scholarly journals Magnetic behavior of rapidly solidified Pr–Co alloys with the TbCu7-type structure

2006 ◽  
Vol 99 (8) ◽  
pp. 08B514 ◽  
Author(s):  
J. Kostogorova ◽  
J. E. Shield
Keyword(s):  
Magnetic Behavior ◽  
Type Structure ◽  
Rapidly Solidified ◽  
Co Alloys

Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

1991 ◽  
Vol 49 ◽  
pp. 784-785
Author(s):  
N. Qiu ◽  
J. E. Wittig
Keyword(s):  
Rapid Solidification ◽  
Ion Beam ◽  
Magnetic Behavior ◽  
High Coercivity ◽  
Magnetic Domains ◽  
Beam Angle ◽  
Tem Analysis ◽  
Intrinsic Coercivity ◽  
Hard Magnets ◽  
Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

scholarly journals Effect of combined metal-carbon additions on the microstructure and structure of Sm2Fe17

2003 ◽  
Vol 18 (2) ◽  
pp. 279-283 ◽  
Author(s):  
B.E. Meacham ◽  
J.E. Shield
Keyword(s):  
Solute Drag ◽  
Type Structure ◽  
Drag Effect ◽  
Microstructural Refinement ◽  
Atomic Size ◽  
Alloying Additions ◽  
Grain Structures ◽  
Fe Alloys ◽  
Rapidly Solidified ◽  
Carbon Additions

The effect of combined alloying additions on the structure and scale of rapidly solidified Sm–Fe alloys was investigated. Transition metal additions tend to promote the formation of the disordered TbCu7-type structure in Sm2Fe17 alloys, as determined by monitoring the long-range order parameter. Essentially no order was observed for M = Ti, Zr, V, or Nb. Thus, the structure was close to the prototypical TbCu7-type structure. With M = Si, a large amount of order was observed (S = 0.62), resulting in a structure closer to the well-ordered Th2Zn17-type. The microstructural scale was also affected by alloying. In this case, refinement depended on the substituent and also on carbon for microstructural refinement. The scale of the as-solidified grain structures ranged from 100 nm for SiC-modified alloys to 13 nm for NbC-modified alloys. The degree of refinement was directly related to the atomic size of the M addition. The refinement was the result of solute partitioning to grain boundaries, resulting in a solute drag effect that lowered the growth rates.

scholarly journals Highly coercive rapidly solidified Sm–Co alloys

2006 ◽  
Vol 99 (8) ◽  
pp. 08B521 ◽  
Author(s):  
S. Aich ◽  
V. K. Ravindran ◽  
J. E. Shield
Keyword(s):  
Rapidly Solidified ◽  
Co Alloys

Undercooling and demixing in rapidly solidified Cu–Co alloys

2007 ◽  
Vol 449-451 ◽  
pp. 7-11 ◽  
Author(s):  
L. Battezzati ◽  
S. Curiotto ◽  
E. Johnson ◽  
N.H. Pryds
Keyword(s):  
Rapidly Solidified ◽  
Co Alloys

Mechano-Synthesis and Characterization of Fe-Co Based Nanocrystalline Magnetic Materials

2005 ◽  
Vol 475-479 ◽  
pp. 3567-3570
Author(s):  
M. Mujahid ◽  
S.H. Sim ◽  
J. Zhu
Keyword(s):  
Grain Size ◽  
Nanocrystalline Materials ◽  
Magnetic Behavior ◽  
Internal Strain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ni Additions ◽  
Co Alloys ◽  
Curie Temperatures

Nanostructured Fe-Co based alloys are believed to be good candidates for imparting improved magnetic behavior in terms of higher permeability, lower coercivity, reduced hysteresis loss and higher Curie temperatures. In the present work, Fe-Co alloys with Ni additions were prepared using mechanical alloying (MA). Grain size and internal strain in the MA powders was measured using X-ray diffraction. It has been shown that the grain size could be reduced down to less than 5 nm in these alloys. Nanocrystalline materials thus obtained were also evaluated for magnetic behavior and the influence of grain size and internal strain on the magnetic properties has been discussed.

A Transmission Electron Microscopy study of the B2-DO3 ordering phase transformations in Fe-6.3wt% Si after rapid quenching and annealing

1988 ◽  
Vol 46 ◽  
pp. 772-773
Author(s):  
J. E. Wittig
Keyword(s):  
Phase Transformations ◽  
Melt Spinning ◽  
Magnetic Behavior ◽  
Microscopy Study ◽  
Rapid Quenching ◽  
Electron Microscopy Study ◽  
Silicon Alloys ◽  
Brittle Behavior ◽  
Transmission Electron ◽  
Rapidly Solidified

Iron-silicon alloys are extensively used in transformer cores owing to exceptional soft magnetic behavior that is optimized at about 6.5 wt% Si. Unfortunately this equilibrium microstructure is completely brittle at room temperature. The brittle behavior coincides with the onset of an ordering reaction of the disordered A2 into the B2 and DO3 superlattices at approximately 5 wt% Si. Rapid solidification methods have been shown to improve the ductility of Fe- 6.3 to 6.5 wt% Si. In this investigation, rapidly quenched and annealed samples of Fe-6.3wt% Si were examined in the transmission electron microscope (TEM) to study the ordering phase transformations of this alloy and its effect on the mechanical behavior.Samples of Fe-6.3wt% Si were rapidly solidified by melt spinning into ribbons (t=20-80 microns) as well as by splatting using an opposing piston double anvil method. Rapidly quenched samples were subsequently heat treated in evacuated quartz tubes at 500, 600, and 700 C for 24 h.

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