LAUSR

The effects of annealing temperature and heating rate on the microstructure, magnetic, and mechanical properties of melt-spun Fe 81.7− x Si 4 B 13 Cu 1.3 Nb x ( x  = 0–4) alloy ribbons have been investigated. With increasing the annealing temperature, a ductile–brittle transition occurs during amorphous structure relaxation, the brittleness becomes severe with more α-Fe precipitation, and the hardness rises continuously. After annealing at respective optimum temperatures under the heating rate of 20 K/min, as the Nb content increases from 0 to 4 at.%, average grain size ( D α-Fe ) and volume fraction ( V α-Fe ) of the α-Fe in the nanocrystalline alloys decrease gradually from 53.3 nm and 52% to 8.7 nm and 42%, respectively; the strain at fracture ( ε f ) representing ductile level increases from 1.33 to 1.72%; and the coercivity ( H c ), saturation magnetic flux densities ( B s ), and Vickers hardness ( H v ) all decrease gradually. As the heating rate rises from 10 to 400 K/min, the D α-Fe of the Fe 81.7 Si 4 B 13 Cu 1.3 alloy decreases from 45.7 to 28.4 nm without considerable variation of the V α-Fe ; the H c lowers from 235 to 25 A/m, the ε f increases from 1.10 to 1.66%, and the B s and H v change slightly. Enriching of Nb weakens the dependence of nanostructure, magnetic softness, and annealing embrittlement on the heating rate. A correlation of ε f  ∝  D α-Fe n is found for the nanocrystalline alloys, where the n rises from − 1 to − 1/2 with enriching of Nb from 0 to 4 at.%. The mechanisms by which nanostructure affects magnetic and mechanical properties have been discussed.