| In the present thesis, Al86Ni9La5amorphous alloy spun with different cooling rates was chosen as the study object. Through mechanical compression, autoclave treatment, low energy ball-milled at room temperature (LE-BM-RT), high energy ball-milled at room temperature (HE-BM-RT) and high energy ball-milled at cryogenic temperature (HE-BM-LT), the effects of different treatment conditions on the amorphous structure, thermodynamic properties, mechanical properties and corrosion resistance were studied.The effects of compression on crystallization behavior, fracture behavior and corrosion resistance of Al86Ni9La5ribbons has been studied by using X-ray diffraction (XRD), differential scanning calorimeter (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and electrochemistry station. The results reveal that:(1) The Al86Ni9La5ribbons spun with Sc=29.3m/s keep fully amorphous under different pressures. However, the ribbons spun with Sc=14.7m/s precipitate crystalline phases in amorphous matrix during the compression. The results indicate that the compression only affects the growth of nuclei instead of nucleation;(2) Compression improves the toughness of the Al86Ni9La5ribbons spun with Sc=29.3and14.7m/s, which is associated with the free volume and shear bands induced by compression;(3) The passive film stability of Al86Ni9La5ribbons is weakened by compression, which induces the free volume and shear bands and the precipitation of crystalline phases into the ribbons. With Sc=14.7m/s, the corrosion potential increases while pitting potential decreases with increasing compression pressure due to the precipitation of crystalline phases;(4) The magnetism of Al86Ni9La5ribbons are related with their structure. The more quenched-in nuclei or crystalline phases exist in the ribbons, the stronger is the paramagetism. While, the higher the content of the amorphous phase, the stronger the diamagnetism is.The Al86Ni9La5ribbons are spun with different circumferential speeds Sc and treated with5MPa compression and autoclave conditions. The thermal properties, microhardness and surface morphology of ribbons have been investigated. From these experimental results, the major conclusions are summarized as the following:(1) The onset temperature Tx2of second crystallization and the contraction degree δ of as-spun ribbons have an increasing tendency with increasing Sc.In contrast, the pre-peak height, deformed zone size l and inter-shear-band spacing near the microhardness indentations of the as-spun ribbons have a decreasing tendency with increasing Sc. These results can be ascribed to the argument that the amount of backbone clusters in the as-spun ribbons is larger at a higher Sc. The backbone clusters can be stabilized by5MPa compression and autoclave treatment;(2) In case of both5MPa compression and autoclave treatment, Al-rich phases precipitate in the ribbons with Sc=14.7m/s, but are absent in the ribbons with Sc=22.0and29.3m/s. In as-spun and treated ribbons, the number of edges of the indentation, from which semi-circular shear bands I emanate, varies from3or4to2when the Sc increases from14.7to29.3m/s. Both phenomena together with the non-linear decrease of a for the as-spun ribbon with increasing Sc can be explained by percolating backbone clusters when Sc reaches a critical value.The Al86Ni9La5ribbons which are treated with low energy ball-milling at room temperature, high energy ball-milling at room temperature and high energy ball-milling at cryogenic temperature at different milling time are studied by XRD, DSC, SEM and electrochemical experiment. It is found that:(1) Compared with low energy ball-milling at room temperature, the Al86Ni9La5ribbons showed higher brittleness after highe energy ball-milled at cryogenic temperature. And the Al86Ni9La5ribbons are grinded into particals with the size of about several micrometers.(2) After different types of ball-milling, the milled Al86Ni9La5ribbons occurs obvious difference:after30and60minutes low energy ball-milling at room temperature, the structure of the Al86Ni9La5ribbons occurs disorder rejuvenation; while, when the milling time increases to120minutes, the structure occurs order transformation. However, the amorphous structure of the Al86Ni9La5ribbons is destroyed after high energy ball-milled. Even the ribbons quenched with the relatively low Sc occured distinct crystallization. And the structure of the ribbons quenched with higher Sc occur order transformation.(3) After both the low energy ball-milling at room temperature and high energy ball-milling at cryogenic temperature, the corrosion potentials of the Al86Ni9La5ribbons increase and the width of passive zones decrease. Especially, the high energy ball-milling at cryogenic temperature led to the obvious shorten of the passive zones. The width of passive zone of Al86Ni9La5alloy is related with the quantity of backbone clusters in the amorphous matrix. The more backbone clusters exist, the larger width is passive zone. |
PDF Full Text Request