The generation of vacancies in metals

Abstract

The regions where injected helium atoms first appear as gas bubbles are those where thermal vacancies originate. Microscopic examination of metals, injected with helium by using them as targets for energetic alpha-particles, reveals grain boundaries as the principal suppliers of vacancies. Detailed examination distinguishes those boundaries which generate vacancies from those which merely conduct them. The behaviour and nature of these boundaries and other vacancy sources are discussed.