Correlation Between Isothermal Expansion and FunctionalProperties Change of the Fe_(81)Bi_3Si_4C_2 Amorphous Alloy

摘要

The structural changes effect on functional properties of ribbon shaped samples ofthe Fe_(81)B_(13)Si_4C_2 amorphous alloy during annealing process was investigated in this paper.Differential scanning calorimetry method has shown that this alloy crystallizes in one stage,in temperature range from room temperature up to 700℃. Structural relaxation process wasinvestigated by sensitive dilatation method in nonisothermal and isothermal conditions. It hasbeen shown that structural relaxation process occurs in two stages by measuring thermalexpansion at constant temperatures of t_1= 420℃, t_2 = 440℃ and t_3 = 460℃. The first stageis characterized by linear logarithmic dependence of thermal expansion upon time at constanttemperature. The second stage of structural relaxation process is characterized by lineardependence of isothermal expansion upon the square root of process time. These results implythat the first stage of structural relaxation process is a rapid kinetic process, while the secondstage of structural relaxation process is a slow diffusion process. The rate constants k_(11) = 2,27·10~(-3)s~(-1), k_(12) = 2,79·10~(-3) s~(-1), k_(13) = 3,6·10~(-3) s~(-1), k_(21) = 0,67·10~(-4)s~(-1), k_(22) = 3,72·10~(-4)s~(-1), k_(23) = 21,53·10~(-4)s~(-1) and activation energies E_1 = 48,64 kJ/mol and E_2 = 366, 23 kJ/mol were determined for bothstages of structural relaxation process. The distinct correlation between structural relaxationprocess and magnetic susceptibility relative change was determined by thermornagneticmeasurements. It has been shown that magnetic susceptibility can be increased by up to 80%,by convenient annealings after structural relaxation process, at magnetic field intensity of 8 kA/m.