Anisotropy of thermal expansion for amorphous Fe 78B 13Si 9 alloy

Abstract

Amorphous alloys are generally considered as fully isotropic, but only in their ideal state. Under real conditions, however, uniaxial anisotropy may be induced by the preparation techniques and conditions or by subsequent thermal, stress and magnetic field treatments. Magnetic properties have been found to be anisotropic; for example, magnetic anisotropy has been studied widely and is applied deliberately to obtain specific properties. The magnetoelastic coupling effects, although formally second-order effects, may contribute significantly to the elastic constants and their anisotropy in magnetic amorphous alloys. In addition, the difference of heat conducting conditions and subjected stress field in different orientations during the forming process may yield a certain anisotropic short range order which results in anisotropic properties in amorphous alloys. The physical and mechanical properties in experimental and theoretical work on amorphous strips formed by melt quenching have been assumed to be isotropic. The basis of that assumption is not clear. Results obtained from amorphous alloys have indicated that practically all of the specimen series tested indicated anisotropic tensile strengths. However, the anisotropy of thermal expansion coefficients and structure have not been understood in amorphous alloys. In the present work the thermal expansions in the longitudinal and transverse directions for amorphousmore » Fe/sub 78/B/sub 13/Si/sub 9/ alloy prepared by various forming conditions were investigated.« less