PRODUCTION OF FLAKY AMORPHOUS POWDERS IN FE-ZR-B SYSTEM BY A SUPERCOOLED LIQUID QUENCHING METHOD, AND THEIR MAGNETIC-PROPERTIES

By using a supercooled liquid (two-stage) quenching method, in which s upercooled liquid droplets produced by high-pressure gas atomization a re flattened at high kinetic energies on a rapidly rotating wheel, fla ky amorphous powders with a thickness of 1-3 mu m and a large aspect r atio of 20-300 were produced for an Fe85Zr8B6Cu1 alloy. This is in con trast to the result that spherical powders produced only by high-press ure gas atomization consist of amorphous, bcc and compound, even in th e particle size range below 25 mu m. The amorphous powder changes to a mostly single bcc phase by annealing for 3.6 ks at 873 K, and the fur ther rise in annealing temperature causes the mixed structure of alpha -Fe + Fe-3(Zr,B). The annealed flaky powders with the bcc phase exhibi t soft magnetic properties of 140 emu g(-1) for saturation magnetizati on sigma(10k) and 0.6 Oe for coercivity, H-c. The composite made from the bcc flaky powders and phenol resin at a weight ratio of 9:1 has a high degree of laminated structure. The composite also exhibits soft m agnetic properties of 5.3 kG for B-100, 150 for mu(max) and 1.1 Oe for H-c. The B-100 value is 2.1 times as high as that for the composite o f amorphous Co-Fe-Si-B flaky powders and resin. Thus the present compo site is expected to be used in applications which require both high sa turation magnetization and soft magnetic properties, which cannot be o btained for the composites made from amorphous Co- and Fe-based flaky powders.