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EFFECT OF THE ADDITION OF NI ON GIANT MAGNETORESISTANCE OF Cu - Co AGED RIBBONS
I. J. Kim,J. Echigoya,K. Fukamichi,Y. Shimada 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Giant magnetoresistance (GMR) of Cu_(85-x)Co_(15)Ni_x melt-spun ribbons is closely correlated with the microstructure produced by the spinodal decomposition. The solid solution range is extanded by the replacement of Cu by Ni in the as-quenched state. The wavelengths obtained by subsequent isothermal aging in Cu-Co-Ni ribbons are shorter than those in Cu-Co binary ribbons, resulting in the increase of the surface-to-volume ratio. The largest MR ratio of 8 % in high field has been achieved in the Cu_(80)Co_(15)Ni_5 aged ribbon. The field dependence of MR ratio in low fields becomes larger with the Ni content.
Evaluation of Embrittlement in Isochronal Aged Fe-Cr Alloys by Magnetic Hysteresis Loop Technique
J. N. Mohapatra,Y. Kamada,H. Kikuchi,S. Kobayashi,J. Echigoya,D. G. Park,Y. M. Cheong 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from 400 ℃ to 900 ℃ with 50 ℃ steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich α’ phase or a σ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-550 ℃ due to formation of a Cr-rich α’ phase. Beyond 500-550 ℃ range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich α’ phase. In the Fe-48% Cr alloy, formation of the σ phase at 700 ℃ reduced the maximum induction of the alloy significantly.
Effect of Cr-Rich Phase Precipitation on Magnetic and Mechanical Properties of Fe-20% Cr Alloy
Mohapatra, J. N.,Kamada, Y.,Kikuchi, H.,Kobayashi, S.,Echigoya, J.,Park, D. G.,Cheong, Y. M. IEEE 2011 IEEE transactions on magnetics Vol.47 No.10
<P>Magnetic Hysteresis Loop (MHL) and micro-Vickers hardness measurements were carried out in isothermal aged Fe-20 wt. % Cr alloy. The results were compared with the existing atom probe data at similar heat treated conditions. Coercivity and hardness of the alloy was increased and remanence of the alloy was decreased with the increase in ageing time. Such increase in the magnetic and mechanical hardness was due to the nucleation and growth of Cr rich α' phase. The size of the Cr rich α' phase precipitates were increased and the number density of the precipitates were decreased with the increase in ageing time observed by atom probe analysis. In this work a good correlation between hardness (H<SUB>v</SUB>) and coercivity (H<SUB>c</SUB>) was found with the combined effect of precipitate size (r) and number density (n). A linear relationship was found with the change in coercivity and hardness of the alloy indicating that the MHL technique would be a good Non-Destructive Evaluation (NDE) tool for the evaluation of thermal embrittlement in structural components made of Fe-Cr alloys.</P>