Ti-5553 Alloy Research Articles

Deformation Heating and Temperature Changes in a Near-β Titanium Alloy during β-Processed Forging

We investigated the temperature increase caused by heat generation from plastic deformation during β-processed forging in a near-β titanium alloy, Ti-17 alloy (Ti-5Al-2Sn-2Zr-4Cr-4Mo, wt%), by inserting thermocouples into large workpieces (100 mm in diameter and 50 mm in height). The workpiece was initially heated and held at 1193 K (920 °C) in the single-β region. It was subsequently forged between hot dies in surrounding heaters at a compression percentage of 75% at strain rates of 0.05 and 0.5 s−1 at 1023–1123 K in the (α + β) region. At 0.05 s−1, the temperature logarithmically increased by 39 K in 28 s for 1023 K; it increased by 30 K in 28 s for 1073 K. However, at 0.5 s−1, the material temperature increased, in 3 s, beyond or close to the β-transus temperature during forging at 1023 and 1073 K. In addition, as the forging temperature decreased, the increase in material temperature moderated, resulting in a difference of 27 K in the last forging stage, between the conditions of 1023 and 1073 K. This would reduce the temperature difference effect on microstructure formation during β-processed forging.

High-Strength Near-Beta Titanium Alloy Fabricated by Direct Hot Pressing of the Machining Swarf

Significant amount of Ti-5553 alloy (a near-beta titanium alloy) swarf is produced during the daily operation of manufacturing high strength titanium alloy components used in industry. However, the direct use of the produced swarf is seldom investigated and reported. In this paper, hot pressing was used to recycle Ti-5553 machining swarf to turn the waste into useful material. The hot-pressed Ti-5553 alloy has an ultimate tensile strength (UTS) of 675 ± 12 MPa, strain to fracture of 0.98 ± 0.04%, and bending strength of 1181±28 MPa. After double-aging at 600 ºC for 4 h followed by 700 ºC for 0.5 h, both strength and ductility of hot-pressed Ti-5553 alloy have a significantly improved, with a yield strength (YS) of 1390 ± 20 MPa, UTS of 1425 ± 12 MPa, a strain to fracture of 2.47 ± 0.07%, and a bending strength 2565±35 MPa. These results demonstrate the hot pressing is a viable processing route to recycle Ti-5553 swarf to cost-effectively produce a qualified solid material for post-processing and engineering applications.

The conflicts between strength and ductility of bimodal Ti-5553 alloy with fine equiaxial prior β grains

In the paper, homogeneous bimodal Ti-5553 alloy with the prior-β grain size of 15 μm is successfully fabricated by elaborate thermo-mechanical processing in α+β field, solution and ageing, in order to explore the combination of strength and ductility accessible to β-titanium alloys. The strengthening curve of ageing at 500°C comprises the incubation period, the strengthening period and the stable period. The attainable yield strength of the alloy aged at 500°C is 1430 MPa, associating with a receivable tensile elongation of 9.5%. During the ageing at 620°C the strength of the bimodal alloy first increases with ageing time, then reaches a maximum value of 1079 MPa after 2 h and finally remains constant within the ageing period from 2 h to 32 h. It is unexpected that the tensile elongation of bimodal alloys aged at 620°C are the same as that of the solution-treated alloy. Interestingly, the ageing at 700°C dose not exhibit the strengthening effects but could make the alloy more ductile. Within the ageing temperature scope of 500°C∼700°C, the precipitating kinetics of grain boundary α (αGB) precipitation is more active than that of the intragranular α (αIntra) precipitation. However, αGB does not have the precipitation strengthening effects. The yield strength of bimodal Ti-5553 alloy depends on the dislocation density of β phase and the size effects of prior β grains. By exploring the tensile damage sources, we find that the ductility of bimodal Ti-5553 alloy of is influenced by the plasticity of αGB and the stress concentration of β/αIntra interface. The combination of strength and ductility of high-strength bimodal Ti-5553 alloy might be further improved by optimizing the thickness of αGB.

Synergistic influence mechanism of microstructure type and loading mode on the long crack propagation in Ti-55531 alloy

This work aims to reveal the synergistic effect mechanism of microstructure type and loading mode on the long crack propagation in the Ti-55531 alloy. The fracture toughness (KIC) and fatigue crack propagation rate (da/dN) of the Ti-55531 alloy with lamellar microstructure (LM) and bimodal microstructure (BM) were investigated and compared at room temperature. The results show that both microstructural factors and the loading mode significantly affect the long crack propagation behavior of the alloy. Under static loading, the KIC of the LM is higher than that of the BM. Under cyclic loading, the da/dN of the BM is lower than that of the LM in the lower stress field intensity factor range (ΔK < 26.47 MPa·m1/2). However, when ΔK > 26.47 MPa·m1/2, the da/dN of the BM is higher than that of the LM. The results of the fracture surface morphology and the crack path analysis show that the difference in microstructure characteristics leads to various behaviors of the long crack propagation under both static and cyclic loadings. The key microstructural factors controlling the long crack propagation in the two microstructures under static and cyclic loadings are discussed. The influence of microstructure characteristics on the long crack propagation in different stages of crack growth is also explained. Moreover, a new calculation model of KIC is proposed. These results could provide support for the reliability design of engineering structures and promote the wider application of the alloy in engineering.

Studies on the surface characteristics of Ti60 alloy induced by turning combined with ball burnishing

Ball burnishing can enhance the service performance of parts and is more and more widely used in industrial production. To reveal the formation mechanism of the surface characteristics of ball burnishing of Ti60 alloy, the turning combining ball burnishing experiment was carried out, and the surface characteristics, such as surface morphology, roughness, residual stress, microhardness, and microstructure were investigated in detail. The results show that the surface roughness ranges from 63.9 nm to 110.3 nm and the height difference of the surface roughness profile is within 600 nm after burnishing. The stress concentration factors after burnishing change between 1.06 and 1.204. There is a positive correlation between the stress concentration factor and the surface roughness. The sinusoidal decay function is an effective method to predict the distribution of residual stress along the depth. After burnishing, the micro-hardness distribution shows a trend of first increasing and then decreasing. In addition, the second α phase (αs) and β phase are observed to be deflected obviously after burnishing. The kernel average misorientation (KAM) indicates that significant plastic deformation occurs in the surface layer after burnishing. The average values of local misorientation before and after burnishing are 0.52° and 0.69° respectively. The geometrically dislocation density increases from 7.02 × 109 mm−2 to 9.31 × 109 mm−2. The grain size is reduced from 13.1 μm to 10.5 μm, and the proportion of low-angle grain boundaries (LAGBs) has increased from 12.7% to 22.5%. Intragranular deformation increases significantly and texture exists after burnishing. The research methods and conclusions can provide technical and data support for better burnishing effect of Ti60 alloy.

Phase transformation of the Ti-5553 titanium alloy subjected to rapid heating

The α → β phase transformation upon heating in the Ti-5553 alloy with lamellar-nodular bimodal microstructure was tracked in situ with high energy X-ray diffraction. Rapid heating at 10, 50 and 100 °C s−1 from room temperature to 1050 °C was tested. Phase transformation on heating was studied by a combined analysis of the microstructural features that provides estimates of mass fractions, mean lattice parameters and full width at half maximum for the two phases. In comparison with equilibrium conditions, the experimental mass fractions reveal a shift of the transformation domain toward high temperatures when the heating rate increases. Also, the dissolution of the α phase is largely impacted by its morphology, the transformation being faster for α lamellae. The combined analysis of mean lattice parameters and full width at half maximum suggests that the α → β phase transformation on heating is diffusion controlled. The β phase therefore inherits the solute content of the adjacent parent α phase, leading to chemical heterogeneities in the β phase regardless of the heating rate.

Microstructure and wear behavior of AlCrTiNbMo high-entropy alloy coating prepared by electron beam cladding on Ti600 substrate

High-entropy alloys have been widely studied as a new and excellent material in the field of surface protection. To improve the low surface hardness and wear resistance of Ti600 alloy, AlCrTiNbMo high-entropy alloy (HEA) coating was prepared by electron beam cladding. The phase structure and microstructure showed the presence of two BCC solid solution phases A2 and B2 within HEA coating. Laves phase Ti3Al and intermetallic compound Mo3Al8 were also present in the coating. The results of hardness and wear resistance tests showed that the microhardness of coating is 813.5 HV0.2，while substrate is 370.7 HV0.2. The mass loss of coating is only 1.02 mg after wear test, while the mass loss of Ti600 is 38.81 mg. There are cracks and delaminations on the worn surface of Ti600, and wear mechanism is a mixture of micro-ploughing and micro-cutting. The worn surface of HEA coating contains only shear surface traces, and the wear mechanism is micro-cutting. The width and depth of grooves on the worn surface of HEA coating are nearly 10 times that of Ti600 substrate. AlCrTiNbMo HEA coating can be used as an excellent wear-resistant coating with wide application prospect.

Microstructure evolution, mechanical properties and high temperature deformation of (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe titanium alloy

The addition of trace (TiB + TiC) reinforcements could minimize the deformation steps and decreases its costs according to recent study. In present work, the hot deformation behavior and microstructure evolution were studied via the isothermal hot compression at different temperature and strain rate. Based on the DMM model, the activation energy Q and processing map were obtained. Subsequently, two billets were hot-rolled and heat-treated, to study the microstructure and tensile properties of the alloy. Results revealed that the flow behavior of the (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy was similar with other near β titanium alloy. When deformation in β region, the deformation mechanism was associated with cDRX by lattice rotation and dynamic recovery; when deformation in (α + β) region, the deformation mechanism was associated with substructure evolution, such as DRX and dynamic recovery. The lower strain rate guarantees abundant time for microstructure transformation, while the higher strain rate leads local flow instability and cracks. The activation energies Q is 264.1 kJ/mol in (α + β) region and 181.8 kJ/mol in the β region. According to the processing map, the optimum deformation windows are 770–800°C and 850–880°C, 0.001 s −1 . In addition, the microstructure of 770R + SAT is characteristic of duplex microstructure with a certain amount of α p , considerable precipitation of fine acicular α s and continuous α GB , which is achieved a UTS of 1414 MPa with a poor ductility. Therefore, the (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy shows excellent deformability and higher strength, which is possible to achieve both high economy (less deformation step) and advancement (high mechanical properties due (TiB + TiC) reinforcements). • The deformation behavior of was associated with grain boundary sliding, dynamic recovery and dynamic recrystallization. • The UTS of 770R + SAT achieved 1414 MPa, which was slight higher than other Ti55531 or Ti1023 titanium alloy. • The fine acicular αs achieved high strength while the continuous αGB decrease the ductility. • The (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy was possible to achieve both high economy and advancement.

Effect of thermomechanical treatment on the microstructure evolution and mechanical properties of lightweight Ti65(AlCrNb)35 medium-entropy alloy

Lightweight Ti65(AlCrNb)35 medium-entropy alloy (Ti-65) ingots were produced through arc melting and drop casting in a water-cooled copper mold. These alloy ingots were then treated through a sequence of homogenization, hot rolling, cold rolling, and recrystallization. The effect of this thermomechanical treatment (TMT) on their microstructures and mechanical properties was investigated through X-ray diffraction (XRD), electron backscatter diffraction analysis through scanning electron microscopy, and mechanical testing. The XRD results demonstrated that the Ti-65 alloy maintained a body-centered cubic structure after 50% hot rolling, 70% cold rolling, and recrystallization at 900 °C, 1000 °C, and 1100 °C, respectively. The fully recrystallized sample had an 80% smaller grain size than the as-cast sample. The cold-rolled Ti-65 alloy specimen exhibited a high tensile strength of 1620 MPa. In comparison with the tensile strength of the as-cast Ti-65 sample (1100 MPa), that of the Ti-65 alloy following annealing and subsequent partial recrystallization was significantly increased (1380 MPa). This tensile strength enhancement is attributable to its heterostructure composition of deformed bands and smaller recrystallized grains. This study demonstrated that an effective strength–ductility synergy of the Ti-65 alloy can be achieved through various TMTs.

A crystal plasticity-based constitutive model for near-[formula omitted] titanium alloys under extreme loading conditions: Application to the Ti17 alloy

A crystal plasticity-based constitutive model is proposed to describe the thermo-mechanical behavior of the Ti17 titanium alloy subjected to extreme loading conditions. The model explicitly incorporates the effect of the crystallographic orientation of the hcp α and bcc β phases. The constitutive equations are built in the context of continuum thermodynamics with internal variables. The general framework of continuum damage mechanics is used to consider the impact of ductile damage on the mechanical behavior. The proposed model is implemented in a finite element method solver. The material parameters are identified from an extensive experimental dataset with an inverse method. According to the results, the impact of the strain rate and the temperature on the mechanical behavior is correctly depicted. The model is then used to evaluate the impact of temperature on strain localization. The role of the local texture on the development of ductile damage is also discussed for different specimen geometries. Finally, the impact of heat exchanges on the mechanical behavior at low and high temperatures is investigated.

The Effect of Neighboring Grain Orientation on Dislocation-Grain Interaction in Ti-5553 Alloy

The Effect of Neighboring Grain Orientation on Dislocation-Grain Interaction in Ti-5553 Alloy

Effect of Ultrasonic Impact Treatment on the Microstructure and Properties of Laser Solid Formed Ti60 Alloy

Effect of Ultrasonic Impact Treatment on the Microstructure and Properties of Laser Solid Formed Ti60 Alloy

Effect of Ultrasonic Impact Treatment on the Microstructure and Properties of Laser Solid Formed Ti60 Alloy

Effect of Ultrasonic Impact Treatment on the Microstructure and Properties of Laser Solid Formed Ti60 Alloy

Formation of residual stresses during quenching of Ti17 and Ti–6Al–4V alloys: Influence of phase transformations

The formation of internal stresses during quenching of titanium alloys from the β phase field are investigated both experimentally and by simulation, in order to show the effects of phase transformations. Two titanium alloys are considered: the β-metastable Ti17 alloy and the α+β Ti–6Al–4V alloy. During the quench into water of laboratory scale samples (40 mm diameter cylinders), no phase transformations occurred in the Ti17 alloy because of its β-metastable character and the fast cooling. However, β→α+β and β→α′ phase transformations occurred in the Ti–6Al–4V sample. Both alloys are compared in order to highlight the effects of the phase transformations. Residual stresses were determined by neutron diffraction, by the contour method and at the surface by the hole drilling method. A model for the coupled thermal, mechanical and metallurgical evolutions is established in order to simulate the quenching operations. The material model for the Ti17 alloy was established in a previous study. Regarding the Ti–6Al–4V alloy, modeling approaches and experimental data from literature are utilized to build the material model. From both experiment and simulation, it is found that the internal stress evolutions are governed by the thermal gradients. The phase transformations have a weak impact because of the small deformation strains induced by the phase change. Nevertheless, good prediction of the phase transformation kinetics is necessary for accurate simulations, because the α and α’ phases strengthen the alloy, thereby limiting the plastic straining at the origin of the residual stresses. As most plastic strains are cumulated at high temperature, the thermomechanical model should be established accurately over the temperature ranges in which there is a significant proportion of β phase.

Influence of microstructure on strain controlled low cycle fatigue crack initiation and propagation of Ti-55531 alloy

Low cycle fatigue (LCF) crack initiation and propagation behavior of Ti-55531 alloy with lamellar and bimodal microstructures were comparatively investigated at room temperature. Results indicated that the two microstructures displayed different sensitivity to the change of cyclic strain, which resulted in significantly different cyclic deformation, fatigue crack nucleation, and crack propagation behavior of two microstructures. Finally, it was found that cyclic lives of two microstructures were entirely different. Moreover, besides slips and deformation twins, stacking faults promoting cracking of αs/β interface may be another important LCF microcrack nucleation mechanism of Ti alloys, which hasn’t been revealed by other researchers.

Impact Toughness of As‐Built and Heat‐Treated Near‐β Ti–5Al–5Mo–5V–3Cr–1Zr Alloys Fabricated by Selective Laser Melting and Electron Beam Melting

Herein, the effects of heat treatment on the microstructure evolution and impact toughness of selective laser‐melted (SLM) and electron beam‐melted (EBM) near‐β Ti–5Al–5Mo–5V–3Cr–1Zr (Ti55531) alloy specimens are systematically investigated. As fabricated SLM and EBM Ti55531 alloys contain metastable β and α + β microstructure, respectively. The metastable β microstructure of SLM‐fabricated Ti55531 is transformed to bilamellar, lamellar, and bimodal structure after supertransus triplex heat treatment, hot isostatic pressing and α/β solution and aging treatments, respectively. In the EBM‐fabricated Ti55531 specimens, the defects are effectively eliminated after hot isostatic pressing. The correlation between microstructure and impact toughness of as‐built and heat‐treated specimens are elucidated. Both SLM and EBM specimens with lamellar microstructure show a high impact toughness due to the deflecting effect on crack propagation of α lamella. In addition, hot isostatic pressing further enhance the impact toughness of EBM‐fabricated Ti55531 via eliminating the defects formed during the fabrication process. This work demonstrates that heat treatment is a potential way to tailor the microstructure and enhanced the impact toughness of additive manufactured near‐β Ti alloys.

Effects of thermomechanical treatment on the evolution pattern of the α phase and mechanical properties of Ti-17 alloy

The effects of thermomechanical treatment (TMT) on the evolution pattern of the α phase and mechanical properties of Ti-17 alloy were investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electronic microscopy (TEM). For the purpose, Ti-17 alloy with initial basketweave microstructure is rolled by 40% at 860 °C and immeiate aging at different temperatures. The results indicated that the α phase was very sensitive to the aging temperature during the TMT process. Rolling led to globularization of primary α phase (αp) and destruction of Burgers orientation relationship between αp and β phases. The subsequent immediate aging yielded further globularization and coarsening of αp, precipitation and coarsening of secondary α phase (αs), and decreasing of the volume fraction of αs. When the aging temperature was increased from 540 to 630 ℃, these changes of the α phase reduced the tensile strength, and enhanced the plasticity and impact toughness. High correlation coefficients (more than 94%) implied that linear equations accurately described the effect of microstructure evolution of the α phase on mechanical properties. Immediate aging at 600 ℃ after hot rolling yielded good comprehensive mechanical properties. This revealed that the structure with suitable matching of globular and lamellar α phase could obtain the optimal combination of strength, plasticity and toughness for Ti-17 alloy.

Studies and Optimization of Surface Roughness and Residual Stress in Ball Burnishing of Ti60 Alloy

Studies and Optimization of Surface Roughness and Residual Stress in Ball Burnishing of Ti60 Alloy

Strength and Ductility Balance of a Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) Alloy with Various Microstructures: Experiment and Machine Learning

Strength and Ductility Balance of a Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) Alloy with Various Microstructures: Experiment and Machine Learning

Physically based constitutive modeling for Ti17 alloy with original basketweave microstructure in β forging: A comparison of three approaches

Based on hot compression tests carried out at 1173–1223 K, 0.001–10 s−1 for Ti17 alloy with original basketweave microstructure in β forging, three physically based constitutive modeling approaches for both peak stress and flow stress considering strain compensation are studied, and the corresponding prediction accuracy and deformation/diffusion mechanisms are analyzed. The established physically based constitutive equation with a fixed creep exponent n = 5 presents poor predictability, which implies that dynamic recovery (DRV) controlled by the glide and climb of dislocations is not the only deformation mechanism in β forging of the alloy. On the other hand, the physically based constitutive equation with exponent n as variable demonstrates good predictability with average absolute relative error (AARE) of 6.18%, correlation coefficient (R) of 0.997 for the peak stress, and AARE of 6.73%, R of 0.995 for the flow stress respectively. This suggests that thermal diffusion mechanism should include lattice diffusion in β forging of the alloy. Furthermore, a revised physically based constitutive model considering the coupling effects of the lattice diffusion and the grain boundary diffusion shows better predictability with AARE of 4.69%, R of 0.994 for the peak stress, and AARE of 4.86%, R of 0.998 for the flow stress respectively. This indicates that thermal diffusion mechanism includes not only lattice diffusion but also grain boundary diffusion in β forging of the alloy. It is believed that the occurrence of DRX in β forging of the alloy is responsible for the obtained exponent n = 2.831, which deviates from the theoretical value of 5.