TiAl Phase Research Articles

Hybrid additive manufacturing of ceramic/aluminum-titanium gradient composites via arc and laser cladding eutectic pools

ABSTRACT There is a great deal of interest in improving the efficiency of arc-directed energy deposition (Arc-DED) of aluminium matrix composites and the uniform introduction of reinforcing particles. In this work, ceramic/aluminum-titanium gradient composites were manufactured by hybrid additive manufacturing with arc and laser cladding eutectic pools. The results show that the laser cladding powder feed method can have a higher powder capture rate compared to bypass feeding. Coupling the laser and powder changed the pulsed base-arc characteristics and increased the peak arc length. After the addition of the powder mixture, the aluminium matrix formed an Al3Ti reinforced phase, which evolved from needles to rods as the amount of powder increased. As the content of ceramic particles and the Al3Ti phase increased, the average hardness of the AMC components increased from 55.5–126 HV0.1 and the wear rate decreased from 6.16 × 10−3–1.25 × 10.−3 mm3·N−1·m−1.

Effect of Al Addition to Mg Melt on Microstructure of Mg-Ti Composites in Liquid Metal Dealloying Process

This study investigates the effect of adding Al to Mg molten metal on the microstructural characteristics and hardness of Mg-Ti composites fabricated via a liquid metal dealloying (LMD) process. The addition of Al to the Mg melt significantly reduces the dealloying rate of Cu in a Ti30Cu70 precursor during LMD. The rapid reaction of Al atoms with Ti results in the formation of a Ti3Al phase, which in turn inhibits the spinodal decomposition of Ti and Cu. This inhibition decreases the formation rate of α-Mg channels, thereby slowing down the dealloying process of Cu. As a result, as the Al content in the Mg melt increases from 0 to 3 to 6 wt%, the residual Cu content in the composite substantially increases from 0 to 42 wt%. The main phases comprising the composite change from Mg and Ti for the composite using a pure Mg melt to TixCuy, TixAly, and MgxCuy for the composites using Mg-Al melts. The hardnesses of the composites fabricated using the Mg-3Al and Mg-6Al melts are 344 and 354 Hv, respectively, which are more than twice that of the composite fabricated using the pure Mg melt (116 Hv). These results demonstrate that adding small amounts of Al to Mg melt considerably influences the dealloying behavior during LMD as well as the resultant microstructure and mechanical properties of the Mg-Ti composite.

Effect of Al-Ti-B-Er on the Microstructure and Properties of Ultrahigh-Strength Aluminum Alloy

To refine the grain size and improve the mechanical properties of ultrahigh-strength aluminum alloy (Al-10Zn-1.9Mg-1.6Cu-0.12Zr), the Al-Ti-B-Er grain refiner was prepared by the melt reaction method using the aluminum melt and Al + Ti + B precursor. The results exhibit that the Al-Ti-B-Er grain refiner is mainly composed of a block TiAl3 phase, and loose agglomerated nano-sized TiB2 and Al3Er phases. The microstructure of ultrahigh-strength aluminum is significantly affected by the Al-Ti-B-Er refiner, which changes from dendrite to equiaxial grain with increasing Al-Ti-B-Er content, and the size of the eutectic phase is significantly refined. The high-efficiency refinement of Al-Ti-B-Er is due to Er promoting the uniform distribution of TiAl3 particles and the formation of loose agglomerated nano-sized TiB2 particles. The optimal addition content of Al-Ti-B-Er into ultrahigh-strength aluminum alloys is 1 wt%, whose grain size is approximately 40 µm. Additionally, the strength and ductility of ultrahigh-strength aluminum alloys are simultaneously improved by adding 1wt% Al-Ti-B-Er after the T6 treatment, reaching 756 MPa and 20%, respectively. This enhancement in strength and ductility is mainly attributed to grain refinement and the eutectic phase refinement.

Hot Deformation Constitutive Analysis and Processing Maps of Ultrasonic Melt Treated A5052 Alloy.

Hot deformation constitutive analysis and processing maps of ultrasonic melt treated (UST) A5052 alloy were carried out based on a hot torsion test in this study. The addition of the Al-Ti master alloy as a grain refiner with no UST produced a finer grain size than the UST and pure Ti sonotrode. The Al3Ti phase particles in the case of the Al-10Ti master alloy acted as a nucleus for grain refinement, while the Ti atoms dissolved in the melt from the sonotrode were considered to have less of a grain refinement effect, even under UST conditions, than the Al3Ti phase particles in the Al-Ti master alloy. The constitutive equations for each experimental condition by torsion test were derived. In the processing maps examined in this study, the flow instability region was not present under UST in the as-cast condition, but it existed under the no UST condition. The effects of UST examined in this study are considered as (i) the uniform distribution of Ti solutes from the sonotrode and (ii) the reduction of pores by the degassing effect. After the homogenization heat treatment, most instability regions disappeared because the microstructures became uniform following the decomposition of intermetallic compounds and distribution of solute elements.

Enhancing Microstructural Characteristics and Mechanical Properties of Ti-Al-Dy Alloy through Ball Milling and SPS Consolidation

In this study, pure Ti, Al, Dy powders were ball-milled with zirconia balls in argon atmosphere for 3 h at 800 rpm, producing a Ti- 6 wt.% Al- 4 wt.% Dy alloy powder. The alloy powder was consolidated by SPS technique at 1373 K for 15 min under 50 MPa pressure in vacuum. The sintered body had approximately 99% in density and 6 μm in grain size. XRD and TEM revealed the presence of the second phases such as Ti3Al, Al3Dy and Ti4Al20Dy phases, and their sizes were approximately 50 nm. Microhardness was approximately 960 Hv at room temperature, which decreased as temperature increased. However, there remained the micro-hardness significantly higher compared to the commercial Ti-6Al-4V alloy. After hardness test at 1173 K, XRD analysis did not show any difference in peaks, while the grain size and second phases size increased by ~4 μm and ~2 nm, respectively.

Research on microstructure and properties of laser cladding Ti-Al-WC composite coating on TC4 surface

Abstract To improve the surface properties of TC4, laser cladding was used to prepare Ti-Al-WC composite coatings with varying WC content on the surface of TC4. XRD and SEM were used to examine the physical phase composition and microstructure of the coatings. At various WC contents, the microhardness distribution and wear friction properties of the coatings were also examined. The results revealed a strong metallurgical connection between the cladding layer and the matrix. When no WC was present, the coating was mostly formed of TiAl and Ti3Al phases; however, when WC was present, the coating also contained WC, TiC, W2C, and MAX phases, as well as a minor amount of partially dissolved WC particles. When compared to the substrate, the average hardness of the coating was increased by 1.08-1.76 times. When the WC content was 20 and the wear amount was 1.9 mg, the best wear resistance was obtained. Mainly abrasive and adhesive wear was observed.

Insights into the effects of La on the grain refinement and mechanical properties of Al-Ti-C intermediate alloy and pure Al: A first-principle study and experimental investigation

This paper employs the self-propagating high-temperature synthesis (SHS) to prepare Al-Ti-C master alloys and explores the effects of integrating the rare earth element lanthanum to create Al-Ti-C-La composites. This research focuses on the microstructural changes in both the master alloy and pure aluminum, which aimed to elucidate the mechanisms that enhance grain refinement and resistance to grain refinement fading. The analysis reveals that when Al-Ti-C-La master alloys are incorporated into molten Al, the predominant structures formed include an Al matrix, rod-like Al3Ti phases, and TiC particles, alongside AlLa phases and substantial Al20Ti2La compounds. The grain refining capability of Al-Ti-C-La master alloys is significantly exceeds that of the Al-Ti-C master alloys. The addition of La markedly reduces the settling of TiC particles, thereby granting the Al-Ti-C-La master alloys excellent resistance to grain refinement fading. The newly formed Al20Ti2La phase plays a crucial role in refining the aluminum matrix, with metallic bond characteristics present on the side towards the Al matrix at the Al20Ti2La/Al interface and distinct covalent bond characteristics on the Al20Ti2La side. Moreover, the Al20Ti2La (110)/Al (110) interface exhibits the highest interfacial adhesion energy and stronger covalent bond features. Consequently, α-Al is prone to heterogeneously nucleate on the Al20Ti2La phase via the Al20Ti2La (110)/Al (110)-HCP orientation, which refines the grains of the aluminum matrix, ultimately enhancing the performance of aluminum-based alloys.

Mechanism and growth kinetics of Al3Ti phase in fifteen-layered Ti Gr.1/A1050 clads produced with the explosive welding technique

This study was dedicated to the detailed characterization of the microstructural changes and the phase analysis of the interfaces formed in explosive welding of multilayered Ti Gr.1/A1050 clads. The significant effect of the detonation source localization on the microstructure of the welded materials interfaces after collision, and consequently on the diffusion processes induced by the elevated temperature was showed. Annealing process at 550 °C for series of time intervals of the Ti/Al clad allowed to determine the growth mechanism of the Al3Ti phase formed along particular interfaces. Moreover, the microstructure observations and calculations evidenced different growth mechanisms related to the localization of the Ti/Al interface in respect to the detonation source.

Microstructure and mechanical properties of Ti modified 7075 aluminum alloy fabricated by selective laser melting

In this study, Ti/7075 aluminum alloy samples were successfully prepared by selective laser melting (SLM). The effects of process parameters and solution treatment on the microstructure and mechanical properties were studied. Research shows that when the laser power is 270 W, the scanning speed is 600 mm/s, and the laser energy density is 166.67 J/mm3, the density of the Ti-added composite powder sample increases from 96.63% to 97.30% compared to the 7075 sample. Ti reacts in situ to generate the Al3Ti phase during the SLM process. Al3Ti has a heterogeneous nucleation effect, which can promote the transformation of columnar crystals into equiaxed crystals and inhibit the occurrence of anisotropy and hot cracks to a certain extent. The average grain size of the sample was refined from 18.71 μm to 2.24 μm. Under the optimal process parameters, the room temperature tensile strength of the as-deposited Ti/7075 aluminum alloy is 358 MPa, and the elongation is 15.5%. After solution treatment, the performance is further improved, the tensile strength is increased to 442 MPa, and the elongation is increased to 20.1%.

Investigation on the interface bonding and reinforcement mechanism of nano Ti/AZ31 magnesium matrix composites

In this study, nano Ti/AZ31 composites were successfully prepared by powder metallurgy method, and the strength and plasticity of the composites were improved in both directions. The SEM shows that the Ti particles were evenly distributed at the grain boundary in the sintered composite, and the Ti particles pin the grain boundary to make the grain of the composite significantly refined. EBSD shows that the addition of nano Ti particles significantly reduces the texture strength of the composite and increases the starting probability of the slip system. TEM shows that nano Ti and AZ31 matrix formed stable Al3Ti and MgO phases at the interface, and shows a strong coherent relationship. The nanoindentation test shows that the Ti/AZ31 interface of the composite was stable, the interface bonding energy and interface fracture toughness were gradiently distributed, and the bonding energy and fracture toughness of the interface bonding area were better than those of the matrix. Tensile test shows that the 1.5 wt%Ti/AZ31 composite obtained the best comprehensive mechanical properties with yield strength, ultimate tensile strength and elongation of 143 MPa, 243 MPa and 11.5%, respectively, obviously higher than those of AZ31 alloys. The increased strength was mainly due to the grain refinement and strengthening at grain boundaries. The improved ductility was the result of weakened texture, increase of slip system start-up probability and strong interfacial bonding between Ti particles and AZ31 matrix.

Effect of Adding Al on the Phase Structure and Gettering Performance of TiZrV Non-Evaporable Getter Materials.

Titanium zirconium vanadium (TiZrV) is a widely used non-evaporable getter (NEG) material with the characteristics of a low activation temperature and a large gas absorption capacity. At present, the research on TiZrV getters mainly focuses on the thin-film state, with little research on the bulk state. In this paper, a TiZrV getter was optimized by adding Al, and the phase structure, activation properties, and gettering performance were studied. With the addition of Al, the α-Zr phase and Ti2Zr phase changed into the Ti-Zr phase and Al-Zr, Al-Ti phase. The newly generated phase promoted the diffusion of hydrogen and oxygen atoms. The activation temperature decreased significantly, as shown in the in situ XPS results. The H2 and CO gettering performance of TiZrVAl samples was promoted to 2073 cm3·s-1 and 1912.8 cm3·s-1, increased by 40.7% and 40.3%. This paper provides valuable ideas for optimizing the properties of bulk TiZrV getters.

Simultaneously improved the strength and ductility of cast Al-3Li-2Cu alloy by Ti addition and heat treatment

This work systematically investigated the impact of minor Ti addition and heat treatment on grain structure, precipitates, precipitate-free zone (PFZ), and the performance of the Al-3Li-2Cu alloy. Minor Ti addition significantly refines the as-cast alloy, leading to a transition from columnar grains to equiaxed grains. The primary Al3Ti phases, with a low mismatch (0.99%) to the matrix, act as heterogeneous nucleation sites for α-Al, while the presence of Ti solutes restricts grain growth. As a result, the average grain size can be refined to 35.2 μm by adding 0.2 wt% Ti. Besides, minor Ti addition affects the corresponding precipitation behavior of the alloy. Detailed TEM observations reveal that the addition of Ti inhibits the growth of δ’(Al3Li) precipitates and the accompanying δ’-PFZ, which should be related to the interaction between Ti solutes and vacancies. Besides, reducing the aging temperature exerts a similar effect. Finally, the 0.2 wt% Ti-modified alloy exhibits excellent mechanical properties after aging at 175 °C for 8 h. It demonstrates a high yield strength (272 MPa), a high ultimate tensile strength (399 MPa), and an acceptable elongation (5.9%), which represent an increase of 8.8%, 34.8%, and 293.3%, respectively, compared to the alloy without Ti addition. The simultaneous improvement in strength and ductility is attributed to the presence of fine and equiaxed grains, high-density and homogenous δ’ precipitates, and a narrow δ’-PFZ. In-depth discussions are provided to elucidate the underlying mechanisms governing the microstructure and mechanical properties.

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.

Exploration of TiAl3 Phase Nucleation Mechanism in Al–5Ti–B Master Alloy

Exploration of TiAl3 Phase Nucleation Mechanism in Al–5Ti–B Master Alloy

Brazing Temperature Effects on the Microstructure and Mechanical Properties of Ti-45Al-8Nb Joints Using TiZrCuNi Amorphous Interlayer

Ti-45Al-8Nb alloy is widely utilized in the lightweight design of the aerospace field because of its excellent properties. In order to make full use of this alloy, it is important to carry out relevant research, such as into the joining process of Ti-45Al-8Nb alloy. In this work, Ti-45Al-8Nb alloys were successfully connected by a TiZrCuNi amorphous interlayer, which was fabricated using the rapid solidification method. Ti-45Al-8Nb joints were composed of two zones. The typical microstructure of a Ti-45Al-8Nb joint was Ti-45Al-8Nb/AlCuTi + Ti3Al/(Ti, Zr)(Cu, Ni) + (Ti, Zr)2(Cu, Ni)/Ti3Al + AlCuTi/Ti-45Al-8Nb. The diffusion of elements between the interlayer and the substrate was enhanced by increasing the brazing temperature, which resulted in an increase in the thickness of the interfacial reaction layer. The maximum shear strength was 171.2 MPa, which was obtained at 930 °C. The typical cleavage fracture was found in all of the Ti-45Al-8Nb joints. The mechanical properties of the joint were compromised at high brazing temperature due to the presence of excessive (Ti, Zr)2(Cu, Ni) phase and coarse Ti3Al phase, both of which are inherently brittle and harmful to the shear strength of the obtained joint.

Tailoring the microstructure of Al/Ti laminated composite through hot press sintering process to achieve superior mechanical properties

A novel method based on hot press sintering was proposed to fabricate the Al/Ti laminated composite, and the effects of sintering parameters on microstructure, interfacial structure, and mechanical properties were thoughtful examined. The results showed that insufficient sintering caused obvious voids and cracks at Al/Ti interface. With the increase of temperature or holding time, a good metallurgical bonding without defects was achieved, and both the recrystallization fraction and grain size of α phase in Ti layer increased, accompanied by the transformation of α to β phase and growth of intermetallic phase. The microstructure variation of Al layer is not evident with changing the sintering parameters. Due to the relatively low formation energy, the nanoscale TiAl3 phase with massive stacking faults formed at Al/Ti interface, and lots of dislocations existed at Al layer near the interface. The voids and cracks formed at Al/Ti interface led to the premature failure of laminate. On the basis of the metallurgical bonding and small TiAl3 phase, the high fraction and texture intensity of α phase were the dominated strengthening factors. Moreover, the back stress generated at Al/Ti interface contributes to an extra strengthening. The superior mechanical properties of Al/Ti laminate with a tensile strength of 670.9 MPa and a fracture strain of 0.33 were obtained with the sintering temperature of 600 °C and holding time of 2 h.

Thermal analyses and weight gain modeling study on Ti–Al – based intermetallic coated Ti6Al4V alloy

Abstract Ti6Al4V alloy is a commonly used α + β alloy among titanium alloys. In this study, in order to improve the oxidation resistance of the Ti6Al4V alloy, Ti–Al – based aluminum coating was deposited to the surface by the pack cementation method. The aluminizing process was carried out in an open atmosphere oven at 700 °C for 4 and 6 h. It has been observed that the coating layer thickness varies between 13 and 17 µm depending on the duration of cementation process. From XRD analysis, it has been detected the TiAl3, TiAl2, and TiAl phases on the coating layer. Aluminum coated and untreated Ti6Al4V alloys were subjected to oxidation tests at 800, 850, and 900 °C for 4, 20, and 40 h. The obtained nonlinear weight gain characteristic has been modeled to determine the coating status of the samples. It was determined that the highest weight gain was in the untreated sample. Using the provided model, samples were classified in terms of coating condition by systematic approach based on weight gain profile versus time. Oxidation tests also supported with DTA and TG analyses.

Cermet Powders Based on TiAl Intermetallic for Thermal Spraying

The paper presents a study of the formation process of cermet powders based on TiAl intermetallic with the addition of non-metallic refractory compounds. Non-metallic refractory compounds B4C, BN, SiC, and Si3N4 were chosen as strengthening components, improving the mechanical properties and resistance to high-temperature oxidation of TiAl-type intermetallic coatings. The composition of the initial mixtures was selected based on thermodynamic analysis of the interaction between TiAl intermetallic and non-metallic refractory compounds. As a result of the mechanochemical synthesis of powder mixtures, 73TiAl-27B4C, 69TiAl-31BN, 88TiAl-12SiC, and 83TiAl-17Si3N4 (wt. %) cermet powders are formed, consisting of titanium aluminide (TiAl, Ti3Al) phases and refractory compounds of aluminium (AlB2 and AlN) and titanium (TiB2, TiC, TiN, Ti5Si3). The conglomeration technology of produced cermet powders has been developed to enhance fluidity. Using conglomerated powders will provide their constant feed to the high-temperature jet and the formation of dense coatings during thermal spraying.

Combustion-synthesised TiAl/NiAl layered intermetallic composite: synthesis, phase composition, and microstructure

ABSTRACT The joining of different intermetallics (e.g. NiAl, TiAl) is important for high-temperature applications. In this study, self-propagating high-temperature synthesis was used for simultaneous joining of (Ni+Al) and (Ti+Al) layered samples of the stoichiometric compositions. The main advantage of such joining by self-propagating high-temperature synthesis is that it could be done at ambient temperature without the use of a furnace. The applied load during combustion synthesis was used to improve the contact between the Ni-Al and Ti-Al layers. The obtained results demonstrate that TiAl/NiAl intermetallics were successfully joined together with a bonding interface of about 170 μm thickness. XRD analysis has shown that the joining area consists of NiAl, TiAl, Ti3Al, and NiTiAl2 phases. The SEM data analysis of the transition zone of NiAl-TiAl conjunction has revealed that the transition zone consists of several intermediate layers: a polycrystalline NiAl layer; an intermediate layer based on Ni-Al-Ti containing NiTiAl2 phase; a layer based on Ni-Al-Ti with mixed dendritic and eutectic regions; and a polycrystalline TiAl layer.The measured microhardness of the transition zone varies from 3200 up to 13,600 MPa with the maximum microhardness of 1355 ± 45 MPa corresponding to the layer identified as the NiTiAl2 phase.

Enhanced strength and ductility of oscillating laser additive manufactured aluminum alloys with micron-sized Ti3AlC2 MAX-phase

Excellent balance of strength and ductility was achieved in oscillating laser additive manufactured aluminum alloys by adding the micron-sized Ti3AlC2 phase, avoiding the aggregation of conventional nano-ceramic phases at grain boundaries. The printed 2024Al alloys samples exhibit a fully equiaxed and refined grain structure, attributed to the solid-phase transformation of the Ti3AlC2 phase, and its in-situ release of Ti atoms to form the Al3Ti phase, providing heterogeneous nucleation for grain refinement. Also, the introduced Ti3AlC2 particles transformed into the Al3Ti phase and the precipitated clusters of TiC and Ti3AlC, where TiC concentrated in the outer region forms a low-mismatch semi-coherent interface with the aluminum matrix. Finally, the printed samples had a yield strength of 255 MPa, a tensile strength of 423 MPa, and an elongation to failure of 13.2%.