Preparation and characterization of Fe-(Cr,Mo,Ga)-(P,C,B) soft magnetic bulk metallic glasses

Using master alloys with nominal compositions Fe77.5-x-y-zCrxMoyGazP12C5B5.5 (x,y,z = 4,4,4; 4,4,2; 4,4,0 and 2,2,2), cylindrical rods up to 3 mm in diameter and 70 mm in length, rectangular bars 2 x 2 mm and 30 mm length and discs with 10 mm in diameter and 1 mm thickness were produced using the copper mold casting technique. By powder metallurgical methods, pellets with even larger dimensions (10 mm in diameter and 3-5 mm in thickness) were prepared. Compression tests reveal that the fracture strength for the as-cast samples sigma(f) is around 3 GPa and the fracture strain epsilon(f) reaches 2%. Upon annealing, the fracture strain drops to 1.6% and no plastic deformation is observed while the fracture stress remains almost the same. The coercivity of the as-cast samples is lower than 10 A/m, decreasing to 0.7 A/m upon annealing. The coercivity of as-milled powder is greater than 1000 A/m, and it decreases to 25 A/m after hot compaction and subsequent annealing, although the latter value is one order of magnitude higher than those for cast samples.