Influence of heat treatment on magnetostrictions and electrical properties of (Fe 1Co 1) 76Mo 8Cu 1B 15

Abstract

The investigation of magnetostriction of (Fe 1Co 1) 76Mo 8Cu 1B 15 metallic glass upon structural changes has been performed on samples with different thermal history. The samples have been annealed for 0.5 h at different temperatures ranging from 573 to 973 K. Measurements of saturation magnetostriction λ S, volume magnetostriction ω and forced magnetostriction ∂ ω/∂H have been performed using direct capacitance method. For the set of annealed samples, the temperature dependence of lambda(s) exhibits local maximum at 828 K. Above 828 K, there is a decrease of lambda(s) by about 1/3 of its maximal value. The dependence of the value of ∂ ω/∂H on the annealing temperature exhibits local minima at 573 and 923 K and local maximum at 678 K. These extremes in λ S and ∂ ω/∂H are related to the changes in CSRO and TSRO, to relaxation processes and to internal stresses. The transformation process has been monitored by temperature dependencies of electrical resistivity. Amorphous samples crystallized after annealing at temperatures above 678 K into nanocrystalline supersaturated solid solution bcc-Fe(Co, Mo) and above 873 K into B 24Fe 84Mo 8, CoMoB and traces of B 2Mo 2Fe and tetragonal Fe 3B. As-quenched samples exhibit the Curie temperature at around 600 K, in the vicinity of the glass transition temperature. At room temperatures, the ribbon exhibits isotropic characteristics. Thermal treatment induces magnetic anisotropy formed in the direction parallel to the ribbon axis during relaxation annealing while during crystallization its direction becomes perpendicular to the ribbon axis. Remanence appears after heat treatment above 920 K.