scholarly journals Strength and fracture mechanism during torsion of ultrafine-grained austenitic steel for medical applications

2021 ◽  
Vol 64 (11) ◽  
pp. 832-838
Author(s):  
G. V. Klevtsov ◽  
R. Z. Valiev ◽  
M. V. Fesenyuk ◽  
N. A. Klevtsova ◽  
M. N. Tyur'kov ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Strength Properties ◽  
Middle Part ◽  
Coarse Grained ◽  
Torsional Strength ◽  
Medical Products ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Relative Shear ◽  
Steel Increase

The article considers evaluation of torsional strength and fracture of austenitic corrosion-resistant steel 08Kh18N9 with an ultrafine-grained (UFG) and coarse-grained (CG) structure, widely used in medicine for the production of plates, screws, rods for bone osteosynthesis and other medical products. The structure of the CG steel was studied using an Axiovert 40 MAT metallographic microscope, and the fine structure of the UFG steel was investigated with a JEM-2100 transmission electron microscope. Torsion tests of the cylindrical samples with a diameter of 10 mm were carried out at a temperature of 20 °C on MK-50 installation. JEOL JCM-6000 scanning electron microscope was used for the microfractographic studies of fracture surfaces. The analysis of the “Torque - torsion angle” diagrams showed that the torsional ultimate strength (τt) and yield strength (τ0.3) of UFG steel increase by 1.3 - 3.8 times, and the relative shear (g) decreases by 2.4 times in comparison with CG steel. High values of torsional strength properties of UFG steel make it possible to provide high torque without destroying the product. Consequently UFG steel 08Kh18N9 in comparison with CG steel is a more promising material for the manufacture of medical screws and other medical products that experience significant loads during the torsion process. Three areas were identified on the surface of all fractures: fibrous central part, transitional (middle) part, and a relatively smooth peripheral part. Fracture begins with the formation of shear pits in the middle and peripheral parts, which, with further rotation of the sample, are completely rubbed out (in case CG steel), or remain (in case of UFG steel). Final failure occurs under the action of normal stresses in the central part of the sample.

scholarly journals Особенности упрочнения структурированного интенсивной пластической деформацией сплава Al-Cu-Zr

2021 ◽  
Vol 63 (10) ◽  
pp. 1572
Author(s):  
Т.С. Орлова ◽  
Д.И. Садыков ◽  
М.Ю. Мурашкин ◽  
В.У. Казыханов ◽  
Н.А. Еникеев
Keyword(s):  
High Pressure Torsion ◽  
High Strength ◽  
Coarse Grained ◽  
X Ray Diffraction ◽  
Microstructural Parameters ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Preliminary Annealing ◽  
Coarse Grained State ◽  
Additional Hardening

The effect of small additions of copper on the microstructure and physic-mechanical properties of an ultrafine-grained Al-1.47Cu-0.34Zr (wt%) alloy structured by high pressure torsion after preliminary annealing at 375 °C for 140 h has been studied. As a result of processing, high values of strength characteristics (conditional yield strength 430 MPa, ultimate tensile strength 574 MPa) with an acceptable level of electrical conductivity (46.1% IACS) and ductility (elongation to fracture ~ 5%) have been achieved. On the basis of the microstructural parameters determined by X-ray diffraction analysis and transmission electron microscopy, hardening mechanisms responsible for such high strength have been analyzed. It was shown that Cu plays the key role in strengthening. The addition of copper significantly contributes to grain refinement and, consequently, to grain-boundary hardening. Alloying with copper leads to significant additional hardening (~ 130 MPa) in the ultrafine-grained alloy, which is not typical for coarse-grained state. Segregation of Cu at grain boundaries and the formation of Cu nanoclusters are the most probable reasons for this hardening.

Phase Transformations and Functional Properties of NiTi Alloy with Ultrafine-Grained Structure

2010 ◽  
Vol 667-669 ◽  
pp. 1059-1064 ◽  
Author(s):  
Egor Prokofiev ◽  
Juri Burow ◽  
Jan Frenzel ◽  
Dmitriy Gunderov ◽  
Gunther Eggeler ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Functional Properties ◽  
Niti Alloy ◽  
Coarse Grained ◽  
Scanning Calorimetry ◽  
Innovation Potential ◽  
Fine Grain ◽  
Transmission Electron ◽  
Ultrafine Grained

Severe plastic deformation (SPD) processes, are successfully employed to produce ultra fine grain (UFG) and nanocrystalline (NC) microstructures in Ni50.7Ti49.3 shape memory alloy. The effect of grain size on phase transformations during annealing is investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results of comparative studies of phase transformations in coarse-grained, UFG and NC alloys after SPD and subsequent long-term (up to 100 hours) annealing at 400С is presented. The functional properties and the innovation potential of UFG NiTi alloys is considered and discussed.

Study of Deformation Behavior of Ultrafine-grained Materials Through in Situ Nanoindentation in a Transmission Electron Microscope

2005 ◽  
Vol 20 (7) ◽  
pp. 1735-1740 ◽  
Author(s):  
M. Jin ◽  
A.M. Minor ◽  
D. Ge ◽  
J.W. Morris
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Transmission Electron Microscope ◽  
Deformation Behavior ◽  
Boundary Migration ◽  
Boundary Motion ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Grain Boundary Motion

The mechanical properties of ultrafine-grained and nanograined materials have received a great deal of recent attention because of their unusual and promising values. However, some of the most important mechanisms of deformation remain unclear. In this work, the deformation behavior of ultrafine-grained Al films and ultrafine-grained Fe is studied through in situ nanoindentation in a transmission electron microscope. Deformation-induced coarsening by grain boundary migration was observed in the ultrafine-grained Al films during deformation at room temperature, whereas no grain boundary motion was found in ultrafine-grained Fe. The lack of grain boundary motion in Fe was attributed to the pinning effect of nano-sized particles at the Fe grain boundaries.

Corrosion Characteristics of an Ultrafine-Grained Al-Mg-Si Alloy (AA6082)

2008 ◽  
Vol 584-586 ◽  
pp. 988-993 ◽  
Author(s):  
Bernhard Wielage ◽  
Daniela Nickel ◽  
Thomas Lampke ◽  
Gert Alisch ◽  
Harry Podlesak ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Before And After ◽  
Eis Measurements

The corrosion behaviour of the aluminium alloy, AA6082, processed by equal-channel angular pressing (ECAP) after different passes (route E, room temperature) was studied in comparison to the coarse-grained counterpart. The results of the electrochemical investigations (cyclovoltammetry; electrochemical impedance spectroscopy, EIS) are presented in correlation with the microstructure before and after the corrosion examinations. Both, chemical (precipitations, phases) and physical (dislocations, high-angle grain boundaries, grain size, low-angle grain boundaries) inhomogeneities characterize the microstructure of this commercially used Al-Mg-Si alloy. Results indicate an improved resistance against pitting of the ECAP material expressed by a reduced pitting density of up to 50 % and lower pit depths. EIS measurements and microstructural examinations (scanning electron microscopy, transmission electron microscopy, 3D topography measurement) confirm that ECAP modifies the number, size and distribution of these inhomogeneities, which leads to a more favourable corrosion behaviour.

Enhancing Mechanical Properties and Formability of AISI 301LN Stainless Steel Sheet by Local Laser Heat Treatment

2013 ◽  
Vol 554-557 ◽  
pp. 885-892 ◽  
Author(s):  
Antti Järvenpää ◽  
Matias Jaskari ◽  
Pentti Karjalainen ◽  
Mikko Hietala
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Laser Beam ◽  
Laser Treatment ◽  
Strength Properties ◽  
Coarse Grained ◽  
Laser Heat Treatment ◽  
Austenite Grain Size ◽  
Laser Heat ◽  
Ultrafine Grained

This study demonstrates applying local laser heat treatment to produce ultrafine-grained austenite (UFGA) structures in an AISI 301LN type commercial austenitic steel. Pieces of 50% cold-rolled sheets containing more than 90% strain-induced martensite were heated locally by a laser beam to various peak temperatures to obtain different degrees of martensite reversion to austenite. Mechanical properties and formability of grain-refined and coarse-grained structures were measured by tensile and Erichsen cup tests. In addition to standard Erichsen cup test, additional interrupted tests were carried out, where cups were first stretched close to the critical strain. Drawn cups were then heated locally by a laser beam to revitalize the structure and thereby enhance the formability in the following cupping test until failure. Results showed that local laser heat treatment is suitable for the reversion treatment to refine the austenite grain size. Various structures were produced: completely reverted microstructures (T > 700 °C) with grain sizes 0.9 - 2 µm in addition to partially reverted structure (T < 700 °C) containing nano- and ultrafine-grained austenite (0.6 µm) with some martensite. The grain refinement by local annealing improved the strength properties. The Erichsen cup tests showed that the formability was equal in the completely reverted ultrafine-grained structures to that of the coarse-grained sheets. It was demonstrated that the local laser treatment restored formability of the drawn cups, allowing stretching to be continued. The second forming step after the laser-treatment provided an enhancement of 19 and 14% in the cup depths in coarse-grained and ultrafine-grained steels, respectively, even though the laser-treatment parameters were not optimized yet.

The direct measurement of the strength of metals on a sub-micrometre scale

1970 ◽  
Vol 317 (1530) ◽  
pp. 367-391 ◽  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Amorphous Layer ◽  
Strength Properties ◽  
Perfect Crystal ◽  
Source Mechanism ◽  
Metallic Surface ◽  
Dislocation Generation ◽  
Transmission Electron ◽  
Soft Metal

Four types of experiment have been carried out to investigate the strength properties of annealed metals when the stressed volume is small enough to lie between the existing dis­locations in a crystal. These are (i) indentation experiments of a soft metal surface with a hard stylus, (ii) blunting of a soft metal tip against a hard surface, (iii) compression of individual metal crystals, and (iv) bending of thin filaments. The experiments were performed in either a scanning electron microscope or a transmission electron microscope with the use of micro­-loading devices capable of applying loads down to 0.1 mgf (10 -6 N). In the blunting experi­ments carried out in the transmission electron microscope it was possible to observe disloca­tions directly in the tip during loading. The majority of the experiments were carried out on gold. The results showed that strengths similar to the theoretical value can be achieved but in the experiments in which the stress was applied at an external surface (experiments (i), (ii) and (iii) above) the strength was strongly dependent on the condition of the interface. The strength that could be sustained by a region of perfect crystal in contact with a hard metallic surface was about five times less than the theoretical strength. These relatively low strengths are probably due to interfacial tractions producing very high local stresses. The introduction of some polymeric or amorphous layer at the interface raised the strength to the theoretical level. It is suggested that this is due to the fact that the polymeric layer removes most of the stress concentration. Transmission electron microscopy through aluminium tips during blunting showed that plastic deformation could take place at quite low stresses in a dislocation-free crystal with no dislocations remaining in the crystal during the early stages of blunting. Dislocation build up only occurred in the later stages of deformation. The yield stress was found to decrease with plastic strain in all the experiments, and could fall to values which were not substantially greater than those observed in large specimens. Comparison of the compressive strength of two spherical gold crystals, 0.5 μ m and 2 mm in diameter respectively, showed that the small crystal was only twice as strong as the large crystal after they had both undergone equal amounts of compression. The maximum strengths observed for gold ( μ /20) are greater than those calculated by Kelly (1966) ( ca . μ /50) and are nearer the value deduced by Brown & Woolhouse (1970) for the generation of dislocations around precipitate particles in alloys. The low strengths observed on deformed crystals are considered in the context of dislocation generation in small volumes and it is concluded that although a source mechanism of the Frank–Read type may be able to operate on this scale, some other source mechanism may also exist.

A Reproducible Selective Stain for Cardiac Sarcoplasmic Reticulum

1974 ◽  
Vol 32 ◽  
pp. 214-215
Author(s):  
R. A. Waugh ◽  
J. R. Sommer
Keyword(s):  
Complex System ◽  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Transmission Electron

Cardiac sarcoplasmic reticulum (SR) is a complex system of intracellular tubules that, due to their small size and juxtaposition to such electron-dense structures as mitochondria and myofibrils, are often inconspicuous in conventionally prepared electron microscopic material. This study reports a method with which the SR is selectively “stained” which facilitates visualizationwith the transmission electron microscope.

Surface Structure of the Spores of Glugea Weissenbergi

1969 ◽  
Vol 27 ◽  
pp. 238-239
Author(s):  
Sanford H. Vernick ◽  
Anastasios Tousimis ◽  
Victor Sprague
Keyword(s):  
Electron Microscope ◽  
Surface Structure ◽  
Transmission Electron Microscope ◽  
Mature Spore ◽  
Spore Surface ◽  
Sectioned Material ◽  
Transmission Electron ◽  
Surface Detail

Recent electron microscope studies have greatly expanded our knowledge of the structure of the Microsporida, particularly of the developing and mature spore. Since these studies involved mainly sectioned material, they have revealed much internal detail of the spores but relatively little surface detail. This report concerns observations on the spore surface by means of the transmission electron microscope.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

The Alteration of the Pore Spaces in Sandstones

1973 ◽  
Vol 31 ◽  
pp. 210-211
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Other ◽  
Coarse Grained ◽  
Depositional Fabric ◽  
Soluble Components ◽  
Scanning Electron ◽  
Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

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