STUDY ON THE TRANSFORMATION MECHANISM OF ALPHA-1 PLATES IN A CU-ZN-AL ALLOY

Transmission electron microscope (TEM) studies of the bainitic transformation in Cu-25.9 pet Zn-3.75 pet Al alloy were performed. At the initial formation stage from the matrix, precipitated alpha(1) plates were without internal stacking faults. It was found that there exist three-dimensional superledges on the broad faces of alpha(1) plates, with a spacing and height of about 50 to 230 nm and 10 to 40 nm, respectively. Terraces on the faces of alpha(1) plates are parallel to the habit plane, which is (114)(alpha 1). Evidence indicates that the superledges are mobile and that the alpha(1) plates thicken by their movement. The results show that growth of alpha(1) plates is consistent with a diffusion-controlled ledgewise mechanism.