Particle analysis and properties of mechanically alloyed Nd16Fe76−xTixB8

Abstract

Abstract Nanocrystalline Nd16Fe76−xTixB8 hard magnetic powders were prepared by mechanical alloying and respective heat treatment at 973–1073 K /30–60 min. The nanocrystalline hard magnetic powders were investigated by the NanoSight Halo LM10TM Nanoparticle Analysis System, AFM, SEM and Mossbauer spectrometry. The nanocrystals have average size of 40 nm and the crystals form agglomerates with an average size of about 180 nm. HaloTM, AFM and SEM techniques are the complementary methods, which give comparable results. The magnets with different Ti content have different magnetic properties and corrosion resistance, too. The addition of 0.5 at.% of Ti to the parent composition results in increase of the coercivity from 796 kA/m up to 1115 kA/m. The highest corrosion resistance is for magnets with 0.5–0.75 at.% of Ti content. It was found, that it is related with phase composition. For Ti content smaller than x ≤ 1 , the Nd16Fe76−xTixB8 powders are single phase. For higher Ti contents ( x > 1 ) the mechanically alloyed powders heat treated at 973 K are no more single phase, and the coercivity as well as corrosion resistance decreases due to the presence of an amorphous phase and α -Fe. A heat treatment at a higher temperature (1073 K) or for a longer time (1 h) results in the full recrystallization of powders and structure homogenization, which result in better corrosion resistance.