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(50)Fe(x)Al(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(C)). Temperature scan magnetic measurements and transmission electron microscopy reveal that a transient rise in the magnetization at temperatures well above the T(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.


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The present study was conducted to reveal the effects of building angles and post heat-treatments (2-step Thermo-Hydrogen Processing (THP) and conventional annealing treatment) on the density, microstructure and texture of Ti6Al4V alloy parts produced by Electron Beam Melting (EBM). The results showed that regardless of the building angle; the density, microstructure and crystallographic texture (defined with respect to building angle) of the as-produced samples were identical; having Widmanstatten a struct...
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Hydroxylapatite (HA)-nanosize alumina composites were synthesized to study their phase stability and mechanical properties. To make these composites, nanosize alpha-Al2O3 powder was used because of its better sinterability and densification as compared to nanosize gamma-Al2O3. The composites were air sintered without pressure and hot pressed in vacuum at 1100 degrees C and 1200 degrees C. In the composites, HA decomposed to tricalcium phosphate faster after the air sintering than hot pressing. Moreover, hex...
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Ga2Se3 and Ga2S3 compounds take attention due to their potential applications in photovoltaics. Defects and impurities may affect the quality of optoelectronic devices. Therefore, it is worthwhile to determine the parameters (activation energy, order of kinetics, frequency factor) of traps associated with the defects and/or impurities. The aim of the present paper is to investigate the trapping parameters of (Ga2Se3)(0.25) - (Ga2S3)(0.75) single crystal which is one of the member of (Ga2Se3)(x) - (Ga2S3)(1-...
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The variations in the microstructure and tensile properties of dual-matrix ductile irons have been investigated non-destructively by Magnetic Barkhausen Noise (MBN) method. Specimens have been intercritically austenitised at 795 degrees C and 815 degrees C for 20 minutes, and then oil-quenched to obtain different martensite volume fractions. Two specimens, namely as-cast and oil-quenched from 900 degrees C, were prepared for comparison purpose. To investigate the effect of tempering, some specimens were tem...
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Citation Formats
N. DUMAN, A. Mehrabov, and M. V. Akdeniz, “Microstructural and magnetic characterization of iron precipitation in Ni-Fe-Al alloys,” MATERIALS CHARACTERIZATION, pp. 606–614, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/43276.