Direct Observation of Monolayer Zones in Al-wt 4% Cu

Author(s):  
B. Jouffrey ◽  
D. Dorignac ◽  
A. Bourret

Since the early works on GP zones and the model independently proposed by Preston and Guinier on the first steps of precipitation in supersaturated solid solution of aluminium containing a few percent of copper, many works have been performed to understand the structure of different stages in the sequence of precipitation.The scheme which is generally admitted can be drawn from a work by Phillips.In their original model Guinier and Preston analysed a GP zone as composed of a single (100) copperrich plane surrounded by aluminum atomic planes with a slightly shorter distance from the original plane than in the solid solution.From X-ray measurements it has also been shown that GP1 zones were not only copper monolayer zones. They could be up to a few atomic planes thick. Different models were proposed by Guinier, Gerold, Toman. Using synchrotron radiation, proposals have been recently made.

2011 ◽  
Vol 11 (4) ◽  
pp. 2873-2881 ◽  
Author(s):  
Akira Saito ◽  
Takehiro Tanaka ◽  
Yasumasa Takagi ◽  
Hiromasa Hosokawa ◽  
Hiroshi Notsu ◽  
...  

1989 ◽  
Vol 159 ◽  
Author(s):  
Koichi Akimoto ◽  
Jun'Ichiro Mizuki ◽  
Ichiro Hirosawa ◽  
Junji Matsui

ABSTRACTSurface superstructures (reconstructed structures) have been observed by many authors. However, it is not easy to confirm that a superstructure does exist at an interface between two solid layers. The present paper reports a direct observation, by a grazing incidence x-ray diffraction technique with use of synchrotron radiation, of superstructures at the interface. Firstly, the boron-induced R30° reconstruction at the Si interface has been investigated. At the a Si/Si(111) interface, boron atoms at 1/3 ML are substituted for silicon atoms, thus forming a R30° lattice. Even at the interface between a solid phase epitaxial Si(111) layer and a Si(111) substrate, the boron-induced R30° reconstruction has been also observed. Secondly, SiO2/Si(100)-2×l interfacial superstructures have been investigated. Interfacial superstructures have been only observed in the samples of which SiO2 layers have been deposited with a molecular beam deposition method. Finally, the interfaces of MOCVD-grown AIN/GaAs(100) have been shown to have 1×4 and 1×6 superstructures.


2014 ◽  
Vol 1061-1062 ◽  
pp. 35-38
Author(s):  
Yun Long Ai ◽  
Xiao Rui Shen ◽  
Wei Hua Chen ◽  
Yao Hui Xie

NCu30-4-2-1 alloy was handled by solid solution at 950°Cfor 2h and then taking aging treatment at different temperatures and holding time. The microstructural evolution of NCu30-4-2-1 alloy in the process of aging treatment was investigated by metallographic microscope, X-ray diffractometer and differential scanning calorimetry. The results show that the phases of as-cast NCu30-4-2-1 alloy is composed by dendritic α-Ni-based solid solution and β-Ni3Si. After solid solution and aging treatment, the block distribution β-Ni3Si dissolves and many small granular dispersed distribution β'-Ni3Si precipitate out. With the increase of aging temperature and holding time, metastable β' tends to transform into stable β-Ni3Si. The precipitation sequence of aged NCu30-4-2-1alloy is supersaturated solid solution of α-Ni, GP zone, β'-Ni3Si and β-Ni3Si.


1994 ◽  
Vol 332 ◽  
Author(s):  
Yasuo Takagi ◽  
Yoshitaka Okitsu ◽  
Toshiyasu Ukena

ABSTRACTDirect observation of diffraction arcs by X-ray from nanoscale precipitates in steels has become possible for the first time by using a highly brilliant and focused synchrotron radiation beam at BL3A of Photon Factory, and also by using an “imaging plate”, a two dimensional X-ray detector which has a wide dynamic range and high sensitivity. For examples, most of the diffraction arcs from ε-Cu precipitates (∼200 Å in diameter and ∼1 at. % in concentration) in Cu-added steels were observed. The method can apply to nondestructive and in-situ observation of creation and growth processes of the precipitates which has close relationships to various physical properties of the matrix steels.


2012 ◽  
Vol 629 ◽  
pp. 85-89 ◽  
Author(s):  
S. Tighiouaret ◽  
H. Azzeddine ◽  
A. Sam ◽  
A. Sari ◽  
B. Alili ◽  
...  

The current study seeks to further understand the precipitation sequence in a WE54 Mg alloy using in situ X-ray diffraction, micro-hardness and electrical resistivity during ageing at 250 and 300 °C. We show that the mean hardening effect is due to the precipitation of β' and β1metastable phases. The analysis of the kinetics of the precipitation shows that both phases nucleate at grain boundaries and within grains in the form of plates.


1988 ◽  
Vol 143 ◽  
Author(s):  
Joe Wong ◽  
Glen A. Slack

The bonding and local atomic structure of a series of 3d metal-beta boron solid solution are investigated using a combination of x-ray absorption near-edge structure (XANES) and extended fine structure (EXAFS) technique utilizing intense synchrotron radiation as a light source. The corresponding metal diborides MB2, (M = Sc, Ti, V, Cr).were also measured and used to model the coordination environment of these metal sites in beta-boron.


2015 ◽  
Vol 44 (23) ◽  
pp. 10681-10688 ◽  
Author(s):  
Samuel Liu ◽  
Peter E. R. Blanchard ◽  
Zhaoming Zhang ◽  
Brendan J. Kennedy ◽  
Chris D. Ling

Synchrotron X-ray powder diffraction patterns of K0.5Bi0.5Ti1−xZrxO3 (KBT-KBZ), showing the pseudocubic tetragonal region at all intermediate compositions in the solid-solution.


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