ROLE OF DEFECT STRUCTURE ON PRECIPITATION HARDENING

Abstract

Role of vacancies and varying amount of cadmium addition on the preiprecipttatiOfl stage of ageing In alp nium`• zinc alloy was studied with the help of resistivity measurements. Activation energies associated with formation and migration of vacancies In three ternary alloys were ovalUa-ted. The binding energy between cadmiumatom and. vacancy has also been estimated. The values are compared with those reported in literature# It has been found that resistivity increases with ageing time and starts Increasing almost instantaneously. It has also been observed that addition of cadmium to the aluminium •. zinc alloy lowers the rate of pre-precipitatIOn and higher the cad-mium content, slower is the ageing process.