A STRUCTURAL INVESTIGATION OF THE CRYSTALLIZATION PRODUCTS OF AN AMORPHOUS NI-P ALLOY

The crystallization product of an amorphous Ni80P20 alloy has been studied using X-ray diffraction and transmission electron microscopy (TEM). The crystallization product is composed of two phases: body-centred tetragonal (b.c.t.) Ni3P compound and face-centred cubic (f.c.c.) Ni austenite, and a new set of orientation relationships between them has been obtained: <001>b.c.t. parallel-to <110>f.c.c., <110>b.c.t. parallel-to <111>f.c.c. According to the orientation relationships, a possible interface model between Ni3P and Ni crystals was proposed. An observation of the crystals was carried out by means of high-resolution electron microscopy (HREM). The morphology of the products is characterized by separated crystalline blocks of the two phases, in which Ni3P blocks contain many kinds of defects. Different kinds of Ni-phase morphology were also analysed. Such a crystallization product which is difficult to interpret by using the classical atom-diffusion mechanism can be understood according to the newly developed crystallization micromechanism. The structure relationship between the coordination clusters (in amorphous state) and the crystallization products was also discussed.