【作者】 陈娜；

【导师】 刘忠侠；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2003， 硕士

【摘要】 本文以工业化应用最为广泛的结构材料之一铝基合金为研究对象，以实现铝基合金的自然加钛为研究目的，分别进行了低钛铝合金的工业化生产试验和应用研究。首先在理论上和生产上探索了电解生产低钛铝合金的可能性和可行性，找出了TiO₂对低钛铝合金电解参数的影响规律，分析了不同含钛量低钛铝合金晶粒尺寸与钛含量的关系。在此基础上，以汽车、摩托车轮毂使用最为广泛的A356合金为研究对象，对比分析了电解加钛A356合金和熔配加钛A356合金在组织、性能上的差异，从而为直接电解低钛铝合金的工业化应用提供科学依据。 通过计算表明，电解质中加入一定比例的TiO₂，Ti原子既可以与铝发生热还原反应析出，也可以在阴极上析出，因此，电解法生产低钛铝基合金在理论上是完全可能的。在80KA中型预焙电解槽上进行了为期三个月的低钛铝合金的工业试验，结果表明，电解槽工作状态稳定，TiO₂的加入对电解槽的主要工艺参数、电流效率、物料和能源消耗影响不大，合金的钛含量稳定，钛的吸收率高；所生产的电解低钛铝基合金的微观组织均匀，晶粒细化效果好，与熔配加钛的细化规律相同。因此电解法生产低钛铝合金在实际上也是可行的。 以不同钛含量的电解低钛铝合金、Al-Ti中间合金和纯铝为主要原料用熔配法和电解法制备三种钛含量共六种A356合金。研究表明，两种方式制备的合金具有相似的微观结构，随着钛含量的增加，二次枝晶臂间距都逐渐减小，合金的强度有所改善，但塑性下降，质量系数Q也稍有下降，两种合金具有相同的变化趋势；对于具有相同钛含量、不同加钛方式制备的合金来说，电解加钛合金的二次枝晶臂间距比熔配加钛合金的稍小，所以前者的性能稍优于后者，并且这种优越性在低含钛量体现的比较明显。通过对拉伸断口近断面金相分析和断口SEM分析可以看出，微裂纹主要在α枝晶边界位置共晶区内Si颗粒处萌生，绕过硅颗粒穿过α基体长大、聚集形成空洞，最终主裂纹在α枝晶边界形成并沿着枝晶边界扩展；铁对合金的力学性能影响很大，特别是延伸率。更多还原

【Abstract】 In this paper, aluminium alloys, which are one of the important metallurgic structural materials, were studied. Aiming at the in-situ titanium alloying of Aluminium alloys, the electrolytic production test and the application of electrolysis low-titanium alloy were investigated, respectively. The feasibility of electrolysis production for low-titanium aluminum alloy was studied and evaluated in theory and in practice. The influence of TiO2 added into electrolyte on electrolysis parameters was investigated. The relationship between titanium content and grain size was analyzed and discussed. Based on the results of the investigation mentioned above, the industrial application of low-titanium aluminium alloys in A356 cast alloy, which is widely used to make car wheels, was studied. Two series of A356 alloys, which contains 0.07%Ti, 0.13%Ti, 0.19%Ti, respectively, were prepared by directly remelting low-titanium aluminium alloy and remelting pure aliminium and Al-Ti master alloy, respectively. The difference of structure and properties between two series of alloys were investigated and analyzed.The thermodynamic calculation results show that, when adding a certain TiO2 in proportion to electrolyte, the titanium atom can be precipitated both by the thermal reduction reaction of TiO2 with aluminium and the electrochemical decomposing of TiO2 at cathode. It is possible to produce low-titanium aluminum alloy directly. Three months of periods of industrial test for production low-titanium aluminum alloy was conducted using the 80kA prebake electrolysis cells. The test results showed that the electrolysis cell can work stably, and the effect of TiO2 added into electrolyte on electrolytic process parameters, current efficiency, consumes of materials and energyare trifling. The titanium content in alloys is stable and the absorbility of Ti is high. The microstructure of electrolytic low-titanium aluminum alloy is homogeneous. The grain refinement effect is excellent comparing with that of alloys added titanium by melting Al-Ti master alloys and both alloys have the same grain refinement trend. Therefore, it is feasible to directly electrolytic produce low-titanium aluminium alloys in practice.The results of tensile tests and metallographic observation showed that the microstructure of alloys made with two methods is similar to each other. Increasing titanium content, the secondary dendrite arm spacing decreases, the strength is slightly improved, but the plasticity and quality index Q are decreased for two series of alloys. If the alloys contain the same Ti content, the secondary dendrite arm spacing of the alloys prepared by direct electrolytic low-titanium alloys is smaller than mat of the alloys prepared by pure alloy and master alloys, and the properties of the former is superior to that of the latter slightly, especially the alloys with low titanium. The results of the optic metallographic observation near fracture surface and the SEM examination of fractography of the tensile samples showed that the microcracks mainly initiate at the sites of the silicon particles in the form of breaking itself or debonding from a matrix, especially in the position with rich iron. Then the microcracks propagate to form voids across through the a matrix in eutectic fields and rounding eutectic silicon particles in the transgranular form and finally aggregate to form main crack in the boundaries of a dendrites. The main crack tends to propagate along a dendrites boundaries. The destructive influence of iron on the properties is dramatic, especially to plasticity.更多还原