Dislocation density and magnetic properties of industrial pure iron during annealing

Abstract

To investigate the microstructure and magnetic properties of hot-rolled industrial pure iron during annealing, X-ray diffraction and magnetic hysteresis analysis were performed. The evolution of dislocation density, and magnetic parameters, i.e. the maximum permeability, coercivity, and remanence, were analyzed respectively. Results show that the near equiaxed grain structure of industrial pure iron has no obvious change before and after annealing, and the grain size number is about 3.70. With the annealing time increasing to 5 h at 650 ℃, the dislocation density gradually decreases from the hot-rolled state of 1.80×1014 m-2 to 1.16×1014 m-2, with an amplitude of 35%. At the same time, the diffraction peaks are observed to shift to the left to a certain extent compared with the hot-rolled state, and then to the right. It indicates that the existence of residual compressive stress in micro scale and a subsequent releasing process. The shape of the magnetic hysteresis loops is narrow and changes little with the increase of annealing time. However, the maximum permeability shows a continuous increment, and some abrupt changes are observed in the coercivity and remanence.This might be attributed to the comprehensive influences of dislocation density, internal stress and carbon content. It is indicated that annealing treatment could improve the magnetic properties of industrial pure iron. With a further consideration of the effects of impurity elements, an integrated strategy of composition and microstructure control will improve the ferromagnetic performance of industrial pure iron and expand its electromagnetic applications.

Keywords

• industrial pure iron
• annealing
• dislocation density
• x-ray diffraction
• magnetic hysteresis