Modification of selective laser melting-forming nickel–iron–molybdenum permalloy by trace copper achieves excellent soft magnetic properties

Abstract

In this study, a nickel–iron–molybdenum (NiFeMo) alloy with 1 wt% copper (Cu) addition, which is referred to as (NiFeMo) ₉₉Cu₁, was prepared by selective laser melting. The effects of the process parameters and trace Cu on the microstructure and magnetic properties of the permalloy were systematically studied. The results revealed that the alloy was primarily composed of a γ-(Ni, Fe) solid solution, and the microstructure consisted primarily of columnar crystals epitaxially grown along the temperature gradient. Under the optimal process parameters, the alloy has the highest saturation magnetic induction intensity (82.3 emu/g) and the lowest coercivity (1.26 Oe), which is primarily attributed to the reduction of metallurgical defects, the decrease of internal stress, the increase of high-angle grain boundaries, and the enhancement of oriented grains. This study confirms that the introduction of trace Cu by adding Ni-coated Cu powder can effectively improve the soft magnetic properties of selective laser melting-formed NiFeMo alloy, which provides a novel and valuable idea for developing high-performance additive manufacturing soft magnetic materials.