Guinier—Preston zones

Figure 23.2 Structures and morphologies of the Cu-rich precipitates which form during precipitation in an A1 + 1.7 at. % Cu matrix, (a) a-matrix phase, (b) Guinier-Preston Zone precipitate, (c) 8" precipitate, (d) 8 precipitate, (e) Final stable 8 precipitate. From Porter and Easterling [4],...

Figure 23.8 Solvus curves for Guinier-Preston zones and 6", 6, and 6 precipitates in...

Fig. 6 Weak-beam DF imaging. Weak-beam DF images of (A) lamellar titanium aluminide showing thickness contours and (B) a spiral dislocation in Al-3 at% Ag, the white speckling is caused by silver-rich Guinier—Preston zones. (View this art in color at www.dekker.com.)...

First-Principles Approach to Guinier-Preston Zones. We have already seen that the combination of first-principles calculations with Monte Carlo methods is a powerful synthesis which allows for the accurate analysis of structural questions. In chap. 6 we noted that with effective Hamiltonians deduced from a lower-level microscopic analysis it is possible to explore the systematics of phase diagrams with an accuracy that mimics that of the host microscopic model. An even more challenging set of related questions concern the emergence of microstructure in two-phase systems. An age-old question of this type hinted at in the previous chapter is the development of precipitates in alloys, with the canonical example being that of the Al-Cu system. 

As in the case of LAXS measurements, the anomalous dispersion effects, arising when the energy is closed to the absorption edge, can be used with the SAXS technique. FONTAINE did ASAXS experiments, at LURE-DCl, to probe the distribution of Zn atoms in phase separated Ai—Zn alloys He measured the variation of SAXS from Guinier-Preston zones when the energy is scanned below the Zn absorption edge (Fig. 5). 

From room temperature up to 150 °C the coherent Cu-rich Guinier-Preston zones I (GPI phase) form they are only one to two 001 layers thick and have a highly strained, coherent phase boundary with the cr-Al matrix phase. 

Baur, R., and Gerold, V. Comparative X-ray and electron-microscopic measnrement of the size of Guinier-Preston zones in an aluminum-silver alloy. Acta Metall. 12 no. 12 (1964) 1449-1453. 

Guinier-Preston zones Zones de Guinier-Preston Guinier-Preston zonen... 

In this section, the theoretical basis of SANS will be exposed as is needed in polymer physics and will be clarified with simple experimental examples. Since the end of 1939, the method of SAS was developed by Guinier and Kratky and was mainly applied for questions in metal physics. In one of his first experiments, Guinier correctly interpreted scattering from copper precipitates in aluminum, the so-called Guinier-Preston zones. Today, SANS techniques are broadly used in soft matter a main reason is the relatively simple possibilities of contrast generation and variation for polymer chains and other hydrocarbon molecular items by the exchange of hydrogen and deuterium. 

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