Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material ava...Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material available for the stress-induced transformation and,thus,lower the elastocaloric effect that originates from the stress-induced latent heat variations.In this study,the individual contributions of the micromechanisms responsible for the functional fatigue in superelastic NiTi at different maximum tensile stress(σ_(max))are critically examined.Results show that the elastocaloric effect degrades significantly with cycling,and the saturated degraded value increases with σ_(max);the steady-state adiabatic temperature change is unexpectedly non-proportional to σ_(max).An overheating treatment(‘healing’)after mechanical fatigue reverts the retained martensite into austenite,making it available for subsequent transformation and restoring the elastocaloric effect significantly.Such a restoration increases exponentially with σ_(max).Consequently,the steady-state elastocaloric effect of the healed NiTi is proportional to σ_(max) and can reach more than twice that of NiTi without healing.The work sheds light on the physical origins of elastocaloric degradation of superelastic NiTi and also provides a feasible method for ameliorating functional fatigue.展开更多
Co-V-Ga-based shape memory alloys have shown great potential in the field of solid-state elastocaloric refrigeration due to their low stress hysteresis(Δσ_(hys)) and excellent superelasticity.However,large applied s...Co-V-Ga-based shape memory alloys have shown great potential in the field of solid-state elastocaloric refrigeration due to their low stress hysteresis(Δσ_(hys)) and excellent superelasticity.However,large applied stress and low adiabatic temperature change(ΔT_(ad)) greatly limit the application of Co-V-Ga-based alloys as elastocaloric materials.Here,we have successfully achieved a breakthrough in material properties by innovatively introducing the co-doping strategy of Mn and Ti elements.It was found that the synergistic effect of Mn and Ti significantly enhanced the mechanical properties of the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy through solid solution strengthening,fine grain strengthening,and precipitation strengthening mechanisms.A large ΔT_(ad) of-11 K was obtained for the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) bulk poly crystalline alloy under a very low applied stress of 380 MPa.This is mainly due to the strong texture of <001>A.Texture strengthening is the key factor to improve the elastocaloric effect of alloys.At the same time,the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy still maintains a ΔT_(ad) of -4 K without an obvious attenuation trend after 350 elastocaloric cycles under the applied stress of 300 MPa.In addition,due to the low energy dissipation(ΔW),the energy conversion efficiency of the elastocaloric response is greatly improved,so that the coefficient of performance(COP) of the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy material is as high as 28.9,far exceeding most of the current shape memory alloy elastocaloric materials.As a result,the co-doping of Mn and Ti elements makes it possible to prepare an elastocaloric refrigeration alloy with low applied stress and a large elastocaloric effect.展开更多
Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large e...Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.展开更多
Functional stability of superelasticity is crucial for practical applications of shape memory alloys.It is degraded by a Lüders-like deformation with elevated local stress concentration under tensile load.By incr...Functional stability of superelasticity is crucial for practical applications of shape memory alloys.It is degraded by a Lüders-like deformation with elevated local stress concentration under tensile load.By increasing the degree of solute supersaturation and applying appropriate thermomechanical treatments,a Ti-Ni alloy with nanocrystallinity and dispersed nanoprecipitates is obtained.In contrast to conventional Ti-Ni alloys,the superelasticity in the target alloy is accompanied by homogeneous deformation due to the sluggish stress-induced martensitic transformation.The alloy thus shows a fully recoverable strain of 6%under tensile stress over 1 GPa and a large adiabatic temperature decrease of 13.1 K under tensile strain of 4.5%at room temperature.Moreover,both superelasticity and elastocaloric effect exhibit negligible degradation in response to applied strain of 4%during cycling.We attribute the improved functional stability to low dislocation activity resulting from the suppression of localized deformation and the combined strengthening effect of nanocrystalline structure and nanoprecipitates.Thus,the design of such a microstructure enabling homogeneous deformation provides a recipe for stable superelasticity and elastocaloric effect.展开更多
We demonstrate giant elastocaloric effect and outstanding refrigeration capacity in a <0 0 1>A textured Ni_(50)Mn_(35)In_(13)Si_(2) alloy with large transformation entropy change △S_(tr) and low-hysteresis △T_...We demonstrate giant elastocaloric effect and outstanding refrigeration capacity in a <0 0 1>A textured Ni_(50)Mn_(35)In_(13)Si_(2) alloy with large transformation entropy change △S_(tr) and low-hysteresis △T_(hys). On unloading from a relatively low compressive stress of 300 MPa, giant adiabatic temperature variation △T_(ad) up to –17.7 K was realized. Moreover, large stress-induced entropy change △S_(σ) of 25.9 J kg^(–1)K^(–1) andgiant refrigeration capacity RC_(σ) of 1330 J kg^(–1) were achieved under the compressive stress of 300 MPa.Simultaneously achieving giant △T_(ad) and outstanding refrigeration capacity indicates that this alloy ispromising to be the candidate material for elastocaloric refrigeration.展开更多
The effects of Co and Fe co-doping Ni-Mn-In alloy on the phase stability,lattice parameters,mag-netic properties,and electronic structures are systematically investigated by using the first-principles calculations.Res...The effects of Co and Fe co-doping Ni-Mn-In alloy on the phase stability,lattice parameters,mag-netic properties,and electronic structures are systematically investigated by using the first-principles calculations.Results indicate that Fe atoms replace the excess Mn2 atoms by direct and indirect coex-istence(Fe→Mn 2 and Fe→In→Mn2);Co substitutes the Ni atoms by direct substitution(Co→Ni)for the Ni-Mn-In alloy.The austenites all exhibit the ferromagnetic(FM)state for the studied composi-tions.The NM martensites are in the ferrimagnetic(FIM-1)state for the Ni_(2)Mn_(1.5)In_(0.5),Ni_(2)Mn_(1.25)In_(0.5)Fe 0.25,Ni_(1.75)Mn_(1.5)In_(0.5)Co_(0.25),and Ni_(1.75)Mn_(1.25)In_(0.5)Co_(0.25)Fe 0.25 alloys,while the other compositions are in the FM state.The phase stability of austenite and martensite decreases with increasing Co and Fe co-doping.A magnetic-structural coupling transition occurs at x<0.25 and y<0.25.The Ni_(1.91)Mn_(1.5)In_(0.5)Co_(0.08)and Ni_(1.91)Mn_(1.42)In_(0.5)Co_(0.08)Fe_(0.08)alloys exhibit an A→6M→NM transformation,accompanied by a magnetic transition.When Co and Fe are co-doped,the hybridization strength between Co and Fe is greater than that between Co/Fe and Mn.The enhancement of magnetocaloric and elastocaloric effects is favored by larger magnetization difference(△M)and lattice volume change(△V/V_(0)).Based on the calculated phase stability,magneto-structure coupling,△V/V 0 and c/a ratio,one can predict that the Ni_(2)-x Mn_(1.5)-y In_(0.5)Co x Fe y alloy with Co content 0≤x≤0.25 and Fe content 0≤y≤0.05 is predicted to have good magneto-controlled functional behavior.展开更多
Solid-state cooling technologies have been considered as potential alternatives for vapor compression cooling systems.The search for refrigeration materials displaying a unique combination of pronounced caloric effect...Solid-state cooling technologies have been considered as potential alternatives for vapor compression cooling systems.The search for refrigeration materials displaying a unique combination of pronounced caloric effect,low hysteresis,and high reversibility on phase transformation was very active in recent years.Here,we achieved increase in the elastocaloric reversibility and decrease in the friction dissipation of martensite transformations in the superelastic nano-grained NiTi alloys obtained by cold rolling and annealing treatment,with very low stress hysteresis(6.3 MPa)under a large applied strain(5%).Large adiabatic temperature changes(△T_(max)=16.3 K atε=5%)and moderate COP_(mater)values(maximum COP_(mater)=11.8 atε=2%)were achieved.The present nano-grained NiTi alloys exhibited great potential for applications as a highly efficient elastocaloric material.展开更多
The NiTi shape memory alloy exhibits excellent superelastic property and elastocaloric effect. The large temperature change（DT） value of 30 K upon loading and-19 K upon unloading are obtained at room temperature, wh...The NiTi shape memory alloy exhibits excellent superelastic property and elastocaloric effect. The large temperature change（DT） value of 30 K upon loading and-19 K upon unloading are obtained at room temperature, which are higher than those of the other NiTi-based materials and among the highest values reported in the elastocaloric materials. The asymmetry of the measured DT values between the loading and unloading process is ascribed to the friction dissipation.The large temperature change originates from the large entropy change during the stress-induced martensite transformation（MT） and the reverse MT. A large coefficient-of-performance of the material is obtained to be 11.7 at ε= 1%, which decreases with increasing the applied strain. These results are very attractive in the present solid-state cooling, which potentially could replace the vapor compression refrigeration technologies.展开更多
Solid refrigeration technology based on the elastocaloric effect has a great potential alternative to the conventional vapor compression cooling. Here we report the large elastocaloric effect in Ti-Ni （50 at%） shape...Solid refrigeration technology based on the elastocaloric effect has a great potential alternative to the conventional vapor compression cooling. Here we report the large elastocaloric effect in Ti-Ni （50 at%） shape memory alloy below its austenite finish temperature Af under different strain. Both Maxwell＇s and Clausius-Clapeyron equations are used to estimate the entropy change. The strain-induced entropy change increases with raising the strain and gets a maximum value at a few kelvins below Af. The maximum entropy changes ASrnax are -20.44 and -53.70 J/kg.K, respectively for 1% and 2% strain changes. Large entropy change may be obtained down to 20 K below Af. The temperature of the maximum entropy change remains unchanged before the plastic deformation appears but moves towards low temperature when the plastic deformation happens.展开更多
<100>-,<112>-and <149>-oriented single crystals of Fe_(75.5)Ga_(24.5) alloy were prepared by optical float zone melting method.The pseudoelasticity behavior and elastocaloric effect of the single cry...<100>-,<112>-and <149>-oriented single crystals of Fe_(75.5)Ga_(24.5) alloy were prepared by optical float zone melting method.The pseudoelasticity behavior and elastocaloric effect of the single crystals were investigated,as well as the associate microstructures.D0_(3) phase structure was realized by solution treatment at 800 0C and annealed at 600℃ for 10 h.The compressive deformation behavior exhibits significant dependence on the crystalline directions.Excellent pseudoelasticity with recoverable strain up to 5% is obtained by compression along <149>direction.The pseudoelasticity disappears after five deformation cycles.Adiabatic temperature change is simultaneously detected during the pseudoelasticity,especially during loading process.展开更多
The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic t...The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic temperature change （ △ Tσ） at room temperature are carried out. The calculation results indicate that ｜△Tσ｜ increases as ｜σ33｜ or ｜μm｜ increases. The largest △ Tσ wlue of--7.81（ is obtained at σ33 = 2 GPa and Um =-0.02. Furthermore, the domain switching behaviors under different gradient coeffcients are different, and finally affect the elastocaloric effect in PTO thin films. These results could provide a guide to choose the substrate and the preparation process in experiments.展开更多
The singular change of the order parameter at the first order martensitic transformation(MT)temperature restricts the caloric response to a narrow temperature range.Here the MT is tuned into a sluggish strain glass tr...The singular change of the order parameter at the first order martensitic transformation(MT)temperature restricts the caloric response to a narrow temperature range.Here the MT is tuned into a sluggish strain glass transition by defect doping and a large elastocaloric effect appears in a wide temperature range.Moreover,an inverse elastocaloric effect is observed in the strain glass alloy with history of zerofield cooling and is attributed to the slow dynamics of the nanodomains in response to the external stress.This study offers a design recipe to expand the temperature range for good elastocaloric effect.展开更多
The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),...The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),thereby hindering the application of NiTi alloys in the refrigeration field.Here,NiTi alloys with alternating high-Ni and low-Ni content were fabricated by tailoring heat input during the wire-arc directed energy deposition(DED)process,which modifies the Ni concentration gradient and enables the modulation of the elastocaloric cooling performance of NiTi alloys.The coefficient of performance of material(COP_(mat))of the high-Ni NiTi alloy samples is relatively high,but theirΔT_(ad) during deformation is lower.On the other hand,the low-Ni NiTi alloy samples,while exhibiting higherΔT_(ad),show poorer stability during cycling.Due to the synergistic effect of the microstructures in the high-Ni and low-Ni region,a favorable combination of low cyclic hysteresis and highΔT_(ad) were achieved in the composite NiTi samples.Additionally,the composite NiTi samples also demonstrate excellent cyclic stability,with a degradation rate of only 4%during the cycling process under a 2%strain condition.This study proposes a feasible approach for regulating the elastocaloric effect of NiTi alloys,paving the way for additive manufacturing to prepare elastocaloric cooling materials.展开更多
A large adiabatic temperature change(△T_(ad))is a prerequisite for the application of elastocaloric refriger-ation.Theoretically,a large volume change ratio(△V/V_(0))during martensitic transformation is favorable to...A large adiabatic temperature change(△T_(ad))is a prerequisite for the application of elastocaloric refriger-ation.Theoretically,a large volume change ratio(△V/V_(0))during martensitic transformation is favorable to enhance△T_(ad).However,the design or prediction of△V/V_(0)in experiments is a complex task because the structure of martensite changes simultaneously when the lattice parameter of austenite is tuned by mod-ifying chemical composition.So far,the solid strategy to tailor△V/V_(0)is still urgently desirable.In this work,a first-principles-based method was proposed to estimate△V/V_(0)for Ni-Mn-based alloys.With this method,the substitution of Ga for In is found to be an effective method to increase the value of△V/V_(0)for Ni-Mn-In alloys.Combined with the strategies of reducing the negative contribution of magnetic en-tropy change(via the substitution of Cu for Mn)and introducing strong crystallographic texture(through directional solidification),an outstanding elastocaloric prototype alloy of Ni_(50)(Mn_(28.5)Cu_(4.5))(In_(14)Ga_(3))was fabricated experimentally.At room temperature,a huge△T_(ad)of-19 K and a large specific adiabatic temperature change of 67.8 K/GPa are obtained.The proposed first-principle-assisted framework opens up the possibility of efficiently tailoring△V/V_(0)to promote the design of advanced elastocaloric refrigerants.展开更多
1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7]...1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.展开更多
This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric mate...This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure.Elastocaloric materials include non-magnetic shape memory alloys,polymers,and rare-earth compounds.Barocaloric materials include magnetic shape memory alloys,ferroelectric ceramics,superionic conductors,and oxyfluorides.The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change.In addition to the thermal effects,other characteristics closely related to the application of mechanocaloric materials are also summarized.Finally,perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed.展开更多
Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts a...Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts as a key part of the elastocaloric refrigeration system contains a large elastocaloric effect,low stress hysteresis,high heat exchange performance,and small driving loads.The first two indices can be realized by material modification;however,the last two are more dependent on a novel porous structure design.However,the conventional porous structure is confronted with some critical challenges,including inhomogeneous stress,a significant hysteresis area,and deformation instability under the alternating cyclic loading.In this study,a NiTi-based elastocaloric structure model with chirality feature and gradient design as innovative elements was presented,bio-inspired by the structure of the plant tendrils.A quantitative optimization for the NiTi-based elastocaloric structure was performed using the finite element analysis(FEA)method.Strain and martensite volume fraction(MVF)fields during the loading and unloading processes were predicted and evaluated.The simulated results indicated that increasing the thickness gradient g_(1) of the strip or decreasing the diameter gradient g_(2) of the structure was beneficial to achieving more homogeneous strain and martensite distribution,simultaneously with higher energy storage efficiency and specific surface area.In addition,these NiTi-based chiral structures with different structural parameters were fabricated by laser powder bed fusion(LPBF).At the optimized structure parameters of g_(1)=2 and g_(2)=1.11,the LPBF-fabricated NiTi-based chiral structure could achieve an adiabatic temperature change ΔT_(ad) of 2.3 K,driving force of as low as 149.11 N,and|ΔT_(ad)/F|of as high as 15.42 K/kN at a recoverable compressive strain of 10%.展开更多
This article reviews the up-to-date progress in mechanocaloric effect and materials near ambient temperature. For elastocaloric materials, we focus on directly measured temperature change and its entropy origin in non...This article reviews the up-to-date progress in mechanocaloric effect and materials near ambient temperature. For elastocaloric materials, we focus on directly measured temperature change and its entropy origin in nonmagnetic and magnetic shape memory alloys. In terms of barocaloric materials, change in magnetic state, volume and shift of transition temperature due to hydrostatic pressure are systematically compared. We propose advantages and challenges of elastocaloric materials for solidstate cooling. Strategies to enhance elastocaloric and mechanical stability under long-term mechanical cycles are presented. Finally, we conclude with an outlook on the prospect of elastocaloric cooling application.展开更多
Thermal energy storage has been a pivotal technology to fill the gap between energy demands and energy supplies.As a solid-solid phase change material,shape-memory alloys(SMAs)have the inherent advantages of leakage f...Thermal energy storage has been a pivotal technology to fill the gap between energy demands and energy supplies.As a solid-solid phase change material,shape-memory alloys(SMAs)have the inherent advantages of leakage free,no encapsulation,negligible volume variation,as well as superior energy storage properties such as high thermal conductivity(compared with ice and paraffin)and volumetric energy density,making them excellent thermal energy storage materials.Considering these characteristics,the design of the shape-memory alloy based the cold thermal energy storage system for precooling car seat application is introduced in this paper based on the proposed shape-memory alloy-based cold thermal energy storage cycle.The simulation results show that the minimum temperature of the metal boss under the seat reaches 26.2°C at 9.85 s,which is reduced by 9.8°C,and the energy storage efficiency of the device is 66%.The influence of initial temperature,elastocaloric materials,and the shape-memory alloy geometry scheme on the performance of car seat cold thermal energy storage devices is also discussed.Since SMAs are both solid-state refrigerants and thermal energy storage materials,hopefully the proposed concept can promote the development of more promising shape-memory alloy-based cold and hot thermal energy storage devices.展开更多
基金financially supported by the Agency for Science,Technology and Research(A*STAR)of Singapore via the Structural Metal Alloys Programme(No.A18B1b0061).
文摘Functional fatigue in the superelastic NiTi shape memory alloys occurs due to the accumulation of dislocations and retention of martensite with the cyclic loading.These mechanisms reduce the amount of the material available for the stress-induced transformation and,thus,lower the elastocaloric effect that originates from the stress-induced latent heat variations.In this study,the individual contributions of the micromechanisms responsible for the functional fatigue in superelastic NiTi at different maximum tensile stress(σ_(max))are critically examined.Results show that the elastocaloric effect degrades significantly with cycling,and the saturated degraded value increases with σ_(max);the steady-state adiabatic temperature change is unexpectedly non-proportional to σ_(max).An overheating treatment(‘healing’)after mechanical fatigue reverts the retained martensite into austenite,making it available for subsequent transformation and restoring the elastocaloric effect significantly.Such a restoration increases exponentially with σ_(max).Consequently,the steady-state elastocaloric effect of the healed NiTi is proportional to σ_(max) and can reach more than twice that of NiTi without healing.The work sheds light on the physical origins of elastocaloric degradation of superelastic NiTi and also provides a feasible method for ameliorating functional fatigue.
基金financially supported by the National Natural Science Foundation of China(Nos.52271172 and 51971085)Heilongjiang Provincial Natural Science Foundation of China(No.LH2024E075)
文摘Co-V-Ga-based shape memory alloys have shown great potential in the field of solid-state elastocaloric refrigeration due to their low stress hysteresis(Δσ_(hys)) and excellent superelasticity.However,large applied stress and low adiabatic temperature change(ΔT_(ad)) greatly limit the application of Co-V-Ga-based alloys as elastocaloric materials.Here,we have successfully achieved a breakthrough in material properties by innovatively introducing the co-doping strategy of Mn and Ti elements.It was found that the synergistic effect of Mn and Ti significantly enhanced the mechanical properties of the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy through solid solution strengthening,fine grain strengthening,and precipitation strengthening mechanisms.A large ΔT_(ad) of-11 K was obtained for the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) bulk poly crystalline alloy under a very low applied stress of 380 MPa.This is mainly due to the strong texture of <001>A.Texture strengthening is the key factor to improve the elastocaloric effect of alloys.At the same time,the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy still maintains a ΔT_(ad) of -4 K without an obvious attenuation trend after 350 elastocaloric cycles under the applied stress of 300 MPa.In addition,due to the low energy dissipation(ΔW),the energy conversion efficiency of the elastocaloric response is greatly improved,so that the coefficient of performance(COP) of the Co_(52)V_(31)Ga_(14)Mn_(1)Ti_(2) alloy material is as high as 28.9,far exceeding most of the current shape memory alloy elastocaloric materials.As a result,the co-doping of Mn and Ti elements makes it possible to prepare an elastocaloric refrigeration alloy with low applied stress and a large elastocaloric effect.
基金supported by the National Natural Science Foundation of China(Nos.52261035,52201223,52371006,52371194)Applied Basic Projects of Yunnan province(No.202101BA070001-233).
文摘Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.
基金the support of National Key Research and Development Program of China(2021YFB3802104)National Natural Science Foundation of China(Grant Nos.51931004,52173228,52271190 and 51571156)the 111 project 2.0(BP2018008)。
文摘Functional stability of superelasticity is crucial for practical applications of shape memory alloys.It is degraded by a Lüders-like deformation with elevated local stress concentration under tensile load.By increasing the degree of solute supersaturation and applying appropriate thermomechanical treatments,a Ti-Ni alloy with nanocrystallinity and dispersed nanoprecipitates is obtained.In contrast to conventional Ti-Ni alloys,the superelasticity in the target alloy is accompanied by homogeneous deformation due to the sluggish stress-induced martensitic transformation.The alloy thus shows a fully recoverable strain of 6%under tensile stress over 1 GPa and a large adiabatic temperature decrease of 13.1 K under tensile strain of 4.5%at room temperature.Moreover,both superelasticity and elastocaloric effect exhibit negligible degradation in response to applied strain of 4%during cycling.We attribute the improved functional stability to low dislocation activity resulting from the suppression of localized deformation and the combined strengthening effect of nanocrystalline structure and nanoprecipitates.Thus,the design of such a microstructure enabling homogeneous deformation provides a recipe for stable superelasticity and elastocaloric effect.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51771048,52171005)the Liaoning Revitalization Talents Program(Nos.XLYC1907082,XLYC1907046,XLYC1802023).
文摘We demonstrate giant elastocaloric effect and outstanding refrigeration capacity in a <0 0 1>A textured Ni_(50)Mn_(35)In_(13)Si_(2) alloy with large transformation entropy change △S_(tr) and low-hysteresis △T_(hys). On unloading from a relatively low compressive stress of 300 MPa, giant adiabatic temperature variation △T_(ad) up to –17.7 K was realized. Moreover, large stress-induced entropy change △S_(σ) of 25.9 J kg^(–1)K^(–1) andgiant refrigeration capacity RC_(σ) of 1330 J kg^(–1) were achieved under the compressive stress of 300 MPa.Simultaneously achieving giant △T_(ad) and outstanding refrigeration capacity indicates that this alloy ispromising to be the candidate material for elastocaloric refrigeration.
基金supported by the National Natural Science Foundation of China(No.51771044)Natural Science Foun-dation of Hebei Province(No.E2019501061)+2 种基金the Fundamental Research Funds for the Central Universities(No.N2023027)Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project of China 2.0,No.BP0719037)the LiaoNing Revitalization Talents Program(No.XLYC1802023).
文摘The effects of Co and Fe co-doping Ni-Mn-In alloy on the phase stability,lattice parameters,mag-netic properties,and electronic structures are systematically investigated by using the first-principles calculations.Results indicate that Fe atoms replace the excess Mn2 atoms by direct and indirect coex-istence(Fe→Mn 2 and Fe→In→Mn2);Co substitutes the Ni atoms by direct substitution(Co→Ni)for the Ni-Mn-In alloy.The austenites all exhibit the ferromagnetic(FM)state for the studied composi-tions.The NM martensites are in the ferrimagnetic(FIM-1)state for the Ni_(2)Mn_(1.5)In_(0.5),Ni_(2)Mn_(1.25)In_(0.5)Fe 0.25,Ni_(1.75)Mn_(1.5)In_(0.5)Co_(0.25),and Ni_(1.75)Mn_(1.25)In_(0.5)Co_(0.25)Fe 0.25 alloys,while the other compositions are in the FM state.The phase stability of austenite and martensite decreases with increasing Co and Fe co-doping.A magnetic-structural coupling transition occurs at x<0.25 and y<0.25.The Ni_(1.91)Mn_(1.5)In_(0.5)Co_(0.08)and Ni_(1.91)Mn_(1.42)In_(0.5)Co_(0.08)Fe_(0.08)alloys exhibit an A→6M→NM transformation,accompanied by a magnetic transition.When Co and Fe are co-doped,the hybridization strength between Co and Fe is greater than that between Co/Fe and Mn.The enhancement of magnetocaloric and elastocaloric effects is favored by larger magnetization difference(△M)and lattice volume change(△V/V_(0)).Based on the calculated phase stability,magneto-structure coupling,△V/V 0 and c/a ratio,one can predict that the Ni_(2)-x Mn_(1.5)-y In_(0.5)Co x Fe y alloy with Co content 0≤x≤0.25 and Fe content 0≤y≤0.05 is predicted to have good magneto-controlled functional behavior.
基金Project supported by the Science Fund of the Key Laboratory of Cryogenic Science and Technology(Grant Nos.CRYO20230203 and CRYO202106)the National Natural Science Foundation of China(Grant Nos.51872299 and 52071223)the National Key Research and Development Program of China(Grant No.2019YFA0704904)。
文摘Solid-state cooling technologies have been considered as potential alternatives for vapor compression cooling systems.The search for refrigeration materials displaying a unique combination of pronounced caloric effect,low hysteresis,and high reversibility on phase transformation was very active in recent years.Here,we achieved increase in the elastocaloric reversibility and decrease in the friction dissipation of martensite transformations in the superelastic nano-grained NiTi alloys obtained by cold rolling and annealing treatment,with very low stress hysteresis(6.3 MPa)under a large applied strain(5%).Large adiabatic temperature changes(△T_(max)=16.3 K atε=5%)and moderate COP_(mater)values(maximum COP_(mater)=11.8 atε=2%)were achieved.The present nano-grained NiTi alloys exhibited great potential for applications as a highly efficient elastocaloric material.
基金Project supported by the Science Fund from the Key Laboratory of Cryogenics,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences(TIPC,CAS)(Grant Nos.CRYOQN201501 and CRYO201218)the National Natural Science Foundation of China(Grant Nos.51577185,51377156,and51408586)
文摘The NiTi shape memory alloy exhibits excellent superelastic property and elastocaloric effect. The large temperature change（DT） value of 30 K upon loading and-19 K upon unloading are obtained at room temperature, which are higher than those of the other NiTi-based materials and among the highest values reported in the elastocaloric materials. The asymmetry of the measured DT values between the loading and unloading process is ascribed to the friction dissipation.The large temperature change originates from the large entropy change during the stress-induced martensite transformation（MT） and the reverse MT. A large coefficient-of-performance of the material is obtained to be 11.7 at ε= 1%, which decreases with increasing the applied strain. These results are very attractive in the present solid-state cooling, which potentially could replace the vapor compression refrigeration technologies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51671192 and 51531008)the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘Solid refrigeration technology based on the elastocaloric effect has a great potential alternative to the conventional vapor compression cooling. Here we report the large elastocaloric effect in Ti-Ni （50 at%） shape memory alloy below its austenite finish temperature Af under different strain. Both Maxwell＇s and Clausius-Clapeyron equations are used to estimate the entropy change. The strain-induced entropy change increases with raising the strain and gets a maximum value at a few kelvins below Af. The maximum entropy changes ASrnax are -20.44 and -53.70 J/kg.K, respectively for 1% and 2% strain changes. Large entropy change may be obtained down to 20 K below Af. The temperature of the maximum entropy change remains unchanged before the plastic deformation appears but moves towards low temperature when the plastic deformation happens.
基金financially supported by the National Natural Science Foundations of China (Nos.51331001 and 51520105002)the Fundamental Research Funds for Central Universities。
文摘<100>-,<112>-and <149>-oriented single crystals of Fe_(75.5)Ga_(24.5) alloy were prepared by optical float zone melting method.The pseudoelasticity behavior and elastocaloric effect of the single crystals were investigated,as well as the associate microstructures.D0_(3) phase structure was realized by solution treatment at 800 0C and annealed at 600℃ for 10 h.The compressive deformation behavior exhibits significant dependence on the crystalline directions.Excellent pseudoelasticity with recoverable strain up to 5% is obtained by compression along <149>direction.The pseudoelasticity disappears after five deformation cycles.Adiabatic temperature change is simultaneously detected during the pseudoelasticity,especially during loading process.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11502078 and 11402222the General Project of Hunan Provincial Department of Education under Grant No 15C0535the Start-up Foundation of High-talent Research Project of Hunan University of Science and Technology under Grant No E51517
文摘The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic temperature change （ △ Tσ） at room temperature are carried out. The calculation results indicate that ｜△Tσ｜ increases as ｜σ33｜ or ｜μm｜ increases. The largest △ Tσ wlue of--7.81（ is obtained at σ33 = 2 GPa and Um =-0.02. Furthermore, the domain switching behaviors under different gradient coeffcients are different, and finally affect the elastocaloric effect in PTO thin films. These results could provide a guide to choose the substrate and the preparation process in experiments.
基金financially supported by the National Key Research and Development Program of China(No.2017YFB0702401)the National Natural Science Foundation of China(Nos.51671157,51571156,and 51931004)the 111 project 2.0(No.BP2018008)。
文摘The singular change of the order parameter at the first order martensitic transformation(MT)temperature restricts the caloric response to a narrow temperature range.Here the MT is tuned into a sluggish strain glass transition by defect doping and a large elastocaloric effect appears in a wide temperature range.Moreover,an inverse elastocaloric effect is observed in the strain glass alloy with history of zerofield cooling and is attributed to the slow dynamics of the nanodomains in response to the external stress.This study offers a design recipe to expand the temperature range for good elastocaloric effect.
基金financially supported by the National Natural Science Foundation of China(Nos.52275374 and 52205414)the Key Research and Development Projects of Shaanxi Province(No.2023-YBGY-361)+1 种基金the Xi’an Jiaotong University Basic Research Funds for Freedom of Exploration and Innovation-Student Programs(No.xzy022024099)the Taihu Lake Innovation Fund for the School of Future Technology of Xi’an Jiaotong University.
文摘The inherent hysteresis of NiTi alloy samples is one of the key factors limiting their elastocaloric cooling performance.However,reducing hysteresis often leads to a decrease in adiabatic temperature change(ΔT_(ad)),thereby hindering the application of NiTi alloys in the refrigeration field.Here,NiTi alloys with alternating high-Ni and low-Ni content were fabricated by tailoring heat input during the wire-arc directed energy deposition(DED)process,which modifies the Ni concentration gradient and enables the modulation of the elastocaloric cooling performance of NiTi alloys.The coefficient of performance of material(COP_(mat))of the high-Ni NiTi alloy samples is relatively high,but theirΔT_(ad) during deformation is lower.On the other hand,the low-Ni NiTi alloy samples,while exhibiting higherΔT_(ad),show poorer stability during cycling.Due to the synergistic effect of the microstructures in the high-Ni and low-Ni region,a favorable combination of low cyclic hysteresis and highΔT_(ad) were achieved in the composite NiTi samples.Additionally,the composite NiTi samples also demonstrate excellent cyclic stability,with a degradation rate of only 4%during the cycling process under a 2%strain condition.This study proposes a feasible approach for regulating the elastocaloric effect of NiTi alloys,paving the way for additive manufacturing to prepare elastocaloric cooling materials.
基金supported by the National Natural Science Foundation of China(Nos.51922026,51975111)the Fundamental Research Funds for the Central Universities(Nos.N2202015,N2230002,N2002021,N2105001)the 111 Project of China(Nos.BP0719037,B20029).
文摘A large adiabatic temperature change(△T_(ad))is a prerequisite for the application of elastocaloric refriger-ation.Theoretically,a large volume change ratio(△V/V_(0))during martensitic transformation is favorable to enhance△T_(ad).However,the design or prediction of△V/V_(0)in experiments is a complex task because the structure of martensite changes simultaneously when the lattice parameter of austenite is tuned by mod-ifying chemical composition.So far,the solid strategy to tailor△V/V_(0)is still urgently desirable.In this work,a first-principles-based method was proposed to estimate△V/V_(0)for Ni-Mn-based alloys.With this method,the substitution of Ga for In is found to be an effective method to increase the value of△V/V_(0)for Ni-Mn-In alloys.Combined with the strategies of reducing the negative contribution of magnetic en-tropy change(via the substitution of Cu for Mn)and introducing strong crystallographic texture(through directional solidification),an outstanding elastocaloric prototype alloy of Ni_(50)(Mn_(28.5)Cu_(4.5))(In_(14)Ga_(3))was fabricated experimentally.At room temperature,a huge△T_(ad)of-19 K and a large specific adiabatic temperature change of 67.8 K/GPa are obtained.The proposed first-principle-assisted framework opens up the possibility of efficiently tailoring△V/V_(0)to promote the design of advanced elastocaloric refrigerants.
基金supported by the National Key R&D Pro-gram of China(No.2022YFB3805701)National Natural Science Foundation of China(NSFC)(No.52371182,51701052,52192592,52192593)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2019QNRC001)the Heilongjiang Touyan Innovation Team Program.
文摘1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474280).
文摘This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure.Elastocaloric materials include non-magnetic shape memory alloys,polymers,and rare-earth compounds.Barocaloric materials include magnetic shape memory alloys,ferroelectric ceramics,superionic conductors,and oxyfluorides.The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change.In addition to the thermal effects,other characteristics closely related to the application of mechanocaloric materials are also summarized.Finally,perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed.
基金This work was supported by National Natural Science Foundation of China(Grant No.52105345)Jiangsu Provincial Key Research and Development plan of China(Grant No.BE2022069-2)Fundamental Research Funds for the Central Universities of China(Grant No.JUSRP122028).
文摘Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts as a key part of the elastocaloric refrigeration system contains a large elastocaloric effect,low stress hysteresis,high heat exchange performance,and small driving loads.The first two indices can be realized by material modification;however,the last two are more dependent on a novel porous structure design.However,the conventional porous structure is confronted with some critical challenges,including inhomogeneous stress,a significant hysteresis area,and deformation instability under the alternating cyclic loading.In this study,a NiTi-based elastocaloric structure model with chirality feature and gradient design as innovative elements was presented,bio-inspired by the structure of the plant tendrils.A quantitative optimization for the NiTi-based elastocaloric structure was performed using the finite element analysis(FEA)method.Strain and martensite volume fraction(MVF)fields during the loading and unloading processes were predicted and evaluated.The simulated results indicated that increasing the thickness gradient g_(1) of the strip or decreasing the diameter gradient g_(2) of the structure was beneficial to achieving more homogeneous strain and martensite distribution,simultaneously with higher energy storage efficiency and specific surface area.In addition,these NiTi-based chiral structures with different structural parameters were fabricated by laser powder bed fusion(LPBF).At the optimized structure parameters of g_(1)=2 and g_(2)=1.11,the LPBF-fabricated NiTi-based chiral structure could achieve an adiabatic temperature change ΔT_(ad) of 2.3 K,driving force of as low as 149.11 N,and|ΔT_(ad)/F|of as high as 15.42 K/kN at a recoverable compressive strain of 10%.
基金supported by the National Natural Science Foundation of China(51371184)Zhejiang Provincial Natural Science Foundation(LR14E010001)
文摘This article reviews the up-to-date progress in mechanocaloric effect and materials near ambient temperature. For elastocaloric materials, we focus on directly measured temperature change and its entropy origin in nonmagnetic and magnetic shape memory alloys. In terms of barocaloric materials, change in magnetic state, volume and shift of transition temperature due to hydrostatic pressure are systematically compared. We propose advantages and challenges of elastocaloric materials for solidstate cooling. Strategies to enhance elastocaloric and mechanical stability under long-term mechanical cycles are presented. Finally, we conclude with an outlook on the prospect of elastocaloric cooling application.
基金supported by the National Natural Science Foundation of China(Grant No.51976149)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No.2019QNRC001).
文摘Thermal energy storage has been a pivotal technology to fill the gap between energy demands and energy supplies.As a solid-solid phase change material,shape-memory alloys(SMAs)have the inherent advantages of leakage free,no encapsulation,negligible volume variation,as well as superior energy storage properties such as high thermal conductivity(compared with ice and paraffin)and volumetric energy density,making them excellent thermal energy storage materials.Considering these characteristics,the design of the shape-memory alloy based the cold thermal energy storage system for precooling car seat application is introduced in this paper based on the proposed shape-memory alloy-based cold thermal energy storage cycle.The simulation results show that the minimum temperature of the metal boss under the seat reaches 26.2°C at 9.85 s,which is reduced by 9.8°C,and the energy storage efficiency of the device is 66%.The influence of initial temperature,elastocaloric materials,and the shape-memory alloy geometry scheme on the performance of car seat cold thermal energy storage devices is also discussed.Since SMAs are both solid-state refrigerants and thermal energy storage materials,hopefully the proposed concept can promote the development of more promising shape-memory alloy-based cold and hot thermal energy storage devices.
