Strong and ductile high temperature soft magnets through Widmanstätten precipitates

Abstract

Fast growth of sustainable energy production requires massive electrification of transport, industry and households, with electrical motors as key components. These need soft magnets with high saturation magnetization, mechanical strength, and thermal stability to operate efficiently and safely. Reconciling these properties in one material is challenging because thermally-stable microstructures for strength increase conflict with magnetic performance. Here, we present a material concept that combines thermal stability, soft magnetic response, and high mechanical strength. The strong and ductile soft ferromagnet is realized as a multicomponent alloy in which precipitates with a large aspect ratio form a Widmanstätten pattern. The material shows excellent magnetic and mechanical properties at high temperatures while the reference alloy with identical composition devoid of precipitates significantly loses its magnetization and strength at identical temperatures. The work provides a new avenue to develop soft magnets for high-temperature applications, enabling efficient use of sustainable electrical energy under harsh operating conditions.

Turning Ultra‐Low Coercivity and Ultra‐High Temperature Stability Within 897 K via Continuous Crystal Ordering Fluctuations

“…[ 32 , 33 ] Though constructing precipitates with a large aspect ratio form a Widmanstätten pattern in a strong and ductile multicomponent alloy, FeCoNiTa alloys achieve excellent high‐temperature magnetic and mechanical properties, not found in reference alloys of the same composition and without precipitates. [ 34 ] Previously, we constructed an ordered dual‐phase nanostructure with an atomistic‐scale coherent interface in Ni 43 Fe 18 Ga 27 Co 12 alloy to induce continuous lattice elastic distortion under applied loading. [ 35 ] This was achieved by uniformly embedding the continuous ordered ω‐like phase in the L 2 1 superlattice, resulting in supercritical elastic behavior.…”

“…Since the dual‐phase nanostructure with continuous coherent interfaces in CCAs is inherently stable, while the long‐range ordering process requires a lengthy period of thermal preservation (above 1300 K), CCAs are expected to exhibit unique soft magnetic properties from room temperature (297 K) to high temperature (797–897 K). [ 30 , 31 , 33 , 34 , 40 , 41 ] In the following sections, we unveil an innovative design concept incorporating a hierarchical microstructure, which enables the construction of an atomic‐level order/disorder entangled structure through continuous crystal ordering (CCO) fluctuations. Such microstructural features realize a dual‐magnetic‐state nature with exchange softening, which can be predicted and controlled for i H c and temperature stability by deliberately manipulating the long‐range ordering process.…”