Thermoelastic martensitic transformations, mechanical properties, and shape-memory effects in rapidly quenched Ni45Ti32Hf18Cu5 alloy in the ultrafine-grained state

Pushin, V. G.; Пушин, А. В.; Куранова, Н. Н.; Кунцевич, Т. Э.; Уксусников, А. Н.; Dyakina, V. P.; Коуров, Н. И.

doi:10.1134/s0031918x16120115

Cited by 8 publications

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“…There exist several ways to improve the ductility of intermetallics, among which grain size reduction and atomic disordering should be mentioned [ 5 , 18 ]. It has been established that the combined technologies of ultra-rapid quenching (URQ) from the melt [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ] and severe plastic deformation (SPD) [ 31 , 32 , 33 , 34 , 35 , 36 ] can provide production of SM alloys of individual chemical compositions based on titanium nickelide and copper, in a high-strength and ductile fine-grained (FG) [or ultra-fine-grained (UFG)] state. A URQ from the melt entails an increase in the strength and ductility of FG alloys with a mean grain size in the interval 0.2–1.0 μm, depending on the regime of subsequent thermal treatment.…”

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confidence: 99%

New Metastable Baro- and Deformation-Induced Phases in Ferromagnetic Shape Memory Ni2MnGa-Based Alloys

et al. 2022

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Structural and phase transformations in the microstructure and new metastable baro- and deformation-induced phases of the Ni50Mn28.5Ga21.5 alloy, typical of the unique class of ferromagnetic shape memory Heusler alloys, have been systematically studied for the first time. Phase X-ray diffraction analysis, transmission and scanning electron microscopy, and temperature measurements of electrical resistivity and magnetic characteristics in strong magnetic fields were used. It was found that in the course of increasing the pressure from 3 to 12 GPa, the metastable long-period structure of martensite modulated according to the 10M-type experienced transformation into a final non-modulated 2M structure. It is proved that severe shear deformation by high pressure torsion (HPT) entails grainsize refinement to a nanocrystalline and partially amorphized state in the polycrystalline structure of the martensitic alloy. In this case, an HPT shear of five revolutions under pressure of 3 GPa provided total atomic disordering and a stepwise structural-phase transformation (SPT) according to the scheme 10M → 2M → B2 + A2, whereas under pressure of 5 GPa the SPT took place according to the scheme 10M → 2M → B2 → A1. It is shown that low-temperature annealing at a temperature of 573 K caused the amorphous phase to undergo devitrification, and annealing at 623–773 K entailed recrystallization with the restoration of the L21 superstructure in the final ultrafine-grained state. The size effect of suppression of the martensitic transformation in an austenitic alloy with a critical grain size of less than 100 nm at cooling to 120 K was determined. It was established that after annealing at 773 K, a narrow-hysteresis thermoelastic martensitic transformation was restored in a plastic ultrafine-grained alloy with the formation of 10M and 14M martensite at temperatures close to those characteristic of the cast prototype of the alloy.

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