Owing to combining the properties of both metal and glass, metallic glasses exhibit superior physical and mechanical properties along with exotic phenomena, so they have a wide application prospect in many areas. In addition, their continuously adjustable composition and simple disordered atomic structure provide ideal model material systems for the study of fundamental questions commonly existing in glassy materials. The discovery of metallic glasses that can form bulk materials has pushed the relevant research to the frontier of condensed matter physics and material science. The EX4 group of the Institute of Physics, Chinese Academy of Sciences, has devoted to the study of glassy materials and physics for many years, and made important contributions to this field. In this paper, we summarize our recent progress of metallic glasses, including the relaxation behavior and stability, surface dynamics, materials functionalities, and new method on materials discovery.
A new rare-earth Pr-based bulk metallic glass (BMG) is obtained in the shape of rod up to 5 mm in diameter by die cast. Unlike other rare-earth based BMGs, it exhibits a distinct glass transition, Tg=409K,the lowest glass transition temperature among the known BMGs, a large and stable supercooled liquid region and paramagnetic property. The glass transition as well as its kinetic nature and the fragility parameters m of the BMG have been studied. The BMG offers an ideal model to investigate the nature of glass transition as well as the relaxation and nucleation with a large experimentally accessible time and temperature window at very low temperature region.
In this paper we report the formation of a new Pr55Al12Fe30Cu3 bulk metallic glass. Cylindrical Pr55Al12Fe30Cu3 specimens of 5 mm in diameter and 100 mm in length were prepared by copper mold suction casting. Differential scanning calorimetry results indicated that the Pr-based bulk metallic glass system has a wide supercooled liquid region about 64K. The melting temperature of the amorphous state is about 140K higher than that of its crystalline state. Hysteresis loops were measured, and the results indicated that the Pr55Al12Fe30Cu3 bulk metallic has hard magnetic property, while the completely crystallized alloy has soft magnetic property at room temperature.
Small amount of rare-earth elements may have negative effects on the formation of some metallic glass alloys. The rare-earth elements may react with some atoms of the alloys to form compounds of high melting points or be absorbed on the surfaces of the heterogeneous catalysts in the alloys to activate the heterogeneous nucleation. In this case, the rare-earth elements have no effects on enhancing the stability of the metallic glass phase but enhance the heterogeneous nucleation and decrease the metallic glass forming ability and thermostability.
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