scholarly journals Change of 0.34Cr-1Ni-Mo-Fe Steel Dislocation Structure in Plasma Electrolyte Hardening

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1928
Author(s):  
Bauyrzhan Rakhadilov ◽  
Zarina Satbayeva ◽  
Sherzod Ramankulov ◽  
Nurdaulet Shektibayev ◽  
Laila Zhurerova ◽  
...  
Keyword(s):  
Crystal Lattice ◽  
Dislocation Structure ◽  
Volume Fraction ◽  
Internal Stresses ◽  
Shear Stresses ◽  
Initial State ◽  
Α Phase ◽  
Quantitative Characteristics ◽  
Before And After ◽  
Plasma Electrolytic

This work deals with the study of changes in the dislocation structure and quantitative characteristics, as well as morphological components, of 0.34Cr-1Ni-Mo-Fe steel before and after plasma electrolytic hardening. According to the electron microscopic studies of the fine structure of 0.34Cr-1Ni-Mo-Fe steel before and after plasma electrolytic hardening, 0.34Cr-1Ni-Mo-Fe steel is a multiphase material containing an α-phase, a γ-phase (retained austenite), and a cementite and carbide phase. It was revealed that, morphologically, the α-phase in the initial state, generally, is present in the form of: lamellar pearlite with a volume fraction of 35%, a ferritocarbide mixture with a volume fraction of 45%, and fragmented ferrite with a volume fraction of 20% of the material. After surface hardening, the morphological components of the structure changed: packet–lamellar martensite with volume fractions of 60% and 40%, 5% and 7% of γ-phase as residual austenite in the crystals of packet–lamellar martensite, 0.6% and 1.5% of cementite in crystals of packet–lamellar martensite, and 0.15% and 0.35% of complex carbide М23С6 in crystals of packet–lamellar martensite, respectively, were observed. The quantitative characteristics of the dislocation structure were estimated by the following calculated indices of packet and lamellar martensite: scalar (ρ) and excess (ρ±) density of dislocations, the value of the curvature-torsion of the crystal lattice (χ), the amplitude of long-range internal stresses (σd), and the amplitude of shear stresses (σL), according to which the plastic nature of the bending-torsion of the crystal lattice was confirmed (σL > σd).

scholarly journals Structural-phase transformations in 0.34C–1CRr–1Ni–1Mo–Fe steel during plasma electrolytic hardening

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
B.K. Rakhadilov ◽  
R.S. Kozhanova ◽  
N.A. Popova ◽  
A.B. Nugumanova ◽  
A.B. Kassymov
Keyword(s):  
Phase Transformations ◽  
Surface Hardening ◽  
Structural Phase ◽  
Heat Removal ◽  
Internal Stresses ◽  
Material Surface ◽  
Thin Foils ◽  
Before And After ◽  
Plasma Electrolytic ◽  
Structural Phase Transformations

Abstract Structural-phase transformations in 0.34C–1Cr–1Ni–1Mo–Fe steel during plasma electrolytic hardening were investigated. Electrolytic-plasma hardening of steel samples was carried out by surface quenching with rapid concentrated heating of the surface by plasma action and subsequent rapid cooling by heat removal from the depth of the sample by electrolyte jet. Plasma electrolytic hardening was carried out in the cathode mode in an electrolyte made from an aqueous solution containing 20 % sodium carbonate and 10 % carbamide. To study the structural-phase states of the modified layer, we used the method of transmission diffraction electron microscopy on thin foils. The study of steel samples was carried out before and after the plasma electrolytic hardening. Initially, the steel was a mixture of pearlite and ferrite grains. Surface hardening of 0.34C–1Cr–1Ni–1Mo–Fe ferrite-pearlite steel led to a change in the structural-phase state and the formation of a packet-lamellar martensite structure. It was found that PEH leads to distortion of the crystal lattice and the formation of long-range internal stresses, as well as to the release of small particles of cementite and carbide of M23C6 type, uniformly distributed throughout the volume of the material. Surface hardening led to the increase in all quantitative parameters of the fine structure (ρ, ρ ±, χ, σL, σd).

scholarly journals Structure and properties of layer, surfaced on HARDOX 450 steel by boron containing wire

2019 ◽  
Vol 62 (8) ◽  
pp. 613-620
Author(s):  
Yu. F. Ivanov ◽  
V. E. Gromov ◽  
D. A. Romanov ◽  
A. A. Klopotov ◽  
Yu. A. Rubannikova
Keyword(s):  
Crystal Lattice ◽  
Cross Sections ◽  
Iron Boride ◽  
Initial State ◽  
Scalar Density ◽  
State Diagrams ◽  
Α Phase ◽  
Transmission Electron ◽  
High Microhardness ◽  
High Level

Analysis of structure phase states and properties of the layers formed on HARDOX 450 low alloy steel by welded-on wires with boron content of 4.5 and 6.5 % wt. was made by the methods of modern physical material science. In the initial state HARDOX 450 steel has the structure of tempered martensite, in the volume and along the boundaries of crystals of it the cementite particles are located. The particles located in the volume have acicular shape and those along boundaries are mainly round. The presence of extinction bend contours has been revealed, indicative of the curvature torsion of crystal lattice of the material’s portion. They originate and finish on the interfaces of martensite crystals. Scalar density of chaotically located dislocations and forming the netlike substructure is 6.2·1010 cm–2. The layer welded on HARDOX 450 steel has microhardness increasing by more than two-fold that of the base. Analysis of state diagrams of Fe – C, Fe – B, B – C systems and polythermal cross–sections in Fe – C – B system has shown that the rapid cooling of Fe23C6 – Fe23B6 alloys from liquid state would facilitate the formation of multiphase structural states. It is stated by the methods of transmission electron diffraction microscopy that the reasons for the high microhardness level of the surface layers are the following: formation of iron borides and crystals of ultafine-dispersion (up to 100 nm) packet martensite with high level (~1011 cm–2 ) of scalar density of dislocations; presence of nanodimentional particles of iron and boron carbides in the volume and on the boundaries of martensite crystals; high level of curvature torsion of crystal lattice of iron borides and α-phase grains, caused by the internal stress fields along interphase (interface of iron boride crystals and α-phase grains) and intraphase boundaries (interface of iron borides and martensite crystals packet). Increase in boron concentration from 4.5 to 6.5 % is accompanied by the sufficient increase (by 1.2 – 1.5 times) in hardness of welded layer. It is caused by the increase of dimensions and relative content of iron boride regions by 1.5 – 2.0 times.

scholarly journals The irreversible thermal expansion of an energetic material

2021 ◽  
Author(s):  
Hervé Trumel ◽  
François Willot ◽  
Thomas Peyres ◽  
Maxime Biessy ◽  
François Rabette
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Volume Fraction ◽  
Energetic Material ◽  
Internal Stresses ◽  
Plastic Yielding ◽  
Initial State ◽  
Expansion Behavior ◽  
Small Volume Fraction

The works deals with a macroscopically isotropic energetic material based on triamino-trinitrobenzene (TATB) crystals bonded with a small volume fraction of a thermoplastic polymer. This material is shown experimentally to display an irreversible thermal expansion behavior characterized by dilatancy and variations of its thermal expansion coefficient when heated or cooled outside a narrow reversibility temperature range. The analysis of cooling results suggests the existence of residual stresses in the initial state, attributed to the manufacturing process. Microstructure-level FFT computations including the very strong anisotropic thermoelastic TATB crystal response and temperature-dependent binder plasticity, show that strong internal stresses develop in the disoriented crystals under thermal load, either heating or cooling. Upon cooling, binder plastic yielding in hindered, thus promoting essentially brittle microcracking, while it is favored upon heating. Despite its low volume fraction, the role of the binder is essential, its plastic yielding causing stress redistribution and residual stresses upon cooling back to ambient.

Direct imaging of order-disorder and antiphase domain structures in Ti3Al intermetallic compound

1990 ◽  
Vol 48 (4) ◽  
pp. 480-481
Author(s):  
H. Q. Ye ◽  
T.S. Xie ◽  
D. Li
Keyword(s):  
Intermetallic Compound ◽  
Volume Fraction ◽  
Fundamental Problem ◽  
Antiphase Domain ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Domain Structures ◽  
Α Phase ◽  
Diffraction Patterns ◽  
Two Phases

The Ti3Al intermetallic compound has long been recognized as potentially useful structural materials. It offers attractive strength to weight and elastic modulus to weight ratios. Recent work has established that the addition of Nb to Ti3Al ductilized this compound. In this work the fundamental problem of this alloy, i.e. order-disorder and antiphase domain structures was investigated at the atomic scale.The Ti3Al+10at%Nb alloys used in this study were treated at 1060°C and then aged at 700°C for 2 hours. The specimens suitable for TEM were prepared by standard jet electrolytic-polishing technique. A JEM-200CX electron microscope with an interpretable resolution of about 0.25 nm was used for HREM.The [100] and [001] projections of the α2 phase were shown in Fig.l.The alloy obtained consist of at least two phases-α2(Ti3Al) and β0 structures. Moreover, a disorder α phase with small volume fraction was also observed. Fig.2 gives [100] and [001] diffraction patterns of the α2 phase. Since lattice parameters of the ordered α2 (a=0.579, c=0.466 nm) and disorder α phase (a0=0.294≈a/2, c0=0.468 nm) are almost the same, their diffraction patterns are difficult to be distinguished when they are overlapped with epitaxial orientation relationships.

Ciliary Flow of Casson Nanofluid with the Influence of MHD having Carbon Nanotubes

2020 ◽  
Vol 16 ◽  
Author(s):  
Adel Alblawi ◽  
Saba Keyani ◽  
S. Nadeem ◽  
Alibek Issakhov ◽  
Ibrahim M. Alarifi
Keyword(s):  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Pressure Rise ◽  
Shear Stresses ◽  
Left Wall ◽  
Coupled Equations ◽  
The Right

Objective: In this paper, we consider a model that describes the ciliary beating in the form of metachronal waves along with the effects of Magnetohydrodynamic fluid over a curved channel with slip effects. This work aims at evaluating the effect of Magnetohydrodynamic (MHD) on the steady two dimensional (2-D) mixed convection flow induced in carbon nanotubes. The work is done for both the single wall nanotube and multiple wall nanotube. The right wall and the left wall possess a metachronal wave that is travelling along the outer boundary of the channel. Methods: The wavelength is considered as very large for cilia induced MHD flow. The governing linear coupled equations are simplified by considering the approximations of long wavelength and small Reynolds number. Exact solutions are obtained for temperature and velocity profile. The analytical expressions for the pressure gradient and wall shear stresses are obtained. Term for pressure rise is obtained by applying Numerical integration method. Results: Numerical results of velocity profile are mentioned in a table form, for various values of solid volume fraction, curvature, Hartmann number [M] and Casson fluid parameter [ζ]. Final section of this paper is devoted to discussing the graphical results of temperature, pressure gradient, pressure rise, shear stresses and stream functions. Conclusion: Velocity profile near the right wall of the channel decreases when we add nanoparticles into our base fluid, whereas an opposite behaviour is depicted near the left wall due to ciliated tips whereas the temperature is an increasing function of B and ߛ and decreasing function of ߶.

scholarly journals Design of Low-Cost and High-Strength Titanium Alloys Using Pseudo-Spinodal Mechanism through Diffusion Couple Technology and CALPHAD

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2910
Author(s):  
Chaoyi Ding ◽  
Chun Liu ◽  
Ligang Zhang ◽  
Di Wu ◽  
Libin Liu
Keyword(s):  
Diffusion Couple ◽  
Titanium Alloys ◽  
High Throughput ◽  
Volume Fraction ◽  
Raw Materials ◽  
Low Cost ◽  
High Strength ◽  
High Yield ◽  
Α Phase ◽  
Cr System

The high cost of development and raw materials have been obstacles to the widespread use of titanium alloys. In the present study, the high-throughput experimental method of diffusion couple combined with CALPHAD calculation was used to design and prepare the low-cost and high-strength Ti-Al-Cr system titanium alloy. The results showed that ultra-fine α phase was obtained in Ti-6Al-10.9Cr alloy designed through the pseudo-spinodal mechanism, and it has a high yield strength of 1437 ± 7 MPa. Furthermore, application of the 3D strength model of Ti-6Al-xCr alloy showed that the strength of the alloy depended on the volume fraction and thickness of the α phase. The large number of α/β interfaces produced by ultra-fine α phase greatly improved the strength of the alloy but limited its ductility. Thus, we have demonstrated that the pseudo-spinodal mechanism combined with high-throughput diffusion couple technology and CALPHAD was an efficient method to design low-cost and high-strength titanium alloys.

A Novel Processing Route for the Fabrication of Monolithic and Composite Silicon Nitride

1992 ◽  
Vol 287 ◽  
Author(s):  
R. V. Raman ◽  
S. V. Rele
Keyword(s):  
Volume Fraction ◽  
Hot Isostatic Pressing ◽  
Thermal Exposure ◽  
Processing Route ◽  
Promising Alternative ◽  
Α Phase ◽  
Key Issues ◽  
Novel Processing ◽  
Composite Silicon

ABSTRACTCurrent hot isostatic consolidation methodology used for the fabrication of complex-shaped Si3N4-based components requires the use of an expensive glass encapsulation technique and extended thermal exposure (in hours) of the specimen. An alternative consolidation approach involving the use of solid pressure transmitting media under high pressure, has enabled the consolidation of Si3N4 alloys without the need for glass encapsulation.Characterization of microstructures and mechanical properties of this (MOR, fracture toughness) material has been carried out and will be presented. It has been noted that in Si 3N4/8%Y2O3-4%Al2O3 composition, consolidated using this approach, a significantly larger volume fraction of α phase has been retained compared with typically observed conversion in α⇒ β in hot isostatically pressed material or sintered material.Key issues for addressing densification and microstructure control using this process are presented. This rapid consolidation approach appears to be a promising alternative to hot isostatic pressing for the fabrication of complex-shaped Si3N4 components.

scholarly journals A Computational Model to Assess Poststenting Wall Stresses Dependence on Plaque Structure and Stenosis Severity in Coronary Artery

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Zuned Hajiali ◽  
Mahsa Dabagh ◽  
Payman Jalali
Keyword(s):  
Coronary Arteries ◽  
Computational Models ◽  
Strong Dependence ◽  
Internal Stresses ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Opening Pressure ◽  
Fibrous Cap ◽  
Stent Restenosis ◽  
Von Mises

The current study presents computational models to investigate the poststenting hemodynamic stresses and internal stresses over/within the diseased walls of coronary arteries which are in different states of atherosclerotic plaque. The finite element method is applied to build the axisymmetric models which include the plaque, arterial wall, and stent struts. The study takes into account the mechanical effects of the opening pressure and its association with the plaque severity and the morphology. The wall shear stresses and the von Mises stresses within the stented coronary arteries show their strong dependence on the plaque structure, particularly the fibrous cap thickness. Higher stresses occur in severely stenosed coronaries with a thinner fibrous cap. Large stress concentrations around the stent struts cause injury or damage to the vessel wall which is linked to the mechanism of restenosis. The in-stent restenosis rate is also highly dependent on the opening pressure, to the extent that stenosed artery is expanded, and geometry of the stent struts. The present study demonstrates, for the first time, that the restenosis is to be viewed as a consequence of biomechanical design of a stent repeating unit, the opening pressure, and the severity and morphology of the plaque.

scholarly journals The Effect of Heat Treatment on the Microstructure and Mechanical Properties of the Novel Low-Cost Ti-3Al-5Mo-4Cr-2Zr-1Fe Alloy

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3798
Author(s):  
Meng Sun ◽  
Dong Li ◽  
Yanhua Guo ◽  
Ying Wang ◽  
Yuecheng Dong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aging Time ◽  
Volume Fraction ◽  
Low Cost ◽  
Solution Treatment ◽  
Solution Temperature ◽  
The Novel ◽  
Α Phase ◽  
The Cost

In order to reduce the cost of titanium alloys, a novel low-cost Ti-3Al-5Mo-4Cr-2Zr-1Fe (Ti-35421) titanium alloy was developed. The influence of heat treatment on the microstructure characteristics and mechanical properties of the new alloy was investigated. The results showed that the microstructure of Ti-35421 alloy consists of a lamina primary α phase and a β phase after the solution treatment at the α + β region. After aging treatment, the secondary α phase precipitates in the β matrix. The precipitation of the secondary α phase is closely related to heat treatment parameters—the volume fraction and size of the secondary α phase increase when increasing the solution temperature or aging time. At the same solution temperature and aging time, the secondary α phase became coarser, and the fraction decreased with increasing aging temperature. When Ti-35421 alloy was solution-treated at the α + β region for 1 h with aging surpassing 8 h, the tensile strength, yield strength, elongation and reduction of the area were achieved in a range of 1172.7–1459.0 MPa, 1135.1–1355.5 MPa, 5.2–11.8%, and 7.5–32.5%, respectively. The novel low-cost Ti-35421 alloy maintains mechanical properties and reduces the cost of materials compared with Ti-3Al-5Mo-5V-4Cr-2Zr (Ti-B19) alloy.

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