Fracture surface analysis of a quenched (α+β)-metastable titanium alloy

Fracture surface analysis is conducted by means of SEM for VT16 titanium alloy specimens solution-treated at temperatures ranging from 700 to 875 °C, water-quenched and subjected to tensile testing. A cup and cone shape failure and dimple microstructure of the fracture surface indicates the ductile behavior of the alloy. Dimple dimensions correlated with the β-grain size of the alloy in quenched condition. The fracture area (namely, the size; the cup and cone shape) depends on the volume fraction of the primary α-phase in the quenched sample. However, the fracture surface changes considerably when the strain-induced β-α''-transformation takes place during tensile testing, resulting in the increase of alloy ductility. © 2017 Author(s).Russian Foundation for Basic Research, RFBR: 15-08-08299 АCouncil on grants of the President of the Russian Federation: MK-6311.2016.8The work was supported by the grant of the President of Russian Federation, No. MK-6311.2016.8, and RFBR grant No. 15-08-08299 А

The Influence of Molybdenum Equivalent on the Anisotropy of Thermal Expansion of Titanium Martensite Lattice

The structure of the martensite formed by quenching in titanium alloys, as well as the connection between the rhombic lattice α - martensite and anisotropy of thermal expansion was investigated. Τhe methods of the X-ray and thermal XRD phase analyzes have been used to study the relationship between martensite crystal lattice, the coefficient of thermal expansion (CTE) and molybdenum and aluminum equivalent.     Keywords: titanium alloys, martensite, CTE, XRD-analysi

An "in situ" study of study of quenched Ti-Al system samples during heating

The study of the Ti-Al system samples containing up to 10 wt.% Al water quenched from different temperatures in β-phase region, was carried out in situ during heating on X-ray diffractometer. XRD analysis of quenched samples showed the presence of α'-martensite only. After quenching the increase of Al content in alloys displayed the decrease of the lattice parameters «a» and «c» and the rise of «c/a» ratio, since the lattice parameter «c» dropped slightly in contrast with the lattice parameter «a». Furthermore, Thermo-XRD (T-XRD) analysis represented the anisotropy of the coefficient of thermal expansion (CTE). Besides, T-XRD analysis indicated, that «c/a» ratio of samples Ti-0.5 wt.% Al with the least amount of Al revealed the fall of «c/a» ratio and at the same time samples contained 7 and 8 wt.% Al remained practically the same during heating. Whereas, samples Ti-10 wt.% Al with the largest quantity of Al showed the rise of c/a ratio during heating. © 2019 IOP Publishing Ltd. All rights reserved

Parameters Evolution of Orthorhombic Martensite Lattice in VT16 Titanium Alloy During Heating

The material of the study was (α + β) -titanium alloy VT16. Samples were quenched from different temperatures and then they were heated in situ on X-ray diffractometer. It has been established that the period “b” of the orthorhombic martensite lattice showed negative values of the coefficient of thermal expansion during heating.     Keywords: titanium alloys, XRD-analysis, orthorhombic martensite, coefficient of thermal expansion

Effect of the method for producing Cu-Cr3C2 bulk composites on the structure and properties

Copper-chromium carbide composites containing a carbide phase of 20-30 vol% were obtained with the use of solid- and liquid-phase mechanosyntheses, followed by magnetic pulse compaction (MPC) and spark plasma sintering. The morphology, structural-phase composition, density, hardness and electrical conductivity of the composites were investigated. The structure of composites obtained by MPC represents regions of copper matrix hardened by superfine carbide precipitates surrounded by a layer of chromium carbide. In the composites obtained by spark plasma sintering, the copper matrix hardened by superfine carbide precipitates was divided into areas surrounded by a copper-chromium layer. A composite obtained by the MPC of the powders synthesized using solid-phase mechanosynthesis (MS) (copper, chromium and graphite) had the highest values ofVickers microhardness (4.6GPa) and Rockwell hardness (HRA 69). The best value of electrical conductivity (36% IACS) was achieved using liquid-phase MS (copper, chromium and xylene) and spark plasma sintering. Liquid-phase MS is the only way to synthesize the powder with a small amount of the carbide phase and without contamination. © 2017 Indian Academy of Sciences.Government Council on Grants, Russian FederationFederal Agency for Scientific Organizations: 0428-2014-0002, 0389-2014-0002This work was supported by the Government of the Russian Federation (Federal Agency for Scientific Organizations) under the themes of the state task, no. 0389-2014-0002 and no. 0428-2014-0002 and by the Program of UD RAS, Project reg. no. AAAA-A17-117040610324-3

A general model for the crystal structure of orthorhombic martensite in Ti alloys

The present work develops a novel unified approach to describe the crystal structure of orthorhombic martensite (α′′) in Ti alloys independent of chemical composition. By employing a straightforward yet highly instructive solid sphere model for the basic tetrahedral structural unit the crystal structures involved in the β ↔ α′′/α′ martensitic transformation are categorized into several intermediate configurations. Importantly, a new metric is introduced, δ, which unambiguously characterizes the atomic positions inside the orthorhombic unit cell depending on unit-cell geometry. Furthermore, the exclusive use of relative quantities to describe unit-cell geometry and atom positions renders the approach developed herein independent of alloy content. In this way, shortcomings of commonly suggested structural metrics for α′′ are eliminated. Subsequently, the novel methodology is applied to analyse and compare the crystal structure of α′′ across a broad range of Ti alloys based on experimentally measured unit-cell parameters. From this analysis it emerges that a large fraction of structural configurations along the b.c.c.-Cmcm-h.c.p. transformation path is not observed in quenched alloys. The threshold between the not-observed and the remaining well observed configurations is identified with an ideal Cmcm crystal structure, relative to which the experimentally found α′′ is compressed along its c axis. © 2021 International Union of Crystallography. All rights reserved.0836-2020-0020The following funding is acknowledged: State Assignment of Russian Federation (grant 0836-2020-0020)

Special features of the structure and phase composition of a Ti-23Al-26Nb/Al layered material obtained by plasma-spark sintering

Special features of formation of the structure of a layered intermetallic material based on titanium aluminide obtained by the method of plasma-spark sintering of foils are studied. The dependence of the structure on the temperature-and-time treatment parameters is determined. © 2013 Springer Science+Business Media New York

Effect of Thermomechanical Treatment Parameters on Structure, Phase Composition and Mechanical Properties of Ti-3Al-5Mo-4.5V Titanium Alloy

The structure, phase composition and mechanical properties of (α+β) - titanium alloy solution treated at 850 C, cold-rolled at the reduction ratio in the range of 0... 45%, followed by ageing at 450, 500, 550 C for 0.5, 1.5, 3 hours was studied using XRD, microindentation and tensile testing. The influence of strain level at cold rolling and time-temperature parameters of ageing on the formation of structure and phase composition of solution treated and water quenched Ti-3Al-5Mo-4.5V alloy was investigated and discussed in terms of tensile properties and microhardness. The parameters of low temperature thermomechanical treatment (LTMT) of the (α+β) - alloy were proposed to obtain a high-strength state. © Published under licence by IOP Publishing Ltd.This study was financially supported by the State Assignment, grant number 0836-2020-0020. The research equipment was purchased with the support from Act 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006

Protein composition of interband regions in polytene and cell line chromosomes of Drosophila melanogaster

<p>Abstract</p> <p>Background</p> <p>Despite many efforts, little is known about distribution and interactions of chromatin proteins which contribute to the specificity of chromomeric organization of interphase chromosomes. To address this issue, we used publicly available datasets from several recent Drosophila genome-wide mapping and annotation projects, in particular, those from modENCODE project, and compared molecular organization of 13 interband regions which were accurately mapped previously.</p> <p>Results</p> <p>Here we demonstrate that in interphase chromosomes of <it>Drosophila </it>cell lines, the interband regions are enriched for a specific set of proteins generally characteristic of the "open" chromatin (RNA polymerase II, CHRIZ (CHRO), BEAF-32, BRE1, dMI-2, GAF, NURF301, WDS and TRX). These regions also display reduced nucleosome density, histone H1 depletion and pronounced enrichment for ORC2, a pre-replication complex component. Within the 13 interband regions analyzed, most were around 3-4 kb long, particularly those where many of said protein features were present. We estimate there are about 3500 regions with similar properties in chromosomes of <it>D. melanogaster </it>cell lines, which fits quite well the number of cytologically observed interbands in salivary gland polytene chromosomes.</p> <p>Conclusions</p> <p>Our observations suggest strikingly similar organization of interband chromatin in polytene chromosomes and in chromosomes from cell lines thereby reflecting the existence of a universal principle of interphase chromosome organization.</p