Automotive PM soft magnetic alloys (relation between magnetic properties and residual pores in PM soft magnetic alloys)

The objective of this study is to elucidate the relation between magnetic properties and residual pores in various PM magnetic alloys typical of car parts, mainly from authors' experimental results. In practice, magnetic properties was discussed and evaluated from the three points of view: porosity and pore size /shape control, acceptable limit of residual pore for practical use, and pore reduction by sintering technique. Soft magnetic properties were more or less affected by pore morphologies (size /shape) as well as porosity and consequently, expressed with linear equation of these parameters, based on the size-shape dispersion diagram. Pore dependence of magnetic degradation caused by material defects (faults), deformation, heat-treatment, corrosion attack etc. was quantitatively evaluated together with magnetically-restoring methods. Several approaches to poreless magnetic alloys were tried by means of pertinent sintering technique such as powder refining-, liquid phase-, spark plasma-sintering and further, micro/macroscopic composite ones are expected as being characteristic of powder metallurgy.