Ti-X Alloys Research Articles

Structural and magnetic properties of rapidly solidified and Bi-bonded hot compacted Mn[formula omitted]Al45C1.7Ti[formula omitted] magnets

This study examines the impact of Ti doping on the phase formation and magnetic properties of Mn-Al-C alloys. Using melt spinning, we synthesized Mn53.3−xAl45C1.7Tix alloys (x values ranging from 0 to 1.5) producing high purity ϵ-phase ribbons. The optimal annealing treatment for the formation of ferromagnetic τ-phase is 20 min at 550 °C for all compositions. However, Ti-doped samples showed the formation of β-phase due to partial phase decomposition, and TiC precipitates were present at high Ti concentrations. Upon doping, the Curie temperature was increased from 557K (Ti free sample) to 600K. To improve the coercivity, a combination of ball milling and hot compaction, introducing Bi as a metallic binder, have resulted in increased coercivity from 0.18 T to 0.33 T. Bi addition lead to formation of a grain boundary phase aiding densification. We demonstrate how modifying composition and processing can improve the magnetic properties of Mn-Al based magnets.

Modeling Short-Range Ordering in Binary BCC Ti-X (X = Nb, V, Zr) Alloys using CE-CVM

Modeling Short-Range Ordering in Binary BCC Ti-X (X = Nb, V, Zr) Alloys using CE-CVM

Significant evolutions of microstructure and mechanical properties of Al0.3CoCrFeNiTix high-entropy alloys under annealing treatment

The effect of annealing treatment on microstructure and mechanical properties of Al0.3CoCrFeNiTix high entropy alloys were investigated. The results indicated that addition of Ti in as-cast alloys caused the formation of L12, Laves, γ and σ phases to increase the hardness and strength of the alloys. The microstructure remained stable below annealing at 700 °C. However, the (Fe, Cr)-rich phase was found in the interdendritic (ID) structure. Simultaneously, annealing at 700 °C increased the volume fraction of L12, γ and σ phases and decreased the volume fraction of FCC and Laves phases. The (Al, Ni, Ti)-rich rod-shaped precipitated (RSP) phase was found in the FCC matrix after annealing at 800 °C. The hardness and yield strength showed a significant enhancement after annealing at 700–800 °C. The coarsening phenomenon of (Fe, Cr)-rich and RSP phases could be observed after annealing at 900–1000 °C. Simultaneously, annealing at 900–1000 °C caused the further decrease in the volume fraction of FCC and Laves, causing the decrease in yield strength and to improve plasticity of the alloys. The main strengthening mechanisms of as-cast and annealed Tix alloys were discussed, confirming that the precipitation strengthening mechanism was the main strengthening mechanism.

Corrosion behaviors related to the microstructural evolutions of as-cast Al0.3CoCrFeNi high entropy alloy with addition of Si and Ti elements

In this work, the electrochemical potentiodynamic polarization and impedance spectroscopy analysis were used to investigate the corrosion behaviors related to microstructural evolutions of Al0.3CoCrFeNiSix and Al0.3CoCrFeNiTix HEAs in the NaCl solution. The results presented that addition of Si promoted the formation of BCC phase, which was regarded as a micro-anode to prevent FCC phase as a micro-cathode from being corroded. While the volume fraction of BCC phase increased to enhance the corrosion resistance of Six alloys with increasing Si content. Furthermore, the reduction in the grain sizes of Six alloys with increasing Si content could also improve corrosion resistance of the alloys. Therefore, the corrosion resistance of Six alloys was increased with increasing Si content. Addition of Ti with a high corrosion resistance of Clˉ caused the reduction in the grain sizes of Tix alloys, which can improve the corrosion resistance of alloys. However, the high Ti content can destroy the corrosion resistance of the alloys due to the formation of a large amount of precipitated phases. Therefore, as Ti with atomic percentage be equal to that of Al can effectively eliminate the negative influence of precipitated phases and microstructure on the corrosion resistance of alloys, meaning the Ti0.3 alloy had the best corrosion resistance in Tix alloys. The analysis of X-ray photo-electron spectroscopy (XPS) identified that the contents of oxidized Cr3+ and Fe3+ in the passive film are the main contribution to improve the corrosion resistance of Six alloy. And the contents of oxidized Cr3+ and Ti4+ in the passive film are the main contribution to improve the corrosion resistance of Tix alloy.

Development of coherent-precipitate-hardened high-entropy alloys with hierarchical NiAl/Ni2TiAl precipitates in CrMnFeCoNiAlxTiy alloys

Coherent precipitates hardening is currently emerging strengthening mechanism of the various high entropy alloys (HEAs). Recently, CrMnFeCoNiAlx HEAs have been studied to show a phase transition from face-centered-cubic (FCC) to body-centered-cubic (BCC) and formation of coherent precipitates (B2-NiAl) within the BCC matrix. The coherent precipitates in the CrMnFeCoNiAlx alloys could contribute to increase the strength but lead to considerable reduction of the ductility. The present work systematically investigated a series of CrMnFeCoNiAl0.5Tix alloys to further improve the strength and plasticity, as compared to the previously reported CrMnFeCoNiAlx HEAs. As a result, an increase of Ti addition leads to the phase transition from FCC to BCC and formation of lamellar structure and hierarchical precipitates reinforced by B2-NiAl and L21-Ni2TiAl phases. Excellent mechanical properties were achieved from CrMnFeCoNiAl0.5Ti0.1 and CrMnFeCoNiAl0.5Ti0.2 alloys. The mechanical properties of the CrMnFeCoNiAl0.5Tix alloys were discussed via theoretical strengthening mechanisms.

Microstructure and soft magnetic properties of Fe85−xSi9.6Al5.4Tix composite magnetic powder cores

In this study, the effects of Ti content on the soft magnetic properties of Fe85-xSi9.6Al5.4Tix soft magnetic powder cores (SMPCs) were studied systematically. The addition of nonmagnetic Ti gradually decreased the saturation magnetization (Ms) of the Fe85-xSi9.6Al5.4Tix alloys powder, whereas the resistivity and density gradually increased, leading to a significant decrease in core loss (Pcv). The SMPCs doped with 0.5 wt% Ti showed the best magnetic properties, including low Pcv of 140.6 mW/cm3, stable effective permeability (μe) of 62.9 up to 1 MHz, and high DC bias performance of 46% at 100 Oe. Furthermore, the corrosion resistance of the Fe85-xSi9.6Al5.4Tix SMPCs gradually improved as the Ti content increased, reaching a maximum at a Ti content of 2.5 wt%, at which the corrosion current density decreased to a minimum of 1.45 × 10−6 A/cm2. The addition of Ti can effectively improve the corrosion resistance of Fe85Si9.6Al5.4 SMPCs.

Evolution of Microstructures and Compressive Properties in Al0.5CrFeNi2.1Mn0.8Tix High Entropy Alloys

The effects of Ti on the microstructures, macrohardness and compressive properties of the as-cast Al0.5CrFeNi2.1Mn0.8Tix HEAs were investigated. The results showed that the microstructures of as-cast Al0.5CrFeNi2.1Mn0.8Tix alloys was changed from FCC phase to a mixture of FCC and BCC phases, then to a mixture of BCC phase and Ti-containing intermetallic compound as the increasing of Ti content. Chrysanthemum-like eutectic microstructure was obtained in the Al0.5CrFeNi2.1Mn0.8Ti0.5 and Al0.5CrFeNi2.1Mn0.8Ti alloys. The area of flower core was composed of BCC2 phase, and eutectic microstructure was achieved in the petal area which contained BCC1 phase and BCC2 phase. Moreover, the macrohardness of the as-cast alloys increased with the increasing of Ti, and the Al0.5CrFeNi2.1Mn0.8Ti0.5 alloy showed excellent comprehensive compressive properties.

Additive manufacturing of dense components in beta‑titanium alloys with crystallographic texture from a mixture of pure metallic element powders

The fabrication of dense components composed of Ti-based alloys, i.e., Ti-X (X = Cr, Nb, Mo, Ta) alloys, from a mixture of pure elemental powders was achieved using selective laser melting (SLM) process. The Ti-Cr alloys comprise β-Ti single-phase components without any non-molten particles and macroscopic defects. The crystallographic texture of these β-Ti-Cr alloys can be controlled effectively by optimizing the build parameters. The development of {001}〈100〉crystallographic orientation during the SLM process is discussed based on the solidification process focusing on the columnar cell growth in the melt pool. These results demonstrate the possibility of fabricating the Ti-based alloy components with well-developed crystallographic texture from the mixture of pure elemental powders using the process of SLM.

Yield of Binary Ti-Cu and Ti-Mn Alloys Produced via Powder Metallurgy

High strength, low density, good corrosion resistance and biocompatibility is the combination of properties that Ti and its alloys can provide for engineering applications. Its costs are the most important limiting factor for the widespread use of Ti. Cost reduction for Ti alloys can derive from the use of cheaper alloying elements as well as the use of alternative manufacturing techniques. In this study binary Ti-X alloys (where X = Cu or Mn) were formulated and produced using the conventional powder metallurgy route of pressing and sintering. These chemical elements were selected because they are β stabilisers and can be used to create α+β Ti alloys. The study shows that with the techniques and processing parameters used handable products without delamination can be pressed. Moreover, chemically homogenous materials with density and mechanical property values comparable to those of other wrought-equivalent Ti alloys produced via powder metallurgy were achieved.

Pressure-induced phase transition in titanium alloys

The structural, elastic, magnetic and electronic properties of titanium-based ferromagnetic (FM) TiX (X = Fe, Co, Ni) alloys are investigated by the first principles calculations based on density functional theory using the Vienna ab initio simulation code. At ambient pressure, all the three alloys TiFe, TiCo and TiNi are highly stable in CsCl structure. The calculated lattice parameters and ground state properties are in good agreement with the available theoretical and experimental results. The density of states explains that these alloys possess the metallic nature at normal and high pressures. A pressure-induced structural phase transitions from CsCl to NaCl phase at 46 GPa and NaCl to ZB phase at 49 GPa in TiFe, CsCl to ZB phase in TiCo at 52 GPa, CsCl to hexagonal phase at 22 GPa and hexagonal to ZB phase at 66 GPa in TiNi are observed. The calculated Debye temperatures of TiX (X = Fe, Co, Ni) alloys are in good agreement with earlier reports. Binding energy shows that the TiCo is the most stable alloy. The magnetic property of TiX (X = Fe, Co, Ni) alloys reveals that TiFe is stable in nonmagnetic phase and the other two alloys, TiCo and TiNi, are stable in FM phase at normal pressure.

Effects of alloying elements on the elastic properties of bcc Ti-X alloys from first-principles calculations

Titanium alloys are great implant materials due to their mechanical properties and biocompatibility. However, a large difference in Young’s modulus between bone (∼10–40 GPa) and common implant materials (ie. Ti-6Al-4V alloy ∼110 GPa) leads to stress shielding and possible implant failure. The present work predicts the single crystal elastic stiffness coefficients (cij’s) for five binary systems with the body centered cubic lattice of Ti-X (X = Mo, Nb, Ta, Zr, Sn) using first-principles calculations based on Density Functional Theory. In addition, the polycrystalline aggregate properties of bulk modulus, shear modulus, Young’s modulus, and Poisson ratio are calculated. It is shown that the lower Young’s modulus of these Ti-alloys stems from the unstable bcc Ti with a negative value of (c11–c12). The data gathered from these efforts are compared with available experimental and other first-principles results in the literature, which set a foundation to design biocompatible Ti alloys for desired elastic properties.

First-principles study of the phase stability and elastic properties of Ti-X alloys (X = Mo, Nb, Al, Sn, Zr, Fe, Co, and O)

Phase stability and elastic properties of Ti1-x-Xx alloys (X = substitutional Mo, Nb, Al, Sn, Zr, Fe, Co, and interstitial O) in body-centered cubic (bcc) (β phase) and hexagonal close-packed (hcp) (α phase) crystal structures were studied using first-principles calculations. The formation energy was used to determine the dependence of the phase stability on the atomic concentration x (0 ≤ x ≤ 0.5 for substitutional elements and 0 ≤ x < 0.02 for O) of the alloying elements and atomic configurations (ordered, disordered, and other compound structures). The disordered configurations of the atoms in the alloys were considered within the framework of the special quasi-random structures (SQS) method. The composition dependence of elastic constants, isotropic elastic moduli and density of states (DOS) were also evaluated.The predicted formation energies and elastic properties agrees well with previous experimental and theoretical results. Addition of Mo was found to stabilize the β phase significantly while destabilizing the α phase. Nb was found to be a weaker β-stabilizer. In Ti-Al and Ti-Sn systems, the compounds form preferentially at a higher concentration. Zr shows little effect on the phase stability, thus Zr is a neutral element. For Ti-O systems, the octahedral site is the most stable site for interstitial oxygen in both bcc and hcp structures. The comparison of formation energies showed that O acts as an α stabilizer. Considering the configurational entropy contribution, we concluded that temperature effect can be significant to stabilize the phases. The elastic constants calculation revealed that adding Mo, Nb, Fe, or Co increases the mechanical stability of bcc Ti, whereas bcc Ti-Al, Ti-Sn, and Ti-Zr systems are mechanically unstable for all the calculated concentrations. For their hcp counterparts, Ti-Mo and Ti-Nb have lower mechanical stability than the Ti-Al, Ti-O, and Ti-Sn systems. It was found in the electronic structures calculation that increasing addition of Nb, Mo, Fe, and Co weakens the covalent-like bonding of hcp system and strengthens the metallic bonding of bcc system. This variation of the TDOSs of these Ti alloys explains why the bcc phase becomes more stable than the hcp phase at high concentration. Due to the similarity of electronic structure, Zr does not change the DOS of the bcc and hcp phases significantly: The Fermi level in DOS profile of Ti-Zr was found to be identical to that of pure Ti system. Ti-Al and Ti-Sn alloys keep the covalent-like bonding, which explains why hcp Ti-Al and Ti-Sn are stable.

Effect of Alloying Elements on Plastic Workability and Corrosion Behavior of Ti-X (X = 6 Co, 8 Cr, 4 Fe, 6 Mn, 10 Mo, and 36 Nb) Binary Alloys

Abstract The purpose of this study was to investigate the effect of the alloying elements on the plastic workability and corrosion behavior of Ti-X (wt.%) (X = 6 Co, 8 Cr, 4 Fe, 6 Mn, 10 Mo, and 36 Nb) binary alloys. The alloys with a molybdenum equivalence of 10 wt.% were fabricated by a vacuum arc re-melting process and were then homogenized at a temperature 20°C greater than the beta transus temperature for 14.4 ks. The plastic workability was investigated under uniaxial cold rolling, while the corrosion behavior was examined in Ringer’s solution at 37°C. Among the Ti-X alloys, the Ti-8 wt.% Cr and Ti-6 wt.% Mn alloys showed an outstanding plastic workability and corrosion resistance, respectively.

Microstructure and mechanical properties of Ti-X alloys fabricated by selective laser melting process for new biomaterial devices

Microstructure and mechanical properties of Ti-X alloys fabricated by selective laser melting process for new biomaterial devices

Theoretical investigation of effect of alloying elements on phase stability in body-centered cubic Ti-X alloys (X = V, Cr, Fe, Co, Nb, and Mo)

The structural and the valence band electronic properties of bcc Ti-X alloys (X=V, Cr, Fe, Co, Nb, and Mo) were studied by first-principles calculations. To determine the effect of the concentration and atomic distribution of the alloying elements on the phase stability, ordered structure models and special quasirandom structure (SQS) models were used for emulating the solid solution state of the alloys.To clarify the phase stability of bcc Ti-X alloys with respect to a hexagonal close-packed (hcp) reference phase, the formation energy, structural parameters, and electronic properties were analyzed. Analysis of the formation energy showed that the hcp phase is more stable than the bcc phase when V, Cr, and Nb are added for all the calculated alloying element fractions x (0 ⩽x⩽0.50), whereas the bcc phase is stabilized when Fe, Co, are Mo are added. The dependence of the lattice constants on the alloying element was examined, and the calculations reproduced the experimental results well. The profile of the density of states in the solid solution changed continuously with the concentration of the alloying elements.

252 第一原理計算によるTi-X合金の溶解熱とエンタルピー曲線

252 第一原理計算によるTi-X合金の溶解熱とエンタルピー曲線

Structure Stability and Elastic Properties of β Type Ti-X (X=Nb, Mo) Alloys from First-Principles Calculations

Abstract The phase stability, the elastic constant and the electronic structure of Ti-X (X=Nb, Mo) alloys having bcc structure were studied from first-principles calculations by the method of supercell and the projector augmented wave within the generalized gradient approximation. The elastic moduli of the polycrystal alloys were estimated from the elastic constants of the single crystal by the Voigt-Reuss-Hill averaging method. The results reveal that Nb and Mo contents have a significant influence on the phase stability and the elastic properties of the β type Ti-X alloys. The phase stability, the elastic constants, the elastic modulus and the shear modulus of β type Ti-X alloys increase with the X content increasing. The lowest elastic modulus of the alloys is achieved as the X content is about 25%. Moreover, the phase stability of the alloys was discussed based on the calculated density of state (DOS).

Theoretical Investigations of Ti-Based Binary Shape Memory Alloys

The electronic structure and ground state properties of TiX (X = Fe, Ni, Pd, Pt and Cu) type Shape Memory alloys have been calculated using the self consistent Tight- Binding Linear Muffin Tin Orbital (TB-LMTO) method. The systematic total energy studies made on TiX alloys in both B2 and (B19/B19’) structures successfully explain the structural stability of these compounds. The equilibrium lattice parameters, bulk moduli (Bo), cohesive energy (Ecoh) and heat of formation (ΔH) are calculated for these systems and compared with the available experimental and other theoretical results. The bonding nature of these TiX alloys is analyzed via the density of states (DOS) histogram.

Magnetic disorder in Ti doped ErCo2: High-magnetic-field study

Magnetization measurements have been carried out on ErCo(2−x)Tix (x=0, 0.01, 0.02, 0.03, 0.04, and 0.05) alloys in the temperature range of 4–300 K under high dc magnetic fields of up to 23 T. The substitution of Ti for Co causes no change in the crystal structure of ErCo2 (cubic Laves phase C15 with space group Fd3¯m). The lattice parameter a decreases almost linearly with increasing x up to x=0.04 and then increases slightly for the largest Ti concentration. The Curie temperature TC shows a similar change with Ti concentration. Above TC all the studied samples show a small but unambiguous hysteresis associated with a metamagnetic transition. The observed hysteresis is attributed to the coexistence of the paramagnetic and the field-induced ferrimagnetic states. Linear temperature extrapolations of the critical fields Hc1 (where the hysteresis sets in) and Hc2 (the highest field where the hysteresis is observed) were done for each sample. Two different critical temperatures were found suggesting the existence of Co clusters. Indeed, weak negative magnetization values in low fields at low temperatures were observed for zero-field-cooling magnetic measurements. The negative magnetization is also attributed to the existence of Co clusters above TC. The spontaneous magnetization values Ms of the samples were deduced as a function of Ti concentration from the high-field data. Ms passes through a maximum for the x=0.03 sample with a maximum value of 7.15μB (6.30μB in pure ErCo2). We show how a decrease in the Er–Co antiferromagnetic exchange coupling with Ti doping may lead to such an observed maximum.

Influence of Nb and Mo contents on phase stability and elastic property of β-type Ti-X alloys

The energetic, electronic structure and elastic property of β-type Ti1-xXx, (X=Nb and Mo, x = 0.041 7, 0.062 5, 0.125 0, 0.187 5, 0.250 0, 0.312 5 and 0.375) binary alloys were calculated by the method of supercell and augmented plane waves plus local orbitals within generalized gradient approximation. The elastic moduli of the polycrystals for these Ti1-xXx alloys were calculated from the elastic constants of the single crystal by the Voigt-Reuss-Hill averaging method. Based on the calculated results, the influence of X content on the phase stability and elastic property of β-type Ti1-xXx alloys was investigated. The results show that the phase stability, tetragonal shear constant C', bulk modulus, elastic modulus and shear modulus of β-type Ti1-xXx alloys increase with an increase of X content monotonously. When the valence electron number of β-type Ti1-xXx alloys is around 4.10, i.e. the content of Nb is 9.87% (molar fraction) in the Ti-Nb alloy and Mo is 4.77% (molar fraction) in Ti-Mo alloy, the tetragonal shear constant is nearly zero. The Ti1-xXx, alloys achieve low phase stability and low elastic modulus when the tetragonal shear constant reaches nearly zero. In addition, the phase stability of β-type Ti1-xXx alloys was discussed together with the calculated electronic structure.