DETERMINATION OF MICROSTRUCTURAL ANISOTROPY IN SB-INSB EUTECTIC BY ELECTRICAL-RESISTIVITY MEASUREMENT

The longitudinal, rho parallel to, and transverse, rho perpendicular t o, resistivities have been measured in Sb-InSb eutectic alloys unidire ctionally solidified over a range of growth rates, 1.2 x 10(-4) to 1.2 x 10(-1) cm s(-1). The measured resistivities differ from the theoret ical values estimated on the basis of macroscopic geometrical approxim ation for the spatial arrangement of Sb rods within the InSb matrix. T he difference between the two is explained in terms of the contributio n of the interface phase, as well as the loss of microstructural aniso tropy. In the present work the interface between the Sb rod and the In Sb matrix was regarded as a definite phase constituting an in situ eut ectic composite. The presence of this interfacial phase was assumed to result in an increase of rho perpendicular to. The deg ree of microst ructural anisotropy, delta, is defined from the geometrical relation d etermined by the rho parallel to value, allowing quantitative descript ion of microstructural anisotropy. As expected, delta gradually decrea ses with increasing growth rate. Some of the quickly grown specimens h ave revealed radial directionality in their microstructure, which is r eflected by the relative size of rho parallel to and rho perpendicular to values.