4-13 First-principles Investigation of Helium Adsorptions at Grain Boundaries in Tungsten

摘要

The tungsten was deemed to be the most promising candidates as plasma facing material(PFM)due to its high melting temperature,good thermal properties,low sputtering yield[1].The PFMs will be exposed to a high flux of helium atoms escaping from the plasma.Helium easily are trapped by vacancies,dislocations,grain boundaries(GBs)to form helium bubbles,which can significantly degrade the mechanical properties of materials.One wellknown example is the high-temperature helium embrittlement(HE),which is the drastic embrittlement of metal at temperatures above 0.5 Tm(Tm:melting temperature)due to helium bubbles formation at GBs,even at extremely low overall helium concentration.To enhance the HE resistance of metal,it is necessary to study adsorptions of helium atoms at GBs firstly.