Grain Refinement In Aluminum Alloys Research Articles

Anti-fading study of Al–Ti–B by adding Ce on 6111 aluminum alloy

It is a practically significant issue to overcome the low efficiency and the short action time of Al–Ti–B master alloy for the grain refinement of aluminum alloys. In this paper, the phase relationship of the Al–Ti–B–Ce system, the effect of rare earth elements on the evolution of the morphology of the refining phases TiB2 and Al3Ti, and the effect of the refiners on the microstructure and properties of the 6111 alloy are investigated. The experimental results show that the addition of rare earths introduces the rare earth phase Ti2Al20Ce into Al–Ti–B. The rare earth phase acts as an effective protective shell, reduces the free energy of Al3Ti, prevents further movement at the Solid/Liquid interface, and inhibits the aggregation and growth of the Al3Ti phase. By adsorbing on the surface of the TiB2 phase, the rare earth reduces the surface energy and size of the TiB2 phase, thus reducing the possibility of agglomeration. The fine and dispersed refining phase results in more effective nucleation sites in the melt, which can maintain grain refining for a long time and has better anti-fading effect. Therefore, the grain refiner Al–5Ti–B + Ce can effectively refine the grain of 6111 alloy, reduce the grain refinement fading shortcoming, and improve the strength and ductility of 6111 aluminum alloy.

Development process and future trends of chemical refining agents' influence on grain refinement in aluminum alloys

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.

Promoting strengthening and grain refinement of aluminum alloy during wire and arc additive manufacturing by adding TiB2 particles

The influence of submicron-sized TiB2 particles on the microstructure and properties of deposited 2319 Al has been investigated. The Al matrix demonstrated a small undercooling (ΔTfg≈1.12 K « ΔTAl-Cu≈13 K) satisfying its own free growth because of the addition of TiB2 particles. This promoted the nucleation and growth of an extremely large number of grains and hindered the migration of grain boundaries, thereby refining the grains from 96.5 to 47.42 μm. The texture features reduced with the decrease of the pole density of Al d from 1.997 to 1.417, and the maximum pole density value of CuAl2 decreased from 8.953 to 3.597. The plentiful θ′ phases precipitated near the grain boundary which restrained the formation of reticular eutectic phase, with a semi-coherent interface with the Al matrix, (112)CuAl2//(111)Al. Resulted in excellent precipitation strengthening of being the best strengthening effect by θ′ phases, the strength of the deposited sample was increased by 30 %, reaching 304 MPa.

Review Of Grain Refinement Performance Of Aluminium Cast Alloys

Improving the utilization of aluminum grain refinement in industrial settings is a continual point of focus for research. Grain refinement serves the dual purpose of not only achieving a fine grain size, but also enhancing the mechanical properties of materials. Numerous researchers have dedicated significant efforts over the last decades to explore the grain refinement of aluminium alloys. There have been a number of studies relating to the mechanisms that explains the observed phenomena associated with grain refinement. The most commonly employed are grain refiners based on Al–Ti–B system. However, a limited efficiency of these grain refiners on aluminium silicon alloys with excessive Si and the effect of alloying elements have been noticed. The review examines the impact of the factors influencing grain refining behaviour of master alloys, including the effects of poisoning elements such as Si, Mg, Zr, and Sr. A large grain refiners used for enhancing the properties of aluminium silicon alloys are reviewed. An overview of new refiners has been given. Also, procedures for assessment of grain refinement have been examined.

Effect of differential temperature on the interfacial microstructure evolution and mechanical properties of asymmetrically rolled Mg/Al composite plates

To investigate the effects of differential temperature on microstructure, interfacial morphology and mechanical properties of Mg/Al composite plates, asymmetric rolling was used to prepare Mg/Al composite plates. The results show that the shear deformation induced slip system at interface is less and the degree of dislocation accumulation is higher in isothermal rolling compared to differential temperature rolling. This results in a higher degree of subgrain in each layer and higher tensile and yield strength of composite plate. However, the plate is prone to stress concentration at interface, which severely reduces elongation and bond strength. The differential temperature rolling can better promote the recrystallization of magnesium alloy and grain refinement of aluminum alloy at interface by introducing temperature gradient. This reduces the occurrence of stress concentrations at interface, resulting in higher elongation and bond strength of composite plate.

Ultrasonic cavitation processing of multi-functional materials

Ultrasonic cavitation processing (USP) is a versatile technique that has gained a lot of momentum in the last decade as a sustainable, environmentally friendly, and cost-effective process. USP uses high-frequency sound to form bubbles that expand, contract, and eventually collapse, generating high-speed liquid jets, powerful shockwaves, and acoustic streaming effects. Despite its widespread application, use of USP remains mostly empirical. For processes involving the synthesis and production of materials, harnessing the power of cavitation requires an understanding of the fundamental mechanisms driving USP. In this presentation, we record recent studies to analyse, optimise, and control USP for applications related to grain refinement of aluminium alloys, exfoliation of 2D nanomaterials, and processing of composites. High-speed cameras and in situ synchrotron imaging were used to visualise cavitation dynamics, coupled with state-of-the-art hydrophones to detect acoustic waves and shockwave emissions. Results show that optimised USP with the help of advanced modelling significantly improves grain refinement of aluminium alloys in processes such as direct-chill (DC) casting, where shockwaves are primarily responsible for the fragmentation of intermetallic crystals/dendrites. Furthermore, shockwaves act as the main driving mechanism for the exfoliation of 2Ds while cavitation activity enhances fibre dispersion in highly viscous polymers, improving matrix stability and strength.

Mechanism of grain refinement in Al-Cu alloy by adding trace La and Al-5Ti-1B

<sec>Grain refinement of aluminium alloys can not only reduce the defects (such as segregation and hot tearing) but also improve the mechanical properties. Adding Al-5Ti-1B master alloy to the melt has become a common method to refine the solidification microstructure of aluminium alloys. A lot of researches have been carried out to uncover the grain refining mechanisms as well as to show the microstructure formation under the effect of grain refiner. These researches demonstrated that the grain refining efficiency is closely related to the number density of TiB<sub>2</sub> particles as well as the solute Ti concentration in the melt. However, there exist still problems to be resolved, such as the limited grain refinement potency of Al-5Ti-1B master alloy. Recently, the addition of trace La to the melt has attracted much attention to control the microstructure of aluminium alloys. The Al-Cu alloys are widely applied to the automobile and aerospace fields due to their high strength, good ductility and high temperature properties. It has been reported that Cu can segregate to Al/TiB<sub>2</sub> interface in the Al-Cu melt inoculated with Al-5Ti-1B master alloy. But the effect of Cu segregation on the grain refinement result is not clear yet. Meanwhile, whether the grain refinement effect of Al-5Ti-1B master alloy on Al-Cu alloy can be improved by the addition of trace La has not been reported.</sec><sec>Solidification experiments are carried out for Al-2Cu alloy with the addition of Al-5Ti-1B master alloy+ trace La. The synergistic effect of trace La and Al-5Ti-1B on the solidification microstructure of Al-2Cu alloy is investigated. It is found that trace La can effectively enhance the refinement result of Al-2Cu alloy and further diminish the nucleation undercooling. Experimental and calculated results demonstrate that solute Cu segregates to the Al/TiB<sub>2</sub> interface and thus increases the interatomic spacing mismatch between Ti (0001) plane of the TiB<sub>2</sub> particles and the interfacial monolayer, while La segregation reduces the interatomic spacing mismatch. The trace La addition reduces the interfacial energy between <i>α</i>-Al and TiB<sub>2</sub> particles, improves the potency of TiB<sub>2</sub> particles to nucleate <i>α</i>-Al, and thus enhances the grain refinement result of Al-5Ti-1B master alloy.</sec>

Effect of Er and Zr additions and aging treatment on grain refinement of aluminum alloy fabricated by laser powder bed fusion

In this work, Al-0.88Er-0.78Zr (wt%) alloy was fabricated via laser powder bed fusion (LPBF). The microstructure, precipitates distribution, electrical conductivity and hardness of as-built and aging treatment specimens were carefully characterized. Results show that LPBF process greatly expand the solid solubility of Er and Zr in Al. The addition of Er can significantly refine the grain size and form a bimodal grain structure consisting of fine equiaxed grains (grain size ~0.53 ± 0.15 µm) at the boundary of molten pool together with coarse columnar grains (width 2.57 ± 0.84 µm) at the center of molten pool. After 375 ℃ for 3 h aging treatment, the particles on the grain boundary inhibit the grain growth; at the same time, a large number of Al3(Er,Zr) particles with L12 structure and size of 2.25 ± 0.3 nm are precipitated, which plays a major role in enhancing the hardness with the peak hardness of about 89.24 ± 3.77 HV. Er and Zr elements are proved to be an alternative way of the additive elements for developing a new 3D printing high-strength aluminum alloy.

Grain Refining of Aluminium and 6063 Alloys Using Al-V Alloy Containing Al3V Intermetallic Compound

The grain refinement of aluminium alloys is one of the important processes in various industrial fields. This work aims to use aluminium-vanadium (Al-V) master alloy as a new grain refiner for grain refinement of aluminium alloys. The new refiner was prepared by reduction of vanadium pentoxide V2O5 using molten aluminium, then it was examined using SEM, EDS, XRD, and optical microscopy. The findings of these tests indicated that the developed master alloy contains blocky-shaped particles evenly distributed within the aluminium matrix Al3V in the form of an intermetallic compound. Different levels of vanadium content were examined (3.5, 5.6, and 8.3) as grain refiners for commercial pure Al and 6063 alloys. It was found that the grain size was decreased from 2000 to 320 mm for commercial pure aluminium and decreased from 1500 to 300 mm for 6063 alloys. The best results were obtained by using vanadium content of 0.03 wt.% in the refined alloy and a holding time of 3 min. Based on the gross restriction factor (GRF), the new grain refiner Al-V master alloy performed well at vanadium contents more than 0.02 wt.% in the refined alloy.

Synergistic Effect of La and TiB2 Particles on Grain Refinement in Aluminum Alloy.

Synergistic effect of TiB2 (in form of Al-5Ti-1B) and La on grain refining results in Al-2Cu alloy was investigated. α-Al grains are significantly refined by Al-5Ti-1B. When trace La is added to the melt, further refinement is exhibited. Average grain size and nucleation undercooling of α-Al reduce first and then almost remain unchanged with La addition. Satisfactory grain refining result achieves when La addition level reaches 600 ppm. When more than 600 ppm La is added to the melt, La-rich particles form and the effect of solute La left in matrix on the microstructure almost no longer changes. Theoretical calculation results demonstrate that solute La segregates to Al melt/TiB2 particles interface along with Ti and Cu prior to α-Al nucleation and the synergistic effect of La and TiB2 particles on grain refinement mainly attributes to the enhancement in the potency of TiB2 particles to heterogeneously nucleate α-Al by trace La addition.

Improved grain refinement in aluminium alloys by re-precipitated TiB2 particles

Al-Ti-B master alloys are widely used to refine aluminium alloys. The reported researches demonstrate that excellent grain refinement result can be achieved only with the coexistence of solute Ti and TiB2 particles of a proper average radius and a narrow radius distribution. However, the traditional grain refinement method can’t meet the requirements for manufacturing high-quality aluminium alloys due to the large radius and wide radius distribution of TiB2 particles in master alloys. This work proposes a new idea for improved grain refinement in aluminium alloys by re-precipitated TiB2 particles. The TiB2 particles with a narrow radius distribution and a small average radius in Al melt are first prepared. The resultant melt is then directly employed to refine aluminium alloys. An improvement in grain refinement result is achieved compared with the traditional refinement method.

In-situ observations and acoustic measurements upon fragmentation of free-floating intermetallics under ultrasonic cavitation in water

Grain refinement in alloys is a well-known effect of ultrasonic melt processing. Fragmentation of primary crystals by cavitation-induced action in liquid metals is considered as one of the main driving mechanisms for producing finer and equiaxed grain structures. However, in-situ observations of the fragmentation process are generally complex and difficult to follow in opaque liquid metals, especially for the free-floating crystals. In the present study, we develop a transparent test rig to observe in real time the fragmentation potential of free-floating primary Al3Zr particles under ultrasonic excitation in water (an established analogue medium to liquid aluminium for cavitation studies). An effective treatment domain was identified and fragmentation time determined using acoustic pressure field mapping. For the first time, real-time high-speed imaging captured the dynamic interaction of shock waves from the collapsing bubbles with floating intermetallic particles that led to their fragmentation. The breakage sequence as well as the cavitation erosion pattern were studied by means of post-treatment microscopic characterisation of the fragments. Fragment size distribution and crack patterns on the fractured surface were then analysed and quantified. Application of ultrasound is shown to rapidly (<10 s) reduce intermetallic size (from 5 mm down to 10 μm), thereby increasing the number of potential nucleation sites for the grain refinement of aluminium alloys during melt treatment.

Kinetic behaviour of TiB2 particles in Al melt and their effect on grain refinement of aluminium alloys

Abstract Solidification experiments were carried out to investigate the kinetic behaviour of TiB2 particles in Al melt and their effect on the grain refinement of commercially-pure Al. A model was proposed to describe the kinetic behaviour of TiB2 particles during the whole process from the addition of TiB2 to the melt to the freezing of the melt. The results indicate that TiB2 particles are not stable in Al melt. They may dissolve and coarsen during the holding period and grow during the cooling period of the melt. The kinetic behaviour of TiB2 particles in the melt has a great influence on their number density and the grain refinement. Solute Ti addition can suppress the dissolution, Ostwald ripening and growth behaviours of TiB2 particles.

On the governing fragmentation mechanism of primary intermetallics by induced cavitation

One of the main applications of ultrasonic melt treatment is the grain refinement of aluminium alloys. Among several suggested mechanisms, the fragmentation of primary intermetallics by acoustic cavitation is regarded as very efficient. However, the physical process causing this fragmentation has received little attention and is not yet well understood. In this study, we evaluate the mechanical properties of primary Al3Zr intermetallics by nano-indentation experiments and correlate those with in-situ high-speed imaging (of up to 1 Mfps) of their fragmentation process by laser-induced cavitation (single bubble) and by acoustic cavitation (cloud of bubbles) in water. Intermetallic crystals were chemically extracted from an Al-3 wt% Zr alloy matrix. Mechanical properties such as hardness, elastic modulus and fracture toughness of the extracted intermetallics were determined using a geometrically fixed Berkovich nano-diamond and cube corner indenter, under ambient temperature conditions. The studied crystals were then exposed to the two cavitation conditions mentioned. Results demonstrated for the first time that the governing fragmentation mechanism of the studied intermetallics was due to the emitted shock waves from the collapsing bubbles. The fragmentation caused by a single bubble collapse was found to be almost instantaneous. On the other hand, sono-fragmentation studies revealed that the intermetallic crystal initially underwent low cycle fatigue loading, followed by catastrophic brittle failure due to propagating shock waves. The observed fragmentation mechanism was supported by fracture mechanics and pressure measurements using a calibrated fibre optic hydrophone. Results showed that the acoustic pressures produced from shock wave emissions in the case of a single bubble collapse, and responsible for instantaneous fragmentation of the intermetallics, were in the range of 20–40 MPa. Whereas, the shock pressure generated from the acoustic cavitation cloud collapses surged up to 1.6 MPa inducing fatigue stresses within the crystal leading to eventual fragmentation.

Grain Refinement of Al–2%Cu Alloy Using Vibrating Mold

Vibration effects on grain refinement in aluminum alloy were investigated by mechanically vibrating metal mold during solidification. Results show that both the frequency and the half amplitude affected the grain refinement, decreasing the average grain size. We hypothesized that the average grain size can be estimated from the excitation force consolidating them. To clarify grain refinement mechanisms, experiments were conducted with different vibration starting times and different vibration periods. Moreover, a water model experiment was conducted using ammonium chloride solution. Both the equiaxed grain size and the columnar grain length were reduced by mold vibration before pouring, irrespective of the vibration period. However, when the mold was vibrated at 15 s after pouring, the columnar grain length increased. Moreover, the equiaxed grain size increased greatly. Water model experiments showed that a vibrated mold made of polycarbonate and aluminum alloy produced many crystals near the mold wall and filled the mold by vibration and induced convection. These results clarified that starting vibration before solidification is important for grain refinement.

Ultimate grain refinement in aluminium alloys of the Al – Zn – Mg – Cu system with zirconium

Ultimate grain refinement in aluminium alloys of the Al – Zn – Mg – Cu system with zirconium

Influence of Methods of Producing the AlTi Master Alloy on Its Structure and Efficiency in the Grain Refinement of Aluminum Alloy

Influence of Methods of Producing the AlTi Master Alloy on Its Structure and Efficiency in the Grain Refinement of Aluminum Alloy

The Grain refinement of Aluminum alloys in Friction Stir Processing: A Review

Most of the industrial applications based upon surface properties. Aluminum and its alloys are mostly used in the surface application industries due to their excellent mechanical and corrosive properties. However, it exhibits poor tribological properties. To enhance the mechanical and wear properties of the material grain refinement mechanism is to be incorporated. To improve the surface properties of the material the Friction stir Processing (FSP) Technique is mostly used nowadays. FSP plays an important role in modifying the surface in an efficient, environmentally friendly, and economical manner. This review article describes the current status of the FSP Technology in grain refinement of Aluminum alloys.

Effect of vanadium carbide on commercial pure aluminum

The effect of vanadium carbide (VC) on the grain size of commercial pure aluminum was experimentally investigated by varying the content of VC, the holding time, and casting temperature. The refining efficiencies of VC and Al5Ti1B were also compared. The refined samples of commercial pure aluminum were examined using optical microscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results suggest that VC is a good refiner of commercial pure aluminum. The addition of only 0.3wt% VC can decrease the grain size of aluminum to 102 μm, whereas the casting temperature and holding time have little effect on the grain size. The refining efficiency of VC is better than that of Al5Ti1B. The VC particles in molten aluminum act as nuclei and the grain refinement of aluminum alloys by VC particles is achieved via heterogeneous nucleation.

A Review on Grain Refinement of Aluminum Alloys: Progresses, Challenges and Prospects

Aluminum becomes the most popular nonferrous metal and is widely used in many fields such as packaging, building transportation and electrical materials due to its rich resource, light weight, good mechanical properties, suitable corrosion resistance and excellent electrical conductivity. Grain refinement, which is obtained by changing the size of grain structure by different techniques, is a preferred method to improve simultaneously the strength and plasticity of metallic materials. Therefore, grain refining of aluminum is regarded as a key technique in aluminum processing industry. Up to now, there have been a number of techniques for aluminum grain refining. All the techniques can be classified as four categories as follows: grain refining by vibration and stirring during solidification, rapid solidification, the addition of grain refiner and severe plastic deformation. Each of them has its own merits and demerits as well as applicable conditions, and there are still some arguments in the understanding of the mechanisms of these techniques. In this article, the research progresses and challenges encountered in the present techniques and the future research issues and directions are summarized.