In-Situ Observations on Interphase Boundary Migration and Grain Growth during α/γ Phase Transformation in Iron Alloys

2004 ◽  
Vol 467-470 ◽  
pp. 819-824 ◽  
Author(s):  
Tadao Watanabe ◽  
Kouichi Obara ◽  
Sadahiro Tsurekawa
Keyword(s):  
Phase Transformation ◽  
Grain Growth ◽  
Boundary Migration ◽  
Triple Junctions ◽  
Nucleation Sites ◽  
Interphase Boundaries ◽  
In Situ Observations ◽  
Bcc Phase ◽  
New Phase

In-situ observations of a/g phase transformation were made to study the effect of grain boundary microstructure of the generation of a new phase and the migration of a/g interphase boundaries in an Iron-4.2at.%Cr alloy. It was found that triple junctions with more random boundaries could be the primary nucleation sites, while triple junctions with low angle and low S coincidence boundaries did not play a role as preferential sites. The migration of a/g interphase boundaries during heating across the transformation temperature showed the two stage behaviour characterized first by a stage with a migration velocity of 0.33-0.75µm/s and secondly a stage with 3.7-7.6 µm/s. It was also found that abnormal grain growth and a high density of S3 coincidence boundaries could occur in the a/bcc phase after cycling of a/g/ a phase transformation.

scholarly journals In Situ Hvem Study of Ion Irradiation-Induced Grain Growth in Au Thin Films

1988 ◽  
Vol 128 ◽  
Author(s):  
Joyce C. Liu ◽  
Jian Li ◽  
J. W. Mayer ◽  
Charles W. Allen ◽  
Lynn E. Rehn
Keyword(s):  
Grain Growth ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Average Grain Size ◽  
In Situ Observations ◽  
Au Thin Films ◽  
Grain Coalescence

ABSTRACTIn situ observations of 1.5 MeV Xe+ ion irradiated Au films at room temperature and at 150°C reveal the evolution of grain growth: the average grain size increases by the mechanisms of grain boundary migration and grain coalescence.

In situ observations of electromigration induced void behavior

1995 ◽  
Vol 53 ◽  
pp. 244-245
Author(s):  
T. Marieb ◽  
J. C. Bravman ◽  
P. Flinn ◽  
D. Gardner ◽  
M. Madden
Keyword(s):  
Electron Microscopy ◽  
Void Nucleation ◽  
Plan View ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Microelectronics Industry ◽  
In Situ Observations ◽  
Backscatter Electron Detector ◽  
Voltage Scanning

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].

Irradiation-Induced Grain Growth: Role of Dislocations

1989 ◽  
Vol 157 ◽  
Author(s):  
Charles W. Allen ◽  
Lynn E. Rehn
Keyword(s):  
Grain Growth ◽  
Point Defects ◽  
Ion Irradiation ◽  
Boundary Migration ◽  
Dislocation Motion ◽  
Boundary Structure ◽  
Thermal Growth ◽  
Growth Phenomenon

ABSTRACTExisting theories of irradiation-induced grain growth assume that growth occurs by the boundary migration mechanism commonly observed for thermal growth and that it is only the point defects generated si boundaries during the irradiation which are responsible for boundary migration. In contrast, in situ observations during ion irradiation of Au films at temperatures less than 20 K even have clearly demonstrated that growth occurs both by boundary migration and by grain coalescence. Here we present further evidence for the latter. Furthermore, the substantial defect cluster activity observed during irradiation suggests that dislocations play a significant role in the growth phenomenon. Here, we also demonstrate qualitatively that glide of such dislocations to or “through” a boundary can produce essentially the same effect on boundary position or structure that the original point defects would have had if they had migrated individually to or through the boundary. Via dislocation motion, point defects originating far from a boundary may induce boundary migration or boundary structure change, and hence, grain growth.

In-Situ Tem Studies of Recrystallization and Grain Growth in Al-Mg-Mn-Zr Alloys

1995 ◽  
Vol 404 ◽  
Author(s):  
John S. Vetrano ◽  
Steve M. Bruemmer ◽  
Ian M. Robertson
Keyword(s):  
Grain Growth ◽  
Boundary Migration ◽  
Dislocation Motion ◽  
Precipitate Size ◽  
In Situ Tem ◽  
Eutectic Constituent ◽  
Cold Worked ◽  
Superplastic Properties ◽  
Zr Alloys

AbstractRecrystallization and grain growth studies of Al-Mg-Mn-Zr alloys have been carried out in-situ in the transmission electron microscope. Nucleation sites were primarily on large (>I μm diameter) eutectic constituent particles. The sub-micron A16Mn dispersoids were observed to be effective as nuclei if present in clusters, and were effective at retarding grain boundary migration and dislocation motion. The smaller A13Zr precipitates seemed to have little effect on nucleation and growth, but were effective in pinning dislocations. These results have been analyzed in terms of precipitate size and shape in both the as-cold-worked microstructure and during recrystallization. The implications on the microstructural refinement of these alloys for improved superplastic properties will be discussed.

The Potential of Combined In-Situ Heating Experiments and Detailed EBSD Analysis in the Investigation of Grain Scale Processes such as Recrystallization and Phase Transformation

2004 ◽  
Vol 467-470 ◽  
pp. 1407-1412 ◽  
Author(s):  
Sandra Piazolo ◽  
Gareth G.E. Seward ◽  
Nick Seaton ◽  
David J. Prior
Keyword(s):  
Phase Transformation ◽  
Grain Growth ◽  
Microstructural Evolution ◽  
Secondary Recrystallization ◽  
Microstructural Development ◽  
Geological Materials ◽  
Scientific Potential ◽  
In Situ Heating ◽  
Similarities And Differences

Experiments in which the microstructural development can be observed at the same time as the crystallography is described fully opens up new, powerful ways to advance our understanding of microstructural processes such as grain growth, primary and secondary recrystallization and phase transformations. In addition, comparison of results of experiments in different materials can be used to develop general laws for the investigated processes. In this study, we briefly review and compare the results from various ongoing studies undertaken in a variety of materials with emphasis on highlighting (a) the scientific potential of such experiments and (b)similarities and differences in their microstructural evolution. Materials studied include metals e.g. Ti, Ni, Al, Mg, Ti-SULC steel and geological materials such as rocksalt (NaCl), hematite and magnetite. Here, we present experimental results and their interpretation in terms of subgrain to grain-scale processes.

In Situ Observations and Measurements of Mechanically Induced Grain Boundary Migration in a Scanning Electron Microscope

2012 ◽  
Vol 715-716 ◽  
pp. 819-824 ◽  
Author(s):  
Tatiana Gorkaya ◽  
Thomas Burlet ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Orientation Contrast ◽  
In Situ Observations ◽  
Set Up ◽  
Scanning Electron

A novel set-up developed to continuously observe and measure stress driven grain boundary migration is presented. A commercially available tensile/compression SEM unit was utilized for in-situ observations of mechanically loaded samples at elevated temperatures up to 850°C by recording orientation contrast images of bicrystal surfaces. Two sample holders for application of a shear stress to the boundary in bicrystals of different geometry were designed and fabricated. The results of first measurements are presented.

In Situ Observation on the Influence of ß Grain Growth on Texture Evolution during Phase Transformation in Ti-6A-4V

2011 ◽  
Vol 702-703 ◽  
pp. 854-857
Author(s):  
Gideon C. Obasi ◽  
R.J. Moat ◽  
D. G. Leo Prakash ◽  
W. Kockelmann ◽  
Joao Quinta da Fonseca ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Neutron Diffraction ◽  
Grain Boundary ◽  
Grain Growth ◽  
Texture Evolution ◽  
Α Phase ◽  
Texture Modification ◽  
The Common ◽  
Grain Boundary Pinning

In the present study, in situ phase transformation experiments have been carried out using neutron diffraction to monitor the texture evolution during the α→ß→α phase transformation in Ti-6Al-4V with and without 0.4% yttrium additions. The aim of adding yttrium was to control ß grain growth above the transus ß by grain boundary pinning. In the present case, strengthening of the ß texture, occurring during ß grain coarsening resulted in strengthening of particular ß texture components, which increases the likelihood of α texture modification by selective growth of α variants on the common (110) ß grain boundaries into unoccupied large β grains.

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