Disorder induced by aging in metal tritides

Due to the decay of tritium to 3He in metals a considerable amount of disorder is introduced into tritium containing alloys. We will first review previous research in this area and then summarize our own studies. The aging experiments presented here include: a) transmission electron microscopy (TEM) on aged VT and ZrT alloys showing the microstructure of tiny, high-pressure 3He bubbles and interstitial dislocation loops after aging for up to more than 2 yrs; b) swelling studies on selected Ta and Nb tritides where the volume expansion of the tritides as well as the volume requirements of the He atoms in the bubbles are investigated; c) acoustic emission experiments with aging Ta and Nb tritides; d) resistivity measurements on V and Ta tritides as a function of aging time; e) observations of grain boundary embrittlement in Ta tritides. The general picture evolving from this and other studies is that the production of insoluble He in the host lattice leads to significant disorder and radiation-like damage severely affecting most properties of the host lattice. This disorder and damage sets in rather early, typically 1 - 2 weeks after the formation of the tritide, with the formation of 1 - 2 nm size high-pressure 3He bubbles. Accelerated 3He release in the aged tritides seems to be associated with the formation of He filled channels