Superelastic Strain Research Articles

Torsional behavior of Ni-rich NiTi alloys obtained by powder metallurgy and hot deformation

The effects of severe plastic deformation on NiTi alloys’ structure and properties have been extensively studied over the past decades. However, there is a notable lack of systematic data regarding the impact of industrial hot deformation techniques on these alloys. This gap arises from challenges in manufacturing processes related to the unevenness of ingots produced by casting technologies. This study investigates the effects of hot rotary swaging, extrusion, and radial shear rolling on the martensitic transformation, shape memory effect, superelasticity, and damping capacity of NiTi Ni-rich alloys fabricated through powder metallurgy. The properties were investigated under torsional load on wires prepared by spark eroding from deformed rods. Our findings indicate that samples after rolling and extrusion exhibit a superelastic strain of 14 ± 0.5% attributed to a high yield stress of approximately 600–800 MPa and torsional testing providing the material to be fully involved in recovery process. Samples after rolling and swaging demonstrate a high level of reversible strain with a one-way shape memory effect ranging from 5 to 7%. Conversely, extrusion, due to the inhomogeneity of resulting workpieces, induces a complex, multi-stage martensitic transformation that undermines the shape memory effect. Furthermore, all deformation methods except extrusion contribute to increased alloy homogeneity, resulting in a narrower temperature range for martensitic transformations. Rotary swaging notably increases the height of an internal friction peak from 0.015 to 0.045 compared to the undeformed material, whereas rolling gives the lowest value of 0.012 among others. This study provides valuable insights into how hot thermomechanical processing influences the properties of NiTi alloys and shows that powder metallurgy combined with hot deformation can be considered an alternative approach for achieving high functional properties of these alloys.

Microstructure and properties of superelastic Ti-18Zr-15Nb alloy subjected to combination of moderate/severe cold drawing and post-deformation annealing

Ti-18Zr-15Nb (at%) shape memory alloy was subjected to a thermomechanical treatment (TMT), combining cold drawing (CD) with moderate (e = 0.5/1.1), and severe (e = 1.9/3.3) true strains, and post-deformation annealing (PDA) at 500–600 °C to fabricate a wire for medical application. The phase composition, microstructure, crystallographic texture, mechanical and functional properties were studied. The combination of cold drawing with true strain e = 0.5 and PDA at 550 °C for 5 min showed remnants of the original deformed grains, inside of which there is apparently a polygonized substructure, and a partially recrystallized structure of β-phase with a low amount of α-phase (grain size of D≈8 μm). With an increase in true strain, annealing temperature and holding time, a fully recrystallized structure and grain growth were observed. After TMT including the moderate cold drawing, a crystallographic texture with preferable orientation in the <101>β direction was formed. As true strain increases to e = 1.9/3.3, the preferable orientation changes to the <210>β direction; the intensity of this crystallographic texture increases as the true strain increases. Maximum difference between the dislocation and transformation yield stresses was observed after CD with true strain e = 1.1 and PDA at 550 °C for 30 min (Δσ ≈ 405 MPa). Elongation to failure about 20 % was observed after CD with a true strain of e = 0.5 and PDА at 600 °C for 30 min (D≈15 μm). During superelastic cyclic testing with 4 % applied strain after CD (e = 1.9–3.3) and PDA at 550 °C for 5–15 min (D≈1–3 μm) the alloy exhibits high values of superelastic (εrse ≈ 1,8–2,1 %) and total elastic+superelastic (εrel+se ≈ 3,3–3,5 %) recovery strains as well as sufficient maximum tensile stress (σmax ≈ 441–472 MPa), and accumulated residual strain (εacc ≈ 0.4–0.7 %).

Comprehensive mapping of mechanical properties and martensitic transformation in Ti–Al–Mo standard ternary system: Integrating literature data and fabricating novel high-Al-content superelastic alloys

Titanium alloys are increasingly used as structural and functional materials owing to their exceptional properties. This study aimed to develop β-Ti shape memory alloys by creating a compositional map of the phase constitution and mechanical properties of the Ti–Al–Mo ternary system at room temperature, particularly near the α″+β phase region. Data for 95 alloy compositions were collected from the literature, and the composition region of Ti–(7–14) mol% Al–(3–7) mol% Mo, which has rarely been reported, was experimentally investigated. The phase constitution of Ti–Al–Mo alloys primarily depends on the Mo concentration; however, at Al concentrations of 10 mol% or higher, the β phase region expands. The yield stress was found to be minimal around 6 mol% Mo on the low-Al side, and this minimum shifted to lower Mo concentrations as the Al content increased, corresponding to the β/(α″+β) boundary. The ultimate tensile strength increased marginally in low-Mo compositions because of the twinning-induced plasticity effect, with the optimal composition near Ti–11 mol% Al–4 mol% Mo. Superelasticity was observed in high-Al regions, particularly in the Ti–11 mol% Al–6 mol% Mo alloy, which exhibited a superelastic recovery strain of 3.2 % and a total shape recovery strain of 6 %. These findings highlight the potential for developing new room temperature superelastic alloys in the Ti–(10–14) mol% [Al]eq–(5–6) mol% [Mo]eq composition region.

Achieving dual-phase structured Cu-Al-Mn-Si alloy with prominent shape memory properties via laser powder bed fusion

In this study, Cu-11.1Al-8.15Mn-0.37Si shape memory alloy was manufactured via laser powder bed fusion (LPBF) and compared with furnace-cooling cast samples. The LPBF-manufactured samples exhibited a dual-phase structure of L21 austenite and 2H martensite, along with uniformly distributed nanoscale Mn5Si3 precipitations observed via TEM. The 2H martensite presented a layer-like morphology and was confirmed to be induced by residual stress during the LPBF process. Such a dual-phase structure could be stabilized by Mn5Si3 precipitations, and yielded the concurrent presence of prominent superelastic (SE) and shape memory effect (SME) properties. Under 6 % pre-strain, LPBF-manufactured samples showed an 80 % SE rate and 83 % SME rate. The recovery SE and SME strain could be up to 4.2 % and 2.1 %. Compared to the cast sample, fracture compressive and tensile strain increased by 68.4 % and 33.3 %. This enhancement was due to regularly arranged columnar crystals and strong [001]//Z texture confirmed by EBSD. These findings suggest that LPBF has the potential to produce Cu-Al-Mn-Si alloys with prominent shape memory properties and provide references for an austenite-martensite dual-phase structure.

A super-elastic wearable strain sensor based on PU/CNTs yarns for human-motion detection

Yarn-based strain sensors increasingly garner attention for their potential applications in intelligent wearable electronic devices. Developing highly elastic conductive composite yarns and integrating them into fabrics poses a significant challenge in manufacturing flexible electronic devices. In this study, a polyurethane (PU)/carbon nanotubes (CNTs) composite nanofiber yarn was successfully and continuously prepared using a simple conjugate spinning technique. The resulting yarn exhibited excellent mechanical properties, with a high tensile strength of up to 56.7 MPa and an elongation at break of 504 %. A yarn with a dual conductive network was created using CNTs ink dip-coating. It demonstrated excellent conductivity (8.77 S/cm), exceptional linear variation, and reusability. The sensor remained stable after 1000 cycles of testing, exhibiting a relative electrical resistance change of up to 594 % under a strain of 350 %. Additionally, taking advantage of the inherent knittability of one-dimensional yarn structures, a susceptible wearable textile-type strain sensor was successfully developed using textile knitting technology. This sensor can be directly attached to the surface of the human body for real-time monitoring of human body dynamics. This sensor showcases significant promise for use in flexible, intelligent, wearable electronic devices.

Superelasticity with narrow stress hysteresis and high cyclic stability in Co–V–Al polycrystalline alloy

Superelasticity of shape memory alloy associated with the martensitic transformation is extremely attractive for applications in sensors and biomedical. This application requires narrow stress hysteresis to reduce energy dissipation and a stable superelasticity cycle is an important factor in their practical applications. Co–V–Al alloys have inimitable advantages due to their narrow stress hysteresis, low-cost, and corrosion resistance, but the low number of superelasticity cycles restricts its development. Here, we report an intrinsic Co58V29Al13 polycrystalline alloy with a superelasticity stress hysteresis of 30 MPa at room temperature, the lowest among the alloys in this system, and a superelasticity strain of 3.6%. In addition, the sample shows no significant decay trend after 500 loading and unloading cycles. The high number of superelasticity cycles is mainly due to the elastic stress field generated around the dislocation during the cycle, which provides internal stress for martensite nucleation and reduces energy dissipation during martensitic transformation. This work provides essential guiding significance for the design of high-performance superelasticity alloys.

Effects of Zr and Hf on superelasticity, shape memory effect and microstructure of β-type (Ti–Zr–Hf)–Nb–Sn multi-principal element alloys with low magnetic susceptibility

(Ti–Zr–Hf)(97−x)–xNb–3Sn (Ti:(Zr + Hf) = 1:1) alloys were designed for biomedical superelastic alloys with magnetic resonance imaging (MRI) compatibility. The effects of Zr and Hf on constituent phases, superelasticity, shape memory effect and magnetic susceptibility were clarified. The specific Nb content for superelasticity and shape memory effect was also explored. It was found that the (Ti–Zr)–6.5Nb–3Sn alloy exhibited a superelastic recovery strain of 5.2 % with lower magnetic susceptibility compared to conventional Ti–Ni and Ti–Nb alloys. The magnetic susceptibility decreased with increasing Hf content. The (Ti–Hf)–9Nb–3Sn alloy showed a superelastic recovery strain of 0.9 % and very low magnetic susceptibility less than half of that of the conventional alloys. Based on the lattice parameters of these alloys, it was found that these alloys exhibited larger transformation lattice strain between a β phase and an α” phase than those of the Ti–Nb alloys, suggesting high potential to exhibit a large superelastic recovery strain. According to orientation analyses of constituting grains, the larger superelastic recovery strain in the (Ti–Zr)–6.5Nb–3Sn alloy than that of the (Ti–Hf)–9Nb–3Sn alloy is considered to be caused by a strong recrystallization texture of {001}β <110>β. By optimization of heat-treatment temperature, superelastic recovery strain of 3.6 % was achieved in the (Ti–0.5Zr–0.5Hf)–7.5Nb–3Sn alloy.

Effect of Ti content on abnormal grain growth of Fe–Mn–Al–Ni–Ti shape memory alloy

In this paper, the effects of Ti content on the solvus temperature of γ-phase and abnormal grain growth (AGG) in Fe43.5−x Mn34Al15Ni7.5Ti x (x = 0, 0.5, 1 and 1.5) shape memory alloys (SMAs) were investigated. It is found that, the increase of Ti content leads to a significant reduction of the solvus temperature of γ-phase, a significant refinement of γ-phase, and a decrease of subgrain size. After 3 times cyclic heat treatments, the average grain size of Fe42Mn34Al15Ni7.5Ti1.5 SMA reaches about 9.0 mm, which is about twice of that for Fe42.5Mn34Al15Ni7.5Ti1 SMA. This is attributed to the small subgrains can provide a higher subgrain boundary energy (ΔG s) and grain boundary (GB) migration rate. The subgrain size of Fe42Mn34Al15Ni7.5Ti1.5 SMA (9.7 μm) is significantly smaller than that of Fe42.5Mn34Al15Ni7.5Ti1 SMA (21.3 μm). Thereby, the ΔG s (15.3 × 10−2 J mol−1) and GB migration rate (11.3 × 10−6 m s−1) of Fe42Mn34Al15Ni7.5Ti1.5 SMA are significantly higher than those of Fe42.5Mn34Al15Ni7.5Ti1 SMA (7.1 × 10−2 J mol−1, 6.3 × 10−6 m s−1). In addition, when the applied strain was up to 10%, the maximum superelastic strain of Fe42Mn34Al15Ni7.5Ti1.5 and Fe42.5Mn34Al15Ni7.5Ti1 were 5.5% and 5.1%, respectively. In summary, the addition of 1.5 at.% Ti in Fe–Mn–Al–Ni–Ti SMA can promote the AGG with relatively small loss in superelasticity.

Data-Driven Design of Nickel-Free Superelastic Titanium Alloys.

In this paper, a CatBoost model for predicting superelastic strains of alloys was established by utilizing features construction and selection as well as model filtering and evaluation based on 125 existing data points of superelastic titanium alloys. The alloy compositions of a TiNbMoZrSnTa system were optimized and three nickel-free titanium alloys with potentially excellent superelastic properties were designed using the Bayesian optimization algorithm using a superelastic strain as the optimization target. The experimental results indicated that only Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn exhibited clear superelasticity due to the absence of relevant information about the alloys' β stability in the machine learning model. Through experimental optimization of the heat treatment regimens, Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn ultimately achieved recovery strains of 4.65% after being heat treated at 853 K for 10 min and 3.01% after being heat treated at 1073 K for 30 min, respectively. The CatBoost model in this paper possessed a certain ability to design nickel-free superelastic titanium alloys but it was still necessary to combine it with existing knowledge of material theory for effective utilization.

Effect of Mo addition on the microstructure and superelastic properties of Fe-Mn-Al-Ni alloy

This study systematically investigated the effect of Mo addition on the microstructure and superelasticity of Fe-Mn-Al-Ni alloy. The findings indicate that the addition of Mo element efficaciously suppressed the formation of γ phase after air cooling. Single crystal samples were prepared through cyclic heat treatment. The size of the precipitates in the solid-solution single crystal was found to be ∼ 12.90 nm. In contrast, the mean precipitates size in the aging single crystal was ∼ 18.07 nm. An excellent superelasticity with an average recoverable strain of ∼ 8 % at an applied strain of ∼ 9.5 % can be obtained in both the solid solution and aging single crystals with a near [-412] orientation. The Mo addition widens the size range of precipitates with good superelasticity up to ∼ 18 nm. Additionally, there is a significant difference in the superelastic performance of single crystals with different orientations. Superelastic strain values for orientated single crystals near [-412], [1-20] and [‐14‐3] were 5.5 %, 4.8 % and 4.4 %, respectively.

Microstructures, transformation temperatures and superelastic properties of the rapidly solidified (TiZrHf)50Ni25Co10Cu15 HESMAs

In this study, the effects of the rapid solidification process on microstructures, transformation behaviors and superelastic properties of the multi-component (TiZrHf)50Ni25Co10Cu15 (at%) high-entropy shape memory alloy (HESMA) were investigated. The as-spun (TiZrHf)50Ni25Co10Cu15 fibers were prepared by a rapid solidification process. The solution-treated (TiZrHf)50Ni25Co10Cu15 alloy bulk specimen consisted of a (NiCoCu)-rich matrix, (TiZrHf)2(NiCoCu)-type phase and carbide, while the as-spun fiber specimen consisted of (TiZrHf)-rich matrix and carbide. The (TiZrHf)2(NiCoCu)-type phase is dissolved in the matrix of as-spun fibers due to the rapid solidification process. The martensitic transformation start temperature of the (TiZrHf)50Ni25Co10Cu15 alloy increased from 53.5 °C to 91.5 °C after the rapid solidification process. Both the (TiZrHf)50Ni25Co10Cu15 alloy bulk and fiber specimens showed clear superelasticity and the total superelastic recovery strain increased from 4.6 % to 5.7% after the rapid solidification process.

Mechanical and Magnetic Properties of Porous Ni50Mn28Ga22 Shape Memory Alloy

A porous Ni50Mn28Ga22 alloy was produced using powder metallurgy, with NaCl serving as the pore-forming agent. The phase structure, mechanical properties, and magnetic properties of annealed bulk alloys and porous alloys with different pore sizes were analyzed. Vacuum sintering for mixed green billets in a tube furnace was employed, which facilitated the direct evaporation of NaCl, resulting in the formation of porous alloys characterized by a complete sinter neck, uniform pore distribution, and consistent pore size. The study found that porous alloys within this size range exhibit a recoverable shape memory performance of 3.5%, as well as a notable decrease in the critical stress required for martensitic twin shear when compared to that of bulk alloys. Additionally, porous alloys demonstrated a 2% superelastic strain when exposed to 353 K. Notably, under a 1.5 T magnetic field, the porous Ni50Mn28Ga22 alloy with a pore size ranging from 20 to 30 μm exhibited a peak saturation magnetization of 62.60 emu/g and a maximum magnetic entropy of 1.93 J/kg·K.

Effects of Cr on the abnormal grain growth of Cu-Al-Mn-Ni-Cr superelastic alloy

Composition design is one of the effective methods to promote abnormal grain growth (AGG) behavior. In this study, a series of CuAlMnNi-Crx (x = 0, 0.5 and 1 at%) alloys are designed to study the effects of Cr on the AGG behavior during the cyclic heat treatments (CHTs) of CuAlMnNiCr alloy. The results indicate that adding 0.5% Cr can promote the AGG behavior, in which the average grain size of the (Cu71.6Al17Mn11.4)97.5Ni2.0Cr0.5 (0.5Cr) is about 1.5 times of that for (Cu71.6Al17Mn11.4)98.0Ni2 (0Cr) after 2 CHTs. Remarkably, the activation energy of grain boundary migration (Q) of 0.5Cr (= 90 kJ/mol) is similar to that of 0Cr (= 91 kJ/mol), while the subgrain boundary energy (ΔGs) of 0.5Cr (= 6.9×10−2 J/mol) is significantly higher than that of 0Cr (= 4.7×10−2 J/mol). The higher subgrain misorientation of 0.5Cr (= 1.25°), as compared with that of 0Cr (= 0.72°) is the main reason. Thus, tuning Cr content can promote the AGG behavior of the CuAlMnNiCr alloy, through controlling the subgrain misorientation. Moreover, a maximum of 13.0% superelastic strain is obtained after adding 0.5% Cr.

The Influences of Element Addition on Compression Properties of β-Ti-Mo (Nb)-based Alloys

The influences of the third element addition on the compression properties of Ti-12Mo-based and Ti-33Nb-based alloys was investigated, with emphasis on the influences of element addition on Young’s modulus, superelastic strain and yield strength of water-cooling samples. It is found that the water-cooling Ti-12Mo alloy has a lower modulus, lower yield strength, and higher hyperelastic strain than that of the furnace-cooled alloy of the same composition. Al and Sn can reduce the modulus and the yield strength, and increase the superelastic strain in the above two water-cooling alloys. The decrease in yield strength and modulus is due to orthogonal martensite ɑ’. The enhancement of the superelastic strain originated from the phase transformation of the ɑ”↔βM under stress. The effect of Sn in water-cooling quaternaryTi-18Nb-5Mo-5Sn alloy is different from the above two ternary alloys, and it increases β Phase stability and volume in water-cooling Ti-18Nb-5Mo-5Sn alloy.

Effect of nanoparticles on mechanical properties in composite coated materials enhanced by metal nanoparticles

The development of modern high-tech urgently needs high-performance materials with low elastic modulus, high yield strength, and large elastic strain performance. However, traditional metal materials lack the characteristics of combining the advantages of these high-performance materials. The metal nanoparticles, with super large elastic strain and ultra-high yield strength, enhance the incomparable superior performance of traditional single materials and have a wide application prospect in many modern high-tech industries. In addition, the nanoparticles will reunite in the collective, which has a certain impact on the mechanical properties of the composite coating materials. Several metal nanoparticles were selected as reinforcing materials and epoxy resin polymer as a matrix material to explore and analyze the influence of nanoparticles in the composite coating materials of metal nanoparticles. The hydrothermal method was used to enhance the properties of the epoxy resin polymer, disperse the epoxy resin, make the Huangyang resin composite coating, and study the effect of nanometer content on the mechanical properties of the composite coating. According to the research results, the appropriate amount of nanometers can optimize the performance of the coating of epoxy resin. When the number of nanoparticles added is 0.05%, the mechanical properties of the coating reach the best.

Ultra-high resolution, multi-scenario, super-elastic inductive strain sensors based on liquid metal for the wireless monitoring of human movement

The paper presents a new liquid metal putty strain sensor that can measure strains from 0.05% to 300%. A wireless motion monitoring system is developed based on this sensor, which is expected to be used for health and motion tracking.

Inverse gradient nanostructure through gradient cold rolling demonstrated with superelasticity improvement in Ti-50.3Ni shape memory alloy

Gradient nanostructured (GNS) metallic materials are commonly achieved by gradient severe plastic deformation with a gradient of nano- to micro-sized structural units from the surface/boundaries to the center. Certainly, such GNS can be inversely positioned, which however has not yet been reported.The present work reports a facile method in deformation gradient control to attain inverse gradient nanostructured (iGNS), i.e., tailoring the cross-section shape, successfully demonstrated in Ti-50.3Ni shape memory alloy (SMA) wire through cold rolling. The microstructure of the rolled wire is characterized by a macroscopic inverse gradient from boundaries to the center—the average sizes of grain and martensite domain evolve from micrometer to nanometer scale. The iGNS leads to a gradient martensitic transformation upon stress, which has been proved to be effectively reversible via in-situ bending scanning electron microscopy (SEM) observations. The iGNS Ti-50.3Ni SMA exhibits quasi-linear superelasticity (SE) in a wide temperature range from 173 to 423 K. Compared to uniform cold rolling, the gradient cold rolling with less overall plasticity further improves SE strain (up to 4.8 %) and SE efficiency. In-situ tensiling synchrotron X-ray diffraction (SXRD) analysis reveals the underlying mechanisms of the unique SE in the iGNS SMAs. It provides a new design strategy to realize excellent SE in SMAs and sheds light on the advanced GNS metallic materials.

Achieving superelastic shape recoverability in smart flexible CuAlMn metamaterials via 3D printing

Despite the remarkable advancements in the additive manufacturing of metamaterials, tradeoffs remain between functionality and mechanical performance owning to static configuration, which limits their application, particularly in areas that require efficient multifunctionality. In this paper, we present a novel approach for fabricating multifunctional smart flexible metal metamaterials using laser powder bed fusion technology. This approach enables the reversible recovery superelastic strain exceeding 20 % with a 100 % recovery rate—ten times higher than that observed in the printed alloy. This is achieved by utilising an innovative metamaterial structural design and a novel shape memory alloy powder. To achieve the aforementioned purpose, the metamaterial unit cells were initially designed to ensure flexible deformation ability with a Poisson's ratio of zero. Then, we prepared a novel shape memory alloy composition of Cu-18at%Al-l0at%Mn-0.3 at%Si, which exhibited excellent printability and adaptability within the laser powder bed fusion additive manufacturing process. Additionally, the printed SMA exhibited superelasticity, one-way and two-way shape memory effect under varying parameters. Furthermore, the combination of multifunctionality into the flexible CuAlMn metamaterials was achieved by manipulating process parameters. Remarkably, the printed metamaterial demonstrates exceptional flexibility deformation, and presents superelasticity or shape memory effect, ensuring the recovery of its original shape after experiencing deformation. This work not only demonstrates the vast potential of utilising additive manufacturing technology for fabricating functional and adaptable metal metamaterials but also presents an innovative approach for creating smart metal metamaterial.

Effect of low and high temperature ECAP modes on the microstructure, mechanical properties and functional fatigue behavior of Ti-Zr-Nb alloy for biomedical applications

A Ti-18Zr-15Nb (at%) shape memory alloy was subjected to a high-temperature thermomechanical treatment (HTMT) combining an equal channel angular pressing (ECAP) at 500 °C for n = 4–8 passes and a short-time post-deformation annealing (PDA) at 600 °C. The phase composition, microstructure, texture, mechanical and functional properties were studied. The functional fatigue behavior observed in this study was compared to that resulted from the reference low-temperature thermomechanical treatment (LTMT) by ECAP at 200 °C for 3 passes + PDA (600 °C for 5 min). The ECAP at 500 °C (n = 4) led to the formation of a highly deformed, dynamically polygonised substructure of β-phase with a crystallographic texture close to the [101] direction. In this state, the alloy exhibited an excellent combination of the static functional and mechanical properties: a relatively high strength (UTS = 670 MPa), a sufficient ductility (δ = 13.3 %), a low Young’s modulus (E < 40 GPa), and a high superelastic recovery strain (εrsemax= 3.1 %). An increase in the number of passes during ECAP to n = 8 led to a greater substructural hardening of the material, grain/subgrain refinement, and the release of α-phase. This significantly increased the alloy strength (UTS = 897 MPa), but reduced its ductility (δ = 5.9 %) and suppressed martensitic transformation. The alloy after both the HTMT (ECAP at 500 °C, n = 4) and TMT (ECAP at 200 °C, n = 3) processes exhibited an equally excellent functional fatigue resistance accompanied by a superior superelastic behavior with small accumulated strains. However, the HTMT process appears to be more technologically advanced, as it eliminates the need for PDA and reduces the risks of specimen cracking during processing.

Achieving near zero-hysteretic superelasticity in a Ni43Fe18Ga27Co12 single-crystalline microwire via Lüders-like phase transformation

Ni43Fe18Ga27Co12 single-crystalline microwires directly fabricated by the Taylor liquid drawing method show the nature of a strong first-order martensitic transformation under external stress or load-biased temperature cycling. By eliminating the nucleation energy barrier through localized plastic deformation, a fully recoverable superelastic strain approaching 11 % with negligible hysteresis is achieved in the course of tensile deformation. Based on in-situ synchrotron high-energy X-ray diffraction analysis, the mechanism of nearly non-hysteretic transformation is unraveled as a sharp, Lüders-like phase transformation. It is found that a single martensitic domain propagates continuously in a monolithic fashion under superelastic cycling with poor crystallographic compatibility of λ2 = 0.950 and small volume change of ∆V = -0.17 % accompanying martensitic transformation. We attributed such near zero-hysteretic transformation characteristics to combining conditions of low crystal defect density, high nucleation barriers but without continual nucleation events, flexibility of the microwire, and small volume change.