材料期刊网

Due to its inert reactivity with almost elements, He-3 produced from tritium decay has extremely detrimental effects on the tritide. To refrain from this He-3-induced damage, an efficient way is to increase the stability of He-3 in metal tritide by alloying. Using a first-principles discrete variational method in two cluster models, one for a low He-3 concentration and the other for a high He-3 concentration, the authors study the alloying effect of 3d and 4d transition metals on the stability of He-3 in TiT2 system. It is found that the preferring and metastable sites of He-3 are affected by He-3 concentration : He-3 prefers to stay at original tetrahedral interstitial site when He-3 concentration is low but moves to octahedral site when He-3 concentration is high enough. A criterion of alloying effect is proposed, according to which Nb, Y, Zr, Pd, Ru, Tc, Rh, Cr, Mo and Ag are suggested to be the beneficial alloying elements for increasing the stability of He-3 in the alloyed TiT2 with a low He-3 concentration and Y, Nb, Mo, Zr, Cr, Tc, Ru, Rh and Cu for that with a high He-3 concentration. Our results of alloying effect are supported by the positron annihilation spectroscopy (PAS) measurements for He-implanted Ti, TiMoYAl and TiZrYAl films. (c) 2006 Elsevier B.V. All rights reserved.