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The effects of site occupation on the phase stability, martensitic transformation, and the magnetic and electronic properties of a full series of Ni-Mn-In alloys are theoretically studied by using the ab initio calculations. Results indicate that the excess atoms of the rich component directly take the sublattices of the deficient components of the Ni2Mn1+xIn1-x, Ni2-xMn1+xIn, and Ni2+xMn1-xIn alloys. Nevertheless, the mixed and indirect site occupations may coexist in the Ni2+xMnIn1-x system. The relevant magnetic configurations of the austenite for the four alloy systems have also been determined. The results show that, except for the austenite in the Ni2-xMn1+xIn alloys, which tend to be ferrimagnetic, the other alloys all present ferromagnetic austenite. Thus, the site occupation and associated magnetic states are the crucial influencing factors of the phase stability, martensitic transformation, and the total magnetic moment. The electronic structure of the austenite phase also shows that the covalent bonding plays an important role in the phase stability. The key finding of this work is both Ni2Mn1+xIn1-x and Ni2+xMnIn1-x alloys serve as the potential shape memory alloys.

The microwave absorption properties of Ti2O3 were systematically investigated. Experimental results indicate that Ti2O3 has microwave absorption performance with a minimum reflection loss value of −37.6 dB at 18.6 GHz and an effective absorption bandwidth (RL

Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys. Recently, experimental studies on B alloying shed new light on this issue. However, the knowledge related to B alloying is limited until now. More importantly, the mechanism of the improved ductility, which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments, is still unclear. In this context, by first-principles calculations, the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems, i.e., (Ni2-xBx)MnGa, Ni2(Mn1-xBx)Ga, Ni2Mn(Ga1-xBx) and (Ni2MnGa)1-xBx. Results show that B prefers the direct occupation manner when it replaces Ni, Mn and Ga. For interstitial doping, B tends to locate at octahedral rather than tetrahedral interstice. Calculations show that the replacement of B for Ga can effectively improve (reduce) the inherent ductility (inherent strength) due to the weaker covalent strength of Ni(Mn)–B compared with Ni(Mn)–Ga. In contrast, B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn) and B, bringing about a significantly improved strength and a greatly reduced ductility. Upon the substitutions for Ni and Mn, they affect both the inherent ductility and strength insignificantly. For phase transition, the replacement of B for Ga tends to destabilize the austenite, which can be understood in the picture of the band Jahn–Teller effect. Besides, the substitution for Ga would not lead to an obvious reduction of magnetization.

The Ni43.75Mn37.5In12.5Co6.25 alloy was obtained by using the spark plasma sintering (SPS) technique. The martensitic transformation, magnetic and mechanical properties of the SPS alloy were investigated. Key findings demonstrate that the martensitic transformation temperature of this alloy is about 10 K lower than that of the as-cast one. Both SPS and as-cast alloys show a 7 layered modulated martensite (7M) at room temperature. The compressive fracture strength and strain of the SPS alloy increase by 176.92% and 33.33% compared with the as-cast alloy, achieving 1440 MPa and 14%, respectively. The maximum magnetic entropy change ΔSm is 17.1 J kg-1 K-1 for the SPS alloy at the magnetic field of 5 T.

In this work, the B2 partial disordered structure of the austenitic parent phase, martensitic transformation, elastic and magnetic properties of the Ni8Mn4+xTi4-x (x = 0, 1 and 2) Heusler alloys have been systematically investigated by the first-principles calculations. The preferential atomic occupation of B2 structure is one Ti atom exchange with the nearest neighboring Mn atom from the view of lowest energy principle. This disordered exchange sites (Mn-Ti) and the excess Mn atoms occupying the Ti sites (MnTi) could reduce the nearest Mn-Mn distance, resulting in the antiferromagnetic state in the austenitic and martensitic phases of the alloys. The total magnetic moment of the alloy decreases with the increasing Mn content; it is ascribed to the antiferromagnetic magnetic moments of the excess Mn atoms. When x = 0, the alloy does not undergo martensitic transformation since the austenite has absolute phase stability. The martensitic transformation will occur during cooling process for x = 1 or 2, owing to the energy difference between the austenite and the martensite could provide the driving force for the phase transformation. The elastic properties of the cubic austenitic phase for the Ni2MnTi alloy is calculated, and the results reveal the reason why Ni-Mn-Ti alloy has excellent mechanical properties. The origin of martensitic transformation and magnetic properties was discussed based on the electronic density of states.

International audience; Determination of strain path across martensitic transformation in materials with two transformation orientation relationships (ORs) is challenging due to the temporal and spatial limitation of the modern techniques. In this work, an analyzing strategy, i.e., the determination of transformation path via the variant organization feature of martensite, was suggested and applied for the Ni-Mn-based alloys as an example, based on the consideration that the different crystallographic symmetries of transformation systems will result in distinct organizations of martensite variants. For the selected Ni-Mn-based alloys, the orientation examination revealed that both the K−S and the Pitsch OR are respected. Further analyses in terms of the strain and stress compatibility condition and the minimum energy criteria showed that, theoretically, the K−S path produces 2 variants as a self-accommodated variant group, whereas the Pitsch path produces 4 variants as a self-accommodated variant group. Compared with the experimental results, the Pitsch path is the energetically favorable transformation path and actually occurs in stress-free austenite of the Ni−Mn based alloys. The significance of this work is multi-fold. It first resolves the long puzzling issue of transformation strain path of Ni-Mn-based alloys. Moreover, the analyzing scheme can be generalized to determine the transformation characters for martensitic transformation in other systems with multiple possible transformation orientation relationships.

Enhanced elastocaloric properties in a directionally solidified Ni55Mn18Ga26Ti1 alloy were achieved by combining composition tuning and microstructural control. Owing to the introduction of Ti and the microstructural feature with coarse columnar grains and strong A preferred orientation, the thermal hysteresis and the stress hysteresis were successfully reduced to 4K and 16MPa, respectively. Large adiabatic temperature change of −6.2K was obtained on removing a low stress of 120MPa, resulting in the specific adiabatic temperature change of 51.7K/GPa. Moreover, the alloy demonstrated enhanced cyclability of elastocaloric effect up to 497 loading/unloading cycles and high coefficient of performance value of 25.6.

Composition dependence of martensitic transformations as well as the magnetic properties for the Ni2Mn1+xIn1-x (0.25 ≤ x ≤ 0.58) alloys were investigated by using the first-principles calculations. Key results demonstrate that the stability of parent austenite (A) decreases gradually with increasing Mn content whilst it is opposite for the martensitic phase. This causes the total energy difference between the austenite and martensite phases increscent with increasing Mn contents. When x = 0.33, the martensite transformation during cooling is PA→FA→NM. When x ≥ 0.42, an intermartensitic transformation occurs from modulated 6 M martensite to non-modulated (NM) martensite with the martensite transformation sequence of PA→FA→6M→NM. The martensitic transformation from austenite to martensite accompanies the transition from ferromagnetic to ferrimagnetic state. This is a typical magneto-structural coupling transformation. The analysis of the density of states demonstrates that the Ni 3d state plays an important role in the phase stability.

Orientation rotation tendency with respect to target orientation in body-centred cubic (bcc) crystal is investigated under different rolling modes. Oriented stability is proposed to describe the ro...

The effects of Si content on the microstructure and yield strength of Al−(1.44−12.40)Si−0.7Mg (wt.%) alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy (LSCM), DSC, TEM and tensile tests. The results show that the recrystallization grain of the alloy sheets becomes more refined with an increase in Si content. When the Si content increases from 1.44 to 12.4 wt.%, the grain size of the alloy sheets decreases from approximately 47 to 10 μm. Further, with an increase in Si content, the volume fraction of the GP zones in the matrix increases slightly. Based on the existing model, a yield strength model for alloy sheets was proposed. The predicted results are in good agreement with the actual experimental results and reveal the strengthening mechanisms of the Al−(1.44−12.40)Si−0.7Mg alloy sheets under the T4 condition and how they are influenced by the Si content.

International audience; Ni–Mn-based shape memory alloy is a promising candidate as the solid-state elastocaloric refrigerant in the micro- or nano-refrigeration fields owing to the required small driving force. In this letter, we report a multielement alloying strategy, i.e., the co-substitution of non-magnetic element and boron for Mn, to improve the elastocaloric refrigeration efficiency and mechanical properties simultaneously. Under Cu and B co-substitution, a large adiabatic temperature change of –12.8 K and a giant specific adiabatic temperature change of 41.0 K/GPa were obtained in the directionally solidified Ni50(Mn31.7Cu2.5B0.3)In15.5 alloy. The proposed alloying manner is also favorable to enhance fracture resistance and cyclability.

Herein, we have revealed the phase transition path and magnetic properties of Ni–Mn–In alloys with excess Ni or Mn (Ni24+xMn12In12-x, Ni24+xMn12-xIn12 and Ni24Mn12+xIn12-x) by using ab initio calculations. It is demonstrated that excess Ni atoms prefer to be adjacent to each other for the Ni24+xMn12In12-x alloys, whereas excess Ni (Mn) atoms tend to keep away from each other for the Ni24+xMn12-xIn12 and Ni24Mn12+xIn12-x alloys. The variation of the lattice constants, which are dominated by the atomic radius, are basically the same for the three alloy systems. Excess-Ni decreases the stability of the ferromagnetic austenite (FA) as well as the 6M and NM martensites. Meanwhile, the Curie temperature (TC) is reduced but the martensitic transformation temperature (TM) is increased due to the presence of excess-Ni. In comparison, excess-Mn destabilizes the FA phase, but stabilizes the 6M and NM phases. Excess-Mn has a similar impact on the increase of TM as that of excess-Ni, but has a weak effect on TC, but increases TM. The critical composition of the martensitic transformation and martensitic transition path are determined. The highest total magnetic moment of the FA phase appears with Mn-excess compositions whilst the smallest total magnetic moment is found with Ni-excess compositions. The changes of the total magnetic moments for the 6M and NM phases demonstrate an opposite trend to that of FA phase. The above results are expected to provide information for the prediction of phase diagram and magnetic properties of Ni–Mn–In alloys.

This study performed field surveys and investigated the formal and technological characteristics of traditional buildings in the Southern area of Hubei province, China, and reviewed the related his...

The martensitic transformation, kinetics, elastic and magnetic properties of the Ni2-xMn1.5In0.5Cox (x = 0-0.33) ferromagnetic shape memory alloys were investigated experimentally and theoretically by first-principles calculations. First-principles calculations show that Co directly occupies the site of Ni sublattice, and Co atoms prefer to distribute evenly in the structure. The optimized lattice constants are consistent with the experimental results. The martensitic transformation paths are as follows: PA ↔ FA ↔ 6 MFIM ↔ NMFIM when 0 ≤ x

International audience; Thermo-mechanical treatment is an effective way to tune the microstructure and enhance the output strain of NiMn-based magnetic shape memory alloys through field driven variant reorientation or structural transformation. Comprehensive knowledge on the microstructural feature and related transformation crystallography is of great importance for the microstructure control and property optimization. In this work, we demonstrate the crossing twin of seven-layered modulated (7 M) martensite assembled in herringbone shape induced by thermo-mechanical treatment in a directionally solidified Ni50Mn30Ga20 alloy. Based on the electron backscatter diffraction (EBSD) measurements, it is found that the crossing twin is composed of four 7 M martensite variants with two mutually crossing systems of twin, i.e., type I twin and compound twin. The type I twin in the crossing twin, being with {1 –2 10}7 M as the twinning plane, is quite different from that of the self-accommodated martensite (i.e., {1 –2 –10}7 M as the twinning plane). A novel transformation orientation relationship between austenite and 7 M martensite in crossing twin is resolved to be {1 0 1}A//{1 –2 10}7 M and A//7 M, in contrast to that of self-accommodated case, i.e., {1 0 1}A//{1 –2 –10}7 M and A//7 M. By using the experimentally determined orientation relationship between two phases to construct the deformation gradient matrix, the underlying mechanism for the selection of twinning system is further discussed.

The effects of Co doping on the phase stability, martensite transformation and magnetic properties of Ni 24- x Mn 17 In 7 Co x ( x = 0–5) ferromagnetic shape memory alloy were systematically investigated by the first-principles calculations. Co atom prefers to occupy the Ni sublattice. Co doping increases equilibrium lattice constant of austenite and decreases phase stability of austenite, 6 M and NM martensites. When 0 ≤ x x ≥ 2, the corresponding martensite transformation is PA→FA→NM. The martensitic transformation from austenite to martensite (6 M and NM) accompanies the ferromagnetic to ferrimagnetic transition in the Co content 0 ≤ x ≤ 2. However, the ferromagnetic state is popular in the whole martensitic transformation process for x > 2. The origin of magnetic properties and magnetostructure transformation were discussed based on electronic density of states.

Ti/Cu multilayered composites were fabricated via accumulative roll bonding (ARB). During co-deformation of the constituent metals, the hard Ti layers necked preferentially and then fragmented with the development of shear bands. Transmission electron microscopy showed that with increasing ARB cycles, grains in Ti were significantly refined even though dynamic recrystallization has occurred. For Cu the significant grain refinement was only found within the shear banded region when the composite was processed after five ARB cycles. Due to the diffusion of Cu atoms into Ti at the heterophase interfaces, amorphization with a width less than 10 nm was identified even in the composite processed by one cycle. At higher ARB cycles, the width of amorphous region increased and intermetallic compounds CuTi appeared from the region. The lattice defects introduced at the heterophase interfaces under roll bonding was responsible for the formation of the nano-scaled compounds. X-ray diffraction showed that an abnormal { 11 2 ¯ 0 } fiber texture was developed in Ti layers, while significant brass-type textures were developed in Cu layers. Some orientations along the { 11 2 ¯ 0 } fiber favored the prismatic slip for Ti. Tensile tests revealed the elevated strength without a substantial sacrifice of ductility in the composites during ARB. The unique mechanical properties were attributed to the significantly refined grains in individual metals, the good bonding between the constituent metals, as well as the development of an abnormal { 11 2 ¯ 0 } fiber texture in Ti layers.

Strong Goss texture ({1 1 0}〈0 0 1〉) in Fe81Ga19 thin sheet is successfully produced by secondary recrystallization process based on the precise control of inhibitor and primary recrystallization texture. Nanometer-sized sulfides of MnS and Cu2S are dispersedly precipitated during hot rolling as inhibitors for secondary recrystallization. Primary recrystallization texture is characteristic of weak Goss and strong γ textures distributed through sheet thickness by appropriate rolling and annealing schedule. The composite nanometer-sized inhibitors accompanied with the primary recrystallization texture can provide a well-matched pinning effect on normal grain growth of matrix grains and induce abnormal grain growth of exact Goss grains in final annealing process. The magnetostriction coefficient as high as 285 ppm is obtained in Fe81Ga19 sheet after complete secondary recrystallization. Thus, an efficient method is proposed for developing sharp Goss texture and upgrading magnetostriction coefficient in Fe-Ga sheet.

The wear property of high-vanadium alloy steel was studied using a dry sand/rubber wheel testing apparatus and the microstructures and failure behaviors were analyzed by scanning electron microscopy, using commercial Cr16 as a reference material. The wear resistance of high-vanadium alloy steel (50 HRC) and high-vanadium alloy steel (65 HRC) was about 3 and 15 times higher, respectively, than that of Cr16. The macroscopic photographs of high-vanadium alloy steel show differences from images of Cr16 and other materials in four different zones on the observed wear scar. Due to the presence of the skeleton structure of the MC carbides, the serious wear zone showed evidence typical of particle rolling, with significant indentations on the surface and little directionality.

Strong η ( ∥RD, rolling direction) recrystallization texture is successfully developed through thickness in Fe81Ga19 sheets with fine-grained microstructure by primary recrystallization process. An excellent combination of magnetic and mechanical properties is achieved with magnetostriction coefficient of 150 ppm, yield strength of 608 MPa and elongation of 11.7%. Quantitative macro/micro-texture analysis indicates that the enhanced η texture derives from number and size advantages established by preferred nucleation and efficient growth. The highly attractive phenomenon is that deformed grains with α ( ∥RD) texture can be extensively consumed by η recrystallized grains in addition to deformed grains with γ ( ∥ND, normal direction) texture. A physical model is proposed that well describes the relationship between strong η texture development in competition with γ and α recrystallization textures, where several critical parameters characteristic of deformation texture and microstructure are included. The correlative effect of these parameters are figured out based on the modeling and experimental data. The present work can provide an effective method for recrystallization texture design and control in body-centered cubic alloy sheets.

The first-order inter-martensitic transformation induced by temperature change or external stress is frequently observed in Ni-Mn-Ga alloys. Here, the inter-martensitic transformation is exploited to strengthen the elastocaloric effect. Through the stress-induced two-step structural transformation, i.e., martensitic and inter-martensitic transformation, giant adiabatic temperature change up to −10.7 K is obtained in a directionally solidified Ni55Mn18Ga27 polycrystalline alloy with 〈001〉A preferred orientation, representing the highest value so far in Ni-Mn-Ga alloys. It is demonstrated that microstructure texturing together with introduction of inter-martensitic transformation could be an effective route to improve the elastocaloric properties in polycrystalline NiMn-based alloys.

Texture evolution of 2.1 wt pct Si non-oriented electrical steel sheets was investigated using macro- and micro-texture analysis. The desirable cube ({001}〈100〉) component successfully dominates the recrystallization texture through sheet thickness. The nucleation sites of cube grains are mainly identified at the interfaces of {001}〈230〉-{001}〈130〉 and {223}〈362〉-{114}〈481〉 oriented deformation bands. The formation of through-thickness cube recrystallization texture can be attributed to the optimization of nucleation environment, featuring quantitative advantage of cube nuclei at both strong plane strain and strong shear strain layers under the superiority of locally low density of cube nuclei.

The complete martensitic transformation sequence and magnetic properties of the non-stoichiometric Ni2Mn1.2Ga0.8 alloy have been revealed by the first-principles calculations. The calculated martensitic transformation sequence of the Ni2Mn1.2Ga0.8 alloy during cooling is Paramagnetic Austenite (PA) → Ferromagnetic Austenite (FA) → 7M → NM, which is consistent with the experimental observations. When the cubic FA phase transforms to a 7M or NM martensitic phase, a significant reduction of the down-spin total density of states occurred at the Fermi level. This makes the martensitic phase more stable than the FA phase at low temperature.

Ni-Co-Mn-Sb alloys can exhibit large elastocaloric effect characterized as stress-induced entropy change ΔSσ. However, the intrinsic large brittleness of polycrystalline alloys makes it difficult to directly measure the stress-induced temperature change ΔTad. Here, we demonstrate large elastocaloric effect in a directionally solidified Ni45.7Co4.2Mn37.3Sb12.8 alloy with enhanced mechanical properties. Large ΔTad up to 9.4 K was realized through compressive stress-induced martensitic transformation with a low transformation strain of 1.5%. Moreover, with integrating large ΔSσ up to 25.4 Jkg−1 K−1 and wide working temperature window of 46 K, a giant refrigeration capacity RCσ of 930 Jkg−1 was achieved under the compressive stress of 250 MPa.

Herein, a simple and efficient method is proposed for fabricating Fe81Ga19 alloy thin sheets with a high magnetostriction coefficient. Sharp Goss texture ({110}&lt, 001&gt, ) was successfully produced in the sheets by rapid secondary recrystallization induced by nanosized NbC particles at low temperatures. Numerous NbC precipitates (size ~90 nm) were obtained after hot rolling, intermediate annealing, and primary recrystallization annealing. The relatively higher quantity of nanosized NbC precipitates with 0.22 mol% resulted in finer and uniform grains (~10 μm) through thickness after primary recrystallization annealing. There was a slow coarsening of the NbC precipitates, from 104 nm to 130 nm, as the temperature rose from 850 °C to 900 °C in a pure nitrogen atmosphere, as well as a primary recrystallization textured by strong γ fibers with a peak at {111} &lt, 112&gt, favoring the development of secondary recrystallization of Goss texture at a temperature of 850 °C. Matching of the appropriate inhibitor characteristics and primary recrystallization texture guaranteed rapid secondary recrystallization at temperatures lower than 950 °C. A high magnetostriction coefficient of 304 ppm was achieved for the Fe81Ga19 sheet after rapid secondary recrystallization.

International audience; In order to figure out the effect of excess Mn atoms on the preference of the martensite structure, the tetragonal distortion was employed in the off-stoichiometric Ni-Mn-In alloys with different Mn contents using the Extra Muffin-tin Orbital combined with the Coherent Potential Approximation (EMTO-CPA). The calculations were conducted with the optimization of the magnetic structure, where the stoichiometric Ni2MnIn alloy was served as the reference. The ground state-energy-resolved tetragonal distortion reveals that the excess Mn changes the preferred stable structure from the perfect cubic L21 structure to the tetragonally distorted structures. The stable tetragonal structure could shift from c/a < 1 to c/a > 1 with the increase of the Mn concentration. Furthermore, to find out more accurate preference of the martensite structure, the formation energies were calculated using different relaxation methods. The chemical disorder method with a 4-atom cell was used for the tetragonal L10 structure by the EMTO-CPA, and the supercell method with a 96-atom cell was applied for the orthorhombic structure by the VASP at 0 K in their ferromagnetic state. The results show that, compared with the perfect cubic L21 structure of the stoichiometric Ni2MnIn alloy, the orthorhombic structure is preferred at lower Mn concentrations (between 29 at. % and 40 at. %), whereas the tetragonal L10 structure is more stable at the higher Mn concentrations (above 40 at. %). Moreover, the effect of the Mn concentration on the magnetic properties was also studied. With the increase of excess Mn content, the magnetic moment increases linearly in the ferromagnetic cubic L21 structure, whereas it varies in the two kinds of martensite. The excess Mn could lead to the coexistence of ferromagnetism and antiferromagnetism. The appearance of the antiferromagnetism could be attributed to the Ni-Mn antiferromagnetic interaction in the tetragonal martensite.

International audience; Valence electron concentration (e/a) dependence of phase transition temperature TM, i.e., a higher e/a leading to an elevated TM, is a well-accepted criterion for the Ni–Mn-based alloys. However, this tendency is not always obeyed by certain alloy systems, such as the Ni2Mn(Ga, Z) alloys (Z = Si, Ge, and Sn). The origin of this abnormal behavior remains uncovered. In this work, by first-principles calculations, the origin of the abnormal e/a dependence of phase stability in the Ni2MnGa1−xSix (x = 0–1) alloys is elucidated through examining the electronic structure, phonon, and magnetism. We find that the abnormal e/a dependence of phase stability intrinsically originated from the chemical composition change. The composition variation brings about a reduction of the minority-spin electronic states near the Fermi energy and the weakness of the Fermi surface nesting. Moreover, the substitution of Si for Ga leads to a decreased magnetization of austenite and an increased magnetization of martensite, which also makes a non-negligible contribution to the abnormal phase stability. The conclusions drawn for the Ni2MnGa1−xSix alloys can be well extended to understand the structural transition in other abnormal alloying systems, such as the Ni2MnGa1−xZx alloys (Z = Ge and Sn). This work clarifies the origin of the abnormal dependence of phase stability on e/a in the Ni–Mn-based alloys and provides solid knowledge for the design of advanced magnetic shape memory alloys.ACKNOWLEDGMENTS

International audience; Solid-state refrigeration based on the caloric effects has been conceived to be a high-efficient and environmental-friendly alternative to replace the vapor-compression refrigeration technique. The implementation of solid-state refrigeration requires that the refrigerants should possess not only remarkable caloric effect but also wide working temperature region. In this work, we demonstrate that various caloric effects can be achieved successively in a multiferroic Ni50Mn35In15 meta-magnetic shape memory alloy prepared by directional solidification, including inverse magnetocaloric effect around inverse martensitic transformation, conventional magnetocaloric effect around Curie transition and elastocaloric effect above Curie transition. Among them, the elastocaloric effect is particular striking, where a giant adiabatic temperature variation up to –19.7 K is achieved on removing a moderate stress of 350 MPa due to the elimination of negative magnetic contribution, with the specific adiabatic temperature change of 56 K GPa–1. Furthermore, through the combination of these successive caloric effects, a broad refrigeration temperature region covering the temperature range from 270 K to 380 K can be achieved. It is demonstrated that the combination of various caloric effects could be a promising way to extend the working temperature range of solid state refrigeration.

Molybdenum vanadate is a novel vanadate. It is a functional material with good magnetic, electrical and catalytic properties. However, it is rarely used in the selective catalytic oxidation field, while the transition metal molybdenum and vanadium are usually used as a catalytic oxidation catalyst, the complex oxide and salt are naturally concerned. The structure of high-quality single crystalline Molybdenum vanadate (V3 .6Mo2.4O16) nanorods was synthesised by sol–gel method and high-temperature solid-state reaction. The effects of vanadium and molybdenum molar ratio and calcination temperature on the preparation of V3.6Mo2.4O16 were studied. The structure of the catalyst was characterised by X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The experimental results show that the molar ratio of vanadium–molybdenum is 10:7 when the precursor calcination temperature is 540°C, the single crystalline V3.6Mo2.4O16 nanorods with regular shape has been obtained, the diameter of about 200 nm and the length up to tens of micrometres and the surface is smooth. Catalytic oxidation of toluene to benzaldehyde is used as a probe reaction for nanoV3.6Mo2.4O16. The catalytic activity of the catalyst is good, the conversion of toluene is 39.8% and the selectivity of benzaldehyde is 70.1%.

International audience; For NiMn-based Heusler alloys, simultaneously achieving high magnetization difference and low thermal hysteresis across the magnetostructural transformation is of crucial importance to obtain large low-field actuated magnetocaloric properties. Here, the fifth element Si was introduced to replace In for reducing the thermal hysteresis in Ni-Co-Mn-In alloys while keeping a large magnetization change through the martensitic transformation. Consequently, a giant maximum entropy change ΔSMmax of 33.6 J kg−1 K−1 under the low field change of 2 T was achieved in a Ni45Co5Mn37In12Si1 alloy, which is among the highest values reported in NiMn-based alloys.

The wrought Mg-containing high-silicon aluminum alloy has become more attractive as an ideal structural material, because it has moderate strength and the ductility, high wear and corrosion resistance, low thermal expansion coefficient and low cost. However, as structural material, the fatigue properties and the fatigue fracture behavior of it should be paid much more attention to, especially the effect of Si content on the fatigue properties of wrought Mg-containing Al-Si alloy. In this paper, the wrought Al-(1.44%, 4.92%, 6.61%, 8.81% and 12.4%)Si-0.7%Mg alloy were prepared through DCC and homogenization treatment, and then hot-rolled and cold-rolled into 1.3mm sheets. The microstructure and fatigue fracture morphology of Al-(1.44~12.4)Si-0.7Mg-T4 alloy sheet after fatigue test were investigated by LSCM and SEM. The results showed that the size of Si particles in Al-(1.44~12.4)Si-0.7Mg alloy sheets was approximately the same, but the number of Si particles increased as the Si content increased. The size of recrystallization grain in Al-(1.44~12.4)Si-0.7Mg alloy sheets decreased from 47μm to 10μm when Si content increased from 1.44% to 12.4%, which indicates that increasing of Si content can refine the grain of Al-(1.44~12.4)Si-0.7Mg alloy sheets. With the increasing of Si content the propagation area of fatigue fracture surface of Al-(1.44~12.4)Si-0.7Mg alloy sheets in T4 temper became rougher, and crack propagation became more difficult. Moreover, dimples in the fast fracture area became larger in amount, smaller in size and more uniform in distribution.

Most of the studies on phase transformation in metallic materials have focused on transformations during cooling processes due to the easiness of the conservation of the product phase. However, for phase transformation happening during heating processes, the experimental investigations have been indirect if the product high temperature phase could not be preserved to the convenient observation temperature, for example the room temperature. The high density Electric Current Pulse (ECP) treatment allows the phase transformation during heating process and the preservation of the high temperature phase to the room temperature, offering possibilities for direct experimental examinations. Thus, in the present work, a cold-rolled Cu–40%Zn alloy was ECP treated and the microstructure of the product phase and the transformation orientation relationship were investigated. Results show that during the ECP treatment, the high temperature beta phase with BCC structure formed in the parent alpha phase with FCC structure. Especially, two kinds of orientation relationships could be detected between the parent alpha phase and the product beta precipitates. The one is the Kurdjumov-Sachs orientation relationship (K-S OR), and the other is the Nishiyama-Wasserman (N-W). In addition, the amount of beta precipitates obeying the K-S OR is more than that of precipitates obeying the N-W OR. The results of this work provide new fundamental information on phase transformation of metallic materials.

In the present study, titanium plate was treated by a novel method of laser quenching, simultaneously combined with liquid-nitrogen cryogenics (LQLNC). The microstructure and properties of the titanium plate after treatment were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, Vickers hardness testing, and friction wear testing. The results show that the treated titanium plate is covered by a nitrided layer with a homogeneous thickness of about 60 μm, while the nitrided layer consists of TiN and α-Ti phases. Compared to general laser quenching, the LQLNC treatment increases the hardness and wear resistance of the surface-modified layer of the titanium plate. As a result of grain refinement in the nitrided layer, the cracking induced by the rapid solidification of the conventional laser-quenching process has also been effectively solved.

A direct chill (DC) cast Al-15% Si alloy was processed by hot rolling with a single pass at a temperature of 520°C with a thickness reduction of 80%. Scanning electron microscopy (SEM), electron ba...

In this work, crystallographic, microstructural and magnetocaloric investigations were performed on textured Ni50Mn35.25In14.75 melt-spun ribbons with low thermal (6 K) and magnetic-field induced hysteresis (−0.73 J kg−1 at 2 T) and moderate maximum magnetic entropy change ΔSMmax (11 J kg−1 K−1 at 5 T) at room temperature (302 K). The austenite in the ribbons crystallizes into a L21 structure, whereas martensite has a monoclinic incommensurate 6 M modulated structure as determined with the superspace theory. By means of electron backscatter diffraction technique, the morphological and crystallographic features of microstructure were systematically characterized. Ribbons possess a fine microstructure with an average grain size (initial austenite phase) of around 10 μm, whereas the 6 M martensite has a self-accommodated microstructure with 4 kinds of twin-related martensite variants. During inverse martensitic transformation, the austenite prefers to nucleate at the grain boundaries of initial austenite. By means of cofactor conditions and crystallographic orientation analyses, the good geometrical compatibility between austenite and martensite was confirmed. Based on the crystal structure and microstructure information obtained, the reason of the low thermal hysteresis was discussed.

For the potential applications in magnetic refrigeration, low-cost and high-performance refrigerants with large magnetocaloric effect at relatively lower field change are highly desired. In this work, we report a large adiabatic temperature variation for a low-field change of 1.5 T near room temperature in a Ni40Co8Mn42Sn10 bulk alloy. With the large magnetization difference between weak magnetic martensite and ferromagnetic austenite, this alloy exhibits significant inverse magnetocaloric effect. Under the field change of 5 T, large magnetic entropy change ΔSM of 21.6 J kg−1K−1 and effective refrigeration capacity RCeff of 293 J kg−1 were achieved. Moreover, a large ΔTad up to −4.4 K was obtained under the low-field change of 1.5 T, which is much higher than previously reported ΔTad values in Ni-Mn-Sn based alloys.

We demonstrate a remarkable magnetocaloric effect in a directionally solidified Ni45.3Co5.1Mn36.1In13.5 alloy with coarse-grained microstructure and strong 〈001〉A texture. Due to this optimized microstructure and the strong magnetostructural coupling, a giant ΔTad up to −5.1 K is achieved under low field change of 1.5 T, which is even superior to that of polycrystalline bulk alloys under the field change of 2 T. Furthermore, it is presented that the reversible ΔTad can be improved after certain predeformation, which should be attributed to the introduction of certain internal stress by predeformation.

Polycrystalline Ni44.5Co5.1Mn37.1In13.3 alloy with coarse columnar-shaped grains and 〈0 0 1〉A preferred orientation was prepared by directional solidification. Due to the strong magnetostructural coupling, inverse martensitic transformation can be induced by the magnetic field, resulting in large negative magnetoresistance up to −58% under the field of 3 T. Such significant field controlled functional behaviors should be attributed to the coarse grains and strong preferred orientation in the directionally solidified alloy.

The kinetic arrest (KA) of martensitic transformation (MT) observed in Ni 45 Co 5 Mn 36.8 In 13.2 melt-spun ribbons has been studied. These alloy ribbons show an ordered columnar-like grain microstructure with the longer grain axis growing perpendicular to ribbon plane and transform martensitically from a single austenitic (AST) parent phase with the L2 1 -type crystal structure to a monoclinic incommensurate 6 M modulated martensite (MST). Results show that the volume fraction of austenite frozen into the martensitic matrix is proportional to the applied magnetic field. A fully arrest of the structural transition is found for a magnetic field of 7 T. The metastable character of the non-equilibrium field-cooled glassy state was characterized by introducing thermal and magnetic field fluctuations or measuring the relaxation of magnetization. The relaxation of magnetization from a field-cooled kinetically arrested state at 5 and 7 T follows the Kohlrausch–Williams–Watts (KWW) stretched exponential function with a β exponent around 0.95 indicating the weak metastable nature of the system under the strong magnetic fields. The relationship between the occurrence of exchange bias and the frozen fraction of AST into the MST matrix was studied.

International audience; An intensive formation of crystal defects in the α-Al matrix of an as-cast Sr-modified eutectic Al–Si alloy, induced by heat treatment with rapid heating, has been studied. This phenomenon arises from the fragmentation of the Si crystals and the diffusion of Al atoms into the cracks of the Si crystals. During the rapid heating process, a large temperature gradient is established within an as-cast Al–Si sample. It creates a tensile environment for the irregular-shaped and interconnected Si crystals, as the thermal expansion coefficient of the α-Al is ten times that of the Si. Under the thermal constraints, some Si crystals are broken, where the cracks produce the so-called “capillary force” that attracts the surrounding α-Al matrix to fill in them. As the migration of the Al atoms is substitutional, the Al diffusion creates fluxes of vacancies to the interior of the αAl matrix; thus, the crack volume is transferred to the αAl matrix. Due to the homogeneous distribution of the Si crystals and the random presence of the cracks, the αAl matrix is subjected to a varied migration of vacancies in site, in quantity and in direction. Such diffusion is further perturbed by local migration of Al atoms to accommodate the spheroidization of the Si induced by its shape instability. In this way, a large amount of crystal defects (vacancies and then dislocations) are produced in the α-Al matrix. The produced crystal defects then promote the recovery and even recrystallization of the α-Al matrix, resulting in its refinement. Such a mechanism of defect production is applicable to polycrystalline materials composed of phases with incompatible thermal and mechanical properties.

In this work, based on composition adjusting and texture control, we demonstrate giant elastocaloric and magnetocaloric effects in a directionally solidified Ni43Mn47Sn10 polycrystalline with strong A texture. On removing a low compressive stress of 210 MPa, giant adiabatic temperature change up to −17.3 K is achieved. Such value is much higher than those in some elastocaloric materials reported previously. Besides, giant magnetic field induced entropy changes of 23.5 Jkg−1K−1 and 37.1 Jkg−1K−1 are also obtained under the magnetic field changes of 2 T and 5 T, respectively. Simultaneously achieving giant elastocaloric and magnetocaloric effects actuated by relatively low external field is of great importance to explore multi-caloric or coupled caloric effects in developing efficient and eco-friendly solid-state refrigeration technology.

The martensitic transformation orientation relationship (OR), the transformation deformation and their impact on variant organization in an Ni50Mn38Sb12 alloy have been thoroughly studied by scanning electron microscopy/electron backscatter diffraction (SEM/EBSD), as they are decisive factors for mechanical and magnetic properties. The transformation OR has been identified and the consequent hierarchical organization of martensite variants has been fully revealed., The mechanical and magnetic properties of Ni–Mn–Sb intermetallic compounds are closely related to the martensitic transformation and martensite variant organization. However, studies of these issues are very limited. Thus, a thorough crystallographic investigation of the martensitic transformation orientation relationship (OR), the transformation deformation and their impact on the variant organization of an Ni50Mn38Sb12 alloy using scanning electron microscopy/electron backscatter diffraction (SEM/EBSD) was conducted in this work. It is shown that the martensite variants are hierarchically organized into plates, each possessing four distinct twin-related variants, and the plates into plate colonies, each containing four distinct plates delimited by compatible and incompatible plate interfaces. Such a characteristic organization is produced by the martensitic transformation. It is revealed that the transformation obeys the Pitsch relation ({0}A // {2}M and 〈01〉A // 〈2〉M; the subscripts A and M refer to austenite and martensite, respectively). The type I twinning plane K 1 of the intra-plate variants and the compatible plate interface plane correspond to the respective orientation relationship planes {0}A and {0}A of austenite. The three {0}A planes possessed by each pair of compatible plates, one corresponding to the compatible plate interface and the other two to the variants in the two plates, are interrelated by 60° and belong to a single 〈11〉A axis zone. The {0}A planes representing the two pairs of compatible plates in each plate colony belong to two 〈11〉A axis zones having one {0}A plane in common. This common plane defines the compatible plate interfaces of the two pairs of plates. The transformation strains to form the variants in the compatible plates are compatible and demonstrate an edge-to-edge character. Thus, such plates should nucleate and grow simultaneously. On the other hand, the strains to form the variants in the incompatible plates are incompatible, so they nucleate and grow separately until they meet during the transformation. The results of the present work provide comprehensive information on the martensitic transformation of Ni–Mn–Sb intermetallic compounds and its impact on martensite variant organization.

Magnetic refrigeration based on the magnetocaloric effect (MCE) is conceived as a promising alternative to the conventional gas compression/expansion technique. For potential applications, the magnetic refrigerants exhibiting high-performance at low field are in great need. In this work, we present large MCE obtained in a directionally solidified polycrystalline Ni50Mn18Cu7Ga25 alloy with the co-occurrence of magnetic transition and martensitic transformation. Such a strong magneto-structural coupling yields large magnetic entropy change of −12.8 Jkg−1K−1 and adiabatic temperature variation of 1.6 K at an external magnetic field change of 1.5 T. It is demonstrated that the fabrication of Ni-Mn-Ga based alloys through composition tuning and directional solidification could be an economical processing route to improve magnetocaloric properties.

A two-degree-of-freedom mass-spring model considering the local effect of the contact component is developed to investigate the dynamic responses of reinforced concrete beams under low-velocity impact actions. The local modified coefficient is proposed by parameter regression from drop-hammer impact test results, and then the simplified model is validated by other relevant research. As shown, the simplified model is able to capture the dynamic responses of reinforced concrete beams. In addition, the impact process is simulated and further analysed. The effects of initial impact velocity and the yield criterion of reinforced-concrete beams are investigated. The energy dissipation levels for various cases with the same initial impact energy are compared. An analysis proposal is also developed to predict the dynamic responses of reinforced concrete beams if the impact action case is uncertain.

A series of misch-metal (MM = 28.27 wt % La, 50.46 wt % Ce, 5.22 wt % Pr, 15.66 wt % Nd)-iron-boron isotropic ribbons with atomic formula (MM)12+xFe82-x-yB6+y (x = 0, 1, 2, 3, 4, y = 0, 0.5, 1, 1.5, 2) are prepared by melt spinning technique. A large energy product (BH)max of 12 MGOe is obtained with the composition of MM13Fe81B6 at optimized processing. The ribbons with both coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are achieved in a wide composition range. All the samples exhibit the tetragonal crystal structure. The magnetization and Henkel plot (δM) measurements indicate that the ribbons have a relatively homogeneous microstructure and strong exchange-coupling interactions. The average grain size of the ribbons is around 30 nm determined via Scherrer's formula. Meanwhile, the transmission electron microscope (TEM) image also verifies that the ribbons have a homogeneous nanoscale microstructure. In addition, the spin reorientation temperature Tsr is investigated by ac susceptibility χac measurement.

The periodontal structure is a particularly exquisite model of hierarchical spatial control of mineralization. Extracellular matrix control in the selective mineralization of the periodontium complex remains elusive since the extracellular matrix is a set of mineralization promoters and inhibitors. The phosphorylated proteins, which are ubiquitous in the extracellular matrix of the periodontium complex, are well-documented as primary factors in the regulation of tissue mineralization. Whether organic phosphates are key regulators in defining the interfaces between dentin, cementum, periodontal ligament and alveolar bone is an issue worthy of research. Here, we investigated the in vitro remineralization process of demineralized and dephosphorylated periodontal tissue sections. When exposed to a metastable mineralization solution, a large number of calcospherulites deposited on the surface of the dephosphorylated sections and the tissue selective mineralization were disrupted. Interestingly, on adding a dentin matrix protein-1 analogue named polyacrylic acid, the surface mineralization rate in the dephosphorylated periodontal complex reduced dramatically. In contrast, hierarchical mineralization was displayed by the demineralized section at the tissue collagen fibrillar levels in both alveolar bone and dentin regions. These results demonstrated that the organic phosphate could prevent surface mineral deposition, and the minerals could penetrate the collagen fibrils to initiate a selective and hierarchal tissue mineralization with the assistance of the dentin matrix protein-1 analogue in the periodontal complex. This study enhances our understanding of the mineralization discrepancy in the periodontal tissues, which will provide some insight into the development of biomaterials for the regeneration of soft-hard tissue interfaces.

4.5 wt.% Si grain-oriented electrical steel sheets were successfully produced by hot rolling, normalizing, warm rolling and annealing, and texture evolution was investigated using macro- and micro-texture analysis. It is found that the recrystallization texture of sheets is very sensitive to the warm rolling reduction, and 83-87% warm rolling reductions are more favorable to η texture (//RD, rolling direction) evolution during secondary recrystallization, and consequently the magnetic induction B8 is significantly improved to 1.69-1.70 T in this rolling reduction range. The decreased B8 in the 89% warm rolled sheet is ascribed to the obviously decreased primary recrystallization η fiber, which leads to the insufficient quantity of η grains in the early stage of abnormal grain growth. The results obtained in the current work can provide an efficient way to improve the recrystallization texture of 4.5 wt.% Si grain-oriented electrical steel sheets.

The crystallographic features associated with the martensitic transformation from austenite to seven-layered modulated (7M) martensite in Ni–Mn–Ga ferromagnetic shape-memory alloys have been investigated through electron backscatter diffraction (EBSD) measurements., For Heusler-type Ni–Mn–Ga ferromagnetic shape-memory alloys, the configuration of the martensite variants is a decisive factor in achieving a large magnetic shape-memory effect through field-induced variant reorientation. Based upon the spatially resolved electron backscatter diffraction technique, the microstructural evolution associated with the martensitic transformation from austenite to seven-layered modulated (7M) martensite was investigated on a polycrystalline Ni53Mn22Ga25 alloy. It was clearly shown that grain interior nucleation led to the formation of diamond-shaped 7M martensite within the parent austenite matrix. This diamond microstructure underwent further growth through an isotropic expansion with the coordinated outward movement of four side habit planes, followed by an anisotropic elongation with the forward extension of a type-I twin pair. A two-step growth model is proposed to describe the specific morphology and crystallography of 7M martensite. In addition, the habit planes were revealed to possess a stepped structure, with the {1 0 1}A plane as the terrace and the {0 1 0}A plane as the step. The characteristic combination of martensite variants and the underlying mechanism of self-accommodation in the martensitic transformation have been analysed in terms of the minimum total transformation strain, where the deformation gradient matrix was constructed according to the experimentally determined orientation relationship between the two phases. The present results may deepen the understanding of special martensite microstructures during the martensitic transformation in ferromagnetic shape-memory alloys.

International audience; The reversibility of the giant magnetocaloric effect (MCE) through the magnetic field–induced magnetostructural transformation in Ni–Mn–In‐based alloys is a key issue towards the potential magnetic refrigeration applications. In this work, Co and Cu are simultaneously doped to tune the reversible magnetocaloric properties associated with the magnetostructural transformation. Owing to the integration of large magnetization difference ΔM, suitable transformation entropy ΔStr, and narrow thermal hysteresis ΔThys in a Ni46Co3Mn35Cu2In14 alloy, the reversible field–induced inverse martensitic transformation is realized in a wide temperature range of 30 K under the field of 5T, yielding a maximum reversible magnetic entropy change ΔSMmax of 16.4 J kg−1 K−1. Moreover, under a low field change of 1.5T, a large reversible adiabatic temperature variation ΔTad of 2.5 K is also obtained, representing the highest value so far under the low field change of 1.5T in Ni–Mn‐based alloys. It is demonstrated that multi‐component alloying by combining the effects of appropriate substitutional elements is an effective way to develop high‐performance magnetocaloric materials.

In the present work, a low-pressure-induced large reversible barocaloric effect was achieved in (MnNiGe)0.91-(FeCoGe)0.09 alloys. The isothermal entropy change and the adiabatic temperature change are as high as 32.8 J·kg−1K−1 and 5.2 K by applying hydrostatic pressure of 1 kbar, respectively. The reversible isothermal entropy change of 19.3 J·kg−1K−1 and reversible adiabatic temperature change of 3.6 K within a temperature span of 16 K at 1 kbar have been achieved. Good reversible barocaloric performance is attributed to the combination of the thermal hysteresis of 6.4 K and the transition temperature shift with the pressure of 6.9 K·kbar−1.