Structure and Phase Composition of a WTaMoNbVCrZrTi Alloy Obtained by Ball Milling and Spark Plasma Sintering In this paper, the structural characteristics of a WTaMoNbVCrZrTi nonequiatomic refractory metal alloy obtained by spark plasma sintering (SPS) of a highenergy ballmilled powder mixture are reported. Highenergy ball milling resulted in the formation of particle agglomerates ranging from several tens to several hundreds of micrometers. These agglomerates were composed of micrometer and submicrometer particles. It was found that, during ball milling, a solid solution of A2 structure formed. The grains of the sintered material ranged from fractions of a micrometer to several micrometers. During SPS, the phase transformations in the alloy led to the formation of a Laves phase of C15 structure and ZrO and ZrO2 nanoparticles. The microhardness of the ballmilled alloy and sintered material was found to be 9.28 GPa xc2xb1 1.31 GPa and 8.95 GPa xc2xb1 0.42 GPa, respectively. The influence of the processing conditions on the structure, phase composition, and microhardness of the alloy is discussed.

BallisticDiffusive Model for Heat Transport in Superlattices and the Minimum Effective Heat Conductivity There has been much interest in semiconductor superlattices because of their low thermal conductivities. This makes them especially suitable for applications in a variety of devices for the thermoelectric generation of energy, heat control at the nanometric length scale, etc. Recent experiments have confirmed that the effective thermal conductivity of superlattices at room temperature have a minimum for very short periods (in the order of nanometers) as some kinetic calculations had anticipated previously. This work will show advances on a thermodynamic theory of heat transport in nanometric 1D multilayer systems by considering the separation of ballistic and diffusive heat fluxes, which are both described by GuyerKrumhansl constitutive equations. The dispersion relations, as derived from the ballistic and diffusive heat transport equations, are used to derive an effective heat conductivity of the superlattice and to explain the minimum of the effective thermal conductivity.