| With the rapid development of the society, Al-based amorphous alloy is potential with its excellent physical properties, such as good toughness, high yield strength and resistance to corrosion and has a huge advantage in the aerospace parts, car ferry and other corrosion-resistant coating direction, Al-based amorphous alloy has a huge potential in application. However, because of the glass forming ability(GFA) of Al-based alloys is very low, so it’s unable to obtain large bulk metallic alloys currently, it limited the application of Al-based amorphous alloys. Therefore, how to improve the glass forming ability of the Al-based metallic alloys has become the focus of current research and difficulty.The oxidation of the alloy in aluminum amorphous alloy resulting in the lower purity of aluminum alloy melt, increasing heterogeneous nucleation rate. Finally, when preparing of the amorphous rod, the gas gap in the copper will lower the cooling rate of the alloy melt, made the alloy melt unable to reach the critical cooling rate of forming bulk amorphous, increase the difficulty for manufacturing Al-based bulk amorphous alloys. Therefore, to purify the aluminum alloy melt and choose the appropriate process of preparation of amorphous bar is the key to get large Al-based amorphous. The main conclusions of this paper are as follows:(1) Determine the composition system of the molten salt and the purification effect and mechanism. According to the principle of selecting the purifying molten salt: low density, low melting point, low surface tension, etc. Selecting CaCl2, MgCl2 and KCl salts as the essential chlorine molten salt system. Then determine the eutectic point components by CaCl2, MgCl2 and KCl ternary phase diagram, 26 wt.% KCl+49wt.% MgCl2+25wt.% CaCl2. Then choose the additional component CaF2, and the addition content of CaF2 is 20%, when the total amount of the molten salt addition is 1%, the surface oxygen intake is the highest. After purification by molten salt, the oxygen content in the alloy substrate decreased from 1.06% to 0.47%, the oxygen content in the defect decreased from 24.99% to 7.17%, up to 3 times. Finally, demonstrate that the molten salt can purify the melt by physical adsorption and chemical reaction mechanisms.(2) Determine the optimum process of the preparation of aluminum based amorphous bar. Through infrafed real-time temperature measuring device detecting of the manufacturing process of the Al-based amorphous bar. Conclude that when the heating temperature is 1050℃, the cooling rate in the edge of amorphous bar can reach 4.5?103K/s, the center position can reach 3.7?103K/s. When the impact speed is 300mm/s, the cooling rate in the edge of amorphous bar can reach 2.5?104K/s, the center position can reach 3.5?103K/s, all of them can satisfy the requirements of critical cooling rate.(3) Preparation of diameter 2mm aluminum based bulk metallic glasses. Preparation of Al-based bulk metallic glass by the highly purification Al-Ni-Y-Co-La melt. Finally, demonstrated that the 2mm bar is fully amorphous through several testing methods. Therefore, by the theoretical analysis and experimental verification of this article, successfully prepared the maximum size of the Al-based bulk metallic glass in the world. |
