Magnetic properties and structure of Fe50Pd50-xNix alloys (x = 4 and 8) in the as-deformed and annealed state

Abstract

The structural and hysteresis properties of ternary Fe50Pd50-xNix (x = 4 and 8) alloys have been studied. In order to accelerate the formation of the hard magnetic L10 phase in these alloys, they were deformed by rolling with a reduction of 96% and by the method of high-pressure torsion (HPT). The annealing treatment for ordering for up to 100 h was performed at 400–500°С. It is shown that the structure transformation of the initial fcc phase into the ordered tetragonal phase at 400°С proceeds very slowly. After annealing for 100 h at this temperature, the Fe50Pd46Ni4 and Fe50Pd42Ni8 alloys are multiphase and contain residues of the cubic phase (Fm3¯m), cubic phase ordered by the L12 type (Pm3¯m), and tetragonal phase L10* appropriately described by the symmetry space group C4/mmm. The isothermal annealing at 400–500 °C for up to 100 h does not result in the maximum of Hc for the as-rolled Fe50Pd46Ni4 and Fe50Pd42Ni8 alloys. Implementation of the annealing routine with a temperature decreasing stepwise from 500 to 400 °C allowed us to increase Hc to 851 and 527 Oe for as-rolled samples and to 1192 and 980 Oe for the HPT samples of the Fe50Pd46Ni4 and Fe50Pd42Ni8 alloys, respectively.