Al3Ti Particles Research Articles

Effect of equal channel angular pressing on microstructure and grain refining performance of Al–5%Ti master alloy

The Al–5%Ti master alloy has been subjected to the equal channel angular pressing (ECAP) by route A at room temperature, and the grain refining performance of Al–5%Ti master alloy before and after ECAP with the use of an industrial purity Al has been evaluated. The effects of the ECAP on the size and the distribution of the TiAl3 particles, grain size, microhardness and electrical conductivity of pure Al ingots with and without adding the Al–5%Ti master alloy have been investigated. The large platelet-like TiAl3 particles were fragmented into the fine blocky TiAl3 particles from ∼270μm to ∼13μm uniformly distributed in the Al matrix after three ECAP passes. It has been revealed that microhardness of pure Al cast samples have been increased by adding the Al–5%Ti master alloy processed by ECAP; however, the electrical conductivity has deteriorated. The Al–5%Ti refiner processed by ECAP appeared to have an enhancing grain refining effect in comparison with that before ECAP. It has been proved that the grain size of α-Al could be well fitted by the length of TiAl3 particles and the growth restriction factor. The conclusion has been made that it is practical to enhance the grain refining effectiveness of the Al–5%Ti master alloy through the ECAP process by no more than three passes.

Microstructure of <i>In Situ</i> Particles/7055Al Matrix Composites with Deep Cryogenic Treatment

Al2O3，Al3Ti and Al3Zr particles reinforced 7055 aluminium matrix composites were fabricated via melt reaction method. The volume fraction is controlled at about 4-5%. After extrusion and solution-aging heat treatment the sample was prepared for deep cryogenic treatment, The microstructure and evolution of mechanical properties of (Al3Ti+Al3Zr)p/7055 composites were analyzed using optical microscopy(OM),scanning electronic microscopy(SEM) and X-ray diffraction(XRD). Some θ(Al2Cu) phases with nanometer size precipitate in the inner grain. As some grains preferred orient the intensity of some main diffraction peaks increase. Compared with those of as-cast and squeezed states the micro hardness has increased by 16.8% and 10.0% separately.

Reactive mechanism and mechanical properties of in situ composites fabricated from an Al–TiO2 system by friction stir processing

In situ (Al3Ti+Al2O3)/Al composites were fabricated from powder mixtures of Al and TiO2 using hot pressing, forging and subsequent multiple-pass friction stir processing (FSP). The reactive mechanism and mechanical properties of the FSPed composites were investigated. Four-pass FSP with 100% overlapping induced the Al–TiO2 reaction, as a result of the enhanced solid diffusion and mechanical activation effect caused by the severe deformation of FSP. Decreasing the size of TiO2 from 450 to 150nm resulted in the formation of more Al3Ti and Al2O3 particles. The formation mechanisms of Al2O3 and Al3Ti during FSP are understood to be a deformation-assisted interfacial reaction and deformation-assisted solution-precipitation, respectively, based on detailed microstructural observations. The microhardness, Young’s modulus and tensile strength of the FSPed composites were substantially enhanced compared with those of FSPed pure Al with the same processing history, and increased as the TiO2 size decreased from 450 to 150nm. The strengthening mechanisms of the FSPed composites included load transferring, grain refinement and Orowan strengthening, among which Orowan strengthening contributed the most to the yield strength of the composites.

Formation of Small Blocky Al3Ti Particles via Direct Reaction Between Solid Ti Powders and Liquid Al

The evolution of titanium powders in the pure aluminum melt at a lower temperature was studied in our research. The process involved some titanium powders being added into the pure aluminum melt at 1003 K (730 °C), and then the melt was cast into an ingot after 5 minutes. A reaction layer composed of some loose Al3Ti particles was formed on the solid Ti surface due to the reactive diffusion between titanium and aluminum. In-situ blocky Al3Ti particles smaller than 5 μm were produced in the aluminum matrix. A reaction-peeling model was suggested to illustrate the formation mechanism of Al3Ti particles, and a simple approach for fabricating in-situ Al3Ti/Al-alloy composites was proposed as well.

Al-Al3Ti nanocomposite produced in situ by two-step hot-press sintering

Aluminum reinforced with a large amount (up to about 55 vol.%) of Al3Ti particles can be fabricated from Al-20Ti elemental nanometer-sized powder mixture via in-situ two step hot press sintering (TSS). For production of intermetallic reinforced in-situ composite, TSS can provide elevated temperature to facilitate the formation of intermetallic phase in situ and hot consolidation to form a fully dense solid. The first step sintering was employed at a higher temperature to obtain an initial high density, and the second step was held at a lower temperature by isothermal sintering for more time than the first one to increase bulk density without significant grain growth. The optimum TSS regime consisted of heating at 625°C for 5 min (1st step) and 570°C for 40 min (2nd step) with applied pressure of 470 MPa, resulting in the formation of near full dense microstructure (0.97 TD) with suppressed grain growth.

In-situ synthesis of Al3Ti particles reinforced Al-based composite coating

Using titanium wires (99.5%, 200 μm in diameter) as a reactive source, an Al-based composite coating reinforced by titanium tri-aluminide (Al3Ti) particles was fabricated by infiltration plus in-situ methods. According to the differential thermal analysis (DTA) curve, the reactive temperature between Ti wires and Al matrix can be determined at 890 °C. The obtained composite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microhardness and wear test. The experimental results show that when holding period is 20 min at 890 °C, the titanium wires react completely to in-situ synthesize Al3Ti particles, which presents blocky and strip-like states. The microhardness of in-situ synthesized Al3Ti particles is about 4.5 times that of the Al-matrix. Under the condition of dry sliding at 10 N load, compared with the unreinforced Al matrix, the composite coating fabricated with 20 min offers unique wear resistance behavior, and its wear mechanism is that the adhesive wear and abrasive wear coexist.

Investigation of Wear Anisotropy in a Severely Deformed Al-Al3Ti Composite

In the current investigation, Al-Al3Ti composite was processed by equal channel angular pressing (ECAP). ECAP was carried out using routes A and BC up to eight passes of deformation. It was observed that increasing the number of ECAP passes causes fragmentation of Al3Ti platelet particles and decreases their sizes compared to their original sizes in the undeformed Al-Al3Ti specimens. Moreover, the microstructure of route A-ECAPed Al-Al3Ti composite samples showed a strong alignment of the fragmented Al3Ti particles parallel to the pressing axis. On the other hand, ECAPed Al-Al3Ti alloy specimens by route BC have a relatively homogeneous distribution of Al3Ti particles. Because of the platelet Al3Ti particle fragmentation by ECAP, all the ECAPed specimens showed small anisotropy in their wear property in spite of this observed anisotropic microstructure induced by route A-ECAP.

The Effect of Ti Addition and Aging on Wear Behavior of AlMgSi Alloys Reinforced with In Situ Al3Ti Particles

The purpose of this study is to investigate the effects of Ti addition (1 and 2% Ti) and aging heat treatment on the mechanical and wear characteristics of Al-12Si-20Mg cast alloys. In preliminary studies conducted to determine the aging parameters, cast alloys were kept at 550 °C for 2 h before being quenched into water and aged at 200 °C for five different periods (3, 6, 9, 12, and 15 h). As the specimen aged for 12 h had the highest hardness value, all the specimens were aged at 200 °C for 12 h. The microstructures of the as-cast and aged specimens were analyzed using an optical microscope and a scanning electron microscope. The hardness of the investigated alloys was measured by micro-hardness test. The wear tests were carried out using the pin-on-disk model wear test apparatus, and the results were evaluated according to weight loss. According to the wear test results, the wear behavior of the investigated alloys changed depending on the aging heat treatment applied and the load. While Ti addition and the aging heat treatment applied reduce the weight loss at low loads (5 N), they increase the weight loss at higher loads (10 and 20 N).

Preparation of <i>In Situ</i> Al<sub>3</sub>TiP/Al-Based Composite Coating

In the paper, titanium tri-aluminide (Al3Ti) particles reinforced aluminium (Al)-based composite coatings were fabricated by infiltration plus in-situ techniques at 891.3 °C. The obtained composite coatings are characterized by XRD, SEM and friction and wear testers. The experimental results show that the reaction between Ti wires and Al molten increases with extending time, Ti wires can totally transform into Al3Ti particles for 20 min, which present blocky and strip-like states, respectively. The wear rates of the composite coatings decrease with increasing time.

Wear Behaviors of AA 6063 Aluminum Alloys Reinforced with in situ Al3Ti Particles

The purpose of this study was to examine the microstructure and room temperature dry sliding wear performance of AA 6063 aluminum alloys containing up to 2% Ti under homogenized and heat-treated conditions. After casting, homogenizing heat treatment was applied to all produced alloys at 500°C for 2 h. Heat treatment included water quenching after being kept at 500°C for 2 h, and then an aging process was applied at four hour intervals up to 48 hours, at 150°C. The microstructure of the homogenized and aged alloys was analyzed using a scanning electron microscope (SEM). Hardness measurements were carried out using a microhardness test. Wear tests were performed using a ball-on-disc method by measuring the wear scar areas. Results of the wear tests proved that the wear rate decreased in alloys containing Ti. Though aging heat treatment improved the wear resistance of Ti-free alloys, the wear resistance of each of the alloys containing Ti decreased.

Enhancement of TiB Grain Refining Effect on A356 Gravity Die Casting with the Addition of Yttrium

The present work investigates the effect yttrium on the grain refining efficiency of Al-5Ti-1B in gravity die cast A356 aluminum alloy. A series of casting experiments were carried out in which the Ti and B contents were maintained constantly at 0.1 and 0.02 wt% respectively. The inoculation level of yttrium was manipulated at the amount of 0, 0.1, 0.2, 0.3, 0.4 and 0.5 wt%. Microstructural characterization of the as-cast A356 alloy was investigated by means of optical microscope and its phases are detected by XRD. XRF is used to determine the contents of inoculating elements such as Ti, B and Y so that their actual optimal ratio in the casting can be approximated. The mechanical properties tested are tensile strength and hardness. The inoculation of yttrium was found to enhance the grain refinement effect of Al-5Ti-1B grain refiner and improve the mechanical properties. The optimal weight percentage of yttrium was discovered to be 0.3. The grain refining efficiency of combining yttrium and Al-5Ti-1B on A356 aluminum alloy was mainly attributed to the heterogeneous nucleation of TiB2 and TiAl3 particles which were dispersed more evenly in the presence of yttrium and also as a result of α-Al grain growth restriction by AlY3compound precipitated at grain boundaries during solidification.

Fabrication Mechanism of in-Situ Synthesized Al<sub>3</sub>Ti-Mg Composites by Vacuum Hot-Pressing

For getting better properties and simplifying processes, the in-situ synthesized Al3Ti/Mg composites were prepared by vacuum hot-pressing. Phase composites and microstructures of composites were researched by methods such as XRD and SEM. The result indicated that fine Al3Ti particulates with size of 0.5~2.0 μm were distributed uniformly in Magnesium matrix and combined closely with the matrix. The mechanism of in-situ synthesized Al3Ti in Magnesium matrix was discussed and a model of micro structural reaction between Ti and Al was brought forward.

Effect of ultrasonic vibration on microstructural evolution of the reinforcements and degassing of in situ TiB 2p/Al–12Si–4Cu composites

Some issues such as clustering of TiB 2 particles, formation of long rod-like Al 3Ti particles, as well as high porosity level usually associate with the fabrication of in situ TiB 2p/Al-alloy composites via conventional stir casting technique using Ti and B as reactants. High-intensity ultrasonic vibration was introduced in our research to solve the above issues. The process involved that the original in situ TiB 2p/Al–12Si–4Cu sample with large clusters of TiB 2 particles, large long rod-like Al 3Ti particles and high porosity was remelted at 850 °C, and then ultrasonic vibration was applied to the melt with an ultrasonic probe. The microstructural evolution of the samples treated by ultrasonic vibration with different time was examined by using SEM. After treated by ultrasonic vibration for 12 min, large clusters of TiB 2 particles were broken up effectively and TiB 2 particles were dispersed uniformly in the matrix, and long rod-like Al 3Ti particles were turned into blocky ones with the size of 10 μm due to the effect of ultrasonic stirring. In the meantime, the porosity in the composites decreased from about 6.5% to 0.86% due to the effect of ultrasonic degassing. Microhardness test suggested that a homogeneous microstructure of the composite was achieved after ultrasonic treatment. An effective approach using high-intensity ultrasonic vibration to optimize the microstructures of the particulate reinforced Al-alloy composites was proposed, and the mechanism of the effect of high-intensity ultrasonic vibration on the microstructural evolution of the reinforcements and degassing of composites was also discussed in our research.

Formation mechanism of in situ Al 3Ti in Al matrix during hot pressing and subsequent friction stir processing

In situ Al 3Ti/Al composites were fabricated by a combination of vacuum hot pressing (VHP) and friction stir processing (FSP). The formation mechanism of the Al 3Ti and the effect of VHP and FSP parameters on the resultant microstructure and mechanical properties were investigated. The Al 3Ti formed due to the reactive diffusion between Al and Ti during VHP, and the number of Al 3Ti particles increased with increasing the temperature and holding time of the VHP. FSP not only induced the Al–Ti reaction, but also resulted in significant refining of the Al 3Ti, thereby creating a homogeneous distribution of Al 3Ti particles in the Al matrix. These microstructural changes led to significant improvement in the tensile properties of the in situ Al 3Ti/Al composite. However, the change trends of the tensile properties of the FSP samples were dependent on the extent of the Al–Ti reaction during VHP.

Effect of Temperature on the Performance of AlTiC Metal Alloys

AlTiC master alloys have been prepared by Contact Reaction Method（CRM）.X-ray diffraction，SEM and EDS were used to analyse the AlTiC master alloys. It showed that morphology and distribution of TiC and Al3Ti particle have correspondingly changed with the transformation of temperature. As a result, the change in morphology and distribution of TiC and Al3Ti particle has considerably affected the gain refining performance of AlTiC master alloys. The result showed that it had excellent grain refining performance for commercially pure aluminum in 800°C.

High temperature interfacial evolution of Ti3Al/Al reaction couples

High temperature interfacial evolution by reaction between liquid Al and solid Ti3Al has been studied by observation of reaction couples isothermally reacted at 700, 800 and 900°C for different time intervals between 1 and 60 min respectively. Only TiAl3 phase was detected in Al/Ti3Al reaction couples up to 900°C. The reaction zone consisted of aluminide particles dispersed in an Al rich matrix. However, microstructures in the inner, central and marginal regions of reaction zone were different and were continuously changing across the width of reaction zone. A model corresponding to evolution progress was drawn schematically. A water quenched experiment confirmed the restriction effect of dispersed TiAl3 particles to Al matrix and suggested that TiAl3p/Al composite could be fabricated by this in situ reaction method.

Microstructural evolution of reinforcements in the remelting in situ TiC/Al–12Si composites treated by ultrasonic vibration

Clusters of reinforced particles and long rod-like Al 3Ti particles are usually present in the matrix of in situ TiC/Al alloy composites fabricated via SHS reaction of the Al–Ti–C system in the molten aluminum alloys. In order to improve the properties of the composites, the above issues should be solved effectively. In our research, high-intensity ultrasonic vibration was introduced into the remelting TiC/Al–12Si composites containing clusters of TiC particles and long rod-like Al 3Ti phase to optimize the microstructure of the composites. The results of SEM showed that long rod-like Al 3Ti particles were turned into small blocky ones and large clusters were broken up into small ones. In the meantime, individual TiC particles could be peeled off from the clusters and distributed uniformly in the matrix. An in situ TiC/Al–12Si composite with a homogeneous microstructure was attained successfully. The evolution of the morphology of Al 3Ti phase and the clusters in the ultrasonic field was also discussed.

Effect of Al-Ti-B Based Master Alloys on Grain Refinement and Hot Tearing Susceptibility of AZ91E Magnesium Alloy

The objective of this study was to examine the potential of Al-5Ti-1B and Al-1Ti-3B master alloys in reducing the hot tearing susceptibility of AZ91E magnesium alloy. The low penetration of magnesium alloys for structural automotive applications can be attributed to their poor castability during permanent mould casting. An improvement in the castability of magnesium alloys will result in the production of larger castings for automotive applications and a reduction in vehicle weight. The addition levels examined for both master alloys were 0.1, 0.2, 0.5 and 1.0 wt.%. The master alloys were added to the AZ91E alloy and stirred for 30 seconds. For the graphite mould castings used to observe grain refinement, the pouring and mould temperatures were 720 and 750 °C respectively. The hot tear castings were produced using a “dog bone” shaped H-13 tool steel mould. The pouring and mould temperatures were 720 and 180 °C respectively. Without master alloy addition, the base AZ91E casting had severe hot tears. The addition of Al-5Ti-1B slightly reduced hot tears while Al-1Ti-3B addition significantly reduced hot tears. The addition of Al-1Ti-3B also significantly reduced the grain size of the castings from 113 µm in the base alloy to 72 µm with 1.0 wt.% addition. The addition of Al-5Ti-1B did not lead to a reduction of hot tears because of large TiAl3 particles acting as stress risers during solidification.

Ultrasound assisted in situ technique for the synthesis of particulate reinforced aluminum matrix composites

Clusters of particle-reinforcement and high porosity are usually present in the in situ particulate reinforced metal–matrix composites (MMCs) fabricated by conventional stir casting technique. We studied the effect of ultrasonic vibration on the microstructures of in situ particulate reinforced aluminum composites. The process involved the addition of titanium and graphite powders into the molten pure aluminum at 850°C. In the meantime, high intensity ultrasonic vibration was applied into the melt to disperse in situ formed particles into the matrix. Microstructural characterization indicated that in situ formed Al3Ti and TiC particles were distributed uniformly in the matrix and a homogeneous microstructure with a low porosity was gotten due to the effects of ultrasonic stirring and degassing. An effective approach using high intensity ultrasonic vibration to optimize the microstructure of in situ particulate reinforced metal matrix composites was given firstly, and the mechanism of ultrasonic vibration was also discussed.

Evaluation of Al-Ti-C Master Alloys as Grain Refiner for Aluminum and Its Alloys

Al-Ti-C master alloys have a great potential as efficient grain refiners for aluminum and its alloys. In the present work, the Al-Ti-C master alloys are synthesized via a relatively novel technique through the reaction of a compacted mixture of K2TiF6 and graphite with molten aluminum. The obtained alloys are examined using scanning electron microscopy (SEM), energy-dispersive spectroscopy, and X-ray diffraction (XRD) methods. The results indicate that the produced Al-Ti-C master alloys contain TiC and TiAl3 particles within the aluminum matrix. Also, these alloys were evaluated using the KBI test mold. The results indicate that the produced Al-Ti-C master alloy is an efficient grain refiner for pure aluminum and its alloys compared with the Al-Ti-B one. The factors affecting the grain refinement of aluminum and its alloys are studied. The proper conditions for evaluating the efficiency of the produced Al-Ti-C master alloy to obtain a minimum grain size are as follows: temperature, 993 K (720 °C); holding time, 2 minutes; and (Ti/Al) weight ratio, 0.01 pct.