Speaker: Dr. Kaiyuan Yu（China University of Petroleum-Beijing）

Chair Person: Prof. Huiling Duan

Date: Nov. 17, 2015, 13:45-14:45

Place: Room 210 COE Building No.1

Report Introduction:

Twin boundaries enable excellent mechanical, physical properties in nanotwinned metals. We present that twin boundaries can also enhance the radiation tolerance of FCC metals. Ag with high density nanoscale twins were in situ irradiated by Kr ions using IVEM facility at Argonne National Laboratory. A large number of stacking fault tetrahedra are removed during their interactions with abundant coherent twin boundaries. Consequently the density of stacking fault tetrahedra in irradiated nanotwinned Ag is significantly lower than that in its coarse-grained counterpart. The interaction mechanisms are discussed and compared to predictions by molecular dynamics simulations. In situ studies also reveal two new phenomena: 1. Radiation induced frequent migration of coherent and incoherent twin boundaries; 2. Self-healing of coherent twin boundaries where defect denuded zones are observed. Such twin boundary behavior is also correlated to the defect-twin boundary interactions. Furthermore, the migration of twin boundaries under irradiation leads to the shrinkage of pre-existed nanovoids in nanotwinned Cu, underscoring the potential of nanotwinned metals in nuclear energy applications.
 

About Speaker:
　　Dr. Kaiyuan Yu is currently an associate professor at the Department of Materials Science at China University of Petroleum-Beijing. Dr. Yu holds a bachelor degree (2006) and a master degree (2009) with Beihang University (Beijing, China). He was awarded a doctoral degree of materials science and engineering by Texas A&M University (College Station, TX, US) in 2013. Later, Dr. Yu worked for the Department of Mechanical Engineering at Texas A&M as a lecturer and for the Department of Electrical and Computer Engineering at Texas A&M as a post-doctoral associate before he joined China University of Petroleum-Beijing in July 2014. The research interests of Dr. Kaiyuan Yu include radiation damage in solids, dynamic characterization of defect-interface coupling under radiation and mechanical properties of nanocomposite materials. He has published more than 20 peer-reviewed papers which has been cited over 230 times, and chaired 6 symposiums at MRS and TMS conferences.