24-10-2012, 11:33 AM
Interdiffusion in Ni/CrMo Composition-Modulated Films
ABSTRACT
The measurement of diffusivity at low temperature in the Ni-CrMo alloy system, relative to the melt point, is
accomplished through the use of a composition-modulated structure. The composition-modulated structure consists of
numerous pairs of alternating Ni and Cr-Mo layers that are each just a few nanometers thick. A direct assessment of alloy
stability is made possible through measurement of the atomic diffusion between these layers that occurs during anneal
treatments. X ray diffraction under the Bragg condition in the(theta)/2(theta) mode is the method used to quantify the changes
that occur in the short-range order, i.e. the artificial composition fluctuation. The relative intensities of satellite reflections
about the Bragg peaks are monitored as a function of the time at temperature. The decay rate of the artificial composition
fluctuation of Ni with Cr-Mo is analyzed using the microscopic theory of diffusion to quantify a macroscopic diffusion
coefficient D as 1. 52 x 10(sup -19) cm(sup 2)(center-dot) sec(sup -1) for Ni(sub 2)(Cr,Mo) at 760 K.
ABSTRACT
The measurement of diffusivity at low temperature in the Ni-CrMo alloy system, relative to the melt point, is
accomplished through the use of a composition-modulated structure. The composition-modulated structure consists of
numerous pairs of alternating Ni and Cr-Mo layers that are each just a few nanometers thick. A direct assessment of alloy
stability is made possible through measurement of the atomic diffusion between these layers that occurs during anneal
treatments. X ray diffraction under the Bragg condition in the(theta)/2(theta) mode is the method used to quantify the changes
that occur in the short-range order, i.e. the artificial composition fluctuation. The relative intensities of satellite reflections
about the Bragg peaks are monitored as a function of the time at temperature. The decay rate of the artificial composition
fluctuation of Ni with Cr-Mo is analyzed using the microscopic theory of diffusion to quantify a macroscopic diffusion
coefficient D as 1. 52 x 10(sup -19) cm(sup 2)(center-dot) sec(sup -1) for Ni(sub 2)(Cr,Mo) at 760 K.