Effects of heat treatment on the microstructures and magnetic properties of selective laser melted Fe-3 wt%Si functional soft magnet

Abstract

Dense selective laser melted (SLMed) Fe-3 wt%Si soft magnet with a very low porosity below 0.5% was obtained successfully. In the present work, the effects of heat treatment on the microstructures and magnetic properties were evaluated. The soft magnet exhibited a typical columnar structure with an oriented growth of building direction (BD) and a< 001 > texture along the BD. The magnet samples before and after post-treatment mainly consisted of a Bcc-Fe phase. Annealing the samples at 750 °C and 850 °C for 3 h did not affect the grain size significantly, the diffusion rate was just sufficient to bring Si segregations into solid solution. When annealing was conducted at 1000 °C for 3 h, resulting in marked grain growth and stress relief. The texture after annealing at 1000 °C for 3 h was the same as that as-built sample,< 001 > was still along the BD. Within the cases of this work, the internal stress of the SLMed parts could be relieved by annealing heat treatment, and it could be further released with the increase of annealing temperature or extension of annealing time. The magnetic properties of the SLMed Fe-3 wt%Si magnet were enhanced comprehensively.