Crystallographic and magnetic alignment in hot-rolled Pr20Fe74B4Cu2 alloys

Ingot material with the composition Pr20Fe74B4Cu2, in the form of a circular cross section billet, was hot-rolled at temperatures 800-1000 degrees C using a strain rate of approximately 3 s(-1). The magnetic measurements revealed that the crystallographic alignment, and as a consequence the remanence J(r) increased significantly in a direction perpendicular to that of the rolling direction, with values of J(r) up to 1000 mT, despite the use of high strain rate processing. The anisotropy is considered to develop through a contribution of grain boundary liquid phase diffusion and rotation of the initial plate-shaped primary crystals. It is possible that this induced alignment was more pronounced at high temperatures as a result, it is proposed, of a higher diffusion rate in the liquid grain boundary phase. In contrast, the coercivity was found to decrease at higher rolling temperatures as a result of the coarsening of the microstructure.