Structure and magnetic properties of (Nd,Dy)16(Fe,Co)76−xTixB8 powders prepared by mechanical alloying

Nanocrystalline (Nd,Dy)16(Fe,Co)76−xTixB8 magnets were prepared by mechanical alloying and respective heat treatment at 973–1073 K/30–60 min. An addition of 0.5 at % of Ti results in an increase of coercivity from 796 to 1115 kA m−1. Partial substitution of Nd by Dy results in an additional increase of coercivity up to 1234 kA m−1. Mössbauer investigations shows that for x⩽1 the (Nd,Dy)16(Fe,Co)76−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 decreases due to the presence of an amorphous phase. A heat treatment at a higher temperature (1073 K) for longer time (1 h) results in the full recrystallisation of powders. The mean hyperfine field of the Nd2Fe14B phase decreases for titanium contents of 0⩽x⩽1, and remains constant for x>1. This indicates that the Ti content in the Nd2Fe14B phase reaches its maximum value.