STUDY OF PHASE TRANSFORMATIONS OF THE MICROSTRUCTURE OF ALLOYS BASED ON BINARY ALLOY OF STOICHIOMETRIC COMPOSITION Ni-Mn

Микроструктуру сплава номинального состава Ni50Mn50 изучали методами микроскопии видимого света (ОМ), сканирующей (СЭМ) и просвечивающей электронной микроскопии (ПЭМ). Анализ изображений выполнен в среде программного обеспечения SIAMS 800 и нейросети SIAMS AIM. Изучена микроструктура сплава в мартенситном состоянии и после естественного старения. Фазовый состав и параметры кристаллических решеток фаз устанавливали методом рентгеноструктурного фазового анализа (РФСА) и дифракции обратно рассеянных электронов (EBSD).The microstructure of the alloy with the nominal composition Ni50Mn50 was studied by visible light microscopy, scanning microscopy, and transmission electron microscopy. Image analysis was performed in the SIAMS 800 software environment and the SIAMS AIM neural network. The microstructure of the alloy in the martensitic state and after natural aging was studied. The phase composition and crystal lattice parameters of the phases were determined by X-ray diffraction phase analysis and electron backscatter diffraction.Работа выполнена в рамках государственного задания МИНОБРНАУКИ России (Шифр «Структура» Г.р. № 122021000033-2). Работа выполнена с использованием оборудования ЦКП «Испытательный центр нанотехнологий и перспективных материалов» ИФМ УрО РАН. При финансовой, технической и программной поддержке ООО «СИАМС»

Influence of Heat Treatment and Deformation on the Structure, Phase Transformation, and Mechanical Behavior of Bulk TiNi-Based Alloys

We present a brief overview of the structural and phase transformations and mechanical properties of bulk binary TiNi shape memory alloys, which demonstrate attractive commercial potential. The main goal of this work was to create a favorable microstructure of bulk alloys using both traditional and new alternative methods of thermal and thermomechanical processing. It was found that the implementation of an ultrafine-grained structure by different methods determined an unusual combination of strength, ductility, reversible deformation, reactive resistance of these alloys to subsequent tensile or torsion tests at room temperature, and, as a consequence, the highly reversible effects of the shape memory and superelasticity. It is shown that the alloys Ti49.8Ni50.2 and Ti49.4Ni50.6 are incapable of aging, and, after being subjected to ECAP, were characterized by their high strength (σu up to 1200 MPa) and ductility (δ up to 60–70%). A combined treatment of multi-pass rolling and HT of the Ti49.5Ni50.5 and Ti49Ni51 alloys prone to aging have provided even greater strength (σu up to 1400–1500 MPa) with slightly lower ductility (25–30%). The microstructure, phase composition, and martensitic transformations in Ti-Ni alloys with varying Ni concentrations ranging from 50 to 51 wt.% were investigated by TEM, SEM, and X-ray methods. The mechanical behavior of the alloys was studied during tensile and torsion tests

Influence of Heat Treatment and Deformation on the Structure, Phase Transformation, and Mechanical Behavior of Bulk TiNi-Based Alloys

We present a brief overview of the structural and phase transformations and mechanical properties of bulk binary TiNi shape memory alloys, which demonstrate attractive commercial potential. The main goal of this work was to create a favorable microstructure of bulk alloys using both traditional and new alternative methods of thermal and thermomechanical processing. It was found that the implementation of an ultrafine-grained structure by different methods determined an unusual combination of strength, ductility, reversible deformation, reactive resistance of these alloys to subsequent tensile or torsion tests at room temperature, and, as a consequence, the highly reversible effects of the shape memory and superelasticity. It is shown that the alloys Ti49.8Ni50.2 and Ti49.4Ni50.6 are incapable of aging, and, after being subjected to ECAP, were characterized by their high strength (σu up to 1200 MPa) and ductility (δ up to 60–70%). A combined treatment of multi-pass rolling and HT of the Ti49.5Ni50.5 and Ti49Ni51 alloys prone to aging have provided even greater strength (σu up to 1400–1500 MPa) with slightly lower ductility (25–30%). The microstructure, phase composition, and martensitic transformations in Ti-Ni alloys with varying Ni concentrations ranging from 50 to 51 wt.% were investigated by TEM, SEM, and X-ray methods. The mechanical behavior of the alloys was studied during tensile and torsion tests