TiZrAlV Alloy Research Articles

Microstructure evolution and vacuum tribological properties of surface nitriding layer on a TiZrAlV alloy fabricated by laser nitriding

The evolution mechanisms of phase, microstructure and vacuum tribological properties for Ti–20Zr-6.5Al–4V under different laser beam diameters have been investigated by using laser surface nitriding (LSN). Results indicate that all the LSN samples are mainly composed of α phase and Ti(Zr)N phase, besides, Ti(Zr)N0.3 phase can also be obtained, which is based on a change in the ratio of liquefied nTi(Zr)/nN. With the laser beam diameter decreasing from 3 to 1 mm, the thickness and density of nitride layer increase significantly, which contribute to the increased energy input density. EPMA results indicate that the nitrides mainly exist in the form of Ti(Zr)xNy, and the distribution transformation of Al and V elements has also been analyzed. As the laser beam diameter decreases, the coefficient of friction decreases, and the sample with 1 mm laser beam diameter display the lowest coefficient of friction (∼0.333). Also, the wear volume and wear rate of the LSN sample with 1 mm laser beam diameter are the smallest, which are both reduced by about 40% compared with the original sample. After analysis, the wear pattern of the LSN samples can be confirmed as the composite of adhesive wear and abrasive wear. Nitride dendrites can form a support skeleton between the wear surface and friction pair, which can significantly reduce the wear of LSN sample surface. The results of this work prove the feasibility of improving the surface wear resistance of Ti–20Zr-6.5Al–4V by LSN.

Tailoring phase composition of a multielement TiZrAlV alloy via electroplastic rolling

• Effect of strain on electroplastic deformed ZrTiAlV alloy was studied. • Martensitic transformation of Ti alloy can be regulated by electroplastic rolling. • Increasing strain enhances the stress-induced martensite transformation and improves the strength. • The optimal mechanical properties of UTS ∼1398 MPa and ε f ∼ 5.77% were obtained at strain 2.28. The TiZrAlV alloy were deformed by electroplastic rolling with strains from e ∼ 1.31 to 2.70, which led to the phase transformation from β phase to α phase and α phase to α˝ phase. The contents of various phases were tailored by rolling strain. As a result, the deformed alloy exhibited an increasing ultimate tensile strength (1286 MPa to 1398 MPa) and failure elongation (4.05% to 5.77%) from e ∼ 1.31 to 2.28. Further increasing the strain to e ∼ 2.70 led to a further increase in strength and a loss in ductility, 1484 MPa and 3.73%. Our work provides an alternative process to improve the mechanical properties of Ti alloys by tailoring various phase compositions and phase transformations.

Microstructure and microhardness of a novel TiZrAlV alloy by laser gas nitriding at different laser powers

The Ti–20Zr–6.5Al–4V (T20Z, wt%) alloy surface was treated by the process of laser surface nitriding. The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120 to 240 W. All laser-treated T20Z samples show two regions with distinctly different microstructural features, as compared with the untreated substrate: dense TiN dendrites and (α + β) − Ti (remelting zone, RMZ), nanoscale α laths doped with part of β phase (heat-affected zone, HAZ). The formation of TiN dendrites can be analyzed by a series of complex reactions during the process of melting and solidification. The increase in laser power results in the increase in content of TiN dendrite which is mainly due to the increase in energy input. In HAZ, the self-quenching effect leads to the formation of nanoscale α laths and the residue of β phase. Microhardness profile of different regions was measured from the surface to the interior, and the highest microhardness was obtained (~ HV 916.8) in the RMZ, as the laser power was set to 240 W. In the present study, we explained various microstructural characteristics induced by laser surface nitriding treatment.

Dry Sliding Behavior of a TiZr-Based Alloy under Air and Vacuum Conditions

In this study, dry sliding tribological properties of a TiZr-based alloy with the chemical composition Ti-20Zr-6.5Al-4V (wt.%) were tested in air and vacuum under different normal loads (10, 20, and 30 N) at various sliding velocities. Results showed that the coefficient of friction in air was lower than that in vacuum, whereas the wear volume at sliding velocity presented an opposite trend. The surfaces and cross-sectional morphology of wear scar on the TiZrAlV alloy was analyzed through scanning electron microscopy to determine the wear mechanisms. The observations showed that abrasive wear and delamination wear were dominant in air. In vacuum, the main wear mechanism changed from slightly abrasive and adhesive wear to severe adhesive wear and delamination wear as the normal load increased. Wear mechanism maps were also constructed and compared. The comparison showed that severe wear (including delamination wear) was prevalent in air.

Vacuum Tribological Properties of Ti-20Zr-6.5Al-4V Alloy as Influenced by Sliding Velocities

This research studied the vacuum tribological properties of annealed Ti-20Zr-6.5Al-4V alloy sliding against AISI 440C steel at various velocities ranging from 0.39 to 1.17 m/s using a ball-on-disc tribometer equipped with a vacuum chamber. The coefficient of friction and wear volumes of the annealed Ti-20Zr-6.5Al-4V alloy were obtained. Results indicated that the coefficient of friction increased at the beginning as the sliding velocity increased to 0.78 m/s and subsequently decreased with further increase in velocity. However, the wear volume increased monotonically with sliding velocity. Scanning electron microscopy was employed to study the wear mechanisms after tribological tests. Under a normal load of 10 N, abrasive wear was predominant at various sliding velocities, whereas the sliding velocity influenced the wear mechanisms significantly when the normal load was increased to 30 N. Under higher normal load, the abrasive wear was indentified as the main wear mechanism at a lower sliding velocity of 0.39 m/s. As the sliding velocity was increased to 1.17 m/s, severer abrasive wear, delamination wear, and plastic deformation were dominant. In addition, at a sliding velocity of 1.17 m/s, the wear mechanisms were abrasive and mild adhesive wear of the TiZrAlV alloy annealed at 1273 K (1000 °C) under the load of 10 N. The mechanism changed to severe plastic deformation and delamination wear when the normal load was increased to 30 N. The three-dimensional topography of the Ti-20Zr-6.5Al-4V disc worn surface was also explored.

Tailoring Microstructure and Tribological Properties of Cold Deformed TiZrAlV Alloy by Thermal Treatment

Microstructure evolution and tribological properties of a new TiZrAlV alloy have been investigated in the present study. Various microstructures, i.e., equiaxed grain structure, dual-phase lamella structure, and heterogeneous lamellar structure, have been successfully prepared, and the effect of the microstructure on tribological properties was explored by means of cold severe plastic deformation combined with subsequent recrystallization annealing and aging treatments. The special heterogeneous lamellar-structured alloy exhibits a high ultimate tensile strength (~1545 MPa), reasonable ductility (~7.9%), and excellent wear resistance as compared with the equiaxed grain-structured and dual-phase lamella-structured alloy. The present study demonstrates an alternative route for enhancing the tribological properties of alloys with heterogeneous lamellar structure.

Microstructure and Mechanical Properties of Graphite Mold Casted TiZrAlV Alloy with Various Zr Contents

Casting is an effective method to reduce costs which is a focus for Ti products. However, not all Ti alloys can be prepared by casting to reducing costs. To discuss whether the new TiZrAlV alloys are suitable for casting, microstructure and mechanical properties of graphite mold casted TiZrAlV alloys with various Zr contents are investigated. Results show that microstructure and mechanical properties of the TiZr‐based castings depend greatly on Zr contents. Furthermore, relations between tensile properties and microstructural parameters are also discussed. The synthesis result indicates that castings with 60 wt% and 75 wt% Zr have favorable formability and obdurability which are suitable for casting alloys. The current work will provide a reference for the design of TiZr‐ and even Ti‐based castings to reduce costs.

The effects of V content on the microstructure and mechanical properties of hot rolled TiZr based alloys

The effects of V content (0–7 wt.%) on the structure and mechanical properties of TiZrAlV alloys were investigated. The phase composition changes as α' → α' + (α″ + β) → α″ + β → β + (α″) → β with increased V content from 0 wt.% to 7 wt.%. Specifically, the single β phase that is impossible to achieve in Ti–V binary alloys was obtained in the TiZrAlV alloy with an increased V content of 7 wt.%. The microstructure of alloys with <1 wt.% V was characterized by martensite filling the original β grains. Dynamic recrystallization occurred in alloys with >3 wt.% V. With increased V content, the recrystallization volume fraction increased, and changes in the elastic modulus and yield strength exhibited an antiparabolic trend. The alloy with 3 wt.% V had the minimum average elastic modulus (68 GPa) and an average yield strength (690 MPa). With increased V content, the trend of elongation was the reverse of the yield strength. However, the trend of tensile strength remarkably differed from that of the yield strength. The alloy with 3 wt.% V had favorable comprehensive properties: a maximum average elongation (12.7%) and a high average tensile strength (1358 MPa). The strengthening and toughening mechanisms of TiZrAlV alloys were also discussed.

Optimization of tensile properties of a hierarchical structured TiZrAlV alloy by proton irradiation

The irradiation of high-energy particles always leads to the deterioration of mechanical properties of materials. Here, we report an abnormal proton irradiation-induced optimization of tensile properties, i.e. an obviously enhanced ductility with a slight decrease of strength, of a hierarchical structured TiZrAlV alloy. The optimization of tensile properties can be attributed to the lattice relaxation caused by irradiation, and the suppressed formation of vacancy clusters in the sample.

Thermal stability of hierarchical and multiphase nanolaminated TiZrAlV

Abstract Microstructures, thermal stabilities and microstructures and properties evolutions of a new β TiZrAlV alloy have been investigated in this paper. Various hierarchical and multiphase nanolaminated (HMN) structures have been successfully produced in the alloy via appropriate thermomechanical processing treatments. The higher thermal stability (Tp ~ 275 °C), i.e., onset temperature of phase transformation, is achieved in a specific HMN structure consisting of nanoscale acicular isothermal α″ martensites, submicroscale α plates and large microscale primary αp grains, compared with that (Tp ~ 105 °C) of its coarse-laminated counterpart without primary αp grains. For this specific HMN structure, thermal exposures at 300–400 °C lead to further precipitation of isothermal α″ martensites, which enhances evidently the strength and reduces the ductility, while the reverse transformation of α″/α to β and the coarsening of previously formed α plates concur during thermal exposures at 500–600 °C, which leads to dramatically decreased strength and increased ductility.

Microstructure evolution and mechanical properties of deformed TiZrAlV upon annealing

The formation of hierarchical structures is an effective way to optimize the mechanical properties of pure metals and simple alloys but not multi-component alloys. In this study, hierarchical structures were introduced into a quaternary TiZrAlV alloy by treating the deformed sample via recrystallization and aging treatment. A combination of high strength (σb = ∼1548 MPa), high ductility (εf = ∼6.6%), and good fracture toughness (KIC = ∼55.1 MPa.m1/2) was achieved in one hierarchically structured sample. The effects of thermal treatment on the microstructure evolution, and tensile and fracture properties of the deformed TiZrAlV were investigated.

A hierarchical and multiphase nanolaminated alloy with an excellent combination of tensile properties

Ti alloys that possess a fine fully lamellar structure generally exhibit high strength but limited ductility. In this study, a hierarchical and multiphase nanolaminated structure that consists of large microscale primary αp grains (~1.5μm), sub-microscale α plates (~200nm) and nanoscale acicular isothermal (orthorhombic) α″ martensites (~15nm) is produced in a TiZrAlV alloy with a fine (~12μm) β grain size through the use of severe plastic deformation (SPD) combined with subsequent recrystallisation annealing and aging treatments. This specific structure results in an excellent combination of tensile properties, e.g., an ultimate tensile strength of σb~1545MPa and an elongation to failure of εf~7.9%. The present study demonstrates an alternative route for enhancing the mechanical properties of titanium alloys with laminated structures.

A hierarchical nanolamella-structured alloy with excellent combinations of tensile properties

Dual phase (α+β)-Ti alloys with a fully fine laminated microstructure usually exhibit a high strength but a limited ductility. In the present study, a hierarchical nanolaminated microstructure consisting of lamellae with nano- and submicrometer-sized widths has been produced in a TiZrAlV alloy by employing severe plastic deformation (SPD) combined with subsequent thermal annealing. The hierarchical nanolamella-structured Ti alloy exhibits excellent combinations of tensile properties, e.g., an ultimate tensile strength σUTS=1600MPa and an elongation to failure εf=6.5%. The high strength can be attributed to the formation of a lot of nanoscale α lamellae in the alloy, and the enhanced ductility results mainly from both the coarse α lamellae that have a high strain hardening capability and the complex strain paths caused by a hierarchical nanolaminated structure.

Effect of the annealing temperature on the microstructural evolution and mechanical properties of TiZrAlV alloy

This study aimed to evaluate the effects of the annealing temperature on the structural evolution and mechanical properties of TiZrAlV alloy. The microstructural evolution and mechanical properties of the alloy were investigated by X-ray diffraction, metallographic analysis, tensile testing, and microhardness testing. The results showed that the thickness of the α phase that precipitated from the parent phase was sensitive to the annealing temperature. With increased annealing temperature, the α-phase tended to exhibit equiaxed grains, except for the specimen annealed at 1050°C. The tensile strength of the equiaxed α grains were also demonstrated to have higher tensile strength than those of the lamellar α phase. The optimal mechanical properties of the alloy was obtained after annealing at 850°C, i.e., σb=1245MPa, σ0.2=1006MPa, and ε=16.89%.