In situ high-pressure x-ray diffraction, low-temperature resistivity, and magnetization experiments were performed on a La 32Ce32Al16Ni5Cu15 bulk metallic glass (BMG). A sudden change in compressibility at Ϸ14 GPa and a rapid increase of resistivity at Ϸ12 K were detected, whereas magnetic phase transformation and magnetic field dependence of the low-temperature resistivity do not occur at temperatures down to 4.2 K. An interaction between conduction electrons and the two-level systems is suggested to explain the temperature and field dependences of resistivity of the BMG alloy. Although the cause of the unusual change in compressibility at Ϸ14 GPa is not clear, we believe that it could be linked with the unique electron structure of cerium in the amorphous matrix. An electronic phase transition in BMG alloys, most likely a second-order amorphous-to-amorphous phase transition, is suggested.bulk metallic glass ͉ phase transition R ecent studies of amorphous materials have revealed that more than one distinct amorphous phase can be formed from the same substance, a phenomenon that is called amorphous polymorphism (1-4). The nature of amorphous-toamorphous transition induced by pressure has been a topic of considerable research activity in several substances, e.g., ice, silicon, silica, and carbon (5-13). All these reports have encouraged the search for polymorphic phase transitions in liquids and glasses (14-19). Bulk metallic glasses (BMGs) as a new kind of amorphous material with a maximum size up to Ϸ70 mm in diameter and wide supercooled liquid regions have been fabricated in the last decade (20,21). To the best of our knowledge, evidence for an amorphous-to-amorphous phase transition has rarely been reported in metallic glasses. Very recently, parallel to our work, Sheng et al. (22) reported similar amorphous-toamorphous phase transition in a binary CeAl metallic glass ribbon sample.For decades, both structural and electronic transitions in pure elemental cerium and its crystalline alloys have been intensively investigated. Cerium, which is the first element in the lanthanide series with one 4f electron, has a complex phase diagram. Depending on pressure and temperature, it can be either a paramagnet, an antiferromagnet, or a superconductor. Cerium is also the only pure element to exhibit a solid-solid critical point in the well known ␥ N ␣ isostructural phase transition (23, 24). Many cerium-bearing alloys are heavy-fermion compounds and have anomalous low-temperature resistivity and magnetization behaviors that are relevant to Kondo coupling (25, 26) and also have first-order phase transitions resembling the ␥ N ␣ phase transition for pure cerium or second-order phase transitions above a critical point (27). Recently, a LaCe-based BMG with a maximum size up to 10 mm (28) and a La-based BMG with a maximum size up to 20 mm were developed (29). An interesting question has been raised: Do LaCe-based BMGs have electronic phase transitions similar to pure cerium and its crystalline alloys?In this work, we report...

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This paper provides an in-depth investigation into the formation of the mechanical mixed layer (MML) and its role in Cu-15Ni-8Sn/graphite composites. Wear tests were conducted at room temperature using a ring-block configuration with the applied load of 50 N and sliding speed of 0.42 m/s. SEM, EDS and XPS were performed to analyze the worn surfaces and sub-surfaces.Results indicated that high graphite content contributed to the formation of a protective MML.When the MML formed on the tribo-surface as graphite content increases, both the friction coefficient and wear rate greatly decreased. The friction coefficient with a stable value of 0.075 and wear rate of 6.10×10 -16 (m 3 /N• m) were the lowest when an apparent tribo-layer appeared at the graphite content of 38 vol. %. The characteristics of the MML and its influences on wear mechanisms of the composites are discussed. The MML existing on the worn surface protected the materials from severe adhesion and abrasion, the predominant wear mechanisms changed to delamination, which resulted in the drastic changes in wear resistance and friction coefficient.

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The different microstructures of Silver-Copper/Molybdenum Disulfide (Ag-Cu/MoS 2 ) composites were manufactured by hot press and hot extrusion processes to investigate the electrical tribological behaviors of both the hot-pressed and hot-extruded composites under air and vacuum. The results showed that microstructures and properties of Ag-Cu/MoS 2 composites were improved by hot extrusion, which decreased the wear rates rapidly in both air and vacuum.In air, the hot extrusion could improve transferred layer and tribo-film, resulting in a significant decrease in contact voltage drop, which goes from more than 70 mV in the hot-pressed composite, to 30 mV at the hot-extruded composite. Under vacuum condition, some wear debris was melted on the worn surface and then transferred to counterface to form the transferred layers which lead to the lower contact voltage drops under vacuum, about 6 mV in hot-pressed Tribology Transactions ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 composite and 3 mV in hot-extruded composites. In addition, the severe adhesive and abrasive were attributed to the molten wear debris and transferred layer, resulting in the dramatic fluctuation of friction coefficient in vacuum.