RESISTOMETRIC STUDY OF AL-10-PERCENT ZN AGED BELOW AND ABOVE HALF OF THE MELTING TEMPERATURE

Ageing characteristics of the alloy Al-10 wt% Zn have been investigate d in the temperature range 110-230 degrees C (below and above 0.5T(m)) by resistivity measurements. With time of ageing, the resistometric s tudy delineated two distinct stages: the first stage characterized by a decrease in resistivity, whereas an increase was observed in the sec ond stage. The decrease in resistivity rho(t) with time t at the diffe rent ageing temperatures was interpreted as due to the formation and g rowth of GP zones, while the increase in rho(t) was attributed to the dissolution of the GP zones to form the rhombohedral transition phase which was emphasized by electron microscope investigation. The activat ion energy of GP zone formation and growth was found to be 0.5 eV in a ccordance with that quoted in literature.