Production of nanocrystalline b.c.c. FeNbB bulk alloys by warm extrusion and their magnetic properties

A bulky Fe₈₄Nb₇B₉ alloy was obtained by extruding the powders ground from amorphous ribbon, at temperatures T_e between 563 K and 723 K at pressures P_e between 824 MPa and 1208 MPa and at a speed of 5 mm s^-1. The bulk Fe₈₄Nb₇B₉ alloy extruded at T_e = 698 K and P_e = 1208 MPa is in a fully consolidated state has a density of about 99%. The bulk alloy is composed of a mostly single b.c.c. phase with a grain size of about 10 nm after annealing for 3.6 ks at temperatures between 873 K and 973 K, and its soft magnetic property tends to better for the bulks extruded at lower pressures. The bulk alloy extruded at T_e = 698 K and P_e = 824 MPa exhibits a high saturation magnetization B_s of 1.40 T and a low coercive force H_c of 64 A m^-1 after annealing at 698 K.