Tailoring the as-cast microstructure of Ti-6Al-4V alloy into a refined, uniform structure through thermomechanical processing (TMP) is critical for optimizing its mechanical properties. Despite the well-established industrial effectiveness of sequential deformation from the single-phase β field to the dual-phase α + β field, the microstructural heredity between consecutive deformation passes remains poorly understood. This study investigates the microstructural evolution and inheritance of as-cast Ti-6Al-4V alloy subjected to hot deformation under different alternative phase field routes and strain rates. The results show that deformation across different phase fields promotes flow softening through the synergistic effects of β grains dynamic recrystallization (DRX) and lamellar α dynamic spheroidization (DS). At low strain rate (0.001 s−1), the inherited fine β grains and lamellar α from single-phase β field deformation accelerate lamellar α DS during subsequent dual-phase α + β field deformation. Concurrently, dual phase α + β field deformation enhances DRX of β grains by promoting the DS of GBα, ultimately leading to homogeneous DS of both grain boundary α (GBα) and intragranular lamellar α. At a high strain rate (0.1 s−1), GBα spheroidizes rapidly, while intragranular lamellar α evolves mainly through bending and fusion. This work provides a scientific basis for designing TMP routes to achieve controlled microstructures.

Ti–6Al–4V titanium alloys are widely utilized in aerospace and high-performance engineering applications due to their exceptional strength and corrosion resistance. However, during the vacuum arc remelting (VAR) process, especially for large-scale ingots, complex heat transfer and aluminum volatilization can induce segregation and microstructural control challenges, posing significant difficulties for solidification management. In this study, a three-dimensional numerical simulation model incorporating actual process parameters was developed to systematically analyze the coupled evolution of thermal fields, solidification behavior, microstructural morphology, and elemental distribution. The simulation successfully reproduced the progressive transformation of the molten pool morphology from shallow-flat to U-shaped and V-shaped configurations, and identified three characteristic regions: a fine-grained and columnar zone at the bottom, inward-converging columnar grains in the midsection, and an extended equiaxed grain region at the top resulting from reduced cooling during hot topping. The results indicated that increasing melting rates deepened the molten pool, reduced the solid fraction, thickened the mushy zone, and aligned grain orientations more closely with the principal heat flow. Aluminum showed central depletion, peripheral enrichment, and significant volatilization at the ingot top. The simulation outcomes were in good agreement with experimental observations, validating the model’s accuracy and applicability. This study provides valuable insights for optimizing VAR processes, enhancing microstructural uniformity, and reducing defect risks.

Ti-6Al-4V is a critical alloy for aircraft engine compressor blades, yet its creep behavior under high-stress and warm temperature remains poorly understood. This study investigated the creep mechanisms in a Ti-6Al-4V alloy at 573-723 K/400-600 MPa focusing on microstructural stability and threshold stress evolution. Microstructure stability was evaluated through dynamic recovery/recrystallization analysis and their impact on microstructural features was studied. Post-creep exposure microstructure was characterized by scanning electron microscopy (SEM) along with EBSD analysis, and transmission electron microscopy (TEM). The dynamic recovery (DRV) and recrystallization (DRX) fractions were quantified by grain orientation spread (GOS) and geometrically necessary dislocations (GNDs) density values evaluation. Results showed that at 573-623 K/450-600 MPa, high threshold stresses (i.e. 378-234 MPa) were related to dominance of DRV and basketweave-like secondary alpha-lath arrangements. At 673 K, threshold stress was dropped to 133 MPa due to high dislocation motion, coarsened secondary alpha-laths (from 1.60 to 1.80 mu m), and reduced aspect ratios of secondary alpha-laths (from similar to 8 to similar to 4). At 723 K, threshold stress was negligible because of the increased dislocation climb motion leading to power-law breakdown creep behavior. It resulted in fast creep rates (>10(-8) s(-1)) and large creep strain (>10%) before fracture. Creep threshold stress was observed to decrease more significantly with the decrease of secondary alpha-lath aspect ratio. These results established that maintaining large alpha-lath aspect ratio is critical for improved creep resistance at 573-723 K and that secondary alpha-lath aspect ra6tio should be considered a microstructure design criterion.

In this study, the deformation mechanisms and damage evolution behavior in a bimodal Ti-6Al-3Nb-2Zr-1Mo (wt.%) alloy were systematically investigated via the combination of advanced in-situ EBSD analysis of tensile testing and transmission electron microscopy (TEM) observation. The slip trace analysis demonstrates that the early stage of plastic deformation is dominated by the prismatic and basal slip systems, whereas the pyramidal and slip systems are gradually activated and become the primary deformation mechanisms at high strain levels. Specifically, the plastic deformation is mainly accommodated by the presence of alpha phase through the basal and the prismatic slip systems. Besides, the Schmid factors of the basal and prismatic slip systems under the given loading direction are significantly lower than that of the pyramidal slip system, and thereby the pyramidal slip is preferential activated during the plastic deformation. With increasing strain, the lamellar alpha phase progressively activates the pyramidal slip systems to accommodate the imposed strain along the c-axis. TEM observations exhibit the presence of high-density dislocation tangles near twin boundaries, and thus the synergistic interaction between dislocation slip and twining can induce the micro-void nucleation and growth, which is driven by the localized stress concentration. This work elucidates the damage mechanisms dominated by the slip-twinning interactions, which can provide theoretical guidance for strength-ductility optimization in bimodal titanium alloys.

TiAl alloys, with low density and excellent high-temperature properties, have become important materials for applications in oxidative environments above 600°C such as LPTBs, achieving the goals of achieving improved engine performance with simultaneous reduction in weight and emissions. TiAl alloys originated from Ti alloy research and have consistently focused on engine weight reduction as their primary objective, filling the gap in light alloys above 600°C. In the last decade, important advances have been made in both research and application of TiAl alloys. However, previous reviews have focused on individual areas. This paper comprehensively reviews the characteristic, history and processes of TiAl alloys, especially recent advances in hot working, additive manufacturing and directional solidification. Furthermore, it points out the potential application fields of TiAl alloys in the post-combustion engine era, as well as the direction for researchers and the industry. This review aims to provide a up-to-date and comprehensive introduction to TiAl alloys, offering guidance for researchers and engineers, and promoting the large production and application of TiAl alloys.

Selective elemental volatilization during vacuum melting strongly influences the separation behavior and compositional stability of multicomponent titanium alloys, particularly under electron beam cold hearth melting (EBCHM) conditions. In this study, the volatilization behavior of alloying elements in Ti-Al-V-Cr-Fe alloys was quantitatively investigated through a coupled thermodynamic-kinetic framework. The intrinsic volatilization tendency of individual elements was evaluated based on saturated vapor pressures, while thermodynamic activities and relative volatilization coefficients in multicomponent melts were determined using CALPHAD-based calculations. By integrating gas-liquid interfacial evaporation kinetics with surface temperature fluctuations, a predictive model was developed to describe elemental mass loss and composition evolution during vacuum melting. The model was validated through laboratory-scale electron beam melting experiments and industrial-scale EBCHM trials, showing good agreement between predicted and measured results. The results indicate that selective volatilization is jointly governed by intrinsic vapor pressure and thermodynamic activity, resulting in an overall volatilization tendency of Cr > Al >> Fe > Ti > V. Although Al contributes the largest absolute cumulative mass loss under laboratory-scale batch melting conditions and the highest mass-loss rate under industrial EBCHM conditions, Cr exhibits the highest percentage volatilization loss and is therefore identified as the critical element affecting compositional stability. The proposed framework provides a quantitative basis for volatilization prediction, separation control, and composition compensation design in multicomponent titanium alloys during EBCHM processing.

Renowned for their exceptional specific strength and excellent corrosion resistance, titanium (Ti) alloys are extensively utilized across numerous industrial sectors. Thermo-mechanical processing (TMP) is crucial for optimizing their engineering performance to meet the specific demands for practical application. One of the most essential metallurgical focuses during TMP is the occurrence of dynamic recrystallization (DRX), which is crucial for microstructure refinement. Recent studies revealed that the DRX of Ti alloys involves distinct mechanisms and their mutual interactions, rendering the TMP design difficult. This review systematically examines the different DRX mechanisms responsible for Ti alloys subjected to TMP, including discontinuous DRX (DDRX), continuous DRX (CDRX), geometric DRX (GDRX), and twin-assisted DRX (TDRX) under various TMP conditions. Moreover, the effects of key TMP parameters such as deformation temperature, strain rate, and strain level on the DRX behavior in Ti alloys during TMP are discussed. Meanwhile, the effects of initial microstructure, second-phase particles, and deformation modes on the DRX behavior of Ti alloys are also assessed. Besides, the impacts of conventional TMP techniques are evaluated on the DRX behavior in Ti alloys, such as surface modification approaches and material joining processes. Moreover, recent advancements in the numerical modeling and multi-scale simulation methods for predicting DRX behavior in Ti alloys are summarized. Finally, challenges and future research directions including advanced characterization and machine learning enabled TMP design of Ti alloys are proposed and discussed.

In this work, HCP-to-FCC phase transformation and its interaction with {1122} compression twins (CTWs) in CP-Ti under ultra-high-strain-rate compression( similar to 10(6)/s) was investigated. Muti-scale characterization and analysis demonstrate the both B-and P-type FCC(Ti )lamellae are profusely generated and exhibit significant growth capability and intensive interaction with the CTWs. Particularly, two adjacent FCCTi lamellae with a twinning relationship can be formed within the CTW and matrix, respectively. Moreover, two adjacent FCC(Ti )lamellae with nearly identical orientation can be formed within the two different CTW variants. Two possible mechanisms were proposed to account for this unique phenomenon.

Additive manufacturing (AM) of titanium alloys via electron-beam powder bed fusion (EBPBF) is attractive due to the great freedom it presents in processing and near-net-shape forming, but it often relies on post-heat treatment to optimize the microstructure and modulate the mechanical properties. In contrast to research on equiaxed Ti-6Al-4V, also known as Ti64, fabricated by thermomechanical processing, the thermal stability of α-Ti laths and the relationship between α-Ti lath growth and mechanical properties in Ti64 ELI (extra-low-interstitial) produced by EBPBF-AM have been little reported. In the present work, the microstructure was characterized, and α-Ti lath coarsening was investigated during long-term aging at 700°C, 800°C, and 900°C for Ti64 ELI fabricated by EBPBF-AM. The time exponent (n) for lath growth at all three temperatures was found to be 5, and the activation energy for α lath growth was found to be 142kJ/mol, indicating a pipe-diffusion-governed mechanism through substantially high-density lath boundaries. Significant coarsening of the α laths resulted in a substantial decrease in the yield strength (YS) and ultimate tensile strength in all three samples. The Hall-Petch relationship was established based on those annealed specimens with high confidence. The low oxygen concentration of 0.06wt.% in the Ti64 ELI was responsible for the low friction stress of 216MPa, which is lower than the 626~803MPa of most Ti64 alloys. Pronounced type prism and basal slip systems and limited type pyramidal slip systems are active during the tensile plastic straining, all of which collectively accommodate arbitrary strains to achieve large macroscopic fracture strain.

In recent years, the widespread application of Ti-6Al-4V titanium alloys across multiple engineering fields has intensified the demand for developing cost-effective, high-performance titanium alloys. In this study, a largescale Ti-6Al-4V-1Fe-1Cr (Ti-6411) alloy plate with low cost and high performance was fabricated by recycling and remelting Ti-6Al-4V return materials followed by a short-route rolling process. In this work, the effects of annealing (6411-AN) and solution treatment plus aging (6411-STA) on the alloy's microstructure evolution and tensile-fatigue properties were systematically investigated. The 6411-STA alloy, characterized by low-aspect-ratio alpha colonies and secondary alpha (alpha s) phases, exhibited an outstanding combination of strength and ductility (Rp0.2 = 1049 MPa, Rm = 1130 MPa, EL = 10.4%) and an excellent high-cycle fatigue strength of 700 MPa. In contrast, the 6411-AN alloy, with high-aspect-ratio lamellar alpha colonies, showed inferior mechanical properties (Rp0.2 = 901 MPa, Rm = 956 MPa, EL = 6.9%) and a lower high-cycle fatigue strength of 675 MPa. Further analysis reveals that, in contrast to the 6411-AN alloy, in which microstructural constraints on dislocation motion result in severe stress concentration and early cracking during the initial deformation stage, the 6411-STA alloy promotes dislocation glide within the coarse alpha lamellae. Additionally, cross-interface slip of dislocations significantly mitigates local stress concentration and prolongs the crack initiation process. Fatigue cracks are typically observed to propagate along basal or prismatic planes with high Schmid factors. These findings deepen the understanding of the tensile and fatigue deformation mechanisms of the Ti-6411 and provide valuable guidance for the design and application of cost-effective titanium alloys with superior mechanical performance.

Developing biomedical titanium alloys with both low Young's modulus and excellent mechanical properties has always been challenging. A novel low-modulus metastable TiZr-based medium-entropy alloy (MEA) Ti45Zr45Nb4Ta4Hf2 was designed using both d-electron-based and valence electron concentration (VEC) methods, whose microstructure, tensile properties, and deformation mechanisms of the MEA are investigated. The as-hot-rolled and annealed MEA had a single-phase beta microstructure with a low Young modulus of 63-70 GPa and fracture strain ranging 9.8-21 %. The MEA exhibited an abrupt increase in strain hardening rate at intermediate strains, resulting from complex deformation mechanisms that involved intensive martensite formation, deformation twins, and dislocation slip. The volume fraction of the alpha phase increased substantially with increasing strain, i.e., a local strain of 13.3 % generated a volume fraction of the alpha phase of 69.9 %, and at fracture strain of 20 % produced nearly complete alpha phase. The strain-induced tension twin variant 87.3 degrees/< -12-10 > and the compression twin variant involving 70.8 degrees/< 1-100 > and 67.7 degrees/< 1-100 > appeared, which can alleviate stress/strain localization and enhance plastic deformability of alpha phase. This work offers new insights into developing bio-HEAs with simultaneous ultra-low Young's modulus and excellent mechanical properties.

In this work, HCP-to-FCC phase transformation and its interaction with {11[Formula: see text]2} compression twins (CTWs) in CP-Ti under ultra-high-strain-rate compression (∼106/s) was investigated. Muti-scale characterization and analysis demonstrate the both B- and P-type FCCTi lamellae are profusely generated and exhibit significant growth capability and intensive interaction with the CTWs. Particularly, two adjacent FCCTi lamellae with a twinning relationship can be formed within the CTW and matrix, respectively. Moreover, two adjacent FCCTi lamellae with nearly identical orientation can be formed within the two different CTW variants. Two possible mechanisms were proposed to account for this unique phenomenon.

Titanium alloys find extensive applications in aviation, maritime, and chemical engineering applications. Nonetheless, these alloys encounter significant challenges during the conventional forging process, which include high deformation resistance, limited processing temperature ranges, and inhomogeneous microstructure. Isothermal forging, as a near-net-shape forming technique, can alleviate the microstructural inhomogeneity caused by deformation dead zones in conventional forging, thus enabling the direct production of complex shapes. This process enhances the overall performance and utilization of materials while reducing manufacturing costs. This paper comprehensively reviews how isothermal near-net-shape forging process parameters influence the intricate microstructure and essential properties of titanium alloys. The unique properties of isothermal forging applied to high-performance titanium alloys are also discussed in depth, and the intricate interplay between process parameters and the microstructure and properties of recoloration is clarified. That is to say, temperature is a vital element influencing the phases and microstructure of titanium alloys during the forming process. Grain size, microstructural homogeneity, and phase transformation are influenced by the strain rate, thereby affecting the plasticity, fracture toughness, and strength of titanium alloys. The extent of deformation significantly governs the grain size, the thickness of secondary α phase, dynamic recrystallization, and primary α phase. Cooling rate affects the grain size and precipitates, contributing to grain refinement. The frequency of isothermal forging affects the grain refinement and microstructural uniformity of titanium alloys. Finally, this paper summarizes the scientific questions that remain unresolved in this field and outlines future research directions to promote the further development of isothermal near-net-shape forging processes and facilitate the broader industrial applications of high-performance titanium alloys and other difficult-to-form alloys.

In this work, HCP-to-FCC phase transformation and its interaction with {11[Formula: see text]2} compression twins (CTWs) in CP-Ti under ultra-high-strain-rate compression (∼106/s) was investigated. Muti-scale characterization and analysis demonstrate the both B- and P-type FCCTi lamellae are profusely generated and exhibit significant growth capability and intensive interaction with the CTWs. Particularly, two adjacent FCCTi lamellae with a twinning relationship can be formed within the CTW and matrix, respectively. Moreover, two adjacent FCCTi lamellae with nearly identical orientation can be formed within the two different CTW variants. Two possible mechanisms were proposed to account for this unique phenomenon.

In order to deepen the understanding of the electron beam cold hearth melting (EBCHM) process in the production of titanium and its alloys, a thermal-fluid coupling model for the cold hearth refining process was established using ANSYS Fluent fluid simulation software. Comprehensive analysis was conducted on the molten pool morphology, temperature field, and flow field to investigate the influence of smelting process parameters on the mentioned aspects. Multi-physics equations were used to predict the migration behavior and residence time of inclusions in the molten pool, revealing that inclusions with low-density and near-matrix density have residence times exceeding 35 seconds, while high-density inclusions settle into the mushy zone within 20 seconds. The analysis of multi-particle inclusion movement behavior demonstrated a removal rate exceeding 93.1 pct for high-density inclusions, indicating excellent effectiveness. The simulation results showed satisfactory consistency with production experiments.

The flow behavior and interaction of microstructure evolution mechanisms for a near alpha Ti-0.3Mo-0.8Ni alloy with as-cast lamellar microstructure are investigated at temperatures of 800 similar to 880 degrees C in the alpha+beta region with wide strain rate range from 0.01s(-1) to 30s(-1) during isothermal compression. It is demonstrated that the main reasons of flow softening in the true stress-true strain curves are the kinking of lamellar alpha, dynamic alpha ->beta transformation (DT), dynamic spheroidization (DS), and dynamic recovery (DRV) of beta grain. The instability phenomena such as adiabatic shear band (ASB) and flow localization (FL) are the main causes of the stress collapse in the curves at higher strain rate. The dislocation density at the kinking position of initial lamellar alpha is higher. With the increase of strain rate, the mechanism of the DS changes from flat separation to slat shear. The diffusion of the beta-stabilizer results in starting the DT, promoted by the thermodynamic coupling. The interactions between different microstructure evolution mechanisms are extremely complex. In the early stage of hot deformation, the DT promotes the kinking of lamellar alpha. With the increase of deformation amount, the DT inhibits the DS at higher strain rates, and conversely, the DS promotes the DT. At lower strain rates, the DT and DS accelerate each other in the middle and late stages of hot deformation. The DT and DS are restricted by the process of lamellar alpha kinking in the middle and late stages of hot deformation.

EN-9 is one of the steel grades, and it is widely used in power plants, automobiles, and the aerospace sector. The availability and ductility of EN9 steel have been limited. Heat-treatment procedures are used to increase the hardness, wear resistance, and percentage of elongation. The main intention of this study is to discover the effect of heat treatment on EN8 steel. In this work, the various kinds of heat-treatment methods like annealing, normalizing, hardening, and tempering were carried out on EN-8 steel. Mechanical properties like hardness, tensile strength, and percentage of elongation are evaluated. The microstructure is examined and compared, before and after the heat treatment process. Hardening and tempering results indicated that EN8 steel has better hardness, yield strength, ultimate tensile strength and elongation when compared to EN9 steel.

For expanding the application in the automotive field, the surface defect control technology for advanced high strength hot dip galvanized automobile sheet was studied. Results showed that the oxygen potential of alloy element was lower than that of Fe during hot rolling, annealing and hot galvanizing processes, resulting in an “internal oxidation” phenomenon, which made defects easily to occur on the surface of galvanized products. Focusing on such four main surface defects as iron leakage, chicken claw print, color difference and pockmarked surface, the main factors causing the defects and the mechanisms for the formation of defects were determined. Through the measure of corresponding production control processes, the commuted rates of defects declined to below 0.58%, 0.19%, 0.52% and 0.15% respectively.

Low-carbon steel is widely used for household appliance and automotive panel steel because of its excellent plasticity. Unfortunately, yield point phenomena easily appear in the low-carbon steel produced by a continuous annealing process and cause degradation to the surface quality during processing. The effect of the coiling temperature (600–750 °C) and annealing temperature (740–820 °C) on the yield point behavior is studied. Tensile tests show that coiling temperature has a greater effect on yield point elongation (YPE) and aging index (AI) than the annealing temperature. Microstructure observations show that coiling temperature at 750 °C would make the micron-sized carbides appearing at the grain boundary disappear and a number of dispersed nanoscale carbides precipitate in grain interior, corresponding to the highest solid solution carbon content in the matrix of 750 °C coiled sample. The experimental results suggest that AI rather than YPE has a positive relationship with the solid solution carbon content of the low-carbon steel. And YPE has a positive relationship with the upper/lower yield strength.

Nanoindentation measurements, tensile tests, and carbon concentration analyses were conducted to study yield behaviors in as received, aged, and prestrained low carbon steel. In aged sample, steel showed both yield point phenomenon (YPP) and grain boundary (GB) pop-ins besides initial pop-in, while steels in other two states showed no YPP and only the initial pop-in. 3-dimensional atom probe (3DAP) analysis in both as-received and aged samples showed that carbon content in the matrix decreased significantly after aging treatment, which is believed to contribute to the occurrence of both YPP and GB pop-in.