신소재공학과

행사일 20180501 

학과 정기 세미나 안내



■ 제 목Principles of Chemically Induced Interface Migration and Abnormal Grain Growth


연 사:  윤덕용 명예교수 (KAIST 신소재공학과)  

 

 일 시:  5월 1일(화) 16:00

 

■ 장 소:  응용공학동 (W1) 1층 영상강의실

 

 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.

No. Subject Author Date Views
Notice 7/25 (Wed) 김창섭 박사 (Department of MSE, MIT) ADMINI 2018.07.24 17
Notice 7/13 (Fri) Prof. Dong Ryeol Whang (Johannes Kepler University Linz,Austria) ADMINI 2018.07.09 13
Notice 6/5 (Tue) 이성환 교수 (Baylor University) ADMINI 2018.06.05 54
Notice 5/29 (Tue) 오상호 교수 (연세대학교 의과대학 피부과학교실) ADMINI 2018.05.29 51
Notice 5/15 (Tue) 김명길 교수 (중앙대 화학과) ADMINI 2018.05.15 93
132 11/28 (금) 오태식 박사 (University of Pennsylvania) Administrator 2014.11.26 2095
131 11/14 (금) Dr. Amanda K. Petford-Long (Argonne National Laboratory) file Administrator 2014.11.04 2044
130 2014 가을학기 정기세미나 일정 Administrator 2014.08.28 4486
129 8/25 (월) 김 현 석 교수(충남대학교 재료공학과) Administrator 2014.08.26 2536
128 8/21 (목) Prof. Frans Spaepen (Harvard University, School of Engineering and Applied Sciences) Administrator 2014.08.14 2134
127 7/21 (월) Jamie Warner (University of Oxford) Administrator 2014.07.16 2593
126 6/12 (목) 정호용 교수 (Florida State University 부임예정) Administrator 2014.06.09 2827
125 6/10 (화) 강성모 총장님 (KAIST) Administrator 2014.06.09 2106
124 6/3 (화) Prof. Alfredo Alexander-Katz (Dept. of MSE, MIT) Administrator 2014.06.03 3078
123 5/20 (화) 윤석진 박사 (한국과학기술연구원, 연구기획조정본부장) Administrator 2014.05.14 2743
122 5/14 (수) 김윤섭 (Univ. of Michigan, Ph.D. candidate) Administrator 2014.05.14 2566
121 4/30 (수) 김지환 박사 (IBM T.J. Watson Research Center) Administrator 2014.05.01 3067
120 4/29 (화) Dr. Aron Walsh (Univ. of Bath, UK) Administrator 2014.05.01 2097
119 4/29 (화) 박상희 교수 (KAIST 신소재공학과) Administrator 2014.04.23 3051
118 4/22 (화) 조은애 박사 (Fuel Cell Research Center, KIST) Administrator 2014.04.21 3449
117 4/15 (화) 김수호 박사 (Chief Technology Offiicer, Alantum Corporation) Administrator 2014.04.11 3033
116 4/8(화) 이종흔 교수 (고려대학교 신소재공학부) Administrator 2014.04.08 3975
115 4/1(화) 장호원 교수 (서울대학교 재료공학부) Administrator 2014.03.26 2935
114 3/27 (목) 남성욱 박사 (IBM T.J. Watson Research Center, Research Scientist) Administrator 2014.03.24 3575
113 3/25 (화) 황현상 교수 (포항공과대학교 신소재공학과) Administrator 2014.03.21 3145