Effect of Mn on the Microstructure and Magnetic Properties in Cu-Fe-Co Alloys
- PDF / 612,153 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 6 Downloads / 196 Views
TRODUCTION
MAGNETIC properties such as coercivity and magnetic saturation of conventional alloys are very sensitive to both the microstructure and chemistry.[1–4] Magnetic properties of a given alloy can be enhanced by reduction of grain size down to the nanometer scale.[3] Attractive magnetic properties such as giant magnetoresistance (GMR) were achieved in microstructures constituted of nanocrystalline dispersion of fine magnetic phases in a conducting matrix.[5] Metastable supersaturated solid solutions are amenable to evolve such two-phase microstructure after appropriate annealing treatment. Among the transition(3d orbital) magnetic elements, Co and Fe display metastable miscibility gap in Co-Cu and Fe-Cu systems, respectively, over the wide composition range[6] and exhibit positive heat of mixing.[1,7] Moreover, the Fe-Co alloy possesses a small negative heat of mixing (–1 kJ/mol) and marginal mutual solubility at room temperature.[8] Therefore, these alloys are amenable to form supersaturated solid solution under the appropriate nonequilibrium processing condition. Earlier, the ternary Cu-Fe-Co system was also studied in order to examine the liquidus temperature and miscibility gap points.[9,10] It was shown that the microstructure of the solidified ternary alloys, over a wide composition range, resembled those of the binary B.N. MONDAL, formerly with the Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, is Technical Superintendent, Department of Central Scientific Services, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India. Contact e-mail: [email protected] A. BASU MALLICK and P.P. CHATTOPADHYAY, Professors, are with the Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103, India. D.N. NATH, Senior Professor, is with the Department of Physical Chemistry, Indian Association for the Cultivation of Science. Manuscript submitted July 10, 2009. Article published online November 4, 2010 METALLURGICAL AND MATERIALS TRANSACTIONS A
Cu-Co and Cu-Fe systems.[6] In such Cu-based systems, the two-phase microstructures formed by annealing of supersaturated alloy result in attractive magnetic properties due to the fact that diamagnetic Cu-matrix reduces the repulsion between the precipitated magnetic phases.[11] In this context, the GMR effect was reported earlier in Fe-Co-Cu multilayers.[12] Attempts were made to study the metastable phase evolution in binary and ternary powder blends comprising Cu, Fe, and Co by ball milling.[7,13–17] Ball milling of different binary systems including Cu50Fe50[7] and Cu50Co50[13] blends evolved homogeneous supersaturated solid solutions. Thermal annealing of the ballmilled products resulted in separation of the constituent phases.[15] Ball milling of ternary Cu-Fe-Co systems also formed single-phase supersaturated solid solutions.[15,18] Annealing of the ternary ball-milled products exhibited separation of the bcc FeCo phase.[14] In such
Data Loading...
