Microstructural and magnetic characterization of iron precipitation in Ni-Fe-Al alloys
The influence of annealing on the microstructural evolution and magnetic properties of Ni{sub 50}Fe{sub x}Al{sub 50-x} alloys for x = 20, 25, and 30 has been investigated. Solidification microstructures of as-cast alloys reveal coarse grains of a single B2 type {beta}-phase and typical off eutectic microstructure consisting of proeutectic B2 type {beta} dendrites and interdendritic eutectic for x = 20 and x > 20 at.% Fe respectively. However, annealing at 1073 K results in the formation of FCC {gamma}-phase particles along the grain boundaries as well as grain interior in x = 20 at.% Fe alloy. The volume fraction of interdentritic eutectic regions tend to decrease and their morphologies start to degenerate by forming FCC {gamma}-phase for x > 20 at.% Fe alloys with increasing annealing temperatures. Increasing Fe content of alloys induce an enhancement in magnetization and a rise in the Curie transition temperature (T{sub C}). Temperature scan magnetic measurements and transmission electron microscopy reveal that a transient rise in the magnetization at temperatures well above the T{sub C} of the alloys would be attributed to the precipitation of a nano-scale ferromagnetic BCC {alpha}-Fe phase. Retained magnetization above the Curie transition temperature of alloy matrix, together with enhanced room temperature saturation magnetization of alloys annealed at favorable temperatures support the presence of ferromagnetic precipitates. These nano-scale precipitates are shown to induce significant precipitation hardening of the {beta}-phase in conjunction with enhanced room temperature saturation magnetization in particular when an annealing temperature of 673 K is used. - Research Highlights: {yields} Evolution of microstructure and magnetic properties with varying Fe content. {yields} Transient rise in magnetization via the formation of ferromagnetic phase. {yields} Enhancements in saturation magnetization owing to precipitated ferromagnetic phase. {yields} Nanoscale precipitation of ferromagnetic BCC {alpha}-Fe confirmed by TEM. {yields} Hardness of the {beta}-phase correlates with room temperature saturation magnetization.
- OSTI ID:
- 22066370
- Journal Information:
- Materials Characterization, Vol. 62, Issue 6; Other Information: Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
- Country of Publication:
- United States
- Language:
- English
Similar Records
Influence of ordered L12 precipitation on strain-rate dependent mechanical behavior in a eutectic high entropy alloy
Room-temperature deformation behavior of directionally solidified multiphase Ni-Fe-Al alloys
Related Subjects
77 NANOSCIENCE AND NANOTECHNOLOGY
ALUMINIUM ALLOYS
ANNEALING
BCC LATTICES
FCC LATTICES
GRAIN BOUNDARIES
HARDNESS
IRON ALLOYS
IRON-ALPHA
MAGNETIC PROPERTIES
MAGNETIZATION
NANOSTRUCTURES
NICKEL ALLOYS
PRECIPITATION
PRECIPITATION HARDENING
SOLIDIFICATION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TRANSITION TEMPERATURE
TRANSMISSION ELECTRON MICROSCOPY