THERMAL-EXPANSION OF TEXTURED POLYCRYSTALLINE AGGREGATES

We examine thermal expansion of textured polycrystalline aggregates and focus on polycrystals containing hexagonal monocrystals. Our analysis is based on the coupling of the Voigt-Reuss-Hill averaging procedures for elastic constants, Roe's [R. J. Roe, J. Appl. Phys. 36, 2024 (1965)] framework for the mathematical description of the crystallite orientation-distribution function (ODF), and the exact connections of Hashin [Z. Hashin, J. Mech. Phys. Solids 32, 149 (1984)] and Schulgasser [K. Schulgasser, J. Mech. Phys. Solids 35, 35 (1987)] between the thermal-expansion coefficients of a polycrystalline aggregate and the corresponding polycrystal elastic constants, monocrystal elastic constants, and monocrystal thermal-expansion coefficients. The results are simple expressions for the polycrystal thermal-expansion coefficient in terms of the monocrystal elastic constants, thermal-expansion coefficients, and the coefficients in the expansion of the crystallite ODF in a series of generalized spherical harmonics. We present numerical results for zinc and zirconium polycrystals with textures typical of rolling and extrusion processes. (C) 1995 American Institute of Physics.