Structure and texture of the Al3CaZn phase in an Al-5 % Ca-5 % Zn superplastic sheet alloy

Abstract

The structure of the intermetallic phase Al₃CaZn present in the superplastic sheet alloy Al-5 % Ca-5 % Zn has been determined by means of x-ray diffraction (XRD) and electrón diffraction (TEM). Also, the texture of this phase has been studied by means of pole figures and the orientation distribution function (ODF). The Al-5 % Ca-5 % Zn alloy is formed by a fine grained aluminum matrix (d ≈ 2-3 μm) and 20 % vol. of Al₃CaZn in the form of round-shaped particles with 0.2-0.5 μm diameter. This alloy undergoes superplastic behavior in a wide range of strain rates and temperatures. It has been found in this work that the structure of the second phase is body-centered tetragonal, with lattice parameters a = b = 0.422 nm and c = 1.131 nm. The texture of the alloy is formed by the fiber <001>, i.e., the crystallites are oriented preferentially with the c-axis perpendicular to the rolling plane. The texture sharpens after severe annealings.