Effect of CeO2 Size on Microstructure, Synthesis Mechanism and Refining Performance of Al-Ti-C Alloy

The effects of CeO2 size on the microstructure and synthesis mechanism of Al-Ti-C alloy were investigated using a quenching experiment method. A scanning calorimetry experiment was used to investigate the synthesis mechanism of TiC, the aluminum melt in situ reaction was carried out to synthesize master alloys and its refining performance was estimated. The results show that the Al-Ti-C-Ce system is mainly composed of α-Al, Al3Ti, TiC and Ti2Al20Ce. The addition of CeO2 obviously speeds up the progress of the reaction, reduces the size of Al3Ti and TiC and lowers the formation temperature of second-phase particles. When the size of CeO2 is 2–4 μm, the promotion effect on the system is most obvious. The smaller the size of CeO2, the smaller the size of Al3Ti and TiC and the lower the formation temperature. Al-Ti-C-Ce master alloy has a significant refinement effect on commercial pure aluminum. When the CeO2 size is 2–4 μm, the grain size of commercial pure aluminum is refined to 227 μm by Al-Ti-C-Ce master alloy.

Microstructural Master Alloys Features of Aluminum–Erbium System

Aluminum master alloys with rare earth metals are widely studied by many scientists around the world, but research on the production of Al-Er master alloys is still limited. The purpose of this work is to study the microstructure parameters of aluminum-erbium master alloys obtained by metallothermic reduction of salt mixtures containing erbium oxide or fluoride. The structural features were investigated by optical and scanning electron microscopy, and the dependence of the microhardness of the eutectic and solid solution fields of obtained master alloys on the content of erbium in the master alloy was determined. Studies have shown that master alloys obtained by metallothermic reduction of erbium compounds from chloride–fluoride melts are characterized by a uniform distribution of Al3Er intermetallic compounds in the volume of double eutectic [(Al) + Al3Er] and have a strong grain refinement effect. The analysis of the microstructure showed that the structure of the master alloys varies depending on the content of erbium. When the content of erbium in the master alloy is up to 6 wt.%, the eutectic structure is preserved. When the content of erbium in the master alloy is 8 wt.% or more, the structure becomes a solid solution with individual inclusions of various shapes and intermetallic compounds.

Preparation Process and Phase Transformation of Al-5Ti-0.25C Master Alloy Adopting Ti Machining Chips

The refining performance of Al-Ti-C master alloys is substantially compromised by the inferior wettability between graphite and molten aluminum. In this paper, the Al-5Ti-0.25C master alloy was successfully prepared by reacting Ti machining chips, graphite, and molten aluminum. In order to determine a simple method of improving the wettability, the optimal preparation process and phase transformation of the Al-5Ti-0.25C master alloy were investigated using an optical microscope, X-ray diffractometer, and scanning electron microscope equipped with an energy dispersive spectrometer. The results show that the feeding method using a prefabricated block made from Ti chips, Al chips, and graphite effectively improves the wettability between graphite and molten aluminum and increases the recovery rate of graphite. When the reaction temperature is low (1223 K), the agglomeration of TiAl3 is caused. When the reaction temperature is high (1373 K), the morphology of TiAl3 changes from block-like to needle-like and increases its size. Further, a short reaction time (30 min) results in the incomplete dissolution of the Ti chips, while a long reaction time (90 min) causes the TiAl3 to transform into needle-like morphologies. The microstructural observation of undissolved Ti chips shows that TiAl3 and TiC are formed around it, which proves the transformation of Ti chips to TiAl3 and TiC. In addition, the enrichment of TiC and Al4C3 was observed in the vicinity of TiAl3, and a reaction model for the formation of TiC from the reaction of Al4C3 and TiAl3 was presented.

Features of Al-10Mo electron-beam produced master-alloy assimilation in liquid aluminum and AlSi9Cu3 alloy

The work is devoted to the Al-10Mo electron-beam prepared master-alloy modifying phases dissolution and assimilation features determination. It is shown that the obtained master-alloy is characterized by uniform distribution and high dispersion of molybdenum aluminide particles. When studying the process of dissolving the master-alloy in pure aluminum, it was determined that the time of modification of the melt more than 20 minutes at a temperature of 740 ± 10 ° C leads to the most complete destruction of the original intermetallics Al22Mo5 and Al17Mo4 and the formation of smaller and evenly distributed particles Al5Mo and Al12Mo with dimensions about 2 μm. As the molybdenum content decreases, the dispersion of the modifying phases and the uniformity of their distribution increase. Increasing the temperature and exposure time do not improve the assimilation of the modifier. The Al-10Mo master-alloy, obtained in the conditions of electron-beam casting technology, has a number of characteristics that allow to consider it as more efficient and cost-effective, compared to known analogues. This is due to the much higher concentration of molybdenum in the modifier (10% wt.), as well as fine dispersion and uniform distribution of the modifying phases. The nonequilibrium composition of aluminides inherent in the ligatures obtained under these conditions contributes to their significant grinding and refining after addition into aluminum melts. The stoichiometry of the phases from Al22Mo5 and Al17Mo4 changes to Al12Mo, which serve as crystallization centers and have a size of about 1 μm, dissolves and changes. The example of industrial casting alloy AlSi9Cu3 shows complete and effective assimilation of the master-alloy in a short time of 5 minutes at a temperature of 740 ± 10 ° C. Such indicators are more economic, in comparison with standard industrial ones, for which both higher temperature of melt preparing ant longer lifetime in liquid state after modification are necessary. Keywords: master-alloys, Al-Mo, modifications, aluminum alloys, AlSi9Cu3, resource saving.