Small Angle X-ray Scattering Profile Analysis and Particle Size Distribution in the Aluminium Alloys Containing G.P.Zones

Abstract

A Simple qualitative method is described, by which the particle size distribution and shape distribution of G.P.zones in aluminium alloys can be determined by one profile factor, V_S, led from the behaviour of the tail part on the profile of small angle X-ray scattering curves. These two distributions can not be separated generally and therefore in this research the Al-Ag alloys are selected for the determination of size distribution, in which the shape of G.P.zones is known to be always spherical. The profile factor V_S for the size distribution and the size distribution obtained from the log normal distribution method are compared in the aged Al-Ag alloys. It is shown that these two size distributions are in qualitatively good agreement. It is also to be noted that the experimentally determined size distribution by transmission electron microscopy is in approximate agreement with the log normal distribution.
In Al-1.00 at% and 2.11 at%Ag alloys aged at 135°C, the profile factor V_S as a function of zone radius shows one peak. This means that the size distribution becomes narrower at first and again wider at the later stage. By the log normal distribution method the latter process is also observed. In this process the integrated intensity Q₀ is found to be constant and therefore the growth mechanism is thought to be due to Ostwald ripening. But the behaviour of G.P.zone size distribution in these Al-Ag alloys is quite different from the results in the Al-Zn alloys obtained by R.W.Gould. The growth mechanism of G.P.zones should be investigated further from the points of view of particle size distribution. In Al-1.00 at%Ag alloys it is also found that R_G⁴ (R_G: Guinier radius) is proportional to ageing time.