Influence of Composition on the Evolution of Dislocation Substructure in the Low-Stability State Polycrystalline Cu-Al Alloys under Plastic Deformation

New concepts of dislocation physics of plasticity and strength are considered using quantitative methods of transmission diffraction electron microscopy. New concepts of dislocation physics of plasticity and strength are considered using quantitative methods of transmission diffraction electron microscopy. The analysis of changes in the parameters of the dislocation substructure (DSS) is given on the example of alloys Cu-0.5 and 14 аt. % Al and the influence of these parameters on the change in the substructure of the material at a temperature T=293 K is considered. It is shown that at each stage of deformation, there are usually two substructures ("old" and "new"). The blurring of the transition from stage to stage is associated with the presence of weakly stable pre-transition structural-phase States at certain degrees of deformation of several types of substructures simultaneously, i.e., a weakly stable structural-phase state of the system. Against the background of the "old" substructure, a "new" one is born, which in the process of deformation becomes the main one, and then the "old" one, in the depths of which another substructure is formed. Experimental evidence of this regularity is obtained for FCC alloys. The presence of grain boundaries complicates the diagrams: a third substructure is formed near the grain boundaries, which corresponds to the following substructures (later) in the sequence of DSS transformations.

Download Full-text

The Influence of Welding Mode on the Structural-Phase State of Steel 0.12С-18Cr-10Ni-1Ti-Fe at Welding by Modulated Current

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.303.118 ◽

2020 ◽

Vol 303 ◽

pp. 118-127

Author(s):

A.N. Smirnov ◽

Natalya A. Popova ◽

E.L. Nikonenko ◽

N.V. Ababkov ◽

K.V. Knyazkov ◽

...

Keyword(s):

Martensitic Transformation ◽

Base Metal ◽

Heat Affected Zone ◽

Phase State ◽

Dislocation Substructure ◽

Structural Phase ◽

Droplet Transfer ◽

Structural Phase State ◽

Fine Droplet ◽

Thin Foils

Investigations conducted by transmission electron microscopy on thin foils were aimed at studying the structural-phase state of heat-affected zone of the welding joint performed by modulated current at two welding modes: coarse-droplet and fine-droplet transfer. Welding was conducted on the austenitic steel 0.12С-18Cr-10Ni-1Ti-Fe using the facility UDI-203. Welding modes were: Ii = 175 А (coarse-droplet transfer) and 140 А (fine-droplet transfer). Welding was performed on thin foils sized 200 × 15 × 4 mm3. Investigations were focused on heat-affected zone at the distance of 1 mm from the weld line towards the base metal – the base metal zone and at the distance of 0.5 mm towards the welded metal – the welded metal zone. The studies showed that in the state before welding the steel matrix presents γ-phase (austenite), which has face-centered cubic (fcc) crystal lattice. Morphologically the steel structure is given as grains where defect structure is presented by only network dislocation substructure, and grains where along with the dislocation substructure there are mechanical (or deformation) microtwins in the form of packages of one, two and three systems. It was established that welding of steel 0.12С-18Cr-10Ni-1Ti-Fe by modulated current with coarse-droplet transfer leads to martensitic transformation γ → ε only in the welded metal zone. At fine-droplet transfer welding leads to martensitic transformation γ → ε both in the base metal zone and in the welded metal zone. In the welded metal zone phase transformation γ → ε occurs more intensively. It was revealed that crystal lattice distortion in the whole heat-affected zone at welding by modulated current has only plastic nature, irrespective of the welding mode. Welding by modulated current with fine-droplet transfer leads to lower internal stresses in the whole heat-affected zone.

Download Full-text

Evolution of dislocation substructure under deformation of ordered and disordered Pd3Fe alloy in the region of low stable structural-phase states

Izvestiya vysshikh uchebnykh zavedenii. Fizika ◽

10.17223/00213411/64/1/90 ◽

2021 ◽

Vol 64 (1) ◽

pp. 90-96

Author(s):

L.I. Trishkina ◽

◽

A.I. Potekaev ◽

A.A. Klopotov ◽

T.V. Cherkasova ◽

...

Keyword(s):

Dislocation Substructure ◽

Structural Phase ◽

Microscopy Study ◽

Electron Microscopy Study ◽

Stable States ◽

Degree Of Deformation ◽

Deformation Curves ◽

Disordered Alloys ◽

Ordered Alloys ◽

Weakly Stable

The results of an electron microscopy study of the evolution of the dislocation structure of a polycrystalline ordered and disordered Pd3Fe alloy in the region of weakly stable structural-phase States are presented. The scheme of rearrangement of dislocation substructures during the transition from stage to stage, which are highlighted on the deformation curves of the Pd3Fe alloy, is constructed. It is established that in the case of both disordered and ordered alloys, each stage of deformation is characterized by its own special types of dislocation substructure (DSS), which are the main carriers of deformation for this stage. Transitions from some types of DSS to other types occur in certain ranges of values of the degree of deformation ε. The appearance of the DSS type characteristic of this stage of deformation occurs at the previous stage, and as the degree of deformation increases, the proportion of this type of DSS increases. At the stage under consideration, their share is the largest, and when moving to the next stage, it gradually decreases until it disappears. In the case of ordered alloys, the types of dislocation substructure-the main carrier of deformation for this stage differ from the types of DSS that are implemented in disordered alloys at the same stage of deformation. It is shown that each stage of deformation has its own DSS - strain carriers. When moving to a new stage, the transition to new structural carriers of deformation occurs. During the transition, these carriers co-exist, which is a characteristic feature of weakly stable States of the system.

Download Full-text

The Effect of Vacuum on the Structure of Vapor Deposited In, V, and Mn

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061471 ◽

1967 ◽

Vol 25 ◽

pp. 292-293

Author(s):

L. E. Murr

Keyword(s):

Electron Microscopy ◽

Grain Size ◽

Vapor Deposition ◽

Structural Phase ◽

Structural Features ◽

Experimental Investigations ◽

Nominal System ◽

Diffraction Electron ◽

System Pressure

It has been observed by transmission and diffraction electron microscopy that the nominal background pressure just prior to the vapor deposition of certain metals, particularly those possessing more than one structure possibility, can be influential in determining the crystallographic structural phase which will form. Previous experimental investigations along this line have also revealed the fact that the nominal system pressure influences such structural features as grain size and epitaxy.

Download Full-text

Studies of structural-phase state of medical titanium alloys by contemporary methods of analytical electron microscopy

Inorganic Materials ◽

10.1134/s0020168513150065 ◽

2013 ◽

Vol 49 (15) ◽

pp. 1320-1330

Author(s):

M. B. Ivanov ◽

Yu. R. Kolobov ◽

S. S. Manokhin ◽

E. V. Golosov

Keyword(s):

Electron Microscopy ◽

Titanium Alloys ◽

Phase State ◽

Structural Phase ◽

Analytical Electron Microscopy ◽

Structural Phase State ◽

Analytical Electron

Download Full-text

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138993 ◽

1995 ◽

Vol 53 ◽

pp. 524-525

Author(s):

Z. Horita ◽

D. J. Smith ◽

M. Furukawa ◽

M. Nemoto ◽

R. Z. Valiev ◽

...

Keyword(s):

Electron Microscopy ◽

Solid Solution ◽

High Resolution ◽

Grain Boundaries ◽

Energy State ◽

High Energy ◽

Grain Structure ◽

Boundary Structure ◽

Solid Solution Alloy ◽

Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

Download Full-text

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012093x ◽

1992 ◽

Vol 50 (1) ◽

pp. 106-107

Author(s):

H.W. Zandbergen ◽

M.R. McCartney

Keyword(s):

Electron Microscopy ◽

Copper Oxide ◽

Grain Boundaries ◽

Atomic Structure ◽

Oxygen Deficiency ◽

Surface Layers ◽

Layer Sequence ◽

Surface Reconstructions ◽

Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

Download Full-text

High-resolution electron microscopy of nanostructured materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137239 ◽

1995 ◽

Vol 53 ◽

pp. 172-173

Author(s):

M. José-Yacamán

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Grain Boundaries ◽

Nanostructured Materials ◽

High Resolution Electron Microscopy ◽

Hrem Image ◽

Small Particles ◽

Resolution Electron ◽

Nanophase Materials

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.

Download Full-text

Novel Approaches to Low-Voltage Scanning Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180586 ◽

1990 ◽

Vol 48 (1) ◽

pp. 366-367

Author(s):

Arthur V. Jones

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Low Voltage ◽

Electron Optics ◽

Current Interest ◽

New Concepts ◽

Opportune Time ◽

Novel Approaches ◽

Voltage Scanning ◽

Scanning Electron

In comparison with the developers of other forms of instrumentation, scanning electron microscope manufacturers are among the most conservative of people. New concepts usually must wait many years before being exploited commercially. The field emission gun, developed by Albert Crewe and his coworkers in 1968 is only now becoming widely available in commercial instruments, while the innovative lens designs of Mulvey are still waiting to be commercially exploited. The associated electronics is still in general based on operating procedures which have changed little since the original microscopes of Oatley and his co-workers.The current interest in low-voltage scanning electron microscopy will, if sub-nanometer resolution is to be obtained in a useable instrument, lead to fundamental changes in the design of the electron optics. Perhaps this is an opportune time to consider other fundamental changes in scanning electron microscopy instrumentation.

Download Full-text