THE COPPER CONTENT OF GUINIER-PRESTON (GP1) ZONES IN AL-1.84 AT-PERCENT CU ALLOY

The (Guinier-Preston) GP1 zones were studied by means of high resoluti on electron microscopy and contrast simulations. In the [110] zone axi s orientation, shearing of a GP1 zone by a dislocation has been observ ed. Different models of monolayer GP1 zones-containing 100, 30, 60, 50 and 40% Cu (balance of Al)-were used for the multislice simulations. According to the contrast analysis of through focus series of experime ntal images and other experimental data, the GP1 zones with the compos ition ranging from 40 to 100% Cu coexist. A simple model of a displace ment field around the GP1 zone was used in simulations in order to int erpret the atomic column displacement measured on some experimental mi crographs. (C) 1998 Acta Metallurgica Inc.