INFLUENCE OF HEAT-TREATMENT ON MAGNETOSTRICTIONS OF FINEMET FE73.5CU1NB3SI3.5B9

The investigation of magnetostriction of metallic glass of the Finemet type upon structural changes has been performed on samples with diffe rent thermal history. One set of samples has been annealed for 1 h at different temperatures ranging from 573 to 873 K; another set of sampl es has been annealed at 823 K for different times. Measurements of sat uration magnetostriction lambda(s), volume magnetostriction omega and partial derivative omega/partial derivative H have been performed usin g direct capacitance method. Spontaneous volume magnetostriction Delta V/V has been determined from dilatometric measurements and has been f ound to be 15 x 10(-3). For the first set of annealed samples the temp erature dependence of lambda(s) exhibits local maxima al 573 and 733 K , above which a steep decrease of lambda(s) by about one order of magn itude is observed. The dependence of the value of partial derivative o mega/partial derivative H on the annealing temperature exhibits local minima at 573 and 793 K and local maximum at 723 K. These extremes in lambda(s) and partial derivative omega/partial derivative H are relate d to the changes in CSRO and TSRO, to relaxation processes and to inte rnal stresses. In the latter case the magnetostriction of the samples strongly decreases after annealing even for a few minutes from the val ue of 24 x 10(-6) by about one order of magnitude. The quantity partia l derivative omega/partial derivative H follows the crystallization pr ocess, exhibiting, however, maxima at 30 and 180 min annealing time. A morphous Finemet samples crystallized after annealing at temperatures above 753 K into nanocrystalline phase containing supersaturated solid solution alpha-Fe(Si), Fe3Si, (FeSi)(3)B, Fe2B and Fe3B. (C) 1997 Els evier Science S.A.