In 1978, a direct production method of 'Sendust' sheet, known as a member of soft magnetic alloys, has been developed in Japan by the Rapid Quenching Technique.
But, until today phase transformation phenomena of Rapid Quenched Sendust alloys was not studied intensively.
In this study, RSP (Rapid Solidification Process) technique was utilized to produce a family of Sendust alloys such as typical 'Sendust' alloy (9.6wt% Si-5.4wt% Al-bal.Fe), 'Super Sendust' and Sendust alloys with boron doping (0.01wt% and 0.05 wt%).
In depth X-ray diffraction analysis was conducted to investigate the phase transformation phenomena following the isothermal annealing at 700℃ and 800℃.
The $DO_3\rightleftharpoons B_2$ order-disorder transition observed at these temperatures.
The lattice parameter and the degree of long range orderness changes rapidly at the on-set of annealing, changed gradually during the middle stage. In the last stage of annealing these properties remained nearly constant.
$DO_3$ and $B_2$ ordered structures were stable phase at 700℃and 800℃, respectively. These results were same for the arcmelted power specimens.
The volume fraction of stable phases at each temperature increases with the increasing annealing time.
In Super Sendust alloy, extra peaks were observed in diffraction pattern and their intensity decreases gradually after each isothermal annealing.
The lattice parameter of boron doped alloys were observed to increase and to reach a equilibrium value at the respective annealing temperature.
