Altering the time cycle of heat treatment by quenched-ln vacancies

Abstract

The role of quenched-in vacancies in altering the time cycle of heat treatment is best exemplified by the process of formation of Guinier-Preston zones. Phase decomposition can be dramatically accelerated by enhanced solute diffusion which results from the high vacancy supersaturation quenched-in attendant to heat treatment. A review is presented of this field from the earliest work through recent developments. Important contributions, principally of a conceptual nature, have come about from quenching studies on pure metals. Impurity additions to these pure metals, as well as to high-purity binary alloys, have led to an understanding of the vacancy-solute binding energy and to the way in which this binding can affect zone formation. The interrelated diffusion of vacancies and of vacancy-solute pairs introduces coupled processes which are complex and need to be considered in a thorough analysis of the problem. Recent theoretical and experimental approaches are examined.