|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Materials Science for High-Performance Permanent Magnets
||Structural Evolution in Alnico -- A Transmission Electron Microscopy and Atom Probe Tomography Study
||Lin Zhou, Wei Guo, Jon Poplawsky, Wei Tang, Iver Anderson, Matt Kramer
|On-Site Speaker (Planned)
Alnico magnetic properties are closely related to spinodal decomposition (SD) that produces Fe-Co based (α1 phase) hard magnetic phase and non-magnetic Ni-Al based phase (α2 phase) after extended magneto-thermal treatment: solutionizing/quenching, magnetic-field annealing for anisotropic growth of the SD phases, and draw annealing to optimize the magnetic properties. Improved performance of alnico requires better understanding between processing conditions and microstructure. We have demonstrated nearly a 2x increase of coercivity between magnetic annealing (MA) and MA with drawing. In order to understand the origin of increased coercivity, we performed a careful microstructure and magnetic property investigation on 32.4Fe-38.1Co-12.9Ni-7.3Al-6.4Ti-3.0Cu (at.%) alnico at different stages during MA and heat treatment. Atom probe tomography, orientation imaging microscopy, and transmission electron microscopy techniques were used to elucidate the structural and chemical evolution of the SD phases in the alnico alloy and their effect on magnetic properties. Supported by USDOE-EERE-VT-EDT through Ames Lab contract DE-AC02-07CH11358.