Production of Bulk Metallic Glass by Rapid Compression and Phase Transition under High Pressure
|School||Southwest Jiaotong University|
|Keywords||rapid compression Bridgman opposite anvil internal heating metallic glass phase transition|
Glass is a kind of typically amorphous material achieved by cooling melt without crystallization. We are familiar with silicate glass and oxide glass and so on. Amorphous Si and Se used as photoelectricity material are simple substance glass. Because of the excellent crystallization capability, it is hard for metallic simple substance to be amorphous. However, it is easy for some metallic alloys to be amorphous and some of them even possess excellent glass forming ability and stability. Therefore alloy glass is well researched now. In the dissertation, alloy glass is researched containing production of alloy glass by rapid compression and phase transition in metallic glass induced by pressure.Firstly, stable internal heating was investigated in Bridgman Anvil. Four internal heating modes were designed in this work. Heater was made of tantalum and graphite flakes. Two thermocouples were used to measure the temperature change of the central and upside section in sample cavity along with the input voltage. The temperature grads were roughly discussed. Stable heating was realized within 1000℃under 5.0 GPa.In our laboratory, a high pressure jump from ambient pressure to 1-10 GPa within 20ms could happen by the 1MN press apparatus. Our group has produced the amorphous sulfur and ethylene terephthalate （PET） on the press by the rapid compression method. In the dissertation, metallic glass La68Al10Cu20Co2 was produced successfully by the rapid compression using Bridgman Anvil and internal heating method. It indicated that rapid compression was a new effect way to prepare metallic glass. The physical properties of the metallic glass was analysis by X ray diffraction、Differential scanning calorimetry analysis and Micro hardness and compared with the metallic glass produced by melt quenching. It is found that the former possess a little higher heat stability and hardness.Previous research indicates that pressure induced amorphous to amorphous phase transition exists in many non-metallic glass. However it was seldom researched in metallic glass. In the dissertation, the phase transition of La68Al10Cu20Co2 and Nd60Al10Ni10Cu20 at room temperature was investigated in Bridgman Anvil under high pressure. Firstly the resistance was measured against pressure and it was found that there were sudden change on 1.44 GPa and 1.17 GPa respectively, indicating that phase transition happened. The thermal measurement under high pressure indicated that there existed the thermal change during the phase transition in the two metallic glasses. It was endothermic process from low pressure phase to high pressure phase. By illation the phase transition was considered to be amorphous to amorphous reversible first-order.In conclusion, it is the first time to produce the metallic glass by rapid compression method in the dissertation. The new method is not restricted by thermal conductivity and promising in application. The resistance and thermal measurement indicate that there exists the pressure induced reversible first-order phase transition in La68Al10Cu20Co2 and Nd60Al10Ni10Cu20 metallic glass. Combining with the phase transition in Ce55Al45 metallic glass, it might be supposed that the pressure induced amorphous to amorphous first-order transition exists universally in lanthanides based metallic glasses.