Information gain from analytical description of isothermal resistivity curves

Abstract

The experimentally gained course of the resistivity of some Al-Zn-Mg alloys during isothermal aging is analyzed by means of a calculation of the extra resistivity of GUINIER-PRESTON zones based on the solution of the BOLTZMANN-equation in the isotropic relaxation time approximation and using XSAS intensities quoted by GUINIER and FOURNET.Applying this equation from the increase of the resistivity information on the time development of the volume fraction of the zones and from the course of the resistivity behind the maximum the growth law of the precipitates can be drawn from the alloys investigated.Die Verlaufe experimenteller Widerstandskurven, gemessen an isotherm im RT-Bereich gealterter AIZnMg-Legierungen, wurde mit Hilfe des berechneten Zusatzwiderstandes von GUINIER-PRESTON-Zonen a-nalysiert. Die Rechnungen basieren auf einer Losung der BOLTZMANN-Gleichung in der isotropen Relaxationszeit-Naherung und auf der Verwendung theoretisch von GUINIER und FOURNET berechneter Intensitaten der RKWS. -Unter Verwendung dieser Gleichung konnen aus dem anfiinglichen Widerstandsanstieg Informationen uber die zeitliche Entwicklung des Volumenanteils der Zonen und vom Verlauf des Widerstandes nach dem Maximum das Wachstumsgesetz der Zonen gewonnen werden.

On the mode of decomposition of AlZn alloys

“…[44]. This mode is further supported by analysis of the time dependence of the course of the electrical resistivity during isothermal ageing of various Al-6 a t % Zn, A1-(3 to 6) atyo Zn-(0.1 to 2) a t % Mg alloys [46]. The R-t curves can be fitted from the start of decomposition up to the time a t which the maximum of resistivity appears by means of the theory developed recently by Radomsky and Loffler [47,481 assuming that only the amount of G P zones increases, but the size of the zones remains constant.…”