The magnetic properties of the (Fe0.53Nd0.37Al0.10)96B4bulk amorphous alloys annealed in the temperature range of 293-623K for 30 min with and without an external pulsed magnetic field of 5T were studied. The results reveal that the remanence and coercivity of the samples are obviously improved with a pulsed magnetic field when annealed below the Curie temperature of the alloy. The increment of remanence reaches 25.9% for the sample annealed at 523K with a pulsed magnetic field, because of the enhancement of exchange coupling roles between the soft and hard magnetic phases. It provides a new way to improve the magnetic properties of the bulk amorphous alloys produced by pulsed magnetic annealing at temperatures below the Curie point of the alloys.
The welded joint surfaces of 16MnR steel were treated using an ultrasonic impact machine. The effects of ultrasonic impact treating (UIT) on the plastic deformation and nanocrystallization mechanism of the welded joints of 16MnR steel were studied. The micro-structural features of the surface layer produced by UIT were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), and micro-hardness measurements were performed. Experimental results showed that the thickness of the plastic deformation layer was approximately 80 μm. It was found that grains in the surfaces of the welded joints of 16MnR were greatly refined by UIT. Obvious grain refinement was observed, with resultant gain sizes less than 100nm. The micro-hardness of the treated surface layer of the welded joint was enhanced significantly compared to that of the untreated sample. The micro-hardness on the treated surface of the welded joint was 62.3% higher than that of the untreated surface.
The microstructure and magnetic viscosity of bulk amorphous Nd60Fe20Al5Co10B5,prepared by suction casting the molten alloy into a copper mold under an argon atmosphere, have been investigated. The results show that clusters with size 3–5 nm are found to be embedded in the amorphous matrix of as-cast bulk amorphous Nd60Fe20Al5Co10B5 alloy. The Nd60Fe20Al5Co10B5 alloy shows hard magnetic behavior at room temperature, with an intrinsic coercivity of 360 kA/m and a remanence of 69.39 mT. The magnetic viscosity of bulk amorphous Nd60Fe20Al5Co10B5 has been investigated on the major hysteresis loop, and simple logarithmic time dependence is observed. A value for the fluctuation field of 8.24 kA/m is obtained. Analysis based on a Henkel plot is used to confirm the existence of magnetic interaction among clusters. The coercivity mechanism responsible for the hard magnetic behavior of bulk amorphous Nd60Fe20Al5Co10B5 alloy is also discussed.
The glass forming ability and magnetic properties were investigated for adding neodymium to the Fe71-xNb4B25Ndx (x=0, 3, 5, 7,10) alloys prepared by copper suction casting. It was found that proper neodymium (x=5~10 at.%) could improve glass forming ability of Fe-Nb-B alloys effectively. Bulk amorphous Fe66Nd5B25Nb4 and Fe64Nd7B25Nb4 samples were obtained and presented high thermal stability and good soft magnetic properties. The value of activation energy of the first crystallization peak for the bulk amorphous alloy Fe64Nd7B25Nb4 is 683 kJ/mol.
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