The effect of subsequent stress‐induced martensite aging on the viscoelastic properties of aged NiTiHf polycrystals

This study investigated the effect of stress‐induced martensite aging under tensile and compressive stresses on the functional and viscoelastic properties in Ni50.3Ti32.2Hf17.5 polycrystals containing dispersed H‐phase particles up to 70 nm in size obtained by preliminary austenite aging at 873 K for 3 h. It was found that stress‐induced martensite aging at 428 K for 12 h results in the appearance of a two‐way shape memory effect of −0.5% in compression and +1.8% in tension. Moreover, a significant change in viscoelastic properties can be observed: an increase in internal friction (by 25%) and a change in elastic modulus in tensile samples. The increase in internal friction during martensitic transformation after stress‐induced martensite aging is associated with the oriented growth of thermal‐induced martensite. After stress‐induced martensite aging, the elastic modulus of martensite (EM) increased by 8 GPa, and the elastic modulus of austenite (EA) decreased by 8 GPa. It was shown that stress‐induced martensite aging strongly affects the functional and viscoelastic properties of material and can be used to control them

The effect of stress-induced martensite aging in tension and compression on B2–B19′ martensitic transformation in Ni50.3Ti32.2Hf17.5 high-temperature shape memory alloy

The present study investigates the high-temperature shape memory effect (SME) in heterophase Ni50.3Ti32.2Hf17.5 polycrystals with nanosized H-phase particles after stress-induced martensite (SIM) aging in tension and compression. SIM aging created the conditions for fully reversible two-way SME with a strain of up to 50% of the one-way shape memory strain. SIM aging altered the viscoelastic properties of material, in particular, the elastic moduli of austenite and martensite increased, as did internal friction. Increased interface mobility is suggested as the reason for internal friction growth

Orientation dependence of superelasticity in quenched high-nickel Ti51.8Ni single crystals

The orientation dependence of the functional and mechanical properties of quenched Ti-51.8at.%Ni single crystals, undergoing a strain-glass transition upon cooling/heating was investigated. It was found that a compressive stress above 800 MPa leads to the B2-B190 martensitic transformation (MT), regardless of orientation. In the high-strength [0 0 1]-orientation, superelasticity (SE) was observed at 203–248 K, with a reversible strain of 2.3%. Degradation of SE at deforming stresses r > 1000 MPa was associated with the formation of {1 1 3}B2 twins during the reverse MT. In the low-strength 1 1 1-orientation, the formation of stress-induced B190 -martensite occurred simultaneously with the plastic deformation of the B2-phase (due to the formation of reorientation bands and dislocation slip) and a reversible strain was not observed

Elastocaloric effect in aged single crystals of Ni54Fe19Ga27 ferromagnetic shape memory alloy

In the present study, the effect of 0-phase dispersed particles on both the L21(B2)-10M/14ML10 martensitic transformations and the elastocaloric effect in aged Ni54Fe19Ga27 single crystals oriented along the [001]-direction was investigated. It was experimentally shown that aging strongly affects the elastocaloric properties of these crystals. The precipitation of semi-coherent 0-phase particles up to 500 nm in size in the crystals aged at 773 K for 1 h leads to a 1.4 times increase in the operating temperature range of the elastocaloric effect up to DTSE = 270 K as compared with the initial as-grown crystals (DTSE = 197 K). The adiabatic cooling values DTad are similar for the as-grown crystals DTad = 10.9 (0.5) K and crystals aged at 773 K DTad = 11.1 (0.5) K. The crystals containing temperature range of DTSE = 255 K with slightly smaller adiabatic cooling DTad below 9.7 (0.5) K. The aged [001]-oriented Ni54Fe19Ga27 single crystals demonstrate high cyclic stability: the number of cycles does not influence the adiabatic cooling values and parameters of loading/unloading curves regardless of the particle size. The ways to improve the elastocaloric cooling parameters and stability of the elastocaloric effect by means of dispersed particles in the NiFeGa ferromagnetic shape memory alloy were discussed.В ст. ошибочно: Nikita S. Suriko

The Effect of Thermal Treatment on Microstructure and Thermal-Induced Martensitic Transformations in Ni44Fe19Ga27Co10 Single Crystals

Heat treatments of single crystals of Ni44Fe19Ga27Co10 (at.%) shape memory alloys cause various microstructures of the high-temperature phase. The nanodomain structure, consisting of regions of the L21- and B2-phases, and nanosized particles are the main parameters that change during heat treatments and determine the mechanism of nucleation and growth of martensite crystals, the size of thermal-induced martensite lamellae, the temperature Ms, and the temperature intervals of the martensitic transformation. In the as-grown single crystals, the high-temperature phase has only the L21-structure and the MT occurs at low (Ms = 125 K) temperatures due to the motion of the practically single interphase boundary in narrow temperature ranges of 3–7 K. The reduction in the volume fraction of the L21-phase to 40% and the formation of nanodomains (20–50 nm) of the L21-and B2-phases due to annealing at 1448 K for 1 h with quenching causes an increase in the MT temperatures by 80 K. The MT occurs in wide temperature ranges of 40–45 K because of multiple nucleation of individual large (300–500 µm) martensite lamellae and their growth. After aging at 773 K for 1 h, the precipitation of nanosized particles of the ω-phase in such a structure additionally increases the MT temperatures by 45 K. The MT occurs due to the multiple nucleation of packets of small (20–50 μm) martensite lamellae

Two-way shape memory effect and viscoelastic properties in NiTiHf polycrystals containing nanosized particles

The effect of stress-induced martensite aging on the microstructure, viscoelastic properties, and one-way and two-way shape memory effect in high-temperature Ni50.2Ti37.3Hf12.5 aged polycrystals in tension was investigated. Stress-induced martensite aging for 6 h resulted in significant changes in the viscoelastic properties of the polycrystals. The elastic module of the martensite and austenite increased (by a factor of two), and a large softening of the elastic module and the growth of internal friction by 30% during MT was observed. Aging in martensite leads to the induction of a two-way shape memory effect with a strain of 1.7%, whose degradation is related to the microstructural change. It is established that both the value and the stability of the high-temperature two-way shape memory effect are defined by the time of the stress-induced martensite aging and the maximum value and stability were observed at an aging time of 6 h

Thermal- and stress-induced martensitic transformations in [0 0 1]-oriented Ni44Fe19Ga27Co10 single crystals

The microstructures and martensitic transformations upon cooling/heating, and under a compressive load have been studied for [001]-oriented Ni44Fe19Ga27Co10 (at.%) single crystals after growth and following annealing at 1448K for 1h, followed by quenching. Heat treatment determined the microstructure of the high-temperature phase (crystal lattice, the presence of γ-phase particles, and the formation of B2-phase nanodomains). A wide superelasticity temperature range of 277K was found. Annealing led to an 80K increase in the martensitic transformations temperatures, widening of transformations intervals, and an increase in the strength properties of the high-temperature phase by 100MPa, which led to a shift of the superelasticity range towards high temperature

Orientation dependence of elastocaloric effect in Ni50Mn30Ga20 single crystals

In this study, the orientation dependence of the elastocaloric effect and superelasticity in Ni50Mn30Ga20 single crystals undergoing L21–10M/14M–L10 martensitic transformations was investigated. The maximum value of the adiabatic temperature change ΔTad at reverse stress-induced martensitic transformations was shown to weakly depends on the orientation and equals 10.8 and 12.3 K in compression along the [001] and [011] directions, respectively. The superelasticity and elastocaloric effect temperature intervals were determined from the crystal orientation and were 80 K from 373 to 453 K for [001]-oriented crystals and 30 K from 373 to 403 K for [011]-oriented crystals. The strong orientation dependence of stress hysteresis Δσ (Δσ = 50–60 MPa for [001]-oriented crystals and Δσ = 110–142 MPa for [011]-oriented crystals) did not significantly affect the ΔTad, but determined the efficiency of the material for practical use as a solid state cooling device. The factors influencing the ΔTad(T) dependence were analyzed

Mineralogical and Geochemical Constraints on Magma Evolution and Late-Stage Crystallization History of the Breivikbotn Silicocarbonatite, Seiland Igneous Province in Northern Norway: Prerequisites for Zeolite Deposits in Carbonatite Complexes

The present work reports on new mineralogical and whole-rock geochemical data from the Breivikbotn silicocarbonatite (Seiland igneous province, North Norway), allowing conclusions to be drawn concerning its origin and the role of late fluid alteration. The rock shows a rare mineral association: calcite + pyroxene + amphibole + zeolite group minerals + garnet + titanite, with apatite, allanite, magnetite and zircon as minor and accessory minerals, and it is classified as silicocarbonatite. Calcite, titanite and pyroxene (Di36–46 Acm22–37 Hd14–21) are primarily magmatic minerals. Amphibole of mainly hastingsitic composition has formed after pyroxene at a late-magmatic stage. Zeolite group minerals (natrolite, gonnardite, Sr-rich thomsonite-(Ca)) were formed during hydrothermal alteration of primary nepheline by fluids/solutions with high Si-Al-Ca activities. Poikilitic garnet (Ti-bearing andradite) has inclusions of all primary minerals, amphibole and zeolites, and presumably crystallized metasomatically during a late metamorphic event (Caledonian orogeny). Whole-rock chemical compositions of the silicocarbonatite differs from the global average of calciocarbonatites by elevated silica, aluminium, sodium and iron, but show comparable contents of trace elements (REE, Sr, Ba). Trace element distributions and abundances indicate within-plate tectonic setting of the carbonatite. The spatial proximity of carbonatite and alkaline ultramafic rock (melteigite), the presence of “primary nepheline” in carbonatite together with the trace element distributions indicate that the carbonatite was derived by crystal fractionation of a parental carbonated foidite magma. The main prerequisites for the extensive formation of zeolite group minerals in silicocarbonatite are revealed

The Effect of Thermal Treatment on Microstructure and Thermal-Induced Martensitic Transformations in Ni₄₄Fe₁₉Ga₂₇Co₁₀ Single Crystals

Heat treatments of single crystals of Ni44Fe19Ga27Co10 (at.%) shape memory alloys cause various microstructures of the high-temperature phase. The nanodomain structure, consisting of regions of the L21- and B2-phases, and nanosized particles are the main parameters that change during heat treatments and determine the mechanism of nucleation and growth of martensite crystals, the size of thermal-induced martensite lamellae, the temperature Ms, and the temperature intervals of the martensitic transformation. In the as-grown single crystals, the high-temperature phase has only the L21-structure and the MT occurs at low (Ms = 125 K) temperatures due to the motion of the practically single interphase boundary in narrow temperature ranges of 3–7 K. The reduction in the volume fraction of the L21-phase to 40% and the formation of nanodomains (20–50 nm) of the L21-and B2-phases due to annealing at 1448 K for 1 h with quenching causes an increase in the MT temperatures by 80 K. The MT occurs in wide temperature ranges of 40–45 K because of multiple nucleation of individual large (300–500 µm) martensite lamellae and their growth. After aging at 773 K for 1 h, the precipitation of nanosized particles of the ω-phase in such a structure additionally increases the MT temperatures by 45 K. The MT occurs due to the multiple nucleation of packets of small (20–50 μm) martensite lamellae