SHAPE ANISOTROPY OF GP ZONE IN EARLY DECO MPOSITION PROCESS OF AL-ZN BINARY ALLOY

The structural anisotropy of GP zone in an Al-Zn binary alloy has been investigated using in situ small angle X-ray scattering measurement w ith a synchrotron radiation source. As a result, 2-dimensional images of scattering intensity showed the orientation dependence. The maxima of scattering intensities were observed along the [001] directions. In the high scattering vector range, the contour of scattering intensiti es also showed anisotropy and the form for the early stage of aging wa s different from that for the late stage. The difference among each Gu inier radii determined from one dimensional profile along the [001], [ 110] and <111> directions predicted a facetting for the {111} interfac e of GP zone. Assuming the form of GP zone is faceted sphere, we calcu lated the structure factors. The result agreed with the experiments in the range, where the scattering intensity gives information on the sh ape of small precipitates like GP zone.