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Aluminum is the world's largest production of non-ferrous metals, with light weight, high specific strength, excellent electrical and thermal conductivity and other characteristics. With the continuous development of aerospace, precision electronic instruments, photovoltaic semiconductors and other emerging strategic industries, the demand for high-performance materials of aluminum alloys has become increasingly strong. This paper reviews the research progress of aluminum alloy melt refinement treatment, summarizes the development history of grain refinement, and evaluates the advantages and disadvantages of various types of refining agents, such as Al–Ti–B, Al–Ti–C, Al–Ti–B/C–Re, etc. The article points out the shortcomings of the current research on the melt refinement treatment of aluminum alloys, and looks forward to the future research direction.

In the present paper, the microstructures of three kinds of in-situ reinforcements Al-Ti-C, Al-Ti-B, and Al-Ti-B-C-Ce were deeply investigated using a combination of scanning electron microscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. The effect of in-situ reinforcements on the room temperature and elevated temperature (350 °C) tensile strengths of Al-13Si-4Cu-1Mg-2Ni alloy were analyzed. It is found that doping with trace amounts of B and Ce, the size of the Al3Ti phase in the in-situ reinforced alloy changed from 80 µm (un-reinforced) to about 10 µm, with the simultaneous formation of the AlTiCe phase. The Al-Ti-B-C-Ce reinforcement which is rapid solidified, was more effective and superior to enhance the tensile strengths of the Al-13Si-4Cu-1Mg-2Ni alloy, both at room and high temperatures than those of addition other reinforcements. The room temperature (RT) strength increased by 19.0%, and the 350 °C-strength increased by 18.4%. [ABSTRACT FROM AUTHOR]

In the present paper, the microstructures of three kinds of in-situ reinforcements Al-Ti-C, Al-Ti-B, and Al-Ti-B-C-Ce were deeply investigated using a combination of scanning electron microscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. The effect of in-situ reinforcements on the room temperature and elevated temperature (350 °C) tensile strengths of Al-13Si-4Cu-1Mg-2Ni alloy were analyzed. It is found that doping with trace amounts of B and Ce, the size of the Al3Ti phase in the in-situ reinforced alloy changed from 80 µm (un-reinforced) to about 10 µm, with the simultaneous formation of the AlTiCe phase. The Al-Ti-B-C-Ce reinforcement which is rapid solidified, was more effective and superior to enhance the tensile strengths of the Al-13Si-4Cu-1Mg-2Ni alloy, both at room and high temperatures than those of addition other reinforcements. The room temperature (RT) strength increased by 19.0%, and the 350 °C-strength increased by 18.4%.

This research investigated the effects of high-intensity ultrasound on the combustion synthesis of TiC particles in Al–Ti–C system. The process involved that high-intensity ultrasound was applied on the surface of a compacted Al–Ti–C pellet directly through a Nb probe during the thermal explosion reaction. By comparing with the sample without ultrasonic treatment, it was found that the thermal explosion reaction for synthesizing TiC phase could take place thoroughly in the ultrasonically treated sample. During the process of synthesizing TiC phase, the dissolution of solid graphite particles into the Al–Ti melt, as well as the nucleation and growth of TiC particles could be promoted effectively due to the effects of ultrasound, leading to an enhancement of the formation of TiC particles. Ultrasound assisted combustion synthesis as a simple and effective approach was proposed for synthesizing materials in this research. [ABSTRACT FROM AUTHOR]

Al–Ti–C master alloy has been known as an efficient grain refiner for a series of Al alloys since 1950s. However, the grain refinement mechanism is still not fully elucidated up to now. Herein, we systematically investigate this mechanism by combining Cs-corrected transmission electron microscopy and theoretical calculations. First, the Al/TiC x nucleation interface is determined to be a "Al ∼ Interfacial transition layer ∼ TiC x " sandwich-like structure, with the orientation relationship of [011]Al//[011]TiC x and (1 1 ¯ 1)[011]Al plane inclined 21° to (1 1 ¯ 1)[011]TiC x plane that is beneficial to eliminate the lattice constant misfit between Al and TiC x. The interfacial transition layer, consisting of Al and Ti atoms, play a crucial role in reducing atomic arrangement mismatch between (1 3 ¯ 3)[011]Al and (1 1 ¯ 1)[011]TiC x , thus promoting Al nucleation. Second, rather than directly reacting with Al melt as conventionally reckoned, TiC x with x < 0.92 actually releases Ti atoms to Al melt first after inoculation (720 °C), contributing to the formation of the Ti-containing interfacial transition layer. On the other hand, after Ti releasing, C/Ti ratio in TiC x is increased, which inversely decreases the Ti-releasing capability and leads to grain refinement fading gradually. This study sheds new light on the grain refinement mechanism in Al–Ti–C-refined Al and should build up the foundation for developing high-efficiency TiC x -containing grain refiners. [Display omitted]. [ABSTRACT FROM AUTHOR]

The settling behaviour of heterogeneous nucleating particles such as TiAl3, TiB2, AlB2 and TiC in liquid Al has been studied through vertical sectioning experiments. The experimental results obtained were correlated with the settling rate of the particles calculated using the Stokes' law. The TiB2 and TiC particles show larger settling tendency among all particles studied. The overall settling behaviour of the particles is largely influenced by their size distribution in their respective master alloys, their agglomeration and dissolution behaviour in the liquid Al. [ABSTRACT FROM AUTHOR]

Abstract: The grain refining response of LM25 (Al–7Si–0.35Mg) alloy has been studied with the newly made Al–5Ti–0.8C and Al–5Ti–1.2C master alloys which have been successfully prepared in the laboratory by reaction of K2TiF6 salt and graphite powder with Al. The results have been compared with the grain refining efficiency of Al–3B, Al–1Ti–3B and Al–5Ti–1B master alloys on LM25 alloy at different addition levels. The results show that the grain refining efficiency of even lowest addition level (0.1wt.%) of both Al–5Ti–0.8C and Al–5Ti–1.2C master alloys are equivalent to the 1.0wt.% addition levels of Al–1Ti–3B and better than 1.0wt.% of Al–3B master alloy. At higher addition levels of Al–5Ti–0.8C and Al–5Ti–1.2C master alloys exhibits fading in grain structure on longer holding due to agglomeration of TiC particles and poisoning of Si. [Copyright &y& Elsevier]

Abstract: Al–5Ti–0.8C and Al–5Ti–1.2C master alloys have been successfully prepared by reaction of K2TiF6 salt and graphite powder with molten Al. While the Al–5Ti–0.8C consists of some TiAl3 particles in addition to TiC particles in the Al matrix, the Al–5Ti–1.2C master alloy revealed the presence of only TiC particles. The grain refining efficiency of these two master alloys has been compared with that of the conventional Al–5Ti–1B master alloy on Al and Al–7Si alloy at different addition levels. Al–5Ti–1.2C master alloy was found to be the most efficient grain refiner for Al amongst the grain refiners studied. Even in case of Al–7Si alloy, the Al–5Ti–0.8C and Al–5Ti–1.2C master alloys performed better than conventional Al–5Ti–1B master alloy. However, the Al–5Ti–1.2C master alloy shows poor response to grain refinement in Al–7Si alloy at higher addition levels than the Al–5Ti–0.8C master alloy, indicating poisoning. [Copyright &y& Elsevier]

The effects of Al–Ti–C and La on the fluidity of a ZL205A alloy after separate and combined addition were studied by conducting a fluidity test. The fluidity of the ZL205A alloy first increased and then decreased with the increasing addition of Al–Ti–C and La; it peaked at 0.3% and 0.1% for Al–Ti–C and La, respectively. The combined addition of Al–Ti–C and La led to better fluidity, which increased by 74% compared with the base alloy. The affecting mechanism was clarified through microstructure characterization and a DSC test. The heterogeneous nucleation aided by Al–Ti–C and La, the number of particles in the melt, and the evolution of the solidification range all played a role. Based on the evolution of the fluidity and grain size, the optimal levels of Al–Ti–C and La leading to both high fluidity and small grain size were identified. [ABSTRACT FROM AUTHOR]