신소재공학과

Seminar

Views 818
Extra Form
Date 20180501

MSE Regular Seminar



■ Title Principles of Chemically Induced Interface Migration and Abnormal Grain Growth


Speaker:  Prof. Duk-Yong Yoon (KAIST MSE)  

 

■ Date and Time :  5/1 (Tue) 16:00

 

■ Venue :  Applied Engineering Department (W1-1) Multimedia Lecture Hall (1st Floor)

 

 Abstract : 

In 1970s it was observed that grain boundaries and intergranular liquid films migrated when they came into contact with solute sources. Solute-rich alloys were produced behind the migrating interfaces.  Hillert proposed that the  solute atoms diffused ahead of the migrating interfaces producing coherency  strains that drove the migration. In this work solute atoms of large and small size  were used to vary the coherency strain from negative to positive values and when the estimated strain was 0, the interfaces did not migrate. This result was a definitive evidence for Hillert’s coherency strain theory and provides a foundation for a new perspective on solute diffusion process in polycrystalline systems .

      In some polycrystals the grains grow normally with a narrow size distribution which remains constant. Polycrystals sometimes show also abnormal grain growth  where only some grains grow to very large sizes while the others remain relatively small. In some alloys prepared by liquid phase sintering at low temperatures the grains are polyhedral with flat surfaces and grow abnormally. These flat surfaces are singular with the minimum surface energy with respect to the surface orientation. The singular surface moves forward by two dimensional nucleation of steps and hence the large grains grow much faster than the rest, resulting in abnormal growth. At high temperatures the grain surfaces undergo roughening transition and the grains become nearly spherical with atomically rough surface. The grains then grow normally.  The polycrystalline single phase alloys (without any liquid phase) also show the same roughening transition of grain boundaries with temperature increase and the change of grain growth from abnormal to normal. These results show that abnormal grain growth is caused by the nucleation and growth of steps on singular interfaces. In some materials  additives or change of atmosphere can also induce interface roughening and hence the change of grain growth behavior. His theory has been applied to the growth of large single crystals of various shapes and compositions from polycrystals.


List of Articles
No. Category Subject Author Date Views
Notice Regular 10/2 (Tue) Prof. Dohwan Kim (Hanyang Univ.) ADMINI 2018.10.01 156
Notice Regular 9/18 (Tue) Prof. Seong Jun Kang (Kyung Hee Univ.) ADMINI 2018.09.17 276
Notice Regular 9/11 (Tue) Dr. Byeongdu Lee (Argonne National Laboratory) ADMINI 2018.09.07 358
Notice Regular 9/4 (Tue) Prof. Kibum Kang (Department of MSE, KAIST) ADMINI 2018.09.03 362
Notice Regular 8/28 (Tue) Prof. Kyung-Min Kim (Department of MSE, KAIST) ADMINI 2018.08.24 387
Notice Special 8/24 (Fri) Prof. Joel W. Ager III (UC Berkeley, Lawrence Berkeley National Laboratory) file ADMINI 2018.08.20 343
268 Special 8/23 (Thu) Prof. Jeehwan Kim (MIT, USA) file ADMINI 2018.08.20 259
267 Special 8/23 (Thu) Prof. YANGUANG LI (Soochow University) file ADMINI 2018.08.20 166
266 Special 7/25 (Wed) Dr. Chang Sub Kim (Department of MSE, MIT) ADMINI 2018.07.24 390
265 Special 7/13 (Fri) Prof. Dong Ryeol Whang (Johannes Kepler University Linz, Austria) file ADMINI 2018.07.09 378
264 Regular 6/5 (Tue) Prof. Sunghwan Lee (Baylor University) ADMINI 2018.06.05 560
263 Regular 5/29 (Tue) Prof. Sang Ho Oh (Yonsei Univ. College of Medicine) ADMINI 2018.05.29 550
262 Regular 5/15 (Tue) Prof. Myung Gil Kim (Dept. of Chemistry, Chung-Ang Univ.) ADMINI 2018.05.15 763
261 Regular 5/8 (Tue) Prof. Ju-Young Kim (UNIST MSE) ADMINI 2018.05.09 676
» Regular 5/1 (Tue) Prof. Duk-Yong Yoon (KAIST MSE) ADMINI 2018.04.30 818
259 Regular 4/24 (Tue) Kyeong Ho Chang (CEO, Innox Advanced Materials) ADMINI 2018.04.23 707
258 Regular 4/10 (Tue) Prof. Ki Jun, Yu (Yonsei Univ., School of Electrical and Electronic Engineering) ADMINI 2018.04.09 795
257 Regular 4/3 (Tue) Master Byung-Gi Choi (Samsung Advanced Institute of Technology) ADMINI 2018.04.02 672
256 Regular 3/27 (Tue) Prof. Seungbum Hong (KAIST MSE) ADMINI 2018.03.26 632
255 Regular 3/20 (Tue) Prof. Jung In-Ho (Seoul National University, MSE) ADMINI 2018.03.20 521
Board Pagination ‹ Prev 1 2 3 4 5 6 7 8 9 10 ... 14 Next ›
/ 14

Designed by sketchbooks.co.kr / sketchbook5 board skin

나눔글꼴 설치 안내


이 PC에는 나눔글꼴이 설치되어 있지 않습니다.

이 사이트를 나눔글꼴로 보기 위해서는
나눔글꼴을 설치해야 합니다.

설치 Cancel

Sketchbook5, 스케치북5

Sketchbook5, 스케치북5

Sketchbook5, 스케치북5

Sketchbook5, 스케치북5