Abstract :
Thermophysical properties of amorphous alloys represent the features of a
given material specimen, and, as such, they are dependent, in general, on
their elemental composition. Some properties are measured at surfaces, and
others are measured for the bulk as a whole. Complications arise when the
elemental composition varies as a function of position within the material
specimen, as demonstrated by simultaneous measurements of thermal diffusivity
and elemental composition by time-resolved spectroscopy of laserproduced
plasma (LPP) plume emissions. To further understand the source
of a rather common near-surface elemental composition anomaly, the evolution
of the surface composition of Wood’s alloy under the influence of thermal
cycling with, and without, a temperature gradient over the specimen has
been investigated. Surface composition modifications have been found to take
place by accumulation of irregularly spaced gray patches of an inhomogeneous
composition on the surface in the presence of a temperature gradient.
Determination of elemental composition by LPP spectroscopy shows the
three-dimensional structure of the patches.
Keywords :
Benard–Marangoni instability , near-surface compositionanomaly , convection , surface tension.
