During Heat Treatment

Precipitation Hardening. With the exception of ferritic steels, which can be hardened either by the martensitic transformation or by eutectoid decomposition, most heat-treatable alloys are of the precipitation-hardening type. During heat treatment of these alloys, a controlled dispersion of submicroscopic particles is formed in the microstmeture. The final properties depend on the manner in which particles are dispersed, and on particle size and stabiUty. Because precipitation-hardening alloys can retain strength at temperatures above those at which martensitic steels become unstable, these alloys become an important, in fact pre-eminent, class of high temperature materials. 

J. Vanhellemont, E. Dornberger, J. Esfandyari, G. KLissinger, M. A. Trauwaert, H. Bender, D. Graef, U. Lambert, W. von Ammon. Defects in as-grown silicon and their evolution during heat treatments. Mater Sci Eorum 0 341, 1997. 

It is hardly surprising that the preparation of surfaces of plain specimens for stress-corrosion tests can sometimes exert a marked influence upon results. Heat treatments carried out on specimens after their preparation is otherwise completed can produce barely perceptible changes in surface composition, e.g. decarburisation of steels or dezincification of brasses, that promote quite dramatic changes in stress-corrosion resistance. Similarly, oxide films, especially if formed at high temperatures during heat treatment or working, may influence results, especially through their effects upon the corrosion potential. 

Flocculation studies, considering the small-strain mechanical response of the uncross-hnked composites during heat treatment (annealing), demonstrate that a relative movement of the particles takes place that depends on particle size, molar mass of the polymer, as well as polymer-filler and filler-filler interactions (Figure 22.2). This provides strong experimental evidence for a kinetic cluster-cluster aggregation (CCA) mechanism of filler particles in the mbber matrix to form a filler network [24]. 

Aside from isomerization, transformation of the 5,6-epoxy to the 5,8-furanoid group is a common alteration during heating treatments of carotenoids. Violaxanthin was found to be the major carotenoid in mangoes however, in commercially processed mango juice, violaxanthin was not detected while auroxanthin, not present in the... 

V (2 ), Cr ( ), Zr (1 ), or Ta (1 ). The role of these promoters in the air cathode is unclear, and some have suggested that the active catalysts are alloys of the Ft with the transition metal (1,4) which form during heat-treatment of the oxide impregnated precursor. In the first section of this paper, we review the work from the Lawrence Berkeley Laboratory on the study of the mechanism of promotion of air cathode performance by these transition metal additives. 

During heat treatment between 250 and 500°C, the formation of three-dimensional networks by diene and addition reactions of Ph—C C, C=C, and m-carborane groups in this system has been characterized by nB MQ-MAS NMR and 13C and 29 Si CP-MAS NMR methods. 

Figure 2.16. (a-c) Simulations of film structural evolution for PZT thin films at various times during heat treatment.15 (d) A representative SEM photomicrograph illustrating the columnar microstructure of PZT.48 The lower layer is the lower Pt electrode, the middle layer is the PZT, and the upper layer is the top Pt electrode, [(a)-(c) Reprinted with permission from Ref. 15. (d) Reprinted with permission from Ref. 9. Copyright 1997 American Chemical Society.] (See color insert.)... 

Spiess, W.E.L., Behsnilian, D., Ferrando, M., Gaiser, M., Gartner, U., Hasch, M., Mayer-Miebach, E., Rathjen, A., and Walz, E. 2002. Mass transfer and related phenomena in plant tissue during heat treatment and osmotic stress. In Engineering and Food for the 21st Century (J. Welti-Chanes, G.V. Barbosa-Canovas, and J.M. Aguilera, eds), pp. 177-191. CRC Press, Boca Raton, FL. 

Main uses of lithium alloys. Li additions often change completely the properties of metals to which it is added, for instance hardness of A1 and Pb (addition of Li to Pb results in the formation of Pb solid solution and a eutectic at 15.7 at.% Li with LiPb) and ductility of Mg. Al-alloys can be of great interest in aerospace industry Li (as Be) simultaneously reduces the density of A1 and increases its modulus of elasticity. Each 1 mass% Li up to the solubility limit (4.2 mass%) reduces density by about 3% and increases modulus by 5%. Precipitates homogeneously distributed of spherical LiAl3 in diluted Li-alloys during heat treatment may improve strength. 

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