3Ti Alloys Research Articles

Role of (Al, Ti) alloying and annealing temperature in precipitation, recrystallization, and mechanical properties of ferrous multi-component alloys

L12-precipitate-strengthened multi-component alloys (MCAs) possess exceptional combination of strength and ductility. However, the high production costs of L12-containing MCAs impede their industrial application. This study introduces a novel approach for designing cost-effective L12-containing MCAs by microalloying Al and Ti with a base composition of Fe50Ni30Cr20 (at%). Three types of MCAs were investigated in this study: Fe50.13Ni28.84Cr18.56Al1.39Ti1.08 (1Ti alloy), Fe46.53Ni27.32Cr19.91Al3.44Ti2.80 (3Ti alloy), and Fe48.51Ni25.93Cr15.75Al5.10Ti4.71 (5Ti alloy) (at%). An increase in the (Al, Ti) content from 1 to 3 at% accelerates the formation of L12 particles, whereas an increase in the (Al, Ti) content from 3 to 5 at% leads to the activation of the brittle B2 and D024 phases. The rapid co-precipitation of the L12, B2, and D024 phases in the 5Ti alloys substantially hinders recrystallization during annealing, whereas the 3Ti alloys exhibit the highest rate of recrystallization upon annealing at 600 and 700 °C, mainly due to the reduction in the stacking fault energy of the matrix. The 5Ti alloys exhibit the highest hardness and the lowest plasticity owing to the presence of brittle B2 and D024 precipitates. By contrast, the 3Ti alloy annealed at 600 °C, in which dense and relatively fine L12 particles precipitated, exhibits a superior combination of hardness and plasticity. This study provides insights into the composition and annealing condition-dependent precipitation, recrystallization, and mechanical properties of ferrous MCAs.

Deformation behavior and stress relaxation modeling of Cu–3Ti alloy prepared by a novel rolling process with the shortened passes

This study explores the effects of hot rolling with a shortened process on the microstructure and properties of Cu–3Ti alloy compared to the traditional multi-pass forming, and the finite element simulation was used to predict the experimental results. At the same time, the residual stress elimination model was used to provide prediction and reference for the relaxation of residual stress during the alloy annealing process. The residual stress of hot rolled samples through the shortened passes is reduced by an average of about 6.7 % after the appropriate annealing treatment, and accompanied by an obvious increase in the yield and tensile strengths compared to that of the traditional multi-pass forming. At the same time, this hot rolled sample by 90 % reduction with 9 passes contains a 45.7 % proportion of high-angle grain boundaries due to the occurrence of extensive dynamic recrystallization, which remains a good consistence with the higher strength under this condition.

Crystallography and diffraction patterns of the precipitates in Cu-3 wt% Ti alloy

Cu–Ti alloys are candidates for replacing Cu–Be alloys owing to their excellent mechanical properties, bending properties, and stress relaxation resistance. However, the precipitation behavior of Cu–Ti alloys remains poorly understood. In this study, diffraction patterns, orientations, and morphologies of continuous and discontinuous precipitates in a Cu–3 wt% Ti (Cu–3Ti) alloy are investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). In the peak-aging condition, numerous rod-like nanosized continuous precipitates (CP) of β′-Cu4Ti are uniformly distributed in the Cu–3Ti alloy. The CP retain their tetragonal structure, and their orientation relationships with the matrix are determined as [001]Cu//[001]β' and (010)Cu//(310)β', exhibiting six variants. With increasing aging time, discontinuous precipitates (DP) of β-Cu4Ti grow at the grain boundaries, displaying an orthorhombic structure (a = 0.453 nm, b = 0.4342 nm, and c = 1.293 nm). The orientation relationships between the DP and the Cu-matrix are determined as (Laughlin and Cahn, 1975; Han et al., 2016; Datta and Soffa, 1976; Han et al., 2020; Huang et al., 2023; Soffa and Laughlin, 2004; Wang et al., 2021; Si et al., 2016; Markandeya et al., 2004; Nagarjuna et al., 2001) [1-10]Cu//[501]β and (111)Cu//(010)β. Typical diffraction pattern models of the CP and DP in different directions were simulated, and the simulations were in good agreement with the experimental data.

Low-temperature wetting of sapphire using Sn–Ti active solder alloys

Monocrystalline alumina, known as sapphire, is one of the most commonly used ceramics in electronic devices. Understanding its wettability is thus of great importance for its engineering applications. In this work, the low-temperature wetting mechanisms of Sn–Ti active solder alloy on C-plane sapphire was comprehensively studied using the sessile drop method. The addition of 0.1 wt % Ti was found to effectively improve the wettability of Sn–Ti alloys, and the lowest contact angle on the sapphire substrate was achieved at 950 °C when Ti content was increased to 3 wt%. Thermal dynamics analysis and experimental results indicated that the isothermal spreading of Sn–3Ti alloy is controlled by the Ti adsorption in the vicinity of wetting triple line. Moreover, sapphire was successfully brazed using Sn–3Ti alloy at 500, 550, and 600 °C, and the maximum shear strength was measured as 30.3 MPa. Our understanding of the wettability of sapphire provides the fundamental theory for developing new bonding technique for this important crystal.

High Temperature Deformation Behavior of L12 Modified Titanium Trialuminides Doped with Chromium and Copper

Crystal structure of the L12 type (Al,X)3Ti alloy (X = Cr,Cu) is analyzed by X-ray diffractometry and the nonuniform strain behavior at high temperature is investigated. The lattice constants for the L12 type (Al,X)3Ti alloys decrease in the order of the atomic number of the substituted atom X, and the hardness tends to increase. In a compressive test at around 473K for Al67.5Ti25Cr7.5, Al65Ti25Cr10 and Al62.5Ti25Cu12.5 alloys, it is found that the stress-strain curves showed serration, and deformation rate dependence appeared. It is assumed that the generation of serration is due to dynamic strain aging caused by the diffusion of solute atoms. As a result, activation energy of 60-95 kJ/mol is obtained. This process does not require direct involvement. In order to investigate the generation of serrations in detail, compression tests are carried out under various conditions. As a result, in the strain rate range of this experiment, serration is found to occur after 470K at a certain critical strain. The critical strain increases as the strain rate increases at constant temperature, and the critical strain tends to decrease as temperature rises under constant strain rate. This tendency is common to all alloys produced. In the case of this alloy system, the serration at around 473K corresponds to the case in which the dislocation velocity is faster than the diffusion rate of interstitial solute atoms at low temperature.

Microstructure and properties of Cu–3Ti–1Ni alloy with aging process

The effects of Ni addition and aging treatment on the microstructure and properties of Cu–3Ti alloy were investigated. The microstructure and phase constituents were characterized by optical microscopy, scanning electron microscopy, X-ray diffractometer and high-resolution transmission electron microscopy, and the hardness and electrical conductivity were measured as well. The results show that NiTi phase forms with addition of Ni into as-cast Cu-3Ti alloy during solidification, and the as-cast microstructure evolves from dentrite to equiaxial structure. After aging treatment, coherent metastable β'-Cu4Ti precipitates from the Cu matrix. However, β'-Cu4Ti precipitation phase transforms into equilibrium, incoherent and lamellar Cu3Ti phase after overaging. Meanwhile, aging treatment results in appearance of annealing twins in the residual NiTi phase, and dislocation lines exist in the Cu matrix. Ni addition enhances the electrical conductivity, but decreases the hardness of Cu–3Ti alloy. In the range of experiments, the optimum aging treatment for Cu–3Ti–1Ni alloy is 300 °C for 2 h and 450 °C for 7 h. The hardness and electrical conductivity were HV 205 and 18.2%IACS (international annealed copper standard), respectively.

Investigating the Relationships Between Structures and Properties of Al Alloys Incorporated With Ti and Mg Inclusions

This study investigates the influence of titanium (Ti) and magnesium (Mg) additions on aluminum (Al) alloys in order to evaluate the relationship between the structure and properties of the new alloys. The alloys obtained at elevated temperatures mainly consist of Al–2Mg–1Ti, Al–2Mg–3Ti, Al–4Mg–2Ti, and Al–6Mg–2Ti alloys, as well as α and τ solid solution phases of intermetallic structures. Microstructural analyses were performed using X-ray diffraction (XRD), optical microscope, and energy dispersive spectrometry (EDS) techniques. Test results show that the average grain size of the alloys decreased with the addition of Ti inclusions during the casting and solidification processes, and the smallest grain size was found to be 90 μm for the Al–6Mg–3Ti alloy. In addition, tensile properties of the Al–Mg–Ti alloys were initially improved and then worsened after the addition of higher concentrations of Ti. The highest tensile and hardness values of the alloys were Al–4Mg–2Ti (205 MPa) and Al–6Mg–3Ti (80 BHN). The primary reasons for having higher mechanical properties may be attributed to strengthening of the solid solution and refinement of the grain size and shape during the solidification process. For this study, the optimum concentrations of Ti and Mg added to the Al alloys were 4 and 2 wt.%, respectively. This study may be useful for field researchers to develop new classes of Al alloys for various industrial applications.

Microstructure and properties of Cu–Ti–Ni alloys

The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu–3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu–3Ti–1Ni and Cu–3Ti–5Ni alloy was 300°C for 2 h and 450°C for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β′-Ni3Ti and β′-Cu4Ti precipitate from the Cu matrix during aging of the Cu–3Ti–5Ni alloy and that some residual NiTi phase remains. The increased electrical conductivity is ascribed to the formation of NiTi, β′-Ni3Ti, and β′-Cu4Ti phases.

Efficiency of binary and ternary alloys from Al–Ti–B system in grain refining aluminium foundry alloys

Several binary and ternary alloys from the Al–Ti–B system were tested for their capacities to grain refine aluminium foundry alloys. The growth restriction factor estimations evidence that the Al–3Ti alloy contributes to the grain refinement of AlSi7Mg0·3 alloy via only growth restriction, providing a twofold reduction in grain size. There is a marked improvement in the grain refining efficiency when Al–Ti–B ternary alloys are employed. While the efficiency increases with increasing B concentration, the mild improvement over a wide range of grain refiner compositions implies that the AlSi7Mg0·3 alloy is not very sensitive to the composition of the ternary Al–Ti–B grain refiners. Al–3B alloy provides the smallest grains at an addition rate of 200 ppm B, producing an average grain size of 298±36 μm in the commercial AlSi7Mg0·3 alloy. The grain refinement efficiency is doubled when the Al–3B grain refiner was added to the Ti free counterpart with average grain size of 145±10 μm.

Spectroscopic studies of the ionic liquid during the electrodeposition of Al–Ti alloy in 1-ethyl-3-methylimidazolium chloride melt

A new approach for the formation of Al–Ti alloy in 1-ethyl-3-methylimidazolium chloride (EmimCl) was investigated. The dissolution of titanium electrodes in presence of EmimCl:AlCl 3 was performed at various potentials to understand the effect of voltage on the reaction rate. It was observed that at low potentials, the presence of titanium hinders the reaction and diminishes the formation of aluminum and aluminum–titanium alloy at the cathode. However, at higher potentials there was substantial formation of Al 3Ti alloy. To understand the reaction mechanism during the electrolysis, the electrolyte was characterized using Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–vis) and nuclear magnetic resonance (NMR) techniques. The material on the cathode was characterized using scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) techniques. From the above analysis it was found that titanium forms a complex with aluminum and also assists in formation of AlCl 4 − phase in the acidic ionic liquid.

Comparative study on corrosion behaviour of plasma sprayed Ni–3Ti and Ni–3Al coatings

Ni–3Al and Ni–3Ti alloys were deposited on AISI 1045 steel substrate using air plasma spraying process. In this regard, mechanically alloyed feedstock powders were used. Open circuit potential EOCP measurements and Tafel polarisation tests were carried out to study corrosion behaviour of the coatings in 3·5%NaCl solution. These tests indicated that the corrosion performance of the Ni–3Ti coating is better than that of the Ni–3Al coating. The corrosion current densities were three times lower in the Ni–3Ti coating than in Ni–3Al coating. In addition, Ni–3Ti coating showed better passive behaviour than Ni–3Al coating. After 10 h of immersion, the surface of Ni–3Al coating became pitted, and rust spots appeared on the surface. In contrast, there was no rusting and pitting on the surface of Ni–3Ti coating even after 10 h of immersion.

Employing X-ray scattering to characterize materials with grain sizes in the nano-regime

This study focuses on characterization of an (Al,Cr)3Ti alloy processed together with titanium powder by reactive mechanical milling (RMM) to produce an ultrafine grained intermetallic alloy matrix with in situ carbide and hydride phases formed during processing. Observations of X-ray scattering as RMM processing time increases show severe broadening of matrix diffraction peaks, accompanied by the appearance of diffraction peaks resulting from the formation of very small crystallites of TiC and TiH1.92 phases with increasing volume fractions, and finally, increasing background intensity as the crystallite size of the matrix phase decreases to ∼2 nm. Estimates of phase volume fractions were made by the direct comparison method, along with crystallite sizes by Warren–Averbach peak profile analysis. The general increase in background intensities has been attributed to random static displacements of the large fraction of atoms located within the grain boundary regions. Further, it has been concluded that the matrix material with a crystallite size of a few nanometers has about half the atoms in statically displaced positions defining the boundary regions. The results argue that background intensity changes should not be ignored and are useful in interpreting scattering from these nano-scale materials.

Effects of technical factors on MgAl 2O 4–TiN composites produced by aluminothermic reduction and nitridation

MgAl 2O 4/TiN composites were formed by aluminothermic reaction between Al, TiO 2, and MgO powders in nitrogen gas. The effects of addition of graphite, α-Al 2O 3 into mixtures 8Al–6TiO 2–4MgO, and shaping pressure on the synthesized composites was investigated by X-ray diffraction. The results showed that: addition of graphite can lead to formation and lattice parameters change of Ti(C, N). When α-Al 2O 3 powder was added into mixtures 8Al–6TiO 2–4MgO, theoretic spinel transformed into alumina-rich spinel and lattice parameters of the spinel became low. Inadequate N 2 gas caused by higher shaping pressure can give rise to the formation of intermediate product Al 3Ti alloy in the synthesis of the composites.

Oxidation of (Al+8%Mn)<sub>3</sub>Ti Intermetallics Synthesized by Mechanical Alloying

The oxidation behavior of (Al+8 at.%Mn)3Ti alloys prepared by mechanical alloying followed by cold isostatic pressing and sintering at high temperatures was investigated at 1000 and 1100°C up to 300 hr in air. Since the Al2O3 barrier layer having some dissolved ions of Ti, and Mn formed, the oxidation resistance of the prepared alloys was excellent.

Structural formation of aluminide phases on titanium substrate

An aluminum layer on titanium substrate has been formed by thermal deposition. The structural formation of aluminide phases on the Ti substrate has been studied. The sequence of structural transformations at the Ti/Al interface is limited by the reaction temperature and time. Kinetics of these transformations are defined by a factor of concentration. At the initial stages at the Ti/Al interface the Al 3Ti alloy starts forming as a result of interdiffusion, and gradually the whole aluminum film is spent on the formation of this layer. The Al 3Ti layer decomposes with increasing temperature (>600 °C). At 800 °C the two-phase (Ti 3Al+TiAl) layer is formed on the titanium surface. The TiAl compound is unstable and later on with the increase of the exposure time at 800 °C gradually transforms into the Ti 3Al. The chain of these successive transformations leads to the formation of the continuous homogeneous layer consisting of the Ti 3Al compound on the titanium surface. At temperatures exceeding the allotropic transformation temperature (>900 °C) the Ti 3Al compound starts decomposing, aluminum atoms diffuse to the substrate and are uniformly distributed within the surface volume. All structural changes taking place at the Ti/Al interface are accompanied by considerable changes in microhardness. Due to the Ti 3Al layer being formed on the titanium surface, its microhardness increased practically by 2.5 times.

Effect of precipitated Co solid solution on moisture-induced embrittlement of L1 2-type Co 3Ti ordered alloys

The moisture-induced embrittlement of the L1 2-type Co 3Ti alloys (with nominal compositions of Co-19, 20 and 20.5 at.% Ti) was studied by tensile test, fractographic and microstructural observation. All the alloys exhibited age hardening at the examined temperatures due to precipitation of fcc Co solid solution in the L1 2 matrix. For the Co-19Ti alloy which contained primary Co solid solution particles, moisture-induced embrittlement did not occur in the solution treated condition but was caused by aging, and then reduced by prolonged aging. For the Co-20Ti and Co-20.5Ti alloys which contained no primary Co solid solution particles, moisture-induced embrittlement occurred in the solution treated condition and was increased by aging but significantly reduced by prolonged aging, similar to the Co-19Ti alloy. These results were discussed in association with the interaction of hydrogen with the Co solid solution particle because this interaction was greatly dependent on the morphology, size and interfacial structure of the second phase particles.

Microstructural characterization of a rapidly solidified Al–Sr–Ti alloy

The microstructure of the melt-spun Al–7Sr–3Ti alloy has been characterized using X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The results show the microstructure of the melt-spun Al–7Sr–3Ti alloy is composed of the equilibrium α-Al, Al 4Sr, Al 3Ti and metastable Al 23Ti 9, different from that of the ingot-like alloy comprising α-Al, Al 4Sr and Al 3Ti. Moreover, the amount of Al 3Ti is much less than that of Al 4Sr and metastable Al 23Ti 9 in the melt-spun alloy. The melting temperature of primary phases and enthalpies of fusion for the melt-spun Al–7Sr–3Ti alloy are lower than those for the ingot-like alloy. The formation mechanism of the microstructure of the melt-spun alloy has also been discussed.

Localized corrosion behavior of Al 3Ti–Cr alloys in 3.5 wt.% NaCl solution

Al 3Ti alloys have received a lot of attention as potential light materials because of their low density and high strength at elevated temperatures. The induction melting method followed by thermomechanical treatment was used for preparation of L1 2-typed Al 3Ti–Cr alloys, i.e. Al 67Ti 25Cr 8, Al 66Ti 24Cr 10 and Al 59Ti 26Cr 15. The corrosion behavior of Al 3Ti–Cr alloys in deaerated 3.5 wt.% NaCl solution was investigated by electrochemical corrosion tests and surface analysis. Particular attention was paid to the effects of Cr addition on the surface film composition and its breakdown related to the corrosion behavior. The result of cyclic potentiodynamic polarization test showed that E pit and E prot increased with increasing Cr content. This indicates that Al 3Ti–Cr alloys with higher Cr content are effective in improving relative resistance to pit initiation and propagation. In electrochemical impedance spectroscopy, an increase of Cr content increased polarization resistance ( R p) and decreased the depressed angle, which is strongly related to pitting resistance. Auger electron spectroscopy analyses were performed in order to characterize in-depth distribution of constituents in the passive film. Cr was detected earlier from the outer surface with increasing Cr content. Energy dispersive X-ray spectroscopy techniques were used to examine the effect of alloying elements inside pit. The amount of Ti inside pit was enriched as increasing Cr content.

Plastic flow instabilities of L1 2 Co 3Ti alloys at intermediate temperatures

The serrated flow of L1 2 Co 3Ti alloys was investigated by tensile tests in terms of the effects of temperature, strain rate, alloy stoichiometry and cooling rate after annealing. The serrated flow was most strongly observed at 673 K and at a strain rate of 3.2×10 −4 s −1. Correspondingly, the maximum stress amplitude and the lowest (negative) strain-rate sensitivity were observed at 673 K. The serrated flow was more significant as the alloy departs from a stoichiometric composition, and also less significant in a water-quenched sample than in a furnace-cooled sample. The static aging at 673 K resulted in a reduced flow stress. The activation energy of the serrated flow was estimated to be about 84 kJ/mol and almost one-half of that of lattice diffusion of the excess Co atoms. The serrated-flow behavior is explained qualitatively on the basis of consideration of the dynamics of the dislocation core structure, and is also discussed in association with the strength anomaly.

Observations of crack tip process zones in cubic titanium trialuminide intermetallics

Despite the fact that the single-phase L1 2-ordered titanium trialuminides, derived from D0 22-ordered Al 3Ti by alloying with fourth-period transition elements such as Cr, Mn, Fe, Co, Ni, Cu, and Zn have a cubic lattice structure, their room temperature fracture toughness remains quite low (4–5 MPa m 1/2). In general, process zones developed at the crack tips determine the fracture toughness of a material. In this work the results of the crack tip fracture studies of cubic (L1 2) Al 3Ti alloys stabilized with Mn are presented. The process zones at the crack tip in nearly stoichiometric single-phase L1 2 9Mn–25Ti (at.%) titanium trialuminides were not observed in most of the specimens studied. Occasionally, two types of process zones were observed: either small, heavily localized process-plastic zones accompanied by a crack tip “collapse”, or “pseudo-bifurcated” ones, reminiscent of those in brittle ceramics. Observations of the crack tip process zones in multiphase, high Ti (up to ∼33 at.%), B-doped trialuminides, exhibiting increased fracture toughness (∼7 MPa m 1/2), show the presence of secondary microcracks in the zone ahead of the crack tip and adjacent to the propagating crack, and more plasticity at the crack tip.