DEVELOPMENT OF IRON-PHOSPHORUS BASED TERNARY ALLOYS BY P/M ROUTE FOR A.C. APPLICATIONS

Abstract

High density Fe-P-Si and Fe-P-Sn ternary alloys were made using hot forging technique. In this process, mechanically alloyed powders were directly forged in a die cavity at room temperature. These forged samples were coated with an oxidation resistant glassy coating and hot forged. The samples were homogenized and hot rolled for further densification. These highly densified products in the form of laminates were annealed to relieve the residual stresses. These alloys were characterized in terms of microstructure, porosity content/densification and hardness. Electrical resistivity, coercivity, as well as total magnetic loss for these alloys have been evaluated in order to assess suitability of these alloys for magnetic applications. Densification as high as 98.55% has been found in this process. Microstructures of these alloys consist of single phase ferrite only. Slightly higher density was found in rolled and annealed samples as compared to forged and homogenized samples. Alloys having high phosphorus, silicon/tin shows higher hardness. Compared to silicon or tin, phosphorus increases more hardness. Fe-0.8P-1 .OSi showed maximum hardness (204 Hv/10kgf). Alloys having high phosphorus, silicon/tin showed higher resistivity and low coercivity. Coercivity of these alloys was found to be varying between 0.76 Oe to 0.47 Oe. The highest resistivity value found is 41.23 μSum. The alloys can be used as very thin sheets. Thickness of rolled samples in this investigation was found to vary between 0.3 mm to 0.5 mm.