Nano-Scale Clusters Formed in the Early Stage of Phase Decomposition of Al-Mg-Si Alloys

2005 ◽  
pp. 357-360
Author(s):  
Shoichi Hirosawa ◽  
Tatsuo Sato
Keyword(s):  
Early Stage ◽  
Phase Decomposition ◽  
Nano Scale

Nano-Scale Clusters Formed in the Early Stage of Phase Decomposition of Al-Mg-Si Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 357-360 ◽  
Author(s):  
Shoichi Hirosawa ◽  
Tatsuo Sato
Keyword(s):  
Early Stage ◽  
Sheet Material ◽  
Three Dimensional ◽  
Natural Aging ◽  
Aging Treatment ◽  
Atom Probe ◽  
Phase Decomposition ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Nano Scale

The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the strengthening b” phase significantly influences two-step aging behavior of Al-Mg-Si alloys. In this work, the existence of two kinds of nanoclusters has been verified in the early stage of phase decomposition by differential scanning calorimetry (DSC) and three-dimensional atom probe (3DAP). Pre-aging treatment at 373K before natural aging was also found to form preferentially one of the two nanoclusters, resulting in the remarkable restoration of age-hardenability at paint-bake temperatures. Such microstructural control by means of optimized heat-treatments; i.e. nanocluster assist processing (NCAP), possesses great potential for enabling Al-Mg-Si alloys to be used more widely as a body-sheet material of automobiles.

Experimental and Theoretical Investigations of the Phase Transformation in Al-rich TiAl Intermetallic Compounds

2000 ◽  
Vol 646 ◽  
Author(s):  
T. Koyama ◽  
M. Doi ◽  
S. Naito
Keyword(s):  
Field Model ◽  
Early Stage ◽  
Phase Field Model ◽  
Oblate Spheroid ◽  
Al Alloy ◽  
Phase Decomposition ◽  
Theoretical Investigations ◽  
Tial Intermetallic Compound ◽  
Two Phases ◽  
Good Agreement

ABSTRACTThe phase decomposition of the Al-rich γ TiAl intermetallic compound in the TiAl(L10) and Ti3Al5(P4/mbm) two phases region is investigated experimentally. On the phase decomposition of the Ti-56at%Al alloy, the single precipitate(Ti3Al5) shape is an oblate spheroid at the early stage of precipitation and each particle is aligned along certain direction of the orientation about 20 degrees from [100]. During coarsening, the precipitates encounter each other, then, the shape of the particle becomes the slanted or bended plate. In the case of phase decomposition of the Ti-58at%Al alloy, the tweed-like structure is observed at the beginning of the aging. The precipitates are connected each other during coarsening, finally the microstructure becomes the large layered structure with a zigzag-shaped interface. These microstructure changes are simulated based on the phase field model. The morphology and the time development of the simulated microstructure are in good agreement with the experimental results.

Atom probe study of early stage phase decomposition in an Al-7.8 at.% Li alloy

1992 ◽  
Vol 40 (11) ◽  
pp. 3027-3034 ◽  
Author(s):  
K. Hono ◽  
S.S. Babu ◽  
K. Hiraga ◽  
R. Okano ◽  
T. Sakurai
Keyword(s):  
Early Stage ◽  
Atom Probe ◽  
Phase Decomposition

HRTEM Observation of β’-Phase in Cu-40.26 at.% Zn Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 2305-2308
Author(s):  
Masaaki Nishiyama ◽  
Daisuke Hamatani ◽  
Kenji Matsuda ◽  
Tokimasa Kawabata ◽  
Yasuhiro Uetani ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Early Stage ◽  
Phase Decomposition ◽  
Hrtem Image ◽  
Β Phase ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
The Matrix ◽  
Cscl Structure ◽  
Zn Alloy

There have been many reports about the bainitic phase decomposition of annealed Cu-Zn alloy. During annealing at 523 K, the hardness of this alloy increased at the early stage of annealing, although the β-phase couldn't be observed in the matrix of β'-phase (CsCl). The crystal structure of β' phase, thus, was investigated by a high-resolution transmission electron microscopy (HRTEM) to find its structural change. As the result, the striations were observed in the HRTEM image of matrix at the early stage of annealing. The selected area diffraction pattern was also obtained from this area, and it showed the extra streaks which couldn't be explained by the normal CsCl structure of the β’-phase.

Control of Nano-Precipitates in Age-Hardenable Aluminum Alloys and Their Mechanical Properties

2005 ◽  
Vol 475-479 ◽  
pp. 337-342 ◽  
Author(s):  
Tatsuo Sato ◽  
Shoichi Hirosawa
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloys ◽  
Mg Alloys ◽  
Phase Decomposition ◽  
Nano Scale ◽  
Initial Stage ◽  
Negative Effect ◽  
New Type ◽  
Microalloying Elements ◽  
Strength And Ductility

The nano-scale precipitate microstructures and properties of age-hardenable aluminum alloys such as Al-Cu, Al-Mg-Si and Al-Zn-Mg alloys were investigated using conventional electrical resistivity and hardness measurements, TEM and 3D-AP techniques. To increase mechanical strength and ductility of the alloys nano-scale precipitates were effectively controlled by applying new type heat treatments and microalloying elements. In the initial stage of phase decomposition of the alloys containing microalloying elements several types of nanoclusters were formed and distinctly detected by the 3D-AP technique. These nanoclusters greatly affect the nucleation of the subsequent precipitates and resultantly mechanical properties. In Al-Mg-Si and Al-Zn-Mg alloys complicated two-step aging behaviors were found to be originated in the positive or negative effect of the nanoclusters with different structures.

Nano-Scale Design of TiAl Alloys Based on β-Phase Decomposition

2006 ◽  
Vol 8 (5) ◽  
pp. 371-376 ◽  
Author(s):  
F. Appel ◽  
M. Oehring ◽  
J. D. H. Paul
Keyword(s):  
Phase Decomposition ◽  
Tial Alloys ◽  
Nano Scale ◽  
Β Phase ◽  
Scale Design

Elastic behavior during early stage of β phase decomposition in a Cu–Al–Ni shape memory alloy

2005 ◽  
Vol 86 (23) ◽  
pp. 231903 ◽  
Author(s):  
V. Recarte ◽  
J. I. Pérez-Landazábal ◽  
V. Sánchez-Alarcos
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Early Stage ◽  
Elastic Behavior ◽  
Phase Decomposition ◽  
Β Phase

Kinetics of Morphological Development in Elastomer Modified Silica Xerogels

1999 ◽  
Vol 72 (1) ◽  
pp. 130-137 ◽  
Author(s):  
G. Beaucage ◽  
L. Guo ◽  
J. Hyeon-Lee
Keyword(s):  
Network Formation ◽  
Early Stage ◽  
Sol Gel ◽  
Morphological Features ◽  
Gel Point ◽  
Initial Reaction ◽  
Morphological Development ◽  
Structural Development ◽  
Pore Collapse ◽  
Nano Scale

Abstract Acid-catalyzed, sol-gel chemistry is used to incorporate polysiloxane elastomers in ceramic gels in order to prevent pore collapse on drying. These rubber-modified, ceramic gels can lead to low-density nano-porous materials for uses such as thermal insulation. The morphological mechanisms by which these materials are toughened by elastomers is the focus of this paper. Structural development in these multiphase systems involves a complex interplay between nano-scale hydrolysis/condensation reactions and colloidal to macroscopic phase separation and network formation. The interplay between these morphological features as a function of reaction time is studied using microscopy as well as small-angle x-ray and light scattering. The initial reaction mixture is phase-separated on a micron scale due to the immiscibility of poly-siloxanes and water. At an early stage of the sol-gel reaction, mass-fractal domains in the nano-scale develop, while micron-scale phase-separated domains are diminished. Near the gel-point, a macroscopic network forms whose morphological features are strongly influenced by the presence of polysiloxane elastomer. A model is proposed for the interplay between these structural levels during growth.

Early-Stage Phase Decomposition in Vitreous Na2O-SiO2

1970 ◽  
Vol 53 (1) ◽  
pp. 62-63 ◽  
Author(s):  
M. TOMOZAWA ◽  
R. K. MacCRONE ◽  
H. HERMAN
Keyword(s):  
Early Stage ◽  
Phase Decomposition
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