Magnetically hard alnico 5 alloy with a mischmetal addition

Abstract

The addition of mischmetal (CeMM) to the Alnico 5 alloy of equiaxial grain structure in the amounts from 0.0 to 0.31 wt% and its effect on the magnetic properties, the crystal structure and on the type of non-metallic inclusions in the alloy has been studied. The addition of CeMM, in amounts within the examined limits, was found to cause a worsening of all magnetic properties of the Alnico 5 alloy, the greatest changes being observed in the maximum magnetic energy product ( BH) max and the smallest in the coercive force H c. CeMM also causes a considerable reduction in the size of grains. The main types of non-metallic inclusions in the Alnico 5 alloy with CeMM addition are: oxide(CeMM) 2O 3, oxysulphides (CeMM) 2O 2S and sulphides (CeMM) xS y type, on the edges of which occur titanium or manganese sulphides. For up to 0.16 wt% of CeMM the mean content of non-metallic inclusions in the alloy is decreasing, whereas it is markedly rising with the content of CeMM over 0.16 wt%. Also the mean size of inclusions is clearly smaller in the alloy with less than 0.16 wt% of CeMM than with higher contents of CeMM. A 0.16 wt% addition of CeMM significantly improves the susceptibility of Alnico 5 alloy to surface finishing treatment by grinding.