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  • 1
    Electronic Resource
    Electronic Resource
    Two-melt separation in supercooled Cu-Co alloys solidifying in a drop-tube (1991)
    Springer
    Journal of materials science 26 (1991), S. 6458-6466 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microstructure of Cu-Co alloys solidified by a free-fall containerless solidification was investigated using scanning electron microscopy. Spherical Cu-Co drops of about 3 mm diameter were solidified in an evacuated 105 m long drop-tube. The microstructures were compared with those obtained by an electromagnetic levitation technique. It was found that the falling drops were at the “liquid + solid” state at the moment of impact on the floor. Upon bumping on to the floor the drop splits into many fragments, which finally solidify in the form of flakes upon retouching the tube floor. The microstructure depends mainly on the solid fraction in the flake, and on its temperature at the moment of impact. Supercoolings up to 0.2TM could be achieved within the drop-tube, causing separation of the liquid into two melts. Under certain conditions the microstructure reveals the occurrence of discarded spheres, suggesting that cooling below a certain temperature (T misc) will cause mixing of the two melts into one liquid. Interpretation of the observed microstructures is based on the current understanding of rapid solidification mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02387830
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  • 2
    Electronic Resource
    Electronic Resource
    Two-melt separation in supercooled Cu-Co alloys solidifying in a drop-tube (1991)
    Springer
    Journal of materials science 26 (1991), S. 6458-6466 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microstructure of Cu-Co alloys solidified by a free-fall containerless solidification was investigated using scanning electron microscopy. Spherical Cu-Co drops of about 3 mm diameter were solidified in an evacuated 105 m long drop-tube. The microstructures were compared with those obtained by an electromagnetic levitation technique. It was found that the falling drops were at the “liquid + solid” state at the moment of impact on the floor. Upon bumping on to the floor the drop splits into many fragments, which finally solidify in the form of flakes upon retouching the tube floor. The microstructure depends mainly on the solid fraction in the flake, and on its temperature at the moment of impact. Supercoolings up to 0.2TM could be achieved within the drop-tube, causing separation of the liquid into two melts. Under certain conditions the microstructure reveals the occurrence of discarded spheres, suggesting that cooling below a certain temperature (T misc) will cause mixing of the two melts into one liquid. Interpretation of the observed microstructures is based on the current understanding of rapid solidification mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551897
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  • 3
    Electronic Resource
    Electronic Resource
    Toughening MoSi2 with niobiúm metal—effects of morphology of ductile reinforcements (1995)
    Springer
    Journal of materials science 30 (1995), S. 849-854 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Morphology effect of ductile reinforcements was evaluated using a four-point bend test on chevron-notched MoSi2 composites reinforced with 20 vol. % niobium. The niobium used had three different morphologies, i.e., fibre, foil and particle. The thickness of the foils was 250 Μm, while the fibres and particles had diameters of 250 and 200 Μm, respectively. Toughness of MoSi2 composites was increased from 3.3 MPa m1/2 for the matrix to 15 MPa m1/2 with the incorporation of the Nb fibres or foils. The particulate composites also exhibited an increase in toughness (∼7 MPa m1/2). The toughening achieved was mainly attributed to ductile phase bridging in all the composites tested. The relatively small toughness improvement in the particulate composites was ascribed to the embrittlement of the Nb particles. The results indicate that toughening by crack bridging depends mainly on the intrinsic properties of the ductile bridging ligaments rather than on their morphology, and that the embrittlement of the bridging ligament is detrimental to the toughening of the composites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178416
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical states of the molybdenum disilicide (MoSi2) surface (1995)
    Springer
    Journal of materials science 30 (1995), S. 5272-5280 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The analysis of the oxidation of MoSi2 at room temperature was carried out using X-ray photoelectron spectroscopy. A clean surface of MoSi2 was obtained by sputter-etching the bulk material inside the spectrometer, and the chemical states of the surface were examined with both high and low take-off angles for the conditions of as-etched and exposed to the air for different times. The commercially pure MoSi2 powder was also investigated in the as-received condition. The analysis indicated that the exposure of a clean molybdenum disilicide to the air for just a few minutes led to the formation of SiO2 and MoO2, and this oxidation would persist at least for more than 24 h with the final surface of MoSi2 being covered by a duplex oxide layer of SiO2 + MoO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356081
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  • 5
    Electronic Resource
    Electronic Resource
    Liquid separation in Cu–Co and Cu–Co–Fe alloys solidified at high cooling rates (1998)
    Springer
    Journal of materials science 33 (1998), S. 3639-3649 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The impact of cooling rates on the microstructure of Cu–Co and Cu–Fe–Co alloys was investigated by scanning electron microscopy. The high cooling rates entailed in the electron beam surface melting of the alloys result in bulk supercooling of at least 150 K, which in turn causes three microstructural effects: (i) melt separation into two liquids, namely copper poor, L1, and copper rich, L2; (ii) microstructural refinement; (iii) enhanced solute trapping of Cu in the Fe- or Co-rich phases. No evidence of metastable liquid separation was found for Cu–50 wt% Co. There are indications that similar dynamic supercooling exists in copper-quenched or arc-melted samples near the splat contact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004663530929
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of supercooling on the microstructure of Al-Nb alloys (2000)
    Springer
    Journal of materials science 35 (2000), S. 2263-2271 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electromagnetic levitation was used to study supercooling effects on solidification characteristics of Al-Nb alloys containing 15–53 at.% Nb. The results indicate that Al3Nb, with a melting temperature of 1980 K, is not a stoichiometric line compound but has a homogeneity range on the Nb side. These results are consistent with the more recently assessed Al-Nb phase diagram, but not with those assessed previously. Significant changes in the microstructural morphology of Al-40 at.% Nb were also observed as a function of the bulk supercooling. These include metastable compositional extensions of Al3Nb, preferential nucleation of Al3Nb in the supercooled liquid and corresponding changes in the solidification path. For example, spherical domains comprising of a mixture of Al3Nb and AlNb2 were revealed in the eutectic microstructure, their volume fraction being an increasing function of the degree of supercooling. Moreover, the Al3Nb and AlNb2 exhibited metastable compositional extensions up to 31 at.% for the former and down to 48 at.% Nb for the latter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004783011253
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  • 7
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    Two-melt separation in supercooled Cu-Co alloys solidifying in a drop-tube (1991)
    Springer
    Details
    Publication Date: 1991-01-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 8
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    Toughening MoSi2 with niobiúm metal—effects of morphology of ductile reinforcements (1995)
    Springer
    Details
    Publication Date: 1995-02-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 9
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    Microstructure of Cu-Co alloys solidified at various supercoolings (1996)
    Springer
    Details
    Publication Date: 1996-12-01
    Print ISSN: 1073-5623
    Electronic ISSN: 1543-1940
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 10
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    On the flow behavior of constrained ductile phases (1993)
    Springer
    Details
    Publication Date: 1993-02-01
    Print ISSN: 1073-5623
    Electronic ISSN: 1543-1940
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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