Mechanical Properties Of Titanium Alloys Research Articles

Investigation into the stress‒strain compatibility and fracture behaviour of a TC18 titanium alloy with a multistage lamellar microstructure

Understanding the fracture mechanism is essential for optimizing the mechanical properties of titanium alloys. The relationship between fracture behaviour and the multistage lamellar microstructure of the TC18 (Ti–5Al–5Mo–5V–1Cr–1Fe) alloy was investigated via in situ tensile and three-point bending tests. The results indicate that the TC18 alloy, featuring a multistage lamellar microstructure (including a β matrix, primary lamellar α phase, bundles, and secondary lamellar α phase), exhibits an excellent combination of strength and ductility. The precipitation of the secondary lamellar α phase significantly enhances the alloy's strength but weakens the stress‒strain compatibility of the microstructure. This results in a smaller crack-tip plastic zone (CTPZ) and causes dislocations to concentrate more at the grain boundaries and, to a lesser extent, at the phase interfaces. Consequently, in the later stages of crack propagation, microvoids and microcracks tend to form at dislocation pile-ups. With increasing stress, these microvoids and microcracks rapidly coalesce, leading to a greater proportion of intergranular fracture and thus reducing the fracture toughness of the alloy.

Effect of Heterogeneous Deformation on Microstructure and Microtexture Evolution of Ti‐6Al‐4V Alloy during Multidirectional Isothermal Forging

The heterogeneous deformation of Ti‐6Al‐4V alloy during multidirectional isothermal forging and its effect on microstructure, microtexture, and related mechanical properties are investigated here. It is found that lowering the deformation temperature, combined with increasing the number of forging times, accelerates the grain refinement and recrystallization process in the as‐received billet, especially in the surface section rather than the inner of the billet. Finally, a heterogeneous lamellar structure is formed after annealing the billet with a fourth step of forging. The heterogeneous lamella structure enables a better synergy of strength and ductility when compared to its equiaxed counterpart, achieving a high tensile strength of 1194 MPa and an elongation of 13.1%. During the deformation, a high proportion of back stress to total flow stress, ranging from 64–67%, denotes that back stress strengthening is one of the main reasons for the better synergy of strength and ductility. This study guides a low‐cost and convenient way for the regulation of microstructure and mechanical properties of titanium alloy with good performance.

Achieving back-stress strengthening at high temperature via heterogeneous distribution of nano TiBw in titanium alloy by electron beam powder bed fusion

Back-stress strengthening has been proven to be an effective strategy in breaking the room temperature strength–ductility dilemma in hetero-structural metals matrix composite materials (MMC). However, back-stress is difficult to achieve at high temperature because of grain boundary softening, grain boundary sliding, dislocation annihilation and grain rotation. Here, back-stress strengthening is exploited to improve the high temperature tensile properties of Ti-6Al-4 V (TC4) alloy by precipitating a heterogeneous distribution of nano TiB whiskers (TiBw). In this work, the rapid solidification associated with electron beam powder bed fusion (EB-PBF) generates heterogeneous in-situ nano TiBw at both grain boundaries and grain interiors. The nano-TiBw on the grain boundaries (GB nano-TiBw) not only refines the grains but can also pin the grain boundaries. The intragranular nano TiBw (IG nano-TiBw) significantly reduces the dislocation mean free path, inhibit dislocation movement, and dramatically enhances the dislocation storage density. Meanwhile, specimens are strengthened by high-density < a + c > dislocations induced by the precipitated nano TiBw. The heterogeneous distribution of nano TiBw achieved a 50 °C increase in the service temperature of TC4 alloy while also increasing stability. This strategy provides a new perspective for further improving the high-temperature mechanical properties of titanium alloys.

Discovering Pyramidal Treasures: Multi-Scale Design of High Strength-Ductility Titanium Alloys.

Mechanical properties of titanium alloys, one of humankind's most essential structural materials, suffer from the lack of 〈c + a〉 dislocations on pyramidal slip planes, failing homogeneous plastic strain accommodation. This mechanical treasure is not easily accessible in titanium alloys because of the required excessively high stress levels. The present work demonstrates that such a dilemma may be overcome by meticulously tuning the c/a ratio, the simplest crystallographic parameter of the hexagonal close-packed lattice, through Sn alloying. Combining this lattice-scale design concept with a cross-rolling based polycrystal-scale design solution, this study showcases a facile route to bimodal (α + β) titanium alloys with exceptional strength-ductility synergy.

Effects of laser power on microstructure and mechanical properties of titanium alloy fabricated by laser-arc hybrid additive manufacturing

Laser-arc hybrid additive manufacturing (LAHAM) based on the synergistic interaction of laser and arc has vast potential applications due to the advantages of high precision and fast manufacturing speed. Titanium alloy is a kind of indispensable material in the aerospace and marine industries because of its superior performance. This study primarily investigates the effect of laser power on formability, microstructure evolution, and mechanical properties of Ti-6Al-4V, a titanium alloy fabricated by LAHAM. The results indicate that the material utilization of the Ti-6Al-4V wire first increases and then decreases with the increasing laser power, reaching a maximum value of 95.48% at a power of 1500 W. As laser power increases, the acicular martensite α′ content in the LAHAM samples decreases, while the α phase increases and exhibits a coarsening phenomenon. Tensile strength increases with the rise in laser power, reaching a maximum horizontal tensile strength of 1080 MPa and a maximum vertical tensile strength of 1100 MPa. However, elongation decreases with increasing laser power. Microhardness decreases with the rise in laser power. The increase in laser power enhances the bonding between deposition layers, significantly improving the tensile strength of the specimens.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Titanium Alloy Fabricated by Laser–Arc Hybrid Additive Manufacturing

Effect of Heat Treatment on Microstructure and Mechanical Properties of Titanium Alloy Fabricated by Laser–Arc Hybrid Additive Manufacturing

Influence of laser treatment on the microstructural evolution and performance of Ti65 alloy

Achieving simultaneous increase in strength and plasticity of metallic materials is a long-term challenge. In this study, we prepared the Ti65 alloy with surface refined structure by laser treatment and studied the evolution of surface and cross-sectional microstructure, as well as its impact on tensile properties. The tensile strength of the Ti65 alloy sheet increases from 1098 to 1136 MPa after laser treatment, and the average fracture strain significantly rises from 6.81% to 10.23%, marking a substantial 50.2% increment. During laser treatment, the fast cooling rate caused the formation of a strengthening layer with fine grains, which leads to an increase in strain hardening rate and non-uniform deformation induced strengthening provided by non-uniform structures. The findings in this work provide a new routine for upgrading mechanical properties of titanium alloy through generating a strengthening layer with fine grains on the surface.

Effects of Co on the microstructure evolution and mechanical properties of Ti-4Al-6Cr-5Mo-8 Nb alloy by ultrasonic vacuum melting

An investigation was conducted into the impact of low cobalt content on the microstructure and mechanical properties of titanium alloys. Ti-4Al-6Cr-5Mo-8 Nb-xCo (x = 0, 2, 3, 4, and 5) alloys were prepared by ultrasonic-assisted melting and casting. The changes in microstructure, mechanical properties, and the strengthening and toughening mechanisms were researched. Results show that, when the cobalt content increases from 0 to 5 wt%, the as-cast structure is all β phase. The lattice parameter of the β phase decreases from 0.3663 to 0.3114 nm, a 15% decrease. The size of primary β grains decreases from 676.8 to 310.7 μm, a 54% decrease. When the cobalt content exceeds 3 wt%, the segregation energy of cobalt increases and grain boundary segregation occurs. Grain refinement is due to constitutional supercooling caused by the β-stable element cobalt, as well as the solute drag caused by the differences in intragranular and grain boundary compositions. In addition, the size mismatch between cobalt and titanium atoms leads to lattice distortion. As the cobalt content increases from 0 to 3 wt%, the tensile strength increases from 918.1 to 1147.8 MPa, a 25% increase, while the fracture toughness increases from 51.7 to 59.7 MPa·m1/2, a 15% increase. At 5 wt% cobalt, the tensile strength and fracture toughness diminished to 247.5 MPa and 14.8 MPa·m1/2, respectively. The decrease in lattice parameters mainly lead to an increase in strength. The secondary crack leads to an increase in toughness. The decline in strength and toughness results from cobalt segregating at grain boundaries, leading to embrittlement.

The Role of Residual Stress in Anisotropic Mechanical Properties of Titanium Alloy after Rolling

The Role of Residual Stress in Anisotropic Mechanical Properties of Titanium Alloy after Rolling

The effects of copper on the mechanical properties of Ti-10Mo alloy prepared by powder metallurgy method

Titanium alloys are currently widely explored and produced for applications in various engineering fields. Alloying metal elements such as Mo, Cu, and Mn bring more advantages among them to help improve the mechanical properties of titanium alloys. This study is intended for the evaluation of mechanical properties through compression and hardness testing performed on a Ti-10Mo alloy with copper addition by powder metallurgy. Ti-10Mo alloys with the addition of copper contents of 3 wt% Cu, 6 wt% Cu, and 9 wt% Cu were prepared to optimize the properties of Ti-10Mo-xCu alloys. With the addition of 3 wt% copper, the compressive strength increased to 577 MPa, which is the maximum compressive strength in this study. On the other hand, with 6 wt% and 9 wt% Cu addition, the compressive strength became 140 MPa and 201 MPa, respectively. A Ti-10Mo alloy with a 3 wt% copper content was able to achieve the maximum hardness of 576 HV. In short, the addition of 3 wt% copper successfully increased the compressive strength as well as the hardness of the prepared titanium alloys.

Overview of Surface Modification Techniques for Titanium Alloys in Modern Material Science: A Comprehensive Analysis

Titanium alloys are acclaimed for their remarkable biocompatibility, high specific strength, excellent corrosion resistance, and stable performance in high and low temperatures. These characteristics render them invaluable in a multitude of sectors, including biomedicine, shipbuilding, aerospace, and daily life. According to the different phases, the alloys can be broadly categorized into α-titanium and β-titanium, and these alloys demonstrate unique properties shaped by their respective phases. The hexagonal close-packed structure of α-titanium alloys is notably associated with superior high-temperature creep resistance but limited plasticity. Conversely, the body-centered cubic structure of β-titanium alloys contributes to enhanced slip and greater plasticity. To optimize these alloys for specific industrial applications, alloy strengthening is often necessary to meet diverse environmental and operational demands. The impact of various processing techniques on the microstructure and metal characteristics of titanium alloys is reviewed and discussed in this research. This article systematically analyzes the effects of machining, shot peening, and surface heat treatment methods, including surface quenching, carburizing, and nitriding, on the structure and characteristics of titanium alloys. This research is arranged and categorized into three categories based on the methods of processing and treatment: general heat treatment, thermochemical treatment, and machining. The results of a large number of studies show that surface treatment can significantly improve the hardness and friction mechanical properties of titanium alloys. At present, a single treatment method is often insufficient. Therefore, composite treatment methods combining multiple treatment techniques are expected to be more widely used in the future. The authors provide an overview of titanium alloy modification methods in recent years with the aim of assisting and promoting further research in the very important and promising direction of multi-technology composite treatment.

Effect of C content on the microstructure and properties of in-situ synthesized TiC particles reinforced Ti composites

Titanium matrix composites (TMCs) have garnered substantial attention from researchers owing to their outstanding properties. Nonetheless, the strength and ductility of TMCs hardly co-exist and often show a trade-off between each other. In this study, we employ an ultra-thin graphite powder sheet as the carbon source and employ Ti/C composites with varying carbon contents, prepared via a layer-stacked laminated sintering method, to ensure a comprehensive in-situ reaction and uniform reinforcement distribution. With increasing carbon content, noticeable alterations occur in the size, concentration, and morphology of the titanium carbide (TiC) particles. The increase of TiC particle content is found to boost the ultimate tensile strength of the composite. However, this improvement comes at the expense of reduced elongation. Notably, as the carbon content reaches 1.81 wt%, the yield strength and ultimate tensile strength of the composites soar to 354.4 MPa and 575.4 MPa, respectively. These values represent a remarkable increase of 75.4% and 65.0% compared to pure titanium, while maintaining an acceptable elongation of 6.45%. This study unveils a promising approach for significantly enhancing the mechanical properties of titanium alloys.

Coherent and semicoherent α/β interfaces in titanium: structure, thermodynamics, migration

The α/β interface is central to the microstructure and mechanical properties of titanium alloys. We investigate the structure, thermodynamics and migration of the coherent and semicoherent Ti α/β interfaces as a function of temperature and misfit strain via molecular dynamics (MD) simulations, thermodynamic integration and an accurate, DFT-trained Deep Potential. The structure of an equilibrium semicoherent interface consists of an array of steps, an array of misfit dislocations, and coherent terraces. Analysis determines the dislocation and step (disconnection) array structure and habit plane. The MD simulations show the detailed interface morphology dictated by intersecting disconnection arrays. The steps are shown to facilitate α/β interface migration, while the misfit dislocations lead to interface drag; the drag mechanism is different depending on the direction of interface migration. These results are used to predict the nature of α phase nucleation on cooling through the α-β phase transition.

Study on effect of heat-assisted rolling on surface morphology and mechanical properties of titanium alloy

This paper mainly investigated the heating influence on surface rolling strengthening of titanium alloy based on the metal thermal softening effect. Surface morphology and mechanical properties of the samples before and after heat-assisted rolling were measured and analyzed. It was found that the surface smoothness and microhardness of the samples rolled at 80°C, 120°C, and 160°C gradually increased as the heating temperature increased. However, the sample rolled at 25°C still had the optimal surface morphology (Ra0.255), the highest surface microhardness (425 HV) and surface residual stress (-497 MPa) because of the characteristics of metal cold work hardening. But the thickness of the hardened layer is much smaller than that of the one rolled at 160°C. In addition, the finite element simulation of the rolling process was carried out, and the dynamic simulation results verified the experimental conclusions. The highest total energy on the surface of the sample rolled at room temperature also indicated its better surface properties.

Study on the microstructure and impact toughness of TC11 titanium alloy by a novel electromagnetic shocking treatment

A novel electromagnetic shocking treatment (EST) has been put forward to optimize interface microstructure and further enhance the mechanical properties of titanium alloys. In details, tensile properties and impact toughness of TC11 titanium alloy have been investigated with room temperature tensile test and Charpy impact testing. Then, tensile fracture and impact fracture as well as microstructure including phase and interface are characterized and analyzed. The results show that after EST, the tensile strength increase slightly, the elongation decreases while the impact energy is enhanced obviously. Besides, with the maximum temperature rising on alloy sample surface being limited to just 210 °C, EST promotes the phase transformation from β to α instantly, also, wrinkling at interface is more commonly observed in EST sample, which indicates that nonlinear interface wetting and bridging are promoted by EST. It demonstrates that the increase of α mainly accounts for the slight improvement of tensile strength and the decrease of elongation. Also, considering that the phase transformation from β to α is unfavorable to the improvement of impact toughness, the degree of interface wetting and bridging which is dependent on the electromagnetic shocking energy plays a decisive role for the enhancement of impact energy of EST sample. This work provides a novel EST method to selectively embellish interface and further to improve the properties and performance of solid alloys related with interface microstructure.

Improvement of antibacterial activity and mechanical properties of titanium alloy by TiAlN/Ag gradient multilayer coatings

Silver coating has an excellent antibacterial activity but low mechanical properties, e.g., microhardness. In order to improve simultaneously the antibacterial activity and surface hardness of titanium alloys, TiAlN/Ag multiple coatings with different gradient distributions in thickness were prepared on titanium alloys by unbalanced magnetron sputtering. The coatings with gradient thickened TiAlN–Ag cosputtered upper layers had a much stronger antibacterial activity, 99.82% in antiseptic Escherichia coli, than those with the gradient thinned upper layers. With increasing gradient cycles of the multiple coatings, the antibacterial activity decreased, whereas the hardness increased. The alternate growth of TiAlN and TiAlN–Ag layers may repeatedly provide an excellent comprehensive antibacterial activity (99.23% for Escherichia coli) and hardness (two times TC4 alloy) for a long term.

Effect of interlayer cooling on the microstructure and mechanical properties of titanium alloys fabricated using directed energy deposition

The effect of interlayer cooling in directed energy deposition on the microstructure and mechanical properties of two titanium alloys (Ti–6Al–4 V and Ti–2.5Fe–4.5Al–0.25Si) was investigated in this study. On the one hand, the general process of directed energy deposition provided sufficient time for element partitioning, resulting in the formation of the isothermal ω. On the other hand, interlayer cooling interfered with element partitioning and isothermal ω formation. It induced the formation of the supersaturated α. The isothermal ω or supersaturated α, generated based on the fabrication conditions, significantly influenced the mechanical properties of these alloys. The higher the β-phase stability of the alloy, the greater is the change in its mechanical properties depending on the fabrication conditions. This study provides guidelines for the design of new alloys manufactured using directed energy deposition.

Effects of tricalcium phosphate-titanium nanoparticles on mechanical performance after friction stir processing on titanium alloys for dental applications

Friction Stir Processing (FSP) is a solid-state method that is widely used in titanium and its alloys to enhance their strength. The FSP technique produces low-defect-density materials with improved mechanical properties, making it potentially valuable for orthopedic and dental applications. It is primarily used for low-melting-point materials such as titanium but can also be applied to high-melting-point metals such as steel, nickel, and titanium alloys. When conducting an FSP test, it is crucial to select appropriate tool geometry, rotational speed, tool speed, and workpiece thickness. Scanning electron microscopy (SEM) are commonly used to analyze the phase and morphology of samples containing Tricalcium Phosphate (TCP) and Titanium oxide nanoparticles (Ti-NPs) ceramic. The effect of hydrogenation on the mechanical properties of titanium alloys mixed with titanium during FSP is also investigated. The composition of TCP and Ti-NP is diffused onto the titanium substrate, and it is recommended that Ti-NP be joined to the substrate using FSP. Using FSP, the microstructure can be altered, and the properties of the new design tool can be studied using mechanical testing. The effects of hydrogenation during FSP of two non-homogeneous metals with Ti-NP can be investigated to evaluate the mechanical properties of the joint area and the worn tool mechanism. The pin tool mainly alters the direction of the secondary metal, allowing for an increase in the number and size of this secondary material attached to titanium. FSP parameters can be optimized based on the volume of the joined area using various established techniques.

Constitutive Behavior of Titanium Alloy With Dual-Phase Microstructures: Experiments and Modeling

AbstractThe complex composition, size, and distribution of microstructures of titanium (Ti) alloy affect the mechanical properties of titanium alloy and its application in aerospace, ocean technology, and bioengineering. In this paper, the microstructural components and mechanical behavior of Ti80 are first investigated experimentally. According to the experimental observations of the dual-phased microstructures, a mechanism and microstructure-based constitutive model of Ti80 is established to study the quantitative relationship between mechanical behavior and equiaxed αp + lamellar αs + β microstructures of titanium alloys. And the influence of dislocation evolution and accumulation on the strengthening and work-hardening of materials is also explored in detail, especially the contribution of dislocation pile-up zone at the phase boundary between α phase and β phase on the strengthening of materials. Numerical results show that the proposed model can describe the constitutive behavior of Ti80 very well, including yield stress and strain hardening. And various strengthening mechanisms originated from the grain boundaries, phase boundaries of β transformation structure and β precipitation are analyzed. The proposed model is further applied to predict the constitutive behaviors of the titanium alloy with different sizes and various volume fractions of microstructure.

Effect of rare earth Ce addition on microstructure and mechanical properties of titanium alloy Ti-6Al-4V

• Effect of Ce on microstructure and mechanical properties of Ti6Al4V are studied. • Ti6Al4V alloy grains are significantly refined after adding Ce. • Ce combines with O in matrix to form CeO 2 , which is coherent with the alloy matrix. • The strength and ductility of Ti6Al4V containing 0.5wt.% Ce are obviously improved. • The frictional performance of Ti6Al4V containing 0.3wt.% Ce is obviously optimized. These Ti6Al4V-xCe (x=0, 0.1, 0.3, 0.5, 0.7 wt.%) were prepared by vacuum non consumable arc furnace. And the microstructure and comprehensive mechanical properties of these Ti6Al4V were systematically explored. The results show that the tensile strength and ductility of Ti6Al4V containing 0.5 wt.% Ce is significantly improved (Ultimate tensile strength: 978.1MPa; Elongation: 7.1%). And the wear resistance of Ti6Al4V containing 0.3 wt.% Ce is significantly optimized (Wear quality: 0.55mg). The excellent balance between strength and plasticity of Ti6Al4V is due to the significant grain refinement and the complete coherent relationship between ceria and Ti6Al4V matrix.