Al3Ti Particles Research Articles

Ultrasound assisted in-situ casting technique for synthesizing small-sized blocky Al3Ti particles reinforced A356 matrix composites with improved mechanical properties

The in-situ 5 wt% Al3Ti/A356 composites with high strength and good ductility were prepared from A356-K2TiF6 system by an ultrasound assisted in-situ casting technique at 800 °C. The microstructures and mechanical properties of ultrasonic-treated (UT) and non-ultrasonic (NU) samples were examined. It was found that Si element had a solubility of 9–11 at. % in the in-situ formed Al3Ti particle-reinforcement and this solution tendency was proved by a first-principles calculation. In the ultrasonic fields, the in-situ Al3Ti particles were changed from rod-like to blocky in morphology with a reduced average size of 4 μm. Also, Al3Ti particles were distributed uniformly in the matrix and most of which located inside the α-Al crystals. Owing to the nucleating effect and uniform distribution of Al3Ti, both the equiaxed transition from long columnar dendrite structure and refining of α-Al crystals occurred in the UT sample, which contributed to the improvement of both strength and ductility. Compared with T6-A356, the yield strength, ultimate tensile strength and elongation of the T6-UT sample were improved by 12.0%, 27.2% and 313.3%, respectively. Furthermore, the mechanisms of the improved mechanical properties, including the strength and ductility, of the composites were investigated in this research.

Laser Welding-Brazing of Immiscible AZ31B Mg and Ti-6Al-4V Alloys Using an Electrodeposited Cu Interlayer

Metallurgical bonding between immiscible system AZ31B magnesium (Mg) and Ti-6Al-4V titanium (Ti) was achieved by adding Cu interlayer using laser welding-brazing process. Effect of the laser power on microstructure evolution and mechanical properties of Mg/Cu-coated Ti joints was studied. Visually acceptable joints were obtained at the range of 1300 to 1500 W. The brazed interface was divided into three parts due to temperature gradient: direct irradiation zone, intermediate zone and seam head zone. Ti3Al phase was produced along the interface at the direct irradiation zone. Ti-Al reaction layer grew slightly with the increase in laser power. A small amount of Ti2(Cu,Al) interfacial compounds formed at the intermediate zone and the (α-Mg + Mg2Cu) eutectic structure dispersed in the fusion zone instead of gathering when increasing the laser power at this zone. At the seam head zone, Mg-Cu eutectic structure was produced in large quantities under all cases. Joint strength first increased and then decreased with the variation of the laser power. The maximum fracture load of Mg/Cu-coated Ti joint reached 2314 N at the laser power of 1300 W, representing 85.7% joint efficiency when compared with Mg base metal. All specimens fractured at the interface. The feature of fracture surface at the laser power of 1100 W was characterized by overall smooth surface. Obvious tear ridge and Ti3Al particles were observed at the fracture surface with increase in laser power. It suggested atomic diffusion was accelerated with more heat input giving rise to the enhanced interfacial reaction and metallurgical bonding in direct irradiation zone, which determined the mechanical properties of the joint.

Study on Strengthening and Toughening Mechanisms of Aluminum Alloy 2618-Ti at Elevated Temperature

AbstractThe tensile properties of the alloy 2618 and 2618-Ti were tested using a tensile testing machine. The morphologies of the fracture of tensile samples were observed using scanning electron microscopy. The strengthening and toughening mechanisms of alloy 2618-Ti at elevated temperature were systematically investigated based on the analyses of experimental results. The results showed that the tensile strength of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 250 and 300 °C. But the elongation of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 200 and 300 °C. The equal-strength temperature of intragranular and grain boundary of alloy 2618-Ti is about 235 °C. When the temperature is lower than 235 °C, the strengthening of alloy 2618-Ti is ascribed to the strengthening effect of fine grains and dispersed Al3Ti/Al18Mg3Ti2 phase. When the temperature is higher than 235 °C, the strengthening effect of alloy 2618-Ti is mainly attributed to the load transfer of Al3Ti and Al18Mg3Ti2 particles. The toughening of alloy 2618-Ti at elevated temperature is mainly ascribed to the fine grain microstructure, excellent combination between matrix and dispersed Al3Ti/Al18Mg3Ti2 particles as well as the recrystallization of the alloy at elevated temperature.

Mechanism of microstructural refinement of deformed aluminum under synergistic effect of TiAl3 and TiB2 particles and impact on mechanical properties

To understand the synergistic effect of TiAl3 and TiB2 particles on grain refinement of α-Al, equal-channel angular pressing (ECAP) of Al-5Ti-1B (wt%) alloy was carried out. The ECAPed Al-5Ti-1B (wt%) alloy was characterized by X-ray Diffraction (XRD), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results reveal that α-Al grains and TiAl3 phase of ECAPed Al-5Ti-1B (wt%) alloy were refined, while the average size of TiB2was marginally decreased. The tensile strength was increased from 128MPa to 218MPa, and the elongation was reduced from 26% to 20.6%. The transformation from dislocations to low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) resulted in continuous dynamic recrystallization (CDRX), which induced grain refinement during ECAP. From 3 to 6 passes of ECAP, CDRX occurred in the alloy, and as ECAP passes increased to 9, the rate of formation of LAGBs and the transformation rate from LAGBs to HAGBs reached a dynamic balance. The present study indicates that the second phase particles promote the formation of LAGBs but prolong complete-recrystallization time, such that complete-recrystallization leads to grain refinement. TiB2 particles are smaller than TiAl3 particles and this is caused by the composition of the alloy and its synthesis method, and compared with TiAl3, TiB2 with a smaller size had a more obvious influence on the formation of LAGBs and grain refinement.

An experimental study of investigating the relationships between structures and properties of al alloys included with high Mg and high Ti

In this study, the influences of high magnesium (Mg) and high titanium (Ti) additions on aluminium (Al) alloys were investigated to peruse the relationship between the structure and properties of the new alloys. Microstructural analyses were performed using X-ray diffraction (XRD), the polarised optical microscope, and scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS). In the microstructure of the alloys, the β-phase (Al3M2) α-solid solution, Ti2Mg3Al18 and TiAl3 particles were revealed. Results showed that the average grain size of Al-Mg-Ti alloys was found to be different in each composition, and the smallest grain size was obtained at Al-12Mg-3Ti alloy as 88 μm. The highest tensile strength (170 MPa) was attained with additions of 8 wt.% Mg and 1 wt.% Ti, but the highest hardness value (125 HBN) was obtained with additions of 14 wt.% Mg and 3 wt.% Ti. It was noted that the smallest average grain size did not behave in accordance with the highest mechanical properties. For the work, the optimal ratios of magnesium and titanium entrained into Al alloys were 8 wt.%, and 1 wt.%, respectively.

Understanding the evolution of microstructural features in the in-situ intermetallic phase reinforced Al/Al3Ti nanocomposite

In the present study, Al/Al3Tinanocomposites were prepared by stir casting technique. The reinforcing intermetallic Al3Ti phases were generated by in-situ reaction between nanosized TiO2 particles and molten Al. Microstructural investigations revealed the presence of plate, needle and nanosized Al3Ti and Al2O3 particles. Morphological evolution of the Al3Ti phase with respect to its content and its effect on the grain size, texture, dislocation density and their type were analysed. At higher vol%, Al3Ti phases acquire plate shaped morphological features which changes to needle shaped at lower vol% of Al3Ti. The overall dislocation density and screw dislocation density in the nanocomposites has been found to increase with increase in vol% of the intermetallic phase. Texture analysis revealed that Brass {011} <211> and P {011} <111> are the dominant texture components in the nanocomposites, which indicate particle stimulated nucleation and recrystallizationof grains.

TiO2 ceramic particles-reinforced aluminum matrix composite prepared by conventional, microwave, and spark plasma sintering

Aluminum-10 wt% TiO2 metal matrix composites were fabricated with conventional, microwave, and spark plasma sintering processes. Aluminum and nano-sized TiO2 powders were mixed using a high-energy mixer, and the sintering process was done at 450℃ by spark plasma sintering and 600℃ under both microwave and conventional heating. The results showed microwave sintering led to form Al3Ti intermetallic compounds with flaky shape, while in the conventional heating at the same sintering temperature, Al3Ti was formed and confirmed by X-ray diffraction and scanning electron microscope investigations. Moreover, the nano-sized TiO2 particles as reinforcement with no additional phase were obtained by spark plasma sintering at the lowest sintering temperature. The maximum bending strength of 254 ± 12 MPa and Vickers hardness of 235 ± 13 were measured for samples sintered in microwave as a consequence of Al3Ti formation. The SEM and energy-dispersive X-ray spectroscopy analyses showed uniform distribution of Al3Ti particles in the microstructure of microwave sintered samples and nonuniform distribution of agglomerated Al3Ti particles and porosities in samples sintered by spark plasma sintering and conventional heating.

Strengthening mechanisms in ultrasonically processed aluminium matrix composite with in-situ Al3Ti by salt addition

Abstract Al3Ti reinforced Aluminium composites with different weight percent of Al3Ti particles were developed by in-situ reaction of aluminium alloy with potassium hexafluorotitanate (K2TiF6). Ultrasonication of the aluminium melt during salt reaction was carried out to refine the cast microstructure and achieve better dispersion of in-situ formed Al3Ti particles. The in-situ composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Al3Ti particles generated in the melt promoted heterogeneous nucleation, which was responsible for grain refinement of the cast microstructure. The well dispersed Al3Ti significantly improved the mechanical properties including ductility, yield strength (YS), ultimate tensile strength (UTS) and hardness. The dominant strengthening mechanism in the composite was the thermal mismatch strengthening followed by Hall-Petch strengthening.

Formation of L12 modified Al2.5Cu0.5Ti phase by heat treatment of spark-plasma-sintered Cu/Al3Ti specimens

In our previous studies, the influence of L12 modified Al2.5Cu0.5Ti and Al2.7Fe0.3Ti particles on the grain refining performance of an Al cast was studied. It has been shown that the L12 modified intermetallic compound particles act as heterogeneous nucleation sites of α-Al solidification. Since nuclei are formed on the surface of the heterogeneous nucleation site particles, only the surface region of the Al3Ti particles must be modified into an L12 structure. In this study, therefore, the formation of the Al2.5Cu0.5Ti phase by the reaction between Al3Ti and Cu is studied. For this purpose, Cu/Al3Ti diffusion couple specimens and specimens of Al3Ti particles dispersed in a Cu matrix are fabricated by a spark plasma sintering (SPS) method, and the reaction between Cu and Al3Ti during heat treatment of these specimens is studied. It is found that the L12 modified Al2.5Cu0.5Ti phase is formed at the Cu/Al3Ti interface by heat treatment.

Processing and tensile properties of A356 composites containing in situ small-sized Al3Ti particulates

This research proposed an in situ casting method for preparing Al3Tip/A356 composites with high strength and good ductility by adding Ti powders into molten A356 at 800°C. A sampling experiment was firstly carried out to explore the evolution process of Ti powders in the A356 melt. Based on which in situ Al3Tip/A356 composites with 1.5 and 3.0wt% Ti additions were fabricated respectively. Both the microstructures and tensile properties of samples after T6 heat treatment were investigated. The results showed that blocky Si-substituted Al3Ti particulates were synthesized in the in situ reaction and the formation of which followed a reaction-peeling model. The utilization ratio of Ti powders in the fabricating process could research 70%. In situ Al3Ti particulates existed inside the α-Al crystals of A356 alloy, with the size smaller than 10µm. Both the equiaxed transition from long columnar dendrite structure and refining of α-Al crystals occurred due to the nucleating effect of Al3Ti. Compared with T6-A356, the yield strength, ultimate tensile strength, and percent elongation of the T6-A356/3.0Ti were improved by 29.2%, 36.0% and 143.6%, respectively. The mechanisms of the improved tensile properties, including the strength and ductility, of the composites were also discussed in this research.

Quality Analysis of AlTi5B1 Master Alloys

Grain refinement in commercial aluminium alloys can be achieved by addition of AlTi5B1 master alloy, containing &alpha; aluminium matrix, TiB2 and Al3Ti particles. These particles act as nucleation points for &alpha; Al matrix, resulting in a uniform fine, equiaxed as cast microstructure. Current grain-refinement practice involves the addition of master alloy (e.g. Al-Ti-B, Al-Ti-C) before casting introducing inoculants particles to the melt. The final size SDAS in aluminium cast alloys depends on the kinetics of both nucleation and growth of solid in the liquid. As per the classical nucleation theory, the critical activation energy (&Delta;G*) to form stable nucleus and the critical radius (rkr.) for the nucleus to grow into a crystal with long order atomic arrangement are inversely proportional to the undercooling. In practical instances, nucleation does not occur heterogeneously on solid substrates such as mould walls. Several works, mainly regarding primary foundry alloys, have been carried out on grain refinement revealing how the TiB2 particles present in AlTi5B1 master alloy provide a germ for heterogeneous nucleation; however, these particles become efficient grain refiners only with excess Ti content. This condition can not only increase the nucleating potency of TiB2 particles, but also reduce the grain growth of primary &alpha; - Al crystals during solidification. At atomic scale the nucleating potency of TiB2 is dictated by the mismatch between the lattice of this particle and the nucleating phase. The performance of AlTi5B1, well established to be the best grain refiner for cast aluminium alloys as AlSi7Mg0.3 and AlSi12Cu2. Producer of the master alloys as AlTi5B1 guarantee the chemical composition but not size of particles that are very important for solidification process. This review focuses on the quality of five AlTi5B1 master alloys.

Influence of AlTi3C0.15 modification treatment on damping properties of ZnAl10 alloy

Zn-Al alloys constitute an interesting group of foundry alloys. Due to a relatively low melting temperature, they allow a decrease in energy-consumption of the melting process and alloy preparation. The vibration damping ability is one of the most interesting properties of the Zn-Al alloys. Zn-Al alloys are divided into two groups: the low-aluminium and high-aluminium alloys. The investigated Zn-10wt.% Al (ZnAl10) alloy is representative of the high-aluminium alloys, which, on account of its tendency of forming coarse-grained structures, has rather low plastic properties, including elongation. In order to improve the plastic properties, a modification treatment is usually applied. The dependence of the damping coefficient of the ultrasound wave on the amount of the introduced inoculant was studied. Investigations were performed using the AlTi3C0.15 inoculant as the modifier of the ZnAl10 alloy. It was found that titanium additions, in a range from 25 to 100 ppm in relation to the melted charge mass, can reduce the damping coefficient value. An increase of the inoculant addition causes a rise of the damping coefficient, which is probably related to the scattering of the ultrasound wave on Al3Ti and TiC particles introduced with the inoculant.

Enhancement of mechanical properties in high silicon gravity cast AlSi9Mg alloy refined by Al3Ti3B master alloy

The microstructure and mechanical properties of high silicon Al9Si0.45Mg alloys without grain refinement and refined by Al5Ti1B and Al3Ti3B master alloys were investigated. The results showed that the primary α–Al grain sizes were 1288 ± 361µm and 645 ± 146µm in the non–refined and Al5Ti1B refined alloys respectively, and that was decreased significantly to 326 ± 116µm in Al3Ti3B refined alloy. After T6 heat treatment, the yield strength, ultimate tensile strength and elongation of the non–refined alloy were 298 ± 2MPa, 350 ± 2MPa and 4.5 ± 0.7% separately. When the grain refiner was changed from Al5Ti1B to Al3Ti3B, the yield strength was increased from 304 ± 2MPa to 311 ± 1MPa, the ultimate tensile strength was increased from 357 ± 3MPa to 366 ± 1MPa, and the elongation was increased significantly by 38.8% from 8.0 ± 1.0% to 11.1 ± 1.2%. The Hall–Petch relation between the yield strength and grain size of the heat–treated alloys was determined as σy = 285.1 + 470.2·d−1/2. It was found that β'' phase was precipitated from the α–Al matrix for the peak strengthening of the heat–treated alloys. TiB2 and TiAl3 particles were found coexisting in Al5Ti1B master alloy, while TiB2 and AlB2 particles were verified coexisting in Al3Ti3B master alloy. The inoculation of AlB2 particles results in the significant grain refinement under Al3Ti3B. The increase of strength in the Al3Ti3B refined alloy is attributed to the refinement of the primary α–Al grains, while the increase of ductility in the Al3Ti3B refined alloy resulted from the reduced oxides and porosity defects as well as decreased grain size.

Influence of Annealing of Al-5Ti-1B Master Alloy on Hot Tearing of Cast Al-7Si-3Cu Alloy

Hot tearing is a common and severe defect encountered in aluminium alloys castings. It is affected by alloy composition as well as processing conditions and variables. In Al–7Si-3Cu presence of copper increases mechanical properties of the alloy, but it makes the alloy susceptible to hot tearing. The observations on the microstructures and the fracture surfaces propose that the hot tearing initiated at the grain boundaries and propagated along them through the thin liquid film. Grain refinement limits the hot tearing tendency of the Al-Si-Cu alloy. An attempt has been made to record the effect of annealed Al-5Ti-1B master alloy on minimizing hot tearing tendency in the gravity die cast of Al-7Si-3Cu alloys. It is observed that grain refining efficiency of Al-5Ti-1B master alloy is increased with increase in annealing temperature. This is attributed to the increased fraction of TiAl3 particles and the possible formation of (Ti,Al)B2 phase. Characterization study has been carried out by OM, SEM and XRD analysis.

Effect of Cooling Rate on Morphology of TiAl3 Particles in Al-4Ti Master Alloy.

The Al–4Ti master alloy was fabricated by aluminum (Al) and sponge titanium particle in a resistance furnace at different cooling rates. This work aims to investigate the relationship between the cooling rate and morphology of TiAl3. The microstructure and composition of master alloys at different cooling rates were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and SEM with energy dispersive spectroscopy (EDS). The results showed that various morphologies of TiAl3 particles in the Al–4Ti master alloy could be acquired at different cooling rates. Petal-like, blocky, and flake-like TiAl3 particles in the Al–4Ti master alloy were respectively acquired at the cooling rates of 3.36 K/s, 2.57 K/s, and 0.31 K/s. It was also found that the morphology of TiAl3 particles in the prepared master alloy changed from petal-like to blocky, then finally to flake-like, with the decrease of cooling rate. In addition, the morphology of the TiAl3 particles has no effect on the phase inversion temperature of Al–4Ti master alloy.

Performance of Al–5Ti–1B Master Alloy After Ball Milling on Minimizing Hot Tearing in Al–7Si–3Cu Alloy

Hot tearing of Al–7Si–3Cu alloys with addition of as received Al–5Ti–1B grain refiner and ball milled grain refiner have been studied with constrained mould casting to investigate the effect of these additions on hot tear resistance. Al–5Ti–1B master alloy contains TiAl3 and sub-microscopic TiB2 particles of sizes, 20–80 and 0.5–2 µm respectively. After ball milling of Al–5Ti–1B master alloy, TiAl3 particles get reduced in size from 80 to 9 µm. Thus the number of finer TiAl3 particles increases, resulting in improvement of grain refining performance of the grain refiner and thus eliminating hot tearing.

Microstructures and Mechanical Properties of Al-Si-Mg-Ti/Egg Shell Particulate Composites

Al-Si-Mg-Ti alloys reinforced with egg shell particles were synthesized by stir casting process. Microstructures of the fabricated composites were examined using colour metallographic technique and the mechanical properties of the composites: elastic behaviour, ultimate tensile strength and fracture toughness were investigated using tensile studies. The dispersion of egg shell particles found easier as their specific gravity matches with aluminium alloys. The microstructure of the Al/Egg shell composites revealed aluminium matrix, hard intermetallic phase consisting of Al2Si, Mg2Si, Al3Ti and dispersed particles of CaO. The intermetallic phases found segregated along interdendritic arms. The addition of egg shell also resulted in grain refinement of Al alloys. The yield strength and UTS showed both increasing and decreasing trends. At lower wt.% of egg shell the tensile strength decreased due to formation of rosette grouping. However higher additions (>1.5 wt.%) had increased yield strength and UTS. The yield point of Al alloys became obvious by the addition of egg shell particles.

Microstructure and grain refining performance of equal-channel angular-pressed Al–5%Ti–1%B master alloy on pure aluminum

Al–5%Ti–1%B master alloy was subjected to equal-channel angular pressing (ECAP) by route A at room temperature. The effect of the ECAP on the size and the distribution of Al3Ti and TiB2 particles, the fading resistance of the Al–5%Ti–1%B master alloy and the grain refining performance of pure Al ingots with the addition of the Al–5%Ti–1%B master alloy before and after ECAP have been investigated. The large platelet Al3Ti particles were fragmented into fine blocky Al3Ti particles from ~88 to ~25 μm after eight ECAP passes, and the TiB2 particles were well dispersed in the Al matrix. It has been revealed that grain refining efficiency was improved by adding the Al–5%Ti–1%B master alloy after ECAP to the Al melt. The mean grain size of α-Al was decreased from ~1220 to ~70 μm with increasing the number of ECAP passes. It has been proved that the grain size of α-Al could be well fitted by the length of Al3Ti particles and the growth restrict factor. Al–5%Ti–1%B master alloy after four ECAP passes appeared to have a better fading resistance due to fine blocky Al3Ti particles.

Effects of Ti Powder Additions in Melt-SHS Process on the Performance of Al-Ti-B Grain Refiner Alloys

Melt-SHS (Self-propagating High-temperature Synthesis) was used for the preparation of Al–5Ti–1B master alloy. The quality ratio of Ti powder/TiO2 in initial powder mixture was varied from 0:1 to 1:0. The AES, XRD and SEM were applied to evaluate the microstructure and phase componet. The results showed that the Al-5Ti-1B master alloy could be successful produced by the reaction of Al powder, TiO2 and H3BO3 in Al melt, while the reaction rate was slow. The microstructure mainly presents the TiAl3 particles with long strip shape. A significant improvement was noted both in reaction rate and in the grain refining efficiency when Ti powder was added to the reactants and the optimized ratio of Ti powder/TiO2 was 2:3. The TiAl3 particles were reduced and the grain refining efficiency turned bad when Ti powder was totally used to supply Ti

Grain Refinement Efficiency in Commercial-Purity Aluminum Influenced by the Addition of Al-4Ti Master Alloys with Varying TiAl₃ Particles.

A series of Al-4Ti master alloys with various TiAl3 particles were prepared via pouring the pure aluminum added with K2TiF6 or sponge titanium into three different molds made of graphite, copper, and sand. The microstructure and morphology of TiAl3 particles were characterized and analyzed by scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The microstructure of TiAl3 particles in Al-4Ti master alloys and their grain refinement efficiency in commercial-purity aluminum were investigated in this study. Results show that there were three different morphologies of TiAl3 particles in Al-4Ti master alloys: petal-like structures, blocky structures, and flaky structures. The Al-4Ti master alloy with blocky TiAl3 particles had better and more stable grain refinement efficiency than the master alloys with petal-like and flaky TiAl3 particles. The average grain size of the refined commercial-purity aluminum always hereditarily followed the size of the original TiAl3 particles. In addition, the grain refinement efficiency of Al-4Ti master alloys with the same morphology, size, and distribution of TiAl3 particles prepared through different processes was almost identical.