Al-based Amorphous Thermal Stability And Glass Forming Ability

The Al-based amorphous alloys have broad possibilities to be applied as structural materials as well as functional materials for their special excellent properties. This thesis focuses on the thermal stabilities and the glass forming abilities (GFA) of the Al-based amorphous alloys. It also presents the works on the exploring of the bulk Al-based glasses.The crystallization behaviors of the Al₈₅Mg₁₀Ce₅ amorphous alloys are systematically studied for the first time using X-ray diffraction (XRD), transmission electron microscope (TEM) and differential scanning calorimeter (DSC). When the sample is continuously heated to165℃ , i.e. the primary stage of the crystallization, it is found that single Al₁₂Mg₁₇ phase instead of single fcc-Al or the composition of the fcc-Al and the intermetallic compoud is primarily formed. The relative bigger radius of the Mg atoms powerfully influence the diffusion freedom, which leads to the diverse of primarily crystallization.According to Kissinger equation, the crystallization activation energies of the Al_(90-X)Mg₁₀Ce_X (X=3～7) alloys have been caculated and then the fragilities are also achieved using the results of the energies caculations. Except for the Al₈₆Mg₁₀Ce₄ alloy which is the only one not forming full amorphous phase, the higher GFA the studied alloy has, the less fragile it is. However, as a result of the existing crystallite, the Al₈₆Mg₁₀Ce₄ alloy has the poorest GFA corresponding to the least fragility.The Al₈₄Ni_(12-X)Zr₄Cu_X and Al₈₄Ni_(12-X)Zr₄Co_X (X = 0～3), amorphous ribbons have been made by the single-roller melt-spinning technology except Al₈₄Ni₉Zr₄Cu₃ alloy. The critical cooling rates are examined by analysising XRD results under different rotational speeds. The reduced crystallization temperature T_rx (T_rx = T_x/T_m) is calculated using DSC results. According to the classical theory, the alloy having high T_rx would show intense GFA. However, it's proved that there's no direct correlation between the two factors for the studied alloys.The total structure factors of the Al₈₄Ni_(12-X)Zr₄Cu_X and Al₈₄Ni_(12-X)Zr₄Co_X (X = 0～3) alloys are calculated by using XRD results. In addition, the prepeaks which...