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

Transmission electron microscope (TEM) studies of the bainitic transfo rmation in Cu-25.9 pet Zn-3.75 pet Al alloy were performed. At the ini tial formation stage from the matrix, precipitated alpha(1) plates wer e without internal stacking faults. It was found that there exist thre e-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, respective ly. Terraces on the faces of alpha(1) plates are parallel to the habit plane, which is (114)(alpha 1). Evidence indicates that the superledg es 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 d iffusion-controlled ledgewise mechanism.