INTERPHASE BOUNDARY STRUCTURES ASSOCIATED WITH THE BETA TO ZETA-M MASSIVE TRANSFORMATION IN A AG-26 AT-PERCENT AL-ALLOY

Interphase boundary structures associated with the b.c.c. beta to h.c.p. zeta(m) massive transformation in Ag-26 at.% Al alloy have been investigated with transmission electron microscopy (TEM). Misfit-compensating ledges with Burgers vectors of the c or (c + a) type were observed on Burgers or near-Burgers related interfaces and of the (c + a) type on Potter or near-Potter related interfaces. The experimentally observed structures are in good agreement with those modeled by means of an extended O-lattice approach. Misfit-compensating ledges were also found to be closely spaced on some irrationally orientated interfaces. High-resolution TEM revealed the detailed structure of misfit-compensating ledges at a beta:zeta(m) boundary across which the orientation relationship deviated slightly from that of Burgers. Overall, the experimental results show that beta:zeta(m) interfaces are partially coherent, as was predicted for massive transformations in general 25 years ago.