Dynamic Scenarios of the Formation of Martensite with the {110} Habits in the Ni50Mn50 Alloy

Martensitic transformation B2–L10 in the ordered alloy Ni50Mn50, which occurs at comparatively high temperatures (980–920 K), is discussed with the use of dynamic concepts of the wave control of the threshold deformation. The proximity of the observed orientations of martensite-crystal habits (and of twin boundaries) to the planes of the {110} family makes it possible to use the longitudinal waves along the axes 〈001〉 (in the basis of the initial phase) as the driving factors. It is shown that at temperatures of the onset of the transformation there is a satisfactory correspondence between the calculated and experimental data on the tetragonality of martensite and on the volume effect. The opportunity of different dynamic scenarios of the formation of the final phase is noted, namely, of separate crystals; layered structures, in which the crystals of martensite with the identical orientation relationships alternate with the untransformed regions of austenite; and packets of pairwise-twinned crystals. Examples are given of morpho-types corresponding to these scenarios. © 2019, Pleiades Publishing, Ltd

Features of martensitic transformation and fine structure of intermetallic compound Ni50Mn50

Transmission and scanning electron microscopy and Xray and electron diffraction are used to investigate the martensitic transformation and martensitic phase structure of the Ni50Mn50 alloy. Its resistivity and coefficient of thermal expansion are measured over a wide temperature range. © 2013 Pleiades Publishing, Ltd

Short-range order and electronic properties of epitaxial graphene

One of the most rapidly developing areas of modern materials science is the study of graphene and materials on its basis. The experimental investigations have revealed different types of defects on the surface of graphene that form the ordered structures of atomic configurations. In the present work, the value of short-range order parameter for different configurations of foreign atoms in a graphene layer was calculated. The effect of various factors on the density of electronic states and electrical resistance in graphene was also investigated. The type of the ordering of foreign atoms in graphene rather than the concentration of impurities, was shown to be responsible for the change in the conductivity of graphene

CRYSTAL STRUCTURE OF MARTENSITE AND ORIENTATION RELATIONSHIP DURING THERMOELASTIC MARTENSITIC TRANSFORMATION IN NI-MN-BASED ALLOYS

By transmission and scanning electron microscopy, orientation relationships (OR) were determined for the B2↔L10 thermoelastic martensitic transformation (TMP) in the Ni50Mn50 alloy, which differed from the Bain OR previously adopted for them. OR were determined for TMP in doped Ni–Mn-based alloys with a long-period crystal lattice. Electron microscopic studies have shown that L10 martensite has a hierarchic morphology of packets of thin plates of pairwise twinned crystals with flat boundaries of habit close to {110}B2.Методами просвечивающей и сканирующей электронной микроскопии определены ориентационные соотношения (о. с.) при термоупругом мартенситном превращении (ТМП) В2↔L10 в сплаве Ni50Mn50, отличные от принятых ранее для них ориентационных соотношений Бейна. Определены о. с. при ТМП и в легированных сплавах на основе Ni–Mn с длиннопериодной кристаллической решеткой. Электронно-микроскопические исследования показали, что тетрагональный L10‑мартенсит имеет преимущественную морфологию в виде иерархии пакетов тонких пластин попарно двойникованных кристаллов с плоскими границами габитусов, близкими {110}B2. Их внутренняя структура образована нанодвойниками того же типа.Работа выполнена в рамках Госзадания (шифр «Структура»), г. р. № АААА-А18-118020190116-6, и при поддержке гранта РФФИ 18-32-00529 мол_а

Multicomponent alloys with thermally, mechanically and magnetically controlled shape memory effects

This paper presents a brief review of the systematic study of the influence of the chemical composition on the structure, phase transformations and physical properties of binary and quasi-binary Ti-Ni, TiNi-TiFe, TiNi-NiCu, NiMn-NiGa and Ni2MnGa-Ni3Ga systems, which undergo thermoelastic martensitic transformations (TMT) and related with them thermally, mechanically, or magnetically controlled shape memory effects (SME). The effect of alloying with a third component on the behavior of critical temperatures and the TMT sequence has been established, and their generalized diagrams have been constructed. It is shown that the morphology of thermoelastic martensite is a hierarchy of packets of thin coherent crystals. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-32-00529 mol_аUral Branch, Russian Academy of Sciences, UB RAS: 18-10-2-39Federal Agency for Scientific Organizations: АААА-А18-118020190116-6This work was performed within the state task of Federal Agency for Scientific Organizations (theme Struktura, no. АААА-А18-118020190116-6), with the support of the Project UB RAS (no. 18-10-2-39) and was partly supported by the Russian Foundation for Basic Research (project no. 18-32-00529 mol_а)

MICROSTRUCTURE AND THERMOELASTIC MARTENCITE TRANSFORMATIONS IN ALLOYS OF SYSTEMS NI–MN–AL

The properties, thermoelastic martensitic transformations (TMT), and the structure of Ni50Mn50–xAlx alloys (x = 5…25) were studied by the methods of measuring the electrical resistivity and microhardness, transmission and scaning electron microscopy, and X‑ray diffraction. Temperature of TMT is found to be decreas with increasing aluminum content, and the structure of martensite changes: 2M (L10) and multilayered 10M and 14M. Martensite has a hierarchic packet morphology of coherent plates of nano- and submicrocrystalline crystals with habit boundaries close to {110}B2.Методами измерений электросопротивления и микротвердости, просвечивающей и растровой электронной микроскопии, дифракции рентгеновских лучей исследованы свойства, термоупругие мартенситные превращения (ТМП) и структура сплавов состава Ni50Mn50–хAlx (x = 5, 10, 18, 20, 22, 24, 25). Установлено, что с повышением содержания алюминия понижается температура ТМП, а также изменяется структура мартенсита. Обнаружены мартенситные фазы 2M (L10) и многослойные 10 М и 14 М, морфология которых преимущественно имеет вид иерархии пакетов когерентных пластин нано- и субмикрокристаллических кристаллов с границами габитусов близкими {110}B2.Работа выполнена в рамках Госзадания (шифр «Структура»), г. р. № АААА-А18-118020190116-6, и при поддержке гранта РФФИ 18-32-00529 мол_а

COMPARATIVE ELECTRON-MICROSCOPIC STUDIY OF SHAPE MEMORY ALLOYS OF SYSTEMS CU–NI–AL AND NI–MN–AL

The microstructure of alloys in a wide range of chemical compositions has been studied by transmission and scanning electron microscopy, diffraction of electrons and X‑rays. The phase composition of all the investigated alloys and the mechanism of the fracture under deformation have been determined.Методами просвечивающей и сканирующей электронной микроскопии (ПЭМ и РЭМ), дифракции электронов и рентгеновских лучей исследована микроструктура сплавов в широком интервале химических составов, определен фазовый состав всех исследованных сплавов, изучен и проанализирован характер изломов при деформации до разрушения.Работа выполнена в рамках Госзадания (шифр «Структура»), г. р. № АААА-А18-118020190116-6, и при поддержке гранта РФФИ 18-32-00529 мол_а

Electron-Microscopic Studiy of Shape Memory of Systems Cu–Ni–Al AND Ni–Mn–fe Alloys

The microstructure of alloys in a wide range of chemical compositions has been studied by transmission and scanning electron microscopy, diffraction of electrons and X-rays. The phase composition of all investigated alloys and the mechanism of the fracture under deformation have been determined.Методами просвечивающей и сканирующей электронной микроскопии (ПЭМ и РЭМ), дифракции электронов и рентгеновских лучей исследована микроструктура сплавов двух систем Cu–Al–Ni и Ni–Mn–Fe, определен фазовый состав всех исследованных сплавов, изучен и проанализирован характер изломов при деформации до разрушения.Работа выполнена в рамках госзадания (шифр «Структура») г. р. № АААА-А18-118020190116–6 и при финаносовой поддержке гранта РФФИ 18–32–00529 мол_а