Addition Of HF Research Articles

Effects of Hf addition on the microstructure and properties of Cu-Sn-P alloy

In this paper, the effects of Hf addition on the mechanical properties, electrical conductivity and microstructure of Cu-Sn-P alloy were investigated. The results show that the Hf addition can enhance the mechanical properties and electrical conductivity of Cu-Sn-P alloy. The alloy with 0.05 wt.% Hf exhibits the best comprehensive performance with yield strength of 625 MPa, tensile strength of 661 MPa and electrical conductivity of 16.8 %IACS. Compared with the Cu-Sn-P alloy without Hf addition, the yield strength and tensile strength are increased by 8.4% and 7.8%, and the electrical conductivity is increased by 24.4%. The increase in the strength of Hf-added alloy can be attributed to the synergistic effect of multiple strengthening mechanisms, including fine grain strengthening, twin strengthening, dislocation strengthening, precipitation strengthening and Σ3n (n = 1, 2, 3) grain boundary strengthening. Moreover, the Hf-P precipitates can be observed in the Hf-added alloy. According to the amount of Hf addition, these precipitates can manifest as the fine HfP2 phase and the coarse HfP phase. The formation of Hf-P precipitates contributes to the precipitation strengthening and the purification of Cu matrix, thus contributing to the improvement of strength and conductivity.

Thermal atomic layer deposition-processed InHfZnO thin film transistors with excellent stability

In recent years, the downscaling of transistors has sparked considerable interest in the advancement of amorphous oxide semiconductors, particularly indium-hafnium-zinc oxide (IHZO) has remarkable potential in applications such as high-resolution displays and 3D NAND. For the first time, we propose the fabrication of IHZO thin film transistors (TFTs) via thermal atomic layer deposition (TH-ALD). The preparation, electrical properties, and stability of IHZO TFTs are investigated. The performance of TFT deposited at 250 °C and annealed in N2 atmosphere at 300 °C exhibits a high field-effect mobility (μ) of 22.53 cm2/Vs, a high Ion/Ioff of ∼107, a low threshold voltage (Vth) of 0.15 V, and a minimum subthreshold swing (SS) of 0.24 V/decade. Furthermore, the threshold voltage shifts (ΔVth) in TFTs annealed in N2 and O2 are 0.31 and 0.16 V, respectively. These enhancements are attributed to the defects suppression and remaining ionized oxygen vacancies result in increased electron concentration in N2-annealed films. In comparison, O2 annealing causes a reduction in field effect mobility but concurrently enhances stability due to the direct passivation of defects, which leads to fewer oxygen vacancies. Additionally, Hf content can also impact the performance of TFT devices, even a small addition of Hf also results in the effective reduction of the carrier concentration. These findings provide valuable insights into the device mechanism of IHZO TFTs, presenting a novel avenue for comprehending and augmenting their overall performance.

Dispersoid evolution in Al–Zn–Mg alloys by combined addition of Hf and Zr: A mechanistic approach

Coherent Al3X-type L12-structured dispersoids have the potential of effectively stabilizing the grain structure and increasing strength. This concept has been successfully demonstrated for non-hardenable and rapidly solidified Al alloys. In precipitation-hardened Al alloys, effective dispersoid addition requires both controlling their high-temperature stability and minimizing their impact on precipitation hardening. The current study focuses on dispersoid-modified AlZn5.0 Mg1.2 alloys, which exhibit MgZn precipitation upon age-hardening and include less than 1 wt% of Zr and Hf for dispersoid formation. Heat treatments between 350 °C and 500 °C for varying times were applied to evaluate dispersoid formation, thermal stability and the related strengthening potential. The microstructure was assessed using transmission electron microscopy (TEM) and atom probe tomography (APT), and the mechanical response was evaluated by hardness testing. TEM after heating at 500 °C reveals Ostwald ripening for the dispersoids. APT results on the dispersoids reveal a core–shell structure development upon longer annealing times. The Zr–Hf-modified alloy exhibits a higher initial strength than the Zr-modified alloy but the latter displays greater strength retention even after prolonged exposure to 500 °C. This effect is attributed to a destabilization of the mixed Zr–Hf dispersoids that arises from lower enthalpic benefits of Al3Hf formation over Al3Zr.

Prevention of hot cracking in Ni-based superalloy via passivation layer formation during additive manufacturing

We investigated the prevention of hot cracking in a non-weldable Ni-based superalloy by utilizing a passivation layer formed through laser-based directed energy deposition. The addition of Hf to the Ni-based superalloy facilitated the formation of a passivation layer consisting of Hf oxide on the surface of the as-deposited sample. An increase in the amount (thickness) of the passivation layers with increasing Hf content resulted in a reduction in hot cracking occurrence. Specifically, the addition of 2.5 wt% Hf led to the formation of uniformly distributed fine oxides without inducing hot cracks. This passivation layer effectively inhibited the formation of coarsened Mo oxides, which typically occur during oxidation in the liquid state and contribute to the hot cracking of Ni-based superalloy. During oxidation in the liquid state, Hf diffuses out to the surface and forms a passivation layer, thereby suppressing the formation and growth of oxides to sizes large enough to induce hot cracking.

Impact of Hf alloying on the functional properties of Ni-Mn-Ga high temperature shape memory alloys

The paper reports on the functional properties and microstructure of polycrystalline Ni-Mn-Ga-Hf high temperature shape memory alloys, in which different amounts of Hf up to 4 at.% are added in substitution of Mn and Ga, while the nominal Ni content is kept constant. The increase in the amount of Hf promotes a decrease in the valence electron concentration (e/a), tetragonality (c/a) of the martensitic unit cell, and martensitic transformation temperatures, as well as a significant decrease of the transformation hysteresis. The non-modulated tetragonal martensite, typical of Ni-Mn-Ga high temperature shape memory alloys, is formed in all the alloys studied here, though the alloy with 4 at.% of Hf also contains a small fraction of modulated 14M martensite. Hf addition improves the thermomechanical response of the alloys under compressive stress up to 300 MPa and leads to nearly closed cycles with minimal irrecoverable strain and low hysteresis (8 K) for the alloys with 3 and 4 at.% of Hf. These alloys also demonstrate excellent stability under repetitive thermal cycling and little change upon aging at 870 K. A second phase rich in Hf and Ni starts to precipitate at 1 at.% of Hf addition and its volume fraction experiences an abrupt and progressive increase for higher Hf contents. The structure of the second phase looks like the usual f.c.c. γ phase reported in other Ni-Mn-Ga-based alloys, but it has a double lattice parameter. Two structural models based on the A6 face-centered tetragonal unit cell with space group I4/mmm (No. 139), equivalent to the double f.c.c. lattice, are proposed for this new phase.

Effects of Hf and/or Ti addition on the morphology, crystal, and metal/oxide interface structures of nanoparticles in FeCrAl-ODS steels

FeCrAl oxide dispersion strengthened (ODS) steel is one of the most promising candidate cladding materials due to its exceptional properties. For 3.8Al–0.46Hf (Fe–15Cr–2W–3.8Al–0.46Hf–0.32Y2O3) and 3Al–0.1Ti–0.6Hf (Fe–15Cr–2W–3Al–0.1Ti–0.6Hf–0.35Y2O3) ODS steels, the morphologies of matrix grains & nanoparticles, and the crystal structures of oxides & metal/oxide interface structures were studied by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). For 3.8Al–0.46Hf and 3Al–0.1Ti–0.6Hf ODS steels, the mean grain size is 1.26 μm and 0.90 μm, respectively, and the dispersion morphology of nanoparticles in the latter is better than that of the former. Crystal & interface structures of 313 and 222 oxides in 3.8Al–0.46Hf and 3Al–0.13Ti–0.6Hf ODS steels were characterized, respectively. The proportions of Y–Hf–O and Y–Al–O particles in the former are 63.3 % and 29.1 %, respectively. However, the Y–Hf–O, Y–Al–O, and Y–Ti–O particles in the latter account for 74.8 %, 16.7 %, and 8.5 %, respectively. The much better dispersion morphology of oxides in 3Al–0.1Ti–0.6Hf ODS steel, relative to 3.8Al–0.46Hf ODS steel, is due to the much higher proportion of Y–Hf–O, the considerably lower proportion of Y–Al–O and the fairly high number fraction of Y–Ti–O. The study delved into the formation mechanisms of various oxides and the strengthening mechanisms in both ODS alloys.

Research on Microstructure, Mechanical Properties, and High-Temperature Stability of Hot-Rolled Tungsten Hafnium Alloy.

W-(0, 0.1, 0.3, 0.5) wt.% Hf (mass fraction, wt.%) materials were fabricated by the powder metallurgy method and hot rolling. The microstructure, mechanical properties, and high-temperature stability of alloys with varying compositions were systematically studied. The active element Hf can react with the impurity O segregated at the grain boundary to form fine dispersed HfO2 particles, refining the grains and purifies and strengthening the grain boundary. The average size of the sub-grains in the W-0.3 wt.% Hf alloy is 4.32 μm, and the number density of the in situ-formed second phase is 6.4 × 1017 m-3. The W-0.3 wt.% Hf alloy has excellent mechanical properties in all compositions of alloys. The ultimate tensile strength (UTS) is 1048 ± 17.02 MPa at 100 °C, the ductile fracture occurs at 150 °C, and the total elongation (TE) is 5.91 ± 0.41%. The UTS of the tensile test at 500 °C is 614 ± 7.55 MPa, and the elongation is as high as 43.77 ± 1.54%. However, more Hf addition will increase the size of the second-phase particles and reduce the number density of the second-phase particles, resulting in a decrease in the mechanical properties of the tungsten alloy. The isochronal annealing test shows that the recrystallization temperature of W-Hf alloy is 1400 °C, which is 200 °C higher than rolling pure tungsten.

Stabilized Hf-doped Ti/Sb-SnO2 electrode for efficient degradation of tetracycline.

The electrochemical advanced oxidation process (EAOP) has shown significant promise in the field of refractory organic wastewater treatment due to its high efficiency and environmentally friendly nature. In this study, Ti/Sb-SnO2 electrodes with varying proportions of Hf were prepared using the sol-gel method. The addition of Hf transformed the original collapsing and broken surface into a flat and regular surface. The results demonstrated that Ti/Sb-SnO2-Hf electrode doped with 6% Hf exhibited a higher oxygen evolution potential (OEP) and excellent stability. The OEP increased from 2.315 V without Hf-doping to 2.482 V, and the corresponding actual life was 321.05% higher than that without Hf. The current density (5-40 mA·cm-2), electrolyte concentration (0.02-0.2 mol·L-1), pH (3-11), and initial pollutant concentration (5-80 mg·L-1) were evaluated to confirm the tetracycline (TC) degradation characterization of Ti/Sb-SnO2-6%Hf electrodes. It was concluded that under the optimal degradation conditions, the removal rate of TC could reach 99.66% within 2 h. The degradation of TC follows first-order reaction kinetics. The oxidative degradation of TC was achieved through indirect oxidation, with ·OH playing a dominant role. TC's electrochemical oxidation degradation pathway has been proposed: Based on LC-MS results, three main pathways are speculated. During the electrocatalytic oxidation process, decarboxylation, deamidation, and ring-opening reactions occur under ·OH attack, producing intermediate compounds with m/z values of 427, 433, 350, 246, 461, 424, 330, 352, 309, 263, and 233. These intermediates are further oxidized to intermediate compounds with an m/z value of 218. This work introduces a new efficient anode electrochemical catalyst for the degradation of TC, providing a strategy for industrial applications.

Investigation of a novel laser powder bed fusion nickel-based superalloy with hf, Y addition: Melt characteristic, microstructure and mechanical properties

In order to resolve the inherent strength-ductility trade-off dilemma observed in precipitation-strengthened nickel-based superalloys with high Al and Ti content, a composition modification strategy was devised. This study explored a novel laser powder bed fusion (LPBF) René104 alloy by incorporating Hf and Y (HfY-René104), examining its melt characteristics, microstructures, and mechanical properties. The experimental results demonstrate that the addition of Hf and Y effectively improves the molten pool structure of the as-built, alters grain orientation, diminishes grain aspect ratio, promotes the formation of cellular structures, AlY phases, stacking faults (SFs), and Lomer-Cottrell (L-C) locks at macro, meso, and micro scales, respectively. The primary contributors to yield strength are grain boundary strengthening and dislocation strengthening. Moreover, a dynamic Hall-Petch effect associated with cellular structures, SFs, and L-C locks ultimately results in remarkable strength (yield strength of 823 MPa, ultimate tensile strength of 1158 MPa) and enhanced ductility (elongation of 24.6 %) of HfY-René104 alloy.

Effect of hafnium and molybdenum addition on inclusion characteristics in Co-based dual-phase high-entropy alloys

Specific grades of high-entropy alloys (HEAs) can provide opportunities for optimizing properties toward high-temperature applications. In this work, the Co-based HEA with a chemical composition of Co47.5Cr30Fe7.5Mn7.5Ni7.5 (at%) was chosen. The refractory metallic elements hafnium (Hf) and molybdenum (Mo) were added in small amounts (1.5at%) because of their well-known positive effects on high-temperature properties. Inclusion characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction method. The results revealed that the addition of Hf can reduce Al2O3 inclusions and lead to the formation of more stable Hf-rich inclusions as the main phase. Mo addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA melt. The calculated coagulation coefficient and collision rate of Al2O3 inclusions were higher than those of HfO2 inclusions, but the inclusion amount played a larger role in the agglomeration behavior of HfO2 and Al2O3 inclusions. The impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.

Comparison of multiple preservation and digestion methods for determination of tungsten concentrations in environmental media using ICP-MS

Tungsten is an emerging environmental pollutant. However, a proved robust method for preserving and determining the concentrations of tungsten in environmental media is still lacking. This study examined and compared the suitability of classic methods and previously reported tungsten-oriented methods on preserving dissolved tungsten and recovering tungsten from soil/sediment matrix. Tungsten concentrations in the water samples and digestates were then determined by inductively coupled plasma mass spectrometry. Our data showed that the tungsten-oriented HF and alkaline preservatives indeed successfully maintained the stability of dissolved tungsten. Even when preserved using HNO3 or HCl, dissolved tungsten concentrations did not notably change in most of our water samples over the course of ∼4 months. Using glass containers for storing water samples also did not produce much difference from using high-density polyethylene containers. Our data further suggested that the addition of HF in digestion was important for tungsten solubilization from soil/sediment matrix. The digestion methods with HNO3/HCl/HF and HNO3/HF/NH4OH/EDTA both yielded quantitative recoveries of tungsten from certified reference materials and known synthetic samples, while the other tested methods had limited recoveries. The methods validated by this study could be used to accurately determine tungsten concentrations in environmental media and thereby to assess the fate and potential risks of tungsten.

Influence of Hf Addition on the Superconducting Properties of Nb3Sn

Influence of Hf Addition on the Superconducting Properties of Nb₃Sn

Effect of HF and ER additions on the mechanical properties and microstructure of AL-MG-SC-ZR system alloys

Effect of HF and ER additions on the mechanical properties and microstructure of AL-MG-SC-ZR system alloys

Design and characterization of (TiZr)95-xHfxMo5 multi-principal element alloys with excellent properties for biomedical applications

Developing new bio-metallic materials with improved performance has attracted intensive research focus over the last decades. In the present work, a new series of (TiZr)95-xHfxMo5 (x = 0, 10, 15, 20, 25, 31.67) multi-principal elements alloys (MPEAs) have been designed for potential implant materials. The mechanical properties, deformation characteristics, tribological properties, corrosion resistance, and in vitro biocompatibility of the MPEAs were characterized. All the TiZrHfMo alloys possess a high yield strength (913–––1083 MPa) and tensile strength (931–––1118 MPa) and a large microhardness (296–––333 Hv). The addition of Hf into the alloys induced severe lattice distortion, which increased the solid-solution strengthening effect. It also resulted in a finer grain size and led to excellent wear resistance. Meanwhile, the results showed that the dislocation glide mode transformed from planar slip to cross-slip and the transformation became apparent with the decrease of Hf. Also, the MPEAs showed a good corrosion resistance compared to CP-Ti, which was credited to the superior passivation films. The in vitro biocompatibility experiments displayed that the TiZrHfMo alloys exhibited high cell viability ratios, which were close to that of CP-Ti. The present work demonstrates the huge potential of TiZrHfMo MPEAs as implant material for biomedical applications.

Effect of Hf addition on structural transformation and aging stability of Cu–15Ni–8Sn alloy

The Cu–15Ni–8Sn-xHf (wt.%, x = 0–0.6) alloys were prepared by vacuum melting, and the effect of Hf on the micro-structure of as-cast, as-solution-treated and as-aged alloys was systematically investigated, as well as the alloy aging stability. The Hf addition provided a significant role on refining the solidification structure and reducing the micro-segregation degree, and it also made γ-D03 phases more likely to form in needlelike-shape rather than lamellar-shape. With the presence of more Hf atoms, their existence form was accordingly changed from solid solute atoms to nano-scale precipitation phases and then to micron-scale segregation phase. A small content of Hf (0.1 wt%) could effectively improve the aging stability by inhibiting the growth of γ-D03. Once its content reached or exceeded 0.3 wt%, the harmful discontinuous precipitation was completely inhibited, and the common lamellar-shape γ-D03 locating around the grain boundary was no longer formed. Even the alloy failed at higher temperatures, it could only be carried out through the continuous precipitation method, namely the generation of needlelike-shape γ-D03 uniformly in the matrix. The appropriate Hf addition was capable of extending the alloy aging window, and the hardness of Cu–15Ni–8Sn-0.3Hf alloy could still exceed 360 HV even after 48 h aging.

Modification of the Ni-Rich Layered Cathode Material by Hf Addition: Synergistic Microstructural Engineering and Surface Stabilization.

The rapid decline of the reversible capacity originating from microcracks and surface structural degradation during cycling is still a serious obstacle to the practical utilization of Ni-rich LiNixCoyAl1-x-yO2 (x ≥ 0.8) cathode materials. In this research, a feasible Hf-doping method is proposed to improve the electrochemical performance of LiNi0.9Co0.08Al0.02O2 (NCA90) through microstructural optimization and structural enhancement. The addition of Hf refines the primary particles of NCA90 and develops them into a short rod shape, making them densely arranged along the radial direction, which increases the secondary particle toughness and reduces their internal porosity. Moreover, Hf-doping stabilizes the layered structure and suppresses the side reactions through the introduction of robust Hf-O bonding. Multiple advantages of Hf-doping allowed significant improvement of the cycling stability of LiNi0.895Co0.08Al0.02Hf0.005O2 (NCA90-Hf0.5), with a reversible capacity retention rate of 95.3% after 100 cycles at 1 C, as compared with only 82.0% for the pristine NCA90. The proposed synergetic strategy combining microstructural engineering and crystal structure enhancement can effectively resolve the inherent capacity fading of Ni-rich layered cathodes, promoting their practical application for next-generation lithium-ion batteries.

Brownification in the Eastern Mediterranean Sea: effect of simulated terrestrial input on the planktonic microbial food web in an oligotrophic sea

Terrestrial input to marine and freshwater ecosystems colors the water yellow-brown, causing a phenomenon called “brownification”. The effect of brownification on the marine pelagic microbial food web was studied in the oligotrophic eastern Mediterranean in June 2021 by adding HuminFeed in a 15-day mesocosm experiment with 2 treatments: Control (C, no addition) and HuminFeed (HF, single dose of HuminFeed, 2 mg L-1); and 3 replicates per treatment. HuminFeed caused shading, leading to a decrease in the abundance of photo-autotrophic organisms (cyanobacteria Synechococcus and diatoms). Bacteria were positively affected by the HF addition (mainly in terms of production rather than abundance), benefiting either directly from the dissolved organic carbon (DOC) contained in HuminFeed or indirectly from the trophic cascade through the food web. Despite the decrease in HF bacterial abundance during the experiment, an increase in both the high nucleic acid containing bacteria% and heterotrophic bacterial production were observed, suggesting higher activity at the single cell level. In the HF treatment, the increased abundance of dinoflagellates observed could be due to either a dominance of mixotrophic species or a release from predation by copepods. Both ciliates and copepods were severely impacted by HuminFeed, showing lower abundance and distorted forms (ciliates) and reduced reproductive potential (copepods). In conclusion, in the ultraoligotrophic eastern Mediterranean, the simulated brownification negatively affected autotrophs and top predators while benefiting bacteria, thus indicating a shift in the structure of the plankton food web.

A First-Principles Study of Mechanical and Electronic Properties of Cr0.5-xAl0.5TMxN Hard Coatings (TM = Ti, V, Y, Zr, Hf, and Ta).

The structural, mechanical, and electronic properties of cubic Cr0.5-xAl0.5TMxN, doped with TM (transition metal) elements (TM = Ti, V, Y, Zr, Hf, and Ta) at low concentrations (x = 0.03 and 0.06), was investigated by first-principles calculations. The results of the structural properties calculations reveal that the addition of Ti, Y, Hf, Zr, and Ta expand the volume, while V has the opposite effect. All doped compounds are thermodynamically stable, and Cr0.5-xAl0.5TMxN with TM = Ti is energetically more favorable than other doped compounds. At the same doping concentration, Cr0.5-xAl0.5VxN possesses the highest stiffness, hardness, and resistance to external forces due to its greatest mechanical properties, and Cr0.5-xAl0.5TaxN possesses the highest elastic anisotropy and the lowest Young's modulus. Substituting Cr atoms with TM atoms in a stepwise manner results in a decrease in the bulk modulus, shear modulus, Young's modulus, and theoretical hardness of Cr0.5-xAl0.5TMxN, while increasing its toughness. Based on the calculation results of the total and partial density of states of Cr0.5Al0.5N and Cr0.47Al0.5TM0.03N, all compounds exhibit metallic behavior as indicated by the finite density of states at the Fermi level. The contribution of Ti-3d, V-3d, and Ta-3d orbitals at Fermi level is significantly higher than that of other TM atoms, resulting in a more pronounced metallic character for Cr0.47Al0.5Ti0.03N, Cr0.47Al0.5V0.03N, and Cr0.47Al0.5Ta0.03N.

In-depth S/TEM observation of Ti–Hf and Ta–Hf-doped Nb3Sn layers

In superconducting Nb3Sn layers with coherence lengths of approximately 3 nm, grain boundaries act as effective pinning sites. Thus, grain refinement is an essential issue that directly affects the superconducting critical characteristics of the Nb3Sn layer. In recent years, Hf addition to Nb3Sn wires co-doped with Ta has attracted notable interest as a method that enables grain refinement down to several tens of nm. In-depth characterization of the Nb3Sn grain morphology in Hf-doping is crucially important to correlate the microstructure with the flux pinning characteristics. In this article, the grain morphologies of Ti–Hf and Ta–Hf-doped Nb3Sn layers were clarified by scanning transmission electron microscopy (STEM) and TEM-based automated crystal orientation mapping (ACOM-TEM). STEM/energy dispersive x-ray spectroscopy (EDS) revealed no significant oxide precipitates in our samples. The grain size distribution was attained by ACOM-TEM. Although Hf-doping attained a grain refinement effect in the Nb3Sn layer in both doping cases, the degree of this effect was relatively small for Ti–Hf. Kernel average misorientation analysis by scanning electron microscopy-electron backscattered diffraction unveiled no appreciable difference between the internal strain states of the Nb-alloy parent phases in Ti–Hf and Ta–Hf. One remarkable new finding through STEM/EDS was the presence of a Cu–Hf compound phase in the Nb3Sn layer. The Cu–Hf compound sounds analogous to the Cu–Ti compounds that form when Nb–47Ti with Cu matrix is heat treated. The STEM/EDS maps revealed a larger amount of Cu flow from the Cu–Sn side along the grain boundaries. The large Cu deposition on the grain boundaries might facilitate grain growth in Nb3Sn. Those findings make a novel contribution to the literature as they provide a deep insight into Nb3Sn phase formation via Hf doping.

The effect of Hf on the microstructure, transformation temperature, and the shape memory properties of Zr–Cu-based high-entropy shape memory alloys

The microstructures, phase transformation temperatures, and shape memory properties of Hf-modified Zr50−xHfxCu25Ni7.5Co17.5 and Zr50−xHfxCu25Ni10Co15 high-entropy shape memory alloys (SMAs) were investigated. Hf additions can alter the valence electron concentration, strengthen the alloy matrix, and introduce more secondary phase particles, which significantly influence the properties of the alloys. The results reveal that high austenitic transformation temperature (over 600 K) with very small thermal hysteresis (70–80 K) can be achieved by tailoring the Hf contents, and the best shape memory recovery strain (up to 2.44%) compared with other Zr–Cu-based SMAs could be obtained in Zr42Hf8Cu25Ni10Co15 alloy. This study demonstrated that high-performance Zr–Cu-based high-entropy SMAs can be realized by incorporating Hf additions.