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  • 1
    Online Resource
    Online Resource
    Use of Numerical Simulation at Optimisation of Technological Processes of Cold Bulk Forming
    VSB - Technical University of Ostrava ; 2012
    In:  Transactions of the VŠB - Technical University of Ostrava, Mechanical Series Vol. 58, No. 1 ( 2012-6-30), p. 175-182
    Details
    In: Transactions of the VŠB - Technical University of Ostrava, Mechanical Series, VSB - Technical University of Ostrava, Vol. 58, No. 1 ( 2012-6-30), p. 175-182
    Type of Medium: Online Resource
    ISSN: 1210-0471 , 1804-0993
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.22223/tr.2012-1
    DOI: 10.22223/tr
    DOI: 10.22223/tr.2012-1/1909
    Language: Unknown
    Publisher: VSB - Technical University of Ostrava
    Publication Date: 2012
    detail.hit.zdb_id: 2549232-9
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  • 2
    Online Resource
    Online Resource
    Metallographic Analysis of ECAP Processed Selected Magnesium Alloys
    Trans Tech Publications, Ltd. ; 2014
    In:  Materials Science Forum Vol. 782 ( 2014-4), p. 404-407
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 782 ( 2014-4), p. 404-407
    Abstract: Magnesium alloys has been used for a wide variety of applications, namely from the reason of their low density and high strength–to–weight ratio. The properties of magnesium alloys are connected with microstructure that is influenced by metallurgical and technological aspects. Scope of utilisation of foundry magnesium alloys is continuously being extended, so if we want to operate as competitive producers, it is necessary to investigate very actively properties of individual alloys, optimise their chemical composition, study issues of their metallurgical preparation, verify experimentally their casting properties and conditions of successful casting of castings by individual methods, including heat treatment. Recently, however, increases also utilisation of formed magnesium alloys namely application of SPD methods. The experimental part deals with hardness and structure determination of selected magnesium alloys after ECAP processing.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.782
    DOI: 10.4028/www.scientific.net/MSF.782.404
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2014
    detail.hit.zdb_id: 2047372-2
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  • 3
    Online Resource
    Online Resource
    New Type of Device for Achievement of Grain Refinement in Metal Strip
    Trans Tech Publications, Ltd. ; 2015
    In:  Advanced Materials Research Vol. 1127 ( 2015-10), p. 91-97
    Details
    In: Advanced Materials Research, Trans Tech Publications, Ltd., Vol. 1127 ( 2015-10), p. 91-97
    Abstract: DRECE - Dual Rolls Equal Channel Extrusion" (dual rolls pressure combined with equal channel extrusion) method is used for production of metallic materials with very fine grain size (hereinafter referred to as UFG structure - Ultrafine Grain Size). During the actual forming process the principle of severe plastic deformation is used. The device is composed of the following main parts: “Nord” type gearbox, electric motor with frequency speed converter, multi-plate clutch, feed roller and pressure rollers with regulation of thrust, and of the forming tool itself – made of Dievar steel type. Metallic strip with dimensions 58×2×1000 mm (width x thickness x length) is inserted into the device. During the forming process the main cylinder in synergy with the pressure roller extrude the material through the forming tool without any change of cross section of the strip. In this way a significant refinement of grain is achieved by severe plastic deformation. This method is used for various types of metallic materials, non-ferrous metals and their alloys. Forming process is based on extrusion technology with zero reduction of thickness of the sheet metal with the ultimate aim - achieving a high degree of deformation in the formed material. The DRECE device is also being verified from the viewpoint of achievement of a UFG structure in a blank of circular cross-section (wire) with diameter of ø 8 mm × 1000 mm (length).
    Type of Medium: Online Resource
    ISSN: 1662-8985
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/AMR.1127
    DOI: 10.4028/www.scientific.net/AMR.1127.91
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2015
    detail.hit.zdb_id: 2265002-7
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  • 4
    Online Resource
    Online Resource
    The Influence of Severe Plastic Deformation Process on Structure and Properties of AZ 31 Alloy after Selected Heat Treatment
    Trans Tech Publications, Ltd. ; 2018
    In:  Solid State Phenomena Vol. 275 ( 2018-6), p. 134-146
    Details
    In: Solid State Phenomena, Trans Tech Publications, Ltd., Vol. 275 ( 2018-6), p. 134-146
    Abstract: The technology of structure refinement in materials with the aim of achieving substantial mechanical properties and maintaining the required plasticity level is becoming increasingly useful in industrial practice. Magnesium alloys are very progressive materials for utilization in practice thanks to their high strength-to-weight ratios (tensile strength/density). The presented paper analyses the effect of the input heat treatment of the AZ31 alloy on the change of structure and strength properties through the process of severe plastic deformation (SPD), which finds an increasing utilization, especially in the automotive and aviation industry. For the study of the influence of the SPD process (ECAP method) on the properties of the AZ31 alloy, two types of thermal treatment of the initial state of the structure were selected. The analysis of the structure of the AZ31 alloy was performed in the initial state without heat treatment and subsequently after heat treatment. In the next part, the influence of the number of passes on the strengthening curves was evaluated. Mechanical properties of the AZ31 alloy after ECAP were evaluated by hardness measurement and completed by structure analysis.
    Type of Medium: Online Resource
    ISSN: 1662-9779
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/SSP.275
    DOI: 10.4028/www.scientific.net/SSP.275.134
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2018
    detail.hit.zdb_id: 2051138-3
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  • 5
    Online Resource
    Online Resource
    SEM EBSD and TEM Structure Studies of α-Brass after Severe Plastic Deformation Using Equal Channel Rolling Followed by Groove Pressing
    Trans Tech Publications, Ltd. ; 2012
    In:  Solid State Phenomena Vol. 186 ( 2012-3), p. 94-97
    Details
    In: Solid State Phenomena, Trans Tech Publications, Ltd., Vol. 186 ( 2012-3), p. 94-97
    Abstract: Commercial brass Ms36, 2mm thick was annealed and deformed in 6 passes in dual rolls equipment with attached equal channel equipment (DRECE). Then, material was deformed again using constrained groove pressing (CGP) by pressing of grooves 4.2 mm thick, and the groove angle of 45 deg. The experiment was performed 8 times (pressing out grooves and straightening at room temperature). Both methods allowed deformation without changing of the thickness of the sample, which was almost constant near 2 mm. The tensile experiment have shown the Yield Strength YS after 8x groove pressing of 210 MPa and Ultimate Tensile Strength UTS increased 27% up to 430 MPa. At the same time total elongation decreased from 34 to 15 %. The structure of the material after DRECE 6 passes was investigated using conventional TEM and have shown only rather uniform distribution of dislocations. After additional 8 groove pressing experiment, frequent, narrow deformation twins were observed accompanied by the formation of subgrains. Orientation imaging microscopy performed have shown average grain size after DRECE process near 5 μm, which decreased after 8 processes of groove pressing down to 2.9 μm. The fraction of low angle boundaries (below 5 deg) decreased after groove pressing down to 73% from 85% after DRECE process and annealing, while the fraction of high angle grain boundaries ( 〉 15 deg) increased after groove pressing up to 24% from 14%, however the total length of high angle boundaries increased more than 2 times since grain size decreased. The structure studies have shown rather mild effect on the grain refinement of both methods and they have to be modified to obtain material approaching nanosize range.
    Type of Medium: Online Resource
    ISSN: 1662-9779
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/SSP.186
    DOI: 10.4028/www.scientific.net/SSP.186.94
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
    detail.hit.zdb_id: 2051138-3
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  • 6
    Online Resource
    Online Resource
    Hot Deformation Behaviour of Mn–Cr–Mo Low-Alloy Steel in Various Phase Regions
    MDPI AG ; 2020
    In:  Metals Vol. 10, No. 9 ( 2020-09-17), p. 1255-
    Details
    In: Metals, MDPI AG, Vol. 10, No. 9 ( 2020-09-17), p. 1255-
    Abstract: The deformation behaviour of a coarse-grained as-cast medium-carbon steel, alloyed with 1.2% Mn, 0.8% Cr and 0.2% Mo, was studied by uniaxial compression tests for the strain rates of 0.02 s−1–20 s−1 in the unusually wide range of temperatures (650–1280 °C), i.e., in various phase regions including the region with predominant bainite content (up to the temperature of 757 °C). At temperatures above 820 °C, the structure was fully austenitic. The hot deformation activation energies of 648 kJ·mol−1 and 364 kJ·mol−1 have been calculated for the temperatures ≤770 °C and ≥770 °C, respectively. This corresponds to the significant increase of flow stress in the low-temperature bainitic region. Unique information on the hot deformation behaviour of bainite was obtained. The shape of the stress-strain curves was influenced by the dynamic recrystallization of ferrite or austenite. Dynamically recrystallized austenitic grains were strongly coarsened with decreasing strain rate and growing temperature. For the austenitic region, the relationship between the peak strain and the Zener–Hollomon parameter has been derived, and the phenomenological constitutive model describing the flow stress depending on temperature, true strain rate and true strain was developed. The model can be used to predict the forming forces in the seamless tubes production of the given steel.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met10091255
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662252-X
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  • 7
    Online Resource
    Online Resource
    Flow Stress and Hot Deformation Activation Energy of 6082 Aluminium Alloy Influenced by Initial Structural State
    MDPI AG ; 2019
    In:  Metals Vol. 9, No. 12 ( 2019-11-22), p. 1248-
    Details
    In: Metals, MDPI AG, Vol. 9, No. 12 ( 2019-11-22), p. 1248-
    Abstract: Stress-strain curves of the EN AW 6082 aluminium alloy with 1.2 Si-0.51 Mg-0.75 Mn (wt.%) were determined by the uniaxial compression tests at temperatures of 450–550 °C with a strain rate of 0.5–10 s−1. The initial structure state corresponded to three processing types: as-cast structure non-homogenized or homogenized at 500 °C, and the structure after homogenization and hot extrusion. Significantly higher flow stress appeared as a result of low temperature forming of the non-homogenized material. Hot deformation activation energy Q-values varied between 99 and 122 kJ·mol−1 for both homogenized materials and from 200 to 216 kJ·mol−1 for the as-cast state, while the Q-values calculated from the measured steady-state stress were always higher than those calculated from the peak stress values. For the extruded state of the 6082 alloy, the physically-based model was developed to reliably predict the flow stress influenced by dynamic softening, temperature, strain rate, and true strain up to 0.6.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met9121248
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2662252-X
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  • 8
    Online Resource
    Online Resource
    Grain Refinement of AZ61 Alloy after ECAP Processing
    Trans Tech Publications, Ltd. ; 2017
    In:  Materials Science Forum Vol. 891 ( 2017-3), p. 372-376
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 891 ( 2017-3), p. 372-376
    Abstract: Electron microscopy techniques were used to characterize the microstructure and deformation behavior of AZ61 alloy proceeded by ECAP. The commercial AZ61 alloy subjected to severe plastic deformation possesses a two-phase microstructure consisting of solid solution matrix and massive γ-phase Mg 17 Al 12 , or Mg 17 (Al,Zn) 12 distributed mostly at grain boundaries. Based on selected area diffraction and electron back scattered diffraction applied to a sample after the third pass, it can be concluded that plastic deformation induced by ECAP occurs mainly by slip mode forming a high density network of dislocation inside the grains. The grains size was significantly refined to 1.4 μm after the third pass of ECAP. The refinement of grain size is probably due to polygonization process associated with formation of high angle grain boundaries due to dislocations rearrangement. (Al, Zn) 12 Mg 17 precipitates of size scattered from 100 to 200 nm and also the primary precipitates of Al6Mn phase were observed in this alloy.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.891
    DOI: 10.4028/www.scientific.net/MSF.891.372
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2017
    detail.hit.zdb_id: 2047372-2
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  • 9
    Online Resource
    Online Resource
    SUPERPLASTIC DEFORMATION OF TWO PHASE MgLiAl ALLOY AFTER TCAP PRESSING
    SciCell ; 2017
    In:  Acta Metallurgica Slovaca Vol. 23, No. 3 ( 2017-09-30), p. 215-221
    Details
    In: Acta Metallurgica Slovaca, SciCell, Vol. 23, No. 3 ( 2017-09-30), p. 215-221
    Abstract: Magnesium based alloy containing 9 wt. % Li, 1,5 wt. % Al, composed of  (hcp + bcc) phases was cast under argon atmosphere and extruded at 350oC as bars of cross section 12x12 mm. Twist Channel Angular Pressing TCAP deformation was applied at a temperature of 160oC using BC rotation of samples in the following passes. TCAP tool consisted of helical part in horizontal area of the channel with an angle of lead γ = 30° to simulate back pressure and thus to increase the extrusion force. The initial grain size of the hexagonal  phase estimated at 30 m decreased in the following passes down to 6 m and that of bcc  phase decreased after TCAP from initial 12 m, down to 5 m. TEM studies after TCAP passes showed higher dislocation density in the  region than in the  phase. Crystallographic relationship (001)  || (110)  indicates parallel positioning of slip planes of both phases due to activation of slip. Electron diffraction indicates increase of grain misorientation with a number of TCAP passes. Stress/strain curves measured at temperature of 200oC show superplastic forming after 1st and 3rd TCAP passes with better superplastic properties with increasing number of passes. Values of strain rate sensitivity coefficient m were calculated at 0.31 after 1 TCAP pass using flow stress values from step strain increase curves. The sample after 3 TCAP passes showed increase of m value up to 0.47 for the strain rate range 10-5 – 5 x 10-4 s-1. Obtained values are slightly lower than those reported in the literature, however increase of a number of TCAP passes has a positive effect on superplastic properties due to fine grains and increase of their misorientation.
    Type of Medium: Online Resource
    ISSN: 1338-1156 , 1335-1532
    URL: Article
    DOI: 10.12776/ams.v23i3.987
    Language: Unknown
    Publisher: SciCell
    Publication Date: 2017
    detail.hit.zdb_id: 2379287-5
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  • 10
    Online Resource
    Online Resource
    Structural discontinuity in the hexagonal R T Al compounds: Experiments and density-functional theory calculations
    American Physical Society (APS) ; 2008
    In:  Physical Review B Vol. 77, No. 13 ( 2008-4-9)
    Details
    In: Physical Review B, American Physical Society (APS), Vol. 77, No. 13 ( 2008-4-9)
    Type of Medium: Online Resource
    ISSN: 1098-0121 , 1550-235X
    URL: Article
    DOI: 10.1103/PhysRevB.77.134106
    RVK:
    UA 6500.3.B
    Language: English
    Publisher: American Physical Society (APS)
    Publication Date: 2008
    detail.hit.zdb_id: 1473011-X
    detail.hit.zdb_id: 2844160-6
    detail.hit.zdb_id: 209770-9
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