From symmetry to entropy: Crystal entropy difference strongly affects early stage phase transformation

2019 ◽  
Vol 115 (26) ◽  
pp. 264103
Author(s):  
C. H. Hu ◽  
Y. C. Chen ◽  
P. J. Yu ◽  
K. Y. Fung ◽  
Y. C. Hsueh ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Early Stage

Microstructural Changes of Welded Zn-AI Alloy

1994 ◽  
Vol 367 ◽  
Author(s):  
Yao Hua Zhu
Keyword(s):  
Phase Transformation ◽  
Early Stage ◽  
Dendritic Structure ◽  
Metastable Phases ◽  
Grain Structure ◽  
Al Alloy ◽  
Cast State ◽  
Microstructural Changes ◽  
Fine Grain ◽  
Ageing Processes

AbstractExtruded eutectoid Zn-Al alloy was welded by a melt of the same eutectoid alloy. Two different microstructures were observed in the joint part and the bulk of the welded alloy. Typical dendritic structure of as cast Zn-Al alloy was observed in the joint part of the welded alloy. The bulk ofthe welded Zn-Al alloy appeared as fine grain structure. Two different metastable phases η'T decomposed from η's of chilled as cast state and η'E of extruded state were found to be unstable during early stage of ageing. A four phase transformation occurred after the decompositions of these two metastable phases of η'T. Microstructures of both joint part and bulk of the welded alloy were investigated parallely during ageing processes.

The Early Stages of the Spinel-Alumina Phase Transformation

1987 ◽  
Vol 94 ◽  
Author(s):  
Y. Kouh Simpson ◽  
C. B. Carter
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Early Stage ◽  
Spinel Phase ◽  
High Resolution Electron Microscopy ◽  
Solid State Reactions ◽  
Alumina Phase ◽  
Transmission Electron ◽  
Resolution Electron ◽  
In Situ Experiments

ABSTRACTThe initial stage of topotactic growth of Ni-Al spinel into Al2O3 has been examined using transmission electron microscopy. A new experimental approach to the study of solid-state reactions, which may be adapted for in-situ experiments for low-temperature systems, has been used in this study. In its present form, the technique involves heating a thin film of one oxide in the presence of a vapor of the second oxide. In the study of the growth characteristics of Ni-Al spinel phase, the orientation of the Al2O3 substrate has been found to influence greatly both the structural and morphological aspects of the spinel growth. In particular, the topotactic relationship between the spinel and the alumina are very different for (0001) and {1120} substrate orientations. The very early stage of the kinetics of the spinel growth, in which the length and the width of the spinel particles are only a few hundred angstroms, is illustrated with the results obtained from the re-heating experiments. The structure of the spinel-alumina interface has also been studied using high-resolution electron microscopy. These results are discussed in relation to the different models proposed for the spinel-alumina phase transformation.

scholarly journals Effect of Different Precipitation Routes of Fe2Hf Laves Phase on the Creep Rate of 9Cr-Based Ferritic Alloys

2021 ◽  
Vol 11 (5) ◽  
pp. 2327
Author(s):  
Satoru Kobayashi ◽  
Toru Hara
Keyword(s):  
Phase Transformation ◽  
Creep Rate ◽  
Early Stage ◽  
Ferrite Matrix ◽  
Laves Phase ◽  
Creep Tests ◽  
Ferritic Alloys ◽  
Δ Ferrite ◽  
The Matrix ◽  
Creep Regime

We performed creep tests for three types of Fe-9Cr-Hf alloys with a ferritic matrix w/o Fe2Hf Laves phase particles formed by two precipitation routes: (1) with fine Fe2Hf particles formed by the conventional precipitation route (hereafter the particles are called CP particles), namely formed in the α-ferrite matrix after γ-austenite ® α-ferrite phase transformation; (2) with fine Fe2Hf particles formed by interphase precipitation (hereafter called IP particles) during δ-ferrite ® γ-austenite phase transformation before γ ® α phase transformation and (3) without Laves phase particles. CP particles were found to be effective in reducing the creep rates from the transient creep regime to the early stage of a slowly accelerating creep regime but were coarsened after the creep tests. IP particles were less effective in reducing the creep rate in the early creep stages but showed a higher stability against particle coarsening than CP particles in the creep tests, suggesting their effectiveness in delaying the recovery and recrystallization processes in the matrix and thereby retarding the onset of a rapid creep acceleration and creep rupture. The effects of the different precipitation routes are discussed based on the results obtained.

scholarly journals Phase Transformation and Characterization of 3D Reactive Microstructures in Nanoscale Al/Ni Multilayers

2021 ◽  
Vol 11 (19) ◽  
pp. 9304
Author(s):  
Yesenia Haydee Sauni Camposano ◽  
Sascha Sebastian Riegler ◽  
Konrad Jaekel ◽  
Jörg Schmauch ◽  
Christoph Pauly ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Cross Sections ◽  
Early Stage ◽  
Annealing Treatment ◽  
Transformation Process ◽  
Atomic Diffusion ◽  
Scanning Calorimetry ◽  
Multilayer Systems ◽  
The Impact

Reactive multilayer systems represent an innovative approach for potential usage in chip joining applications. As there are several factors governing the energy release rate and the stored chemical energy, the impact of the morphology and the microstructure on the reaction behavior is of great interest. In the current work, 3D reactive microstructures with nanoscale Al/Ni multilayers were produced by alternating deposition of pure Ni and Al films onto nanostructured Si substrates by magnetron sputtering. In order to elucidate the influence of this 3D morphology on the phase transformation process, the microstructure and the morphology of this system were characterized and compared with a flat reactive multilayer system on a flat Si wafer. The characterization of both systems was carried out before and after a rapid thermal annealing treatment by using scanning and transmission electron microscopy of the cross sections, selected area diffraction analysis, and differential scanning calorimetry. The bent shape of multilayers caused by the complex topography of silicon needles of the nanostructured substrate was found to favor the atomic diffusion at the early stage of phase transformation and the formation of two intermetallic phases Al0.42Ni0.58 and AlNi3, unlike the flat multilayers that formed a single phase AlNi after reaction.

scholarly journals Effect of Phase Changes on the Axial Modulus of an FeMnSi-Shape Memory Alloy

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4815
Author(s):  
Yajiao Yang ◽  
Matteo Breveglieri ◽  
Moslem Shahverdi
Keyword(s):  
Plastic Deformation ◽  
Phase Transformation ◽  
Shape Memory ◽  
Early Stage ◽  
Phase Changes ◽  
Stress And Strain ◽  
Interaction Forces ◽  
Strain Behavior ◽  
Different Temperatures ◽  
The Relationship

The axial modulus ESMA(κ) of FeMnSi-based shape memory alloys (FeMnSi-SMAs) is a parameter introduced in this study to characterize the relationship between stress and strain behavior at the early stage of tensile loading. ESMA(κ) can be used to correctly estimate and model the interaction forces between FeMnSi-SMAs and other materials. Unlike the conventional Young’s modulus, which is usually given at room temperature, the ESMA(κ) is evaluated at different temperatures and strongly depends on phase transformation and plastic deformation. This study investigated the evolution of ESMA(κ) during and after pre-straining as well as in the course of the activation processes. The effect of different factors (e.g., phase transformation and plastic deformation) on the magnitude of ESMA(κ) is discussed. The result shows that the ESMA(κ) can differ significantly during activation and thus needs to be modified when interaction forces between FeMnSi-SMAs and other substrates materials (e.g., concrete) must be modeled and evaluated.

scholarly journals New Structural Insight into Interface-Controlled α–σ Phase Transformation in Fe-Cr Alloys

2018 ◽  
Vol 2 (4) ◽  
pp. 27
Author(s):  
Wael Al Khoury ◽  
Nobumichi Tamura ◽  
Guillaume Geandier ◽  
Philippe Goudeau
Keyword(s):  
Phase Transformation ◽  
Tetragonal Phase ◽  
Early Stage ◽  
Phase Interface ◽  
The Body ◽  
Ex Situ ◽  
Body Centered Cubic ◽  
Σ Phase ◽  
Two Phases ◽  
Insight Into

Synchrotron Laue microdiffraction scanning is used for the ex situ study of the body-centered, cubic-to-tetragonal phase transformation that occurs in equiatomic polycrystalline Fe-Cr alloys at temperatures between 550 and 800 °C. Grain orientation and grain strains were scanned with a micron step resolution after annealing at 700 °C for 12 h. Further microstructural details on the early stage of the transformation, and more particularly on the cubic-to-tetragonal phase interface, were achieved. Only the α and ordered σ phases were detected. The crystallographic relationships at the interface between the two phases did not follow the predicted rules; this result is discussed in relation to the measured microstrains.

Magnetic Field-Induced Granular Pearlite at Early Stages of Phase Transformation

2013 ◽  
Vol 650 ◽  
pp. 178-184 ◽  
Author(s):  
Xiao Ling Zhou ◽  
Ke Han ◽  
Zhong Ming Ren ◽  
Zeng Li
Keyword(s):  
Phase Transformation ◽  
Early Stage ◽  
Ferrite Matrix ◽  
Nucleation Mechanism ◽  
High Magnetic Fields ◽  
Eutectoid Temperature ◽  
Tem Analysis ◽  
Granular Pearlite ◽  
Lamellar Pearlite ◽  
Lamellar Cementite

ffects of high magnetic fields (HMF) up to 19.81T on pearlite phase transformation are studied by examination of the microstructures of a Fe-0.47C-2.3Si-3.2Mn (wt %) alloy partially isothermally processed above the eutectoid temperature. The results show that granular pearlite (GP) can be obtained at earlier transformation stages. The evolution of the granular pearlite is always accompanied by the formation of lamellar pearlite. TEM analysis reveals the existence of sub-grain boundaries within GP colonies and indicates that the nucleation of ferrite matrix in GP belongs to multiple nucleation mechanism. Most of carbides at the early stage of pearlite formation are found to precipitate at the α/γ interface--the growing front of ferrite phases, and some of coarse carbides can further develop into thin lamellar cementite.

Early Stage Reversed Crystal Growth of Zeolite A and Its Phase Transformation to Sodalite

2009 ◽  
Vol 131 (49) ◽  
pp. 17986-17992 ◽  
Author(s):  
Heather Greer ◽  
Paul S. Wheatley ◽  
Sharon E. Ashbrook ◽  
Russell E. Morris ◽  
Wuzong Zhou
Keyword(s):  
Phase Transformation ◽  
Crystal Growth ◽  
Early Stage ◽  
Zeolite A
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