Cohesive and magnetic properties of grain boundaries in bcc Fe with Cr additions

Structural, cohesive, and magnetic properties of two symmetric $\Sigma3(111)$ and $\Sigma5(210)$ tilt grain boundaries (GBs) in pure bcc Fe and in dilute FeCr alloys are studied from first principles. Different concentration and position of Cr solute atoms are considered. We found that Cr atoms placed in the GB interstice enhance the cohesion by 0.5-1.2 J/m$^2$. Substitutional Cr in the layers adjacent to the boundary shows anisotropic effect on the GB cohesion: it is neutral when placed in the (111) oriented Fe grains, and enhances cohesion (by 0.5 J/m$^2$) when substituted in the boundary layer of the (210) grains. The strengthening effect of the Cr solute is dominated by the chemical component of the adhesive binding energy. Our calculations show that unlike the free iron surfaces, Cr impurities segregate to the boundaries of the Fe grains. The magnetic moments on GB atoms are substantially changed and their variation correlates with the corresponding relaxation pattern of the GB planes. The moments on Cr additions are 2-4 times enhanced in comparison with that in a Cr crystal and are antiparallel to the moments on the Fe atoms

Разработка информационной системы обеспечения мероприятий организации техническими средствами

Дипломная работа включает в себя: 125 с., 40 рис., 21 таблиц, 17 источников. Возрастающий объем поступающих данных и трудоемкость их обработки, возрастающая нагрузка на сотрудников, обусловили необходимость в информационной системе, позволяющей оперативно работать с поступающим потоком данных и осуществляющей поиск информации, хранящейся в базе данных. Данная работа посвящена проектированию и созданию информационной системы для проведения технических и организационных мероприятий в Администрации Томской Области. В рамках данной работы была создан программный продукт – информационная система по работе с базой данных для обеспечения и техническогоThesis consists of: 125, Figure 40, 21 tables, 17 sources... Increasing the volume of incoming data and the complexity of their treatment, increasing the load on the employees, led to the need for an information system allowing operatively to work with the incoming data stream and search for information stored in the database. This work is dedicated to the design and development of an information system for technical and organizational measures in the Tomsk Oblast Administration. As part of this work was to create a software product - information system for working with the database and to provide technical support for the activities

Modulated Martensite: Why it forms and why it deforms easily

Diffusionless phase transitions are at the core of the multifunctionality of (magnetic) shape memory alloys, ferroelectrics and multiferroics. Giant strain effects under external fields are obtained in low symmetric modulated martensitic phases. We outline the origin of modulated phases, their connection with tetragonal martensite and consequences for their functional properties by analysing the martensitic microstructure of epitaxial Ni-Mn-Ga films from the atomic to macroscale. Geometrical constraints at an austenite-martensite phase boundary act down to the atomic scale. Hence a martensitic microstructure of nanotwinned tetragonal martensite can form. Coarsening of twin variants can reduce twin boundary energy, a process we could follow from the atomic to the millimetre scale. Coarsening is a fractal process, proceeding in discrete steps by doubling twin periodicity. The collective defect energy results in a substantial hysteresis, which allows retaining modulated martensite as a metastable phase at room temperature. In this metastable state elastic energy is released by the formation of a 'twins within twins' microstructure which can be observed from the nanometre to millimetre scale. This hierarchical twinning results in mesoscopic twin boundaries which are diffuse, in contrast to the common atomically sharp twin boundaries of tetragonal martensite. We suggest that observed extraordinarily high mobility of such mesoscopic twin boundaries originates from their diffuse nature which renders pinning by atomistic point defects ineffective.Comment: 34 pages, 8 figure