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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 128-132 
    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 aim of the present work is to study the influence of the partial substitution of Si byGe on the formation of the apatite-type La9.33Si2Ge4O26 phase by mechanical alloying andsubsequent annealing. Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball millingat increasing rotation speeds of 150, 250 and 350 rpm and milling times up to 50 h. The resultingmixtures were subsequently annealed at increasing temperatures up to 1100 ºC. Single phaseapatite-like La9.33Si2Ge4O26 was obtained during mechanical alloying at high rotation speed. Thehigher the rotation speed the lower was the time required for the lanthanum germanosilicate phaseformation. For the samples in which complete reaction between initial phases did not occur duringmilling, La9.33Si2Ge4O26 was always obtained during the annealing process. The more severe wasthe mechanical alloying process the lower was the annealing temperature required for the apatitephase formation. The formation of apatite phase during mechanical alloying did not provokesignificant changes in densification behavior of the milled samples. The addition of GeO2 as rawmaterial promotes a faster formation of the apatite phase as compared to the results obtained usingonly La2O3 and SiO2
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 587-588 (June 2008), p. 420-424 
    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
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