Formation And Thermodynamics Properties Of Zrcu-based Bulk Metallic Glass

ZrCu-based metallic glasses are regarded as promising materials due to high tensile strength, excellent plasticity, innocuous and free of noble elements, large GFA (Glass Forming Ability), and wide composition range. Controlled crystallization from bulk amorphous ZrCu-based alloys is proved to be an effective way to get the expected properties. Thus, investigations on kinetics of the controllable crystallization process became more and more popular.During this thesis, the study adopted water cooled copper mold casting and spun method with Ar shied produced a series of metallic glasses with the diameter of 5mm, 2mm and spun samples. And the study researched the structure of the samples by XRD and DSC. What`s more, the study researched the effect of the content of Al on the GFA and the result revealed that we can enhance the GFA by addtion of proper Al content. The research found a new component Zr46Cu44Al10 with high GFA by addition of different content of Al. The study can produced the full amorphous sample Zr46Cu44Al10 with the diameter of 5mm by water cooled copper mould casting. At last, the study try to analyse the reasons why Al could enhance the GFA.The study also researchs the effect of Al on the thermal stability, and the research results that the proper content of Al element could markedly enhance the thermal stability of the metallic glasses. The glass transition temperature (Tg), and the crystallization temperature (Tx) and the crystallization peak temperature (Tp), were found to be depended on the heating rate during the continuous heating. The apparent activation energy Ex was deduced by the Kissinger equation. The research results that the samples with the diameter of 2mm get better thermal stability than the samples with the diameter of 5mm, and the spun samples get better thermal stability than the samples with the diameter of 2mm.The results also show that the amount of Al content can markedly enhance the thermal stability, the characteristic temperature (Tg, Tx) and features of activation energy (Eg, Ex) were significantly increased. And the samples with the diameter of 2mm get higher thermal stability than the samples with the diameter of 5mm, the spun samples get better thermal stability. At last, the study researched the crystallization kinetics of the ZrCuAl amorphous alloys. As to the cast samples, during the begining crystallization process, the crystallization activation energy increase with the fraction of crystallization, and when the crystalline fraction is more than about 50%, the crystallization activation energy will decrease with the crystallization fraction increase. As for the spun samples, the energy for crystallization increases with crystallized fraction, so we can get the information that the crystallization process of the spun samples is more difficult than the cast samples, so the thermal stability of the spun samples is better than the cast samples. The crystallization activation energy of the cast samples with the diameter of 2mm is more than the cast samples with the diameter of 5mm.