No abstract

The structural phase transition of ?-Fe precipitates in a Cu matrix is studied using the x-ray diffraction technique. At low temperature, the FCC lattice uniformly contracts along the c axis by 0.17%. In the c plane the mean value of the lattice spacing expands by 0.19%, but the atomic positions are modulated by a sinusoidal wave propagating along the [ l 1 01 direction with the (1 i 0) polarisation vector. Various properties of the periodic lattice wave (PLW) are studied. The wavelength and amplitude of the PLW depend on the size of the precipitates. The origins of the PLW and the size effects are discussed.

A parallel-slit analyzer (PSA) has been developed for the purpose of lowering tails in diffraction pro®les from powders and thin ®lms. In the present work, four different materials were used for the foils: sintered and hot-pressed tungsten (W), cold-worked stainless steel (SUS), beryllium bronze (Cu 98 Be 2 ) and chemically surface-processed beryllium bronze (CuOx). The PSAs were tested in a parallel-beam geometry using Cu K radiation collimated with a graded d-spacing parabolic multilayer mirror. The W and CuOx PSAs gave pseudoVoigt pro®les of $80% Gaussian in the direct-beam case. Textured and roughened surfaces of W and CuOx foils are considered effective for depressing totalre¯ection effects from the surfaces of the foil materials, and consequently for lowering the tails of diffraction peaks.