DETERMINATION OF THE EFFECTIVE VACANCY CONCENTRATIONS AND THE VACANCY LOSSES AFTER THE QUENCH OF AL ZN MG ALLOYS

On the basis of 1. The experimental observation of dislocation loops by means of TEM, 2. The conclusion from this that the concentration of vacancies in the dislocation loops exists at the cost of the vacancy concentration primarily present at T(q), and 3. The inversion of the decomposition kinetics of Al-Zn-Mg alloys found out by means of resistivity and microhardness measurements, the effective vacancy concentration C(v,eff) being at disposal for the GP-zone formation was found out by means of the relation [GRAPHICS] being the time required to reach the maximum of resistivity) and the Arrhenius plot in T(R,max) = f(1/T(q)) of the isothermal resistivity measurements. From the comparison of C(V,eff) with the theoretical V concentration at T(q) it is possible to derive statements about the loss of vacancies during and after the quench through loop formation, building-in of vacancies in GP-zones and annealing of vacancies at lattice defects. From this comparison follows: The ideal ZnV concentration at T(q) (calculated by means of the Lomer equation) is sufficiently great to account for the effective vacancy concentration. The part of C(MgV) in the loss concentration is rising with increasing C(Mg). Both these statements support the hypothesis that the initial process of the decomposition in Al-Zn-Mg alloys is caused by the ZnV diffusion.