3D shape and crystallographic orientation of grains within polycrystalline samples. The presence of orientation relationships as such encountered between Σ3n annealing twins found in Cu and Ni lead to systematic diffraction spot overlap, since a significant fraction of the lattice planes is shared between the parent and twin crystal lattices. If not correctly addressed, these overlaps will lead to artifacts in the individual grain reconstruction. In this paper we introduce a strategy for joint, tomographic reconstruction of Twin Related Domains (TRD) and cost function weights into DCT to improve the grain reconstruction quality. A large-grained polycrystalline sample made from pure Ni is used for testing this approach and its ability to reveal intragranular orientation gradients related to plastic strain localization at the onset of plastic deformation in this type of materials.

Revisiting the phase transformations involving Cu6Sn5 intermetallic: resolving local domain structures induced by ordering

Cu6Sn5 is one of the most important intermetallics present in solder joints based on Cu and Sn. Due to still uncertain reasons for failure of these joints, detailed microstructural research can help to figure out the underlying mechanisms. For Cu- and as well for Sn-rich environments of the Cu6Sn5 the microstructural occurrence of the phase transformations are investigated. During the formation of stable η′ from the disordered high temperature η phase the formation of metastable modulated incommensurately ordered η′′ takes place. For the copper rich samples long-range ordering and twin-related domain formation within η′′ was observed. Although conventional Hough-based EBSD analysis was not able to identify the correct domain orientation, Kikuchi pattern matching using simulated patterns was able to resolve the correct microstructure. As ordered intermetallics tend to be brittle in nature, the current microstructure research provides a basis to investigate unresolved problems in the initiation of failure.

On the critical strain of thermal-mechanical processing to tailor grain boundary character distribution in INCOLOY 925 alloy

Through a series of thermal-mechanical processing (TMP) routes with various ratios of cold rolling and subsequent high-temperature annealing, the samples with different critical strain states were prepared to explore the evolution of grain boundary character distribution (GBCD) in INCOLOY 925 during grain boundary engineering (GBE). The GBE microstructure was characterized using the electron backscatter diffraction to study the influence of TMP parameters on the evolution of GBCD and the penetration of random high angle grain boundaries. The results show that the different states of pre-strain correspond to the variational formation mechanism of grain boundary network (GBN). The strain induced boundary migration is the predominant mechanism with the rolling reduction lower than critical strain. With the slight increase of strain, the recrystallization nucleation can be initiated to generate the strain-free grains at a certain annealing temperature. Moderate strain is needed to ensure adequate growth for twin related domains (TRDs). Besides, with the increase of strain and temperature, the dominant mechanism of GBCD gradually transfers from the new twinning mechanism to the Σ3 regeneration mechanism. Specifically, the TMP sample with 10% rolling reduction followed by annealing at 1075 °C for 10min shows relatively higher grain size difference ratio and average grains numbers in the TRDs, indicating that a larger initial grain size can increase critical strain and delay the nucleation of strain-free grains during TMP treatment. The moderately higher grain size shows an opposite effect on the formation of GBN. Finally, an estimation model of critical strain, as a function of initial grain size and annealing temperature, was constructed based on the artificial neural network, and the predicted results show a high consistency with the actual microstructure evolution.

Effect of thermomechanical processing via rotary swaging on grain boundary character distribution and intergranular corrosion in 304 austenitic stainless steel

In the present work, the thermomechanical processing consisting of rotary swaging deformation and annealing treatment was performed to optimize the grain boundary character distribution (GBCD) of 304 austenitic stainless steel. To systematically investigate the effect of GBCD evolution on intergranular corrosion (IGC), double loop electrochemical potentiokinetic reactivation and electrolytic oxalic acid etch tests were employed. The experimental results show that the fraction of low-Σ coincident site lattice (CSL) boundaries increased from 58.1% to 74.0% for the specimen swaged to 0.06 true strain and then annealed at 1050 °C for 5 min duration. By characterizing the evolution of GBCD as a function of strain level in terms of low-Σ CSL boundaries fraction, average twin-related domain (TRD) size, average number of grain per TRD and fractal dimension of the maximum random boundary connectivity, the grain boundary engineering (GBE) microstructure was realized by the occurrence of prolific multiple twinning events during strain-induced boundary migration while static recrystallization has a detrimental effect on optimizing GBCD for the prolific of new strain-free grains with random boundaries. The IGC resistance of the GBE-treated 304 austenitic stainless steel is enhanced by inhibiting the nucleation and propagation of IGC cracks, resulting from the increase in the fraction of low-Σ CSL boundaries, especially Σ3 boundaries and the disruption of random boundary network connectivity.

Induction of large twin related domains and the grain boundary evolution during hot plate rolling and annealing of 316H-type stainless steel

Special thermomechanical processing (TMP) routes of hot rolling and annealing were designed to induce large twin related domains (TRDs) in nuclear-grade 316H plates, and the evolution of twin-related (Σ3n, 1 ≤ n ≤ 3) boundaries and random high-angle grain boundaries (RHAGBs) was clarified. Results demonstrated that the large TRDs and poor RHAGB connectivity could be induced through hot rolling at 800℃ with low-strain followed by annealing. Optimized GB character distributions (GBCDs) presented favourable resistance to intergranular corrosion. Quasi in-situ heating observations showed that the operation of GB migration, recrystallization and grain growth during annealing were necessary to form large TRDs, and the slight deformation storage energy played important role to induce their initiation.

Mitigation of hydrogen embrittlement in alloy custom age 625 PLUS® via grain boundary engineering

Hydrogen embrittlement is the deterioration of mechanical properties in a metal exposed to hydrogen, often characterized by brittle, intergranular fracture at low applied stresses. While grain boundary engineering has been applied to mitigate this issue, ambiguity in the mechanisms behind hydrogen embrittlement leads to ambiguity in the mechanism by which grain boundary engineering helps to mitigate this problem. In this study, grain boundary engineering was applied to improve resistance to hydrogen embrittlement in Custom Age 625 PLUS®, an alloy frequently used in corrosive environments where hydrogen embrittlement is of particular concern. Iterative low strain cold rolling followed by annealing at intermediate temperature successfully produced a grain boundary engineered microstructure with large twin-related domains and a high fraction of interconnected coincident site lattice (CSL) boundaries. Rising step load testing demonstrated that grain boundary engineering increased the stress intensity at which failure from hydrogen embrittlement occurred and caused a shift from intergranular to transgranular crack propagation. Evidence of localized plasticity on fracture surfaces suggest that hydrogen-enhanced localized plasticity (HELP) is the dominant mechanism of hydrogen embrittlement.

Grain boundary engineering of AL6XN super-austenitic stainless steel: Distinctive effects of planar-slip dislocations and deformation twins

To explore the influence of deformation microstructures on the gain boundary engineering (GBE), a series of thermo-mechanical processes (TMPs) were performed on an AL6XN super-austenitic stainless steel (ASS). The deformation microstructures of cold-rolled samples and the TMPed microstructures were characterized by transmission electron microscopy and electron back-scatter diffraction, respectively. The results show that the deformation microstructures, including planar slip bands and deformation twins (DTs), play a distinctive role in the GBE treatment. Planar slip bands are in favor of the GBE treatment, since the migrating boundaries of twin related domains might generate “stacking accidents” in a sequence of closely packed atomic planes via absorbing the planar-slip dislocations, and thus derive the formation of annealing twins. In contrast, DTs are detrimental to GBE for they hinder the growth of twin related domains. Therefore, the optimal prior strain (namely cold-rolling reduction) of TMP for the GBE treatment of AL6XN super-ASS is suggested to be slightly less than the threshold strain for the appearance of DTs. The GBE-quantifying parameters are greatly improved by cold-rolling with 7% reduction and subsequently annealing at 1323 K for 12 h, and the fraction of special boundaries is increased up to 74.5%, thus effectively disrupting the connectivity of random high angle grain boundary network.

New perspectives on twinning events during strain-induced grain boundary migration (SIBM) in iteratively processed 316L stainless steel

Characterization of microstructure and grain boundary character distribution (GBCD) during iterative thermo-mechanical processing (TMP) of 316L stainless steel were done using electron backscatter diffraction (EBSD). Results from EBSD scans were analyzed in terms of the fraction of special boundaries, their deviation from ideal misorientation, connectivity of random high-angle grain boundaries, and grain size. In order to understand the efficacy of the iterative processing route leading to a well-connected twin boundary network, additional analysis was done in terms of twin-related domain statistics and triple junction distribution. Results from these analyses show that initial iteration results in a microstructure with insufficient twin boundary density, and a poor twin boundary network. Although the next iteration leads to a small increase in twin statistics, it also does not significantly improve the statistics of favorable grain boundaries and their network. However, the fourth iteration of the processing results in a large improvement in both the population and distribution of favorable grain boundaries. All the subsequent iterations were found to result in microstructural deterioration in terms of both population and network of these grain boundaries. Based on the analysis, role of underlying mechanisms such as strain-induced grain boundary migration and static recrystallization in the effective optimization of GBCD was analyzed. The present research gives important insights into these mechanisms and their control during TMP in order to achieve an engineered microstructure.

Assessing the potential of sparsely nucleated recrystallized grains to lead grain boundary engineering during extending annealing in Alloy 600H

Alloy 600H is subjected to a lower extent of deformation (7.5% and 10%) followed by annealing at a higher temperature (1273 K and 1373 K) for different time duration (5 min to 600 min) to explore whether sparsely nucleated recrystallized grains can promote grain boundary engineering (GBE). Since strain-induced boundary migration (SIBM) may also occur in the aforementioned deformation-annealing conditions, this study is expected to explicate the relative role of recrystallization vs. SIBM on GBE. It is observed that the sparsely nucleated grains formed during annealing (60 min at 1273 K) of the specimen subjected to critical strain (i.e., 10%) for recrystallization does not lead to a GBE microstructure following extended annealing treatment even up to 600 min. This is due to the dominant nucleation of new strain-free grains during the extended annealing treatment, rather than the growth of initially nucleated recrystallized grains. As a result, the product microstructure post extended annealing treatment yields lower fraction of Σ3n boundaries and lesser numbers of grains per twin-related domains (TRDs) with concomitant increase in random high angle boundaries (HAGBs) connectivity, as corroborated by its higher fractal dimension (Df) and lower J2/1-J3 value. In contrast, significant SIBM has happened in the specimens subjected to 7.5% deformation (i.e., lower than the critical strain for recrystallization) when annealed at 1373 K. During such SIBM, the existing TRDs in the as-received specimen have grown allowing the occurrence of multiple twinning behind the migrating grain boundaries. The evolution of a higher fraction of Σ3n boundaries, promoted via SIBM, and complete suppression of recrystallization in these specimens lead to the significant disruption in random HAGBs connectivity as substantiated by their lower Df and a higher J2/1-J3 value.