A series of the amorphous Gd75-55A125-5Fe0-40 alloy ribbons were prepared by melt spinning. The structure, magnetic properties and magnetocaloric effect （MCE） of these alloys were investigated. The prepared samples ...A series of the amorphous Gd75-55A125-5Fe0-40 alloy ribbons were prepared by melt spinning. The structure, magnetic properties and magnetocaloric effect （MCE） of these alloys were investigated. The prepared samples have shown the characteristics of a second-order phase transition with zero hysteresis loss and the Tc can be tuned by changing the Fe contents. For the different compositions, the magnetic entropy change （-△Sm） for a field change of 0-5 T reached a maximum value of 7.14 J kg 1 K1 in the Gd70A120Fel0 alloy near its Curie temperature （To） of 149 K. The non-linear composition dependence of （- △ Sin） could be caused by the competitions between Fe-Fe, Fe-Gd and Gd-Gd interactions. The refrigeration capacity （RC） values of these al- loys are about 532-780 J/kg under a magnetic field change of 0-5 T. The results indicate that amorphous GdFeA1 alloys can be considered as ideal candidates for a magnetic refrigerant in the temperature range of 104-222 K.展开更多
Bulk metallic glasses (BMGs) with large supercooled liquid region are promising materials for superplastic forming. In this paper, we demonstrate a microstructure-based strategy to pinpoint the composition with the la...Bulk metallic glasses (BMGs) with large supercooled liquid region are promising materials for superplastic forming. In this paper, we demonstrate a microstructure-based strategy to pinpoint the composition with the largest supercooled liquid region in La 86 x Al 14 Cu x (x=16 at%-20 at%) metallic glass system. By monitoring the changes in crystallization behavior of the glassy alloys with composition to search for the alloys exhibiting eutectic crystallization, the glassy alloys with the largest supercooled liquid region in the given alloy system can be found. The metallic glasses with Cu contents of 16 at%-19 at% exhibited two crystallization peaks, and the primary crystallization product was identified to be α-La by means of DSC, XRD and TEM. The increase in Cu content resulted in the decay of the primary crystallization peak and the increase in onset temperature of crystallization, leading to the enlargement of supercooled liquid region. By further suppressing the α-La primary crystallization with increasing Cu content up to 20 at%, the eutectic crystallization of α-La and LaCu 13 through one crystallization reaction occurred upon heating, where the largest supercooled liquid region of 65 K for La 66 Al 14 Cu 20 glassy alloy was located. This study indicats that, in a given glassy alloy system, a larger supercooled liquid region can be achieved by optimizing the alloy compositions to suppress the primary crystallization.展开更多
基金supported by the Guangdong Provincial Science and Technology Program (Grant Nos. 2010B050300008, 2007B010600043)the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2009ZM0291)
文摘A series of the amorphous Gd75-55A125-5Fe0-40 alloy ribbons were prepared by melt spinning. The structure, magnetic properties and magnetocaloric effect （MCE） of these alloys were investigated. The prepared samples have shown the characteristics of a second-order phase transition with zero hysteresis loss and the Tc can be tuned by changing the Fe contents. For the different compositions, the magnetic entropy change （-△Sm） for a field change of 0-5 T reached a maximum value of 7.14 J kg 1 K1 in the Gd70A120Fel0 alloy near its Curie temperature （To） of 149 K. The non-linear composition dependence of （- △ Sin） could be caused by the competitions between Fe-Fe, Fe-Gd and Gd-Gd interactions. The refrigeration capacity （RC） values of these al- loys are about 532-780 J/kg under a magnetic field change of 0-5 T. The results indicate that amorphous GdFeA1 alloys can be considered as ideal candidates for a magnetic refrigerant in the temperature range of 104-222 K.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50631010, 50771005 and 50771006)the National Basic Research Program of China (Grant No. 2007CB613900)
文摘Bulk metallic glasses (BMGs) with large supercooled liquid region are promising materials for superplastic forming. In this paper, we demonstrate a microstructure-based strategy to pinpoint the composition with the largest supercooled liquid region in La 86 x Al 14 Cu x (x=16 at%-20 at%) metallic glass system. By monitoring the changes in crystallization behavior of the glassy alloys with composition to search for the alloys exhibiting eutectic crystallization, the glassy alloys with the largest supercooled liquid region in the given alloy system can be found. The metallic glasses with Cu contents of 16 at%-19 at% exhibited two crystallization peaks, and the primary crystallization product was identified to be α-La by means of DSC, XRD and TEM. The increase in Cu content resulted in the decay of the primary crystallization peak and the increase in onset temperature of crystallization, leading to the enlargement of supercooled liquid region. By further suppressing the α-La primary crystallization with increasing Cu content up to 20 at%, the eutectic crystallization of α-La and LaCu 13 through one crystallization reaction occurred upon heating, where the largest supercooled liquid region of 65 K for La 66 Al 14 Cu 20 glassy alloy was located. This study indicats that, in a given glassy alloy system, a larger supercooled liquid region can be achieved by optimizing the alloy compositions to suppress the primary crystallization.
