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  • 1
    Electronic Resource
    Electronic Resource
    Joining of Superalloys to Intermetallics Using Nanolayers (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 59 (Dec. 2008), p. 225-229 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Joining nickel based superalloys to gamma-TiAl intermetallic alloys will contribute to a more efficient application of these advanced materials, particularly in extreme environments. In this study, Inconel alloy and gamma-TiAl are joined using as filler alternated nanolayer thin films deposited onto each base material. The nanolayers consisted in Ni/Al exothermic reactive multilayer thin films with periods of 5 and 14 nm deposited by d.c. magnetron sputtering in order to improve the adhesion to the substrates and to avoid the reaction between Ni and Al. Diffusion bonding experiments with multilayer coated alloys were performed under vacuum at 800ºC by applying 50 MPa during 1h. Bonding was achieved in large areas of the centre of the joints where regions without cracks or pores were produced, especially when using multilayer thin films with a 14 nm modulation period
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.59.225.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Joining of Gamma-Based Titanium Aluminides – A Review (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 514-516 (May 2006), p. 483-489 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The optimisation of joining technologies is essential to the application of advancedmaterials in the design of parts and devices. The development of intermetallic compounds, as structural materials, inevitably requires a new approach to join these compounds to themselves or to other materials. Among different intermetallic classes, titanium aluminides are one of the most studied. However, the industrial application is far from being proportional to the research, due to different problems, where joining processes have an important role. The present paper highlightsthe state of art on joining γ-TiAl alloys. A review is presented with special emphasis on solid-state diffusion bonding process, because it seems to be the most suitable technique to produce high quality joints of advanced materials. The influence of the bonding conditions on the physical and mechanical properties of the joints is highlighted and the introduction of single or multiple interlayers to assist in the bonding process is discussed. A novel approach developed by the authorsto the solid-state diffusion bonding of γ-TiAl alloys using Ti/Al multilayer thin films as bonding materials is proposed. The improvement of the solid-state diffusion bonding will induce sound joints at lower temperatures or pressures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.514-516.483.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Annealing Conditions on the Grain Size of Nanocrystalline Copper Thin Films (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 483-487 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Nanocrystalline metals demonstrate a broad range of fascinating mechanical properties atthe nanoscale, namely a significant increase in hardness and superior yield stress. In this regard,understanding grain growth in nanocrystalline metals is crucial, particularly because nano sizegrains are characterized by a high curvature, which results in a high driving force for grain growth.In this work, the effect of annealing conditions on grain size of copper nanocrystalline thin filmswas investigated. The nanocrystalline copper thin films were first deposited by d.c. magnetronsputtering on a copper substrate. The specimens were then annealed in vacuum at 100, 300 and500ºC from 10 minutes to 5 hours. Transmission electron microscopy observations revealed that theas-deposited thin films have a bimodal grain size distribution; an average grain size of 43±2nm andthe presence of nanotwins. Abnormal grain growth was observed for some samples annealed.Increasing the annealing time induced significant grain growth and promoted twin formation in thelarger grains. Finally, the hardness of these nanocrystalline Cu thin films was determined usingatomic force microscope. The relation between mechanical properties, annealing conditions andgrain size was analyzed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.587-588.483.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Strain Path Change Effect on Deformation Behaviour of Materials with Low-to-Moderate Stacking Fault Energy (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 420-424 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Stacking fault energy (SFE) plays an important role in face centred cubic (f.c.c.) metalsand alloys in determining the prevailing mechanisms of plastic deformation. Low SFE metals andalloys have a tendency to develop mechanical twinning, besides dislocation slip, during plasticdeformations. Deformation behaviour and microstructure evolution under simple and complexstrain paths were studied in 70/30 brass, with small and intermediate grain sizes, which correspondsto a f.c.c. material with low SFE. Simple (rolling and tension) and complex (tension normal toprevious rolling) strain paths were performed. The macroscopic deformation behaviour of materialsstudied is discussed in terms of equivalent true stress vs. equivalent true strain responses and strainhardening rates normalized by shear modulus (dσ/dε)/G as vs. (σ – σ0)/G (σ0 is the initial yieldstress of the material and G is the shear modulus). The mechanical behaviour is discussed withrespect to dislocation and twin microstructure evolution developed in both, simple and complexstrain paths
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.587-588.420.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion Brazing of a γ-TiAl Alloy Using Tini 67: Microstructural Evolution of the Interface (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 425-429 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A detail study focussing the microstructural evolution of the interfacial zone in the courseof the processing of Ti-47Al-2Cr-2Nb joints using Tini 67 as filler alloy was carried out in thisinvestigation. Experiments, aiming the understanding of the mechanisms that promote the meltingof the braze alloy, were performed below the solidus temperature of the filler, at 750 and 900ºC.Diffusion brazed samples were joined at 1000 and 1100ºC, with no dwelling stage and subsequentlyquenched in water in order to frozen the microstructure formed at the bonding temperature. Theinterfaces were analysed by scanning electron microscopy (SEM) and by energy dispersive X-rayspectroscopy (EDS), respectively. In the course of the heating stage, several single phase layerswere formed within the filler alloy due to the solid state interdiffusion of Ti and Ni atoms. At900ºC, the microstructure of the filler evolved form the initial Ti (α)/(Ni)/Ti/ (α) layers to aTi (β)/Ti2Ni/TiNi/TiNi3/TiNi/Ti2Ni/Ti (β) layered microstructure. The filler alloy begun to melt dueto the eutectic reaction between the contiguous layers composed of Ti (β) and Ti2Ni. After joining,the main phases detected at the interfaces were α2-Ti3Al, Ti-Ni-Al and Ti-Ni intermetallics. Forjoining at 1000ºC, a substantial amount of residual filler (Ti2Ni and Ti (α) particles) was alsodetected at the central zone of the interface. No marked evidences of residual filler zones werenoticed for joining at 1100ºC; instead, a mixture α2-Ti3Al with Ti-Ni-Al or Ti2Ni intermetallics wasdetected at the centre of the interface
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.587-588.425.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Bonding γ-TiAl Alloys Using Ti/Al Nanolayers Doped with Ag (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 488-491 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Successful solid state bonding of titanium aluminides requires the use of hightemperature and pressure. In previous works, authors have demonstrated that the use of Ti/Almultilayer thin film as an interlayer, deposited by d.c. magnetron sputtering onto the joiningsurfaces, can effectively lower the bonding temperature. The enhanced diffusivity of thesenanometric layers and the heat evolved by the formation of γ-TiAl improves the joinability oftitanium aluminide by solid-state diffusion bonding. In the present work, further improvement of theprocess was pursued by doping the interlayer with 2.8 at.% of Ag; previous studies have confirmedthat silver favours the transformation Ti+Al→γ-TiAl. The solid-state diffusion bonding experimentswere performed in vacuum by applying 50 MPa at 900ºC for 1 h. The effect of the third element onthe microstructure and chemical composition along the bonding interface has been analyzed.Microstructural characterisation of the interface was performed by scanning and transmissionelectron microscopy. Chemical compositions were analysed by energy dispersive X-rayspectroscopy. No defects were observed at the interface and sound bonding was achieved betweenthe interlayers and base γ-TiAl. The bonding interface shows a fine-grained microstructure, slightlycoarser than the one formed at the same temperature with the undoped Ti/Al multilayer
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.587-588.488.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Joining of TiAl Using a Thin Multilayer (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 514-516 (May 2006), p. 1323-1327 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: As TiAl based alloys begin to approach maturity, the development of successful and costeffective joining methods will be required. The growing industrial interest in these materials,particularly in aerospace and automotive industry, led to an interesting challenge - how to joint partsand components in order to produce integrated and resistant structures. Diffusion bonding ofmaterials produces components with thinner interfaces than other joining techniques do. Theabsence of abrupt microstructure discontinuity and the small deformation induced maximize jointstrength.This work focuses on the joining of TiAl using a thin multilayer obtained by alternating nanometriclayers of titanium and aluminium. The Ti/Al layers were deposited onto the γ-TiAl samples by DCmagnetron sputtering. The interfaces of these diffusion bonded joints depend on processing anddeposition conditions. In this work we describe the influence of bilayer thickness (period) and onmicrostructure and chemical composition of the joining interfaces
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.514-516.1323.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Assessing the Influence of Heat Treatments on γ-TiAl Joints (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 514-516 (May 2006), p. 1333-1337 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The heat treatment of γ-TiAl alloy (Ti-47Al-2Cr-2Nb (at.%)) diffusion brazed joints wasinvestigated. Joining was performed using a Ti/Ni/Ti clad-laminated braze alloy foil at 1050 and1150ºC with a dwell time of 10 minutes. The joints were subsequently heat treated at 1250 and1350ºC for 240 and 30 minutes, respectively. The microstructure and the chemical composition ofthe interfaces were analysed by scanning electron microscopy (SEM) and by energy dispersiveX-ray spectroscopy (EDS), respectively. Microhardness tests performed across the interface wereused to roughly predict the mechanical behaviour of the as-diffusion brazed and of the heat treatedjoints. Diffusion brazing produced interfaces with two distinct layers essentially composed ofα2-Ti3Al and of TiNiAl; γ-TiAl was also detected for joining at 1150ºC. After heat treating, theas-diffusion brazed microstructure of the interface was completely replaced by a mixture essentiallycomposed of γ-TiAl and α2–Ti3Al single phase grains and of (α2 + γ) lamellar grains.Microhardness tests showed that the hardness of the as-diffusion brazed interfaces, which rangesfrom 567 to 844 HV (15 gf), is significantly higher than that of the titanium aluminide alloy(272 HV). All post-joining heat treatments lowered substantially the hardness of the interface, as thehardness of the main phases detected at the interfacial zone after heat treating the joints iscomprised between 296 and 414 HV
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.514-516.1333.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Thermo-Mechanical Processing of a Ti 49.5Al 1.25Ag Alloy (2002)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 230-232 (Oct. 2002), p. 23-26 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/46/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.230-232.23.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    The Influence of the Processing Temperature on the Microstructure of γ-TiAl Joints Brazed with a Ti-15Cu-15Ni Alloy (2003)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 426-432 (Aug. 2003), p. 4159-4166 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/07/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.426-432.4159.pdf
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