Energetic Study of Helium Cluster Nucleation and Growth in 14YWT through First Principles

Materials

Yingye Gan¹  Huijuan Zhao¹  David T. Hoelzer³  Di Yun² 

[1] Department of Mechanical Engineering, Clemson University, Clemson, SC 29631-0921, USA;School of Nuclear Science and Technology, Xi’an Jiao Tong University, 28 Xi’an Ning West Road, Xi’an 710049, China;Materials Science & Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6136, USA;

关键词: helium bubbles;    nanostructured ferritic alloys;    first principles theory;    formation criteria;   

DOI  :  10.3390/ma9010017

来源: mdpi

【 摘 要 】

First principles calculations have been performed to energetically investigate the helium cluster nucleation, formation and growth behavior in the nano-structured ferritic alloy 14YWT. The helium displays strong affinity to the oxygen:vacancy (O:Vac) pair. By investigating various local environments of the vacancy, we find that the energy cost for He cluster growth increases with the appearance of solutes in the reference unit. He atom tends to join the He cluster in the directions away from the solute atoms. Meanwhile, the He cluster tends to expand in the directions away from the solute atoms. A growth criterion is proposed based on the elastic instability strain of the perfect iron lattice in order to determine the maximum number of He atoms at the vacancy site. We find that up to seven He atoms can be trapped at a single vacancy. However, it is reduced to five if the vacancy is pre-occupied by an oxygen atom. Furthermore, the solute atoms within nanoclusters, such as Ti and Y, will greatly limit the growth of the He cluster. A migration energy barrier study is performed to discuss the reduced mobility of the He atom/He cluster in 14YWT.

【 授权许可】

CC BY   
© 2016 by the authors; licensee MDPI, Basel, Switzerland.