Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic mod...Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic modulus makes Elinvar alloys highly desirable in precision-control applications,including aerospace,electronics,and optical instruments.Currently,most of the used and studied Elinvar alloys are ferromagnetic alloys(FeNi and Fe-Pt)and antiferromagnetic alloys(Fe-Mn and γ-MnCu)[2–4].The Elinvar effect in these alloys typically originates from magnetostriction or magnetoelastic effects,which are magnetic fieldor magnetic transition-dependent[5].Consequently,these Elinvar alloys cannot function properly in the presence of a magnetic field owing to their Elinvar effect being closely tied to magnetic phase transition.Therefore,developing non-magneticdependent Elinvar alloys is highly essential to widen their practical applications.展开更多
Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been fr...Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been frequently reported in HEAs,however,nanoscale microstructural phase evolution has not been investigated to the same extent.Herein,we have prepared the Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA and investi-gated the strain glass transition and its associated properties using dynamic mechanical analysis and mi-crostructure characterization.We have found that the elastic modulus in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA deviates from Wachtman’s equation and observed the Elinvar effect in the form of temperature-independent mod-ulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 K.The strain glass transition has been evidenced in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy(TEM)cooling,and substantiated by the broken ergodicity during zero-field-cooling/field-cooling.The strain glass transition is believed to account for the Elinvar effect,where the modulus hardening of nano-sized domains compensates dynam-ically with the modulus softening of the transformable matrix.展开更多
Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic tran...Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic transformation of shape memory alloys via plastic deformation.However,these reversible mechanisms are restricted generally in a narrow temperature range of less than 300 K.Here reports,by tuning a spinodal decomposition in a Ti-Nb-based titanium alloy via aging treatment,both the Elinvar effect in a wide temperature range of about 500 K and a high strength-to-modulus ratio of about 1.5%can be obtained by a continuous and reversible crystal ordering mechanism.The results demonstrate that the alloy aged at 723 K for 4 h has a nanoscale plate-like modulatedβ+α"two-phase microstructure and its elastic modulus keeps almost constant from 100 to 600 K.Synchrotron and in-situ X-ray diffraction measurements reveal that the crystal ordering parameter of theα"phase increases linearly with temper-ature from 0.88 at 133 K to 0.97 at 523 K but its volume fraction keeps a constant of about 33.8%.This suggests that the continuous ordering of theα"phase toward the high modulusαphase induces a posi-tive modulus-temperature relation to balance the negative relation of the elastically stableβphase.The aged alloy exhibits a high yield strength of 1200 MPa,good ductility of 16%and a high elastic admissible strain of 1.5%.Our results provide a novel strategy to extend the Elinvar temperature range and enhance the strength by tuning the crystal ordering of decomposition alloys.展开更多
The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Ti and Al during isothermal aging at 700℃ have been investigated by atom probe field ion microscopy and microhardness measureme...The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Ti and Al during isothermal aging at 700℃ have been investigated by atom probe field ion microscopy and microhardness measurements.The γ′ precipiates are spherical and coherent with the matrix.The chemical composition of the precipitates are(Ni_(0.53)Fe_(0.47)_3 (Ti_(0.(?))Al_(0.4)). During aging,a Lifshitz-Wagner type dissolution and coarsening reaction of the precipitates has been observed,The hardness of the material varies with the aging time and reaches maxi- mum when the average diameter of the precipitates was about 11 nm.展开更多
Super strength and toughness,excellent deformation resistance,and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings(TBCs).The limited mobil...Super strength and toughness,excellent deformation resistance,and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings(TBCs).The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength–plasticity and the reduction of service performance.Introducing preexisting twin boundaries and stacking faults(SFs)or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics.However,due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature,the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs.In this paper,the deformation behavior of high configuration entropy Zr6Ta2O17 ceramics at 25 to 1,200°C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment.A remarkable Elinvar-like effect appears in the Zr_(6)Ta_(2)O_(17) ceramic.More interestingly,mechanical deformation dominates the severe lattice distortion(deformation twins,SFs)and the disorder–order transition of chemical order at the atomic scale,while temperature can further enhance the degree of lattice distortion and ordering of Zr6Ta2O17 ceramics.Furthermore,the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr6Ta2O17 ceramics.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52401161)the Natural Science Foundation of Sichuan Province for Young Scholars(No.24NSFSC6582)+3 种基金the Postdoctoral Fellowship Program of CPSF(No.GZC20231761)the National Natural Science Foundation of China(No.52271249)the Key Research and Development Program of Shaanxi(No.2023-YBGY-488)the Xi'an Talent Plan(No.XAYC240016).
文摘Elinvar alloys exhibit temperature-independent elastic modulus within a specific temperature range,known as the Elinvar effect,which was first observed in Fe-Ni alloys[1].The unique temperature-independent elastic modulus makes Elinvar alloys highly desirable in precision-control applications,including aerospace,electronics,and optical instruments.Currently,most of the used and studied Elinvar alloys are ferromagnetic alloys(FeNi and Fe-Pt)and antiferromagnetic alloys(Fe-Mn and γ-MnCu)[2–4].The Elinvar effect in these alloys typically originates from magnetostriction or magnetoelastic effects,which are magnetic fieldor magnetic transition-dependent[5].Consequently,these Elinvar alloys cannot function properly in the presence of a magnetic field owing to their Elinvar effect being closely tied to magnetic phase transition.Therefore,developing non-magneticdependent Elinvar alloys is highly essential to widen their practical applications.
基金supported by the National Key Research and De-velopment Program of China(No.2022YFB3800052)the National Natural Science Foundation of China(Nos.12002013,51971009,and 51831006)+1 种基金the Zhejiang Natural Science Foundation(No.LZ23E010004).H.L.Hou also acknowledges the support of the Fundamental Research Funds for the Central Universities(No.501LKQB2020105028)the Opening Fund of the State Key Lab-oratory of Nonlinear Mechanics.
文摘Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical mechanisms.Macroscopic martensitic phase tran-sition has been frequently reported in HEAs,however,nanoscale microstructural phase evolution has not been investigated to the same extent.Herein,we have prepared the Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA and investi-gated the strain glass transition and its associated properties using dynamic mechanical analysis and mi-crostructure characterization.We have found that the elastic modulus in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA deviates from Wachtman’s equation and observed the Elinvar effect in the form of temperature-independent mod-ulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 K.The strain glass transition has been evidenced in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy(TEM)cooling,and substantiated by the broken ergodicity during zero-field-cooling/field-cooling.The strain glass transition is believed to account for the Elinvar effect,where the modulus hardening of nano-sized domains compensates dynam-ically with the modulus softening of the transformable matrix.
基金supported by the National Natural Science Foundation of China (Nos.51771209 and 51901042)the Foun-dation 91960202 and CAS (No.QYZDJ-SSW-JSC031).
文摘Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic transformation of shape memory alloys via plastic deformation.However,these reversible mechanisms are restricted generally in a narrow temperature range of less than 300 K.Here reports,by tuning a spinodal decomposition in a Ti-Nb-based titanium alloy via aging treatment,both the Elinvar effect in a wide temperature range of about 500 K and a high strength-to-modulus ratio of about 1.5%can be obtained by a continuous and reversible crystal ordering mechanism.The results demonstrate that the alloy aged at 723 K for 4 h has a nanoscale plate-like modulatedβ+α"two-phase microstructure and its elastic modulus keeps almost constant from 100 to 600 K.Synchrotron and in-situ X-ray diffraction measurements reveal that the crystal ordering parameter of theα"phase increases linearly with temper-ature from 0.88 at 133 K to 0.97 at 523 K but its volume fraction keeps a constant of about 33.8%.This suggests that the continuous ordering of theα"phase toward the high modulusαphase induces a posi-tive modulus-temperature relation to balance the negative relation of the elastically stableβphase.The aged alloy exhibits a high yield strength of 1200 MPa,good ductility of 16%and a high elastic admissible strain of 1.5%.Our results provide a novel strategy to extend the Elinvar temperature range and enhance the strength by tuning the crystal ordering of decomposition alloys.
文摘The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Ti and Al during isothermal aging at 700℃ have been investigated by atom probe field ion microscopy and microhardness measurements.The γ′ precipiates are spherical and coherent with the matrix.The chemical composition of the precipitates are(Ni_(0.53)Fe_(0.47)_3 (Ti_(0.(?))Al_(0.4)). During aging,a Lifshitz-Wagner type dissolution and coarsening reaction of the precipitates has been observed,The hardness of the material varies with the aging time and reaches maxi- mum when the average diameter of the precipitates was about 11 nm.
基金supported by the National Natural Science Foundation of China(grant no.12372102)the Science and Technology Innovation Program of Hunan Province(grant no.2022RC1082)+1 种基金the Scientific Research Foundation of Hunan Provincial Education Department(grant no.21A0120)Postgraduate Scientific Research Innovation Project of Hunan Province(grant nos.XDCX2021B139,CX20230551,and CX20220559).
文摘Super strength and toughness,excellent deformation resistance,and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings(TBCs).The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength–plasticity and the reduction of service performance.Introducing preexisting twin boundaries and stacking faults(SFs)or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics.However,due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature,the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs.In this paper,the deformation behavior of high configuration entropy Zr6Ta2O17 ceramics at 25 to 1,200°C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment.A remarkable Elinvar-like effect appears in the Zr_(6)Ta_(2)O_(17) ceramic.More interestingly,mechanical deformation dominates the severe lattice distortion(deformation twins,SFs)and the disorder–order transition of chemical order at the atomic scale,while temperature can further enhance the degree of lattice distortion and ordering of Zr6Ta2O17 ceramics.Furthermore,the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr6Ta2O17 ceramics.
