SURFACE-RELIEF ASSOCIATED WITH MARTENSITE AND BAINITE IN A CU-ZN-AL ALLOY MEASURED BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy was employed to quantitatively study the surfa ce relief accompanying martensite and bainite in a Cu-Zn-Al alloy. It is demonstrated that the surface relief angle associated with martensi te is 14.3 degrees, in good agreement with the theoretical result dedu ced from the phenomenal theory of martensite crystallography (PTMC). H owever, the surface relief angle associated with bainite is 2.0 degree s-3.2 degrees, which disagrees with the PTMC result. This indicates th at the transformation mechanism of bainite is different from that of m artensite. The fine structures of the surface relief associated with m artensite and bainite are also investigated. The surface relief of mar tensite is composed of the small parallel relief caused by small marte nsite plates, and that of bainite is composed of small cells induced b y subunits in bainite. (C) 1996 American Institute of Physics.