Investigation Of The Electrolytic Producing Technology And The Mechanical Properties Of Low-Titanium Aluminum Alloys

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.