Thermal diffusivity of sintered stainless steel-alumina composites
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INTRODUCTION
THE metal-matrix composite material with an oxide as a second phase is a heterogeneous material, belonging to the class of multiphase mixtures.[1] The physical properties of composite materials are of much practical and theoretical interest. In particular, a great deal of work has been devoted to the investigation of thermal conductivity k of two-phase composite, which is expected to depend on the conductivity k1 of matrix material (phase 1) and the conductivity k2 of the filler (phase 2, consisting of many inclusions dispersed throughout the matrix).[2] The problem of determining the effective thermal conductivity of randomly packed granular materials is one that frequently occurs in engineering practice. A detailed solution of the conduction problem would require knowledge of the shape, size, location, and conductivity of each particle in the system together with the interaction between particles. Such knowledge is difficult to represent in randomly packed systems. To overcome these difficulties, investigators have tended to make a series of simplifying assumptions. The two basic approaches may generally be classified as (1) Fourier’s law models, which use an idealized geometry, for which the temperature field may be solved and (2) Ohm’s law models, where simplified repetitive geometries are assumed to be representative of the randomly packed system.[3] From simplifying hypotheses regarding the dispersion of the discontinuous phase, an overall value of the thermal conductivity can be obtained for a unit cube of the mixture.[4] Recently, Hayashi et al.[5] and Pai and Raghavan[6] have developed new Ohm’s law models by assuming that the equivalent electrical network is established and the thermal conductivity of the system is obtained from the thermalelectrical analog. Rayleigh[7] and Maxwell[8] had proposed a theoretical relationship to predict the overall physical properties of composite materials constituting components with different R. ABDUL ABAS, Graduate Student, and S. SEETHARAMAN, Professor, are with the School of Industrial Engineering and Management, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden. Contact e-mail: [email protected] Manuscript submitted January 3, 2006. METALLURGICAL AND MATERIALS TRANSACTIONS B
physical characters. In view of the thermophysical characteristics of a composite material, Liu and Fu[9] and Hasselman and Johanson[10] have modified the relationship of the Rayleigh-Maxwell theory by introducing a concept of ‘‘interfacial resistance’’ and have developed a somewhat more realistic approach in predicting the thermal conduction behavior of brittle composite materials. The aim of the current study is to measure the thermal conductivity of composite material with AISI 304 austenitic stainless steel as the matrix and aluminum oxide Al2O3 filler material over the temperature range between room temperature and 1473 K. Furthermore, the effect of Al2O3 content on the thermal conductivity component was examined and the results were
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