Interface engineering is a key strategy for mitigating irradiation damage in materials, as interfaces can act as preferential sinks for trapping irradiation-induced defects. Compared with conventional duplex titanium alloys, β titanium alloys offer superior high strength and tunable microstructure interfaces. A nano-scale α precipitation-strengthening strategy was employed to design a novel β-Ti alloy (Ti-1500 G) with high interface density. Through tailored heat treatments, the microstructures of the alloys were engineered into three specific interface architectures (single, dual, and triple), providing a platform to study interface-related phenomena. The triple-interface structure (β-GB, αp/β, and αs/β) achieved an increase of 2140% in interface density compared to the single-interface structure (β-GB). Microstructural characterization revealed that irradiation defects, such as helium bubbles, exhibit size variations across different phases and tend to aggregate at the αp/β phase interfaces. Mechanical tests demonstrated that the triple-interface structure with high interface density exhibited increases in nano-hardness and yield strength of only 12.8% and 7.5% after irradiation, significantly lower than the 43.0% and 13.0% increases observed in the single-interface structure. The synergistic interactions between β-GB, αp/β, and αs/β interfaces and dislocation movement within the triple-interface architecture effectively trigger multiple slip systems. This complex interfacial network not only suppresses substantial irradiation-induced hardening but also acts as a prolific sink for radiation-induced defects, thereby suppressing the formation of dislocation loops and enhancing irradiation stability. This work provides a new design perspective for interface engineering in next-generation irradiation-resistant titanium alloys.

Developing innovative heterostructures in titanium matrix composites (TMCs) is promising for breaking the strength-ductility trade-off dilemma. In this study, a dual-heterostructured (TiB +TiC)/Ti6Al4V composite integrating a tri-modal grain structure and heterogeneously distributed nano-reinforcements was successfully constructed by powder genetic engineering and low-temperature sintering. The tri-modal grain structure comprised lamellar coarse grains in the alloy region and a bimodal grain structure in the composite region, consisting of equiaxed coarse grains (ECGs) and fine grains (EFGs). The dualheterostructured composite achieved superior strength-ductility synergy with ultimate tensile strength (UTS) of similar to 1216 MPa and uniform elongation (UEL) of similar to 7.4 %, representing a 104 MPa increase in UTS and a remarkable 60.9 % increase in UEL compared to its homostructured counterpart. In-situ tensile experiments revealed multilevel hetero-deformation induced (HDI) effects driven by geometrically necessary dislocation pile-ups at the alloy/composite (macro-level) and ECG/EFG (micro-level) interfaces. The exceptional strength was attributed to the high strengthening efficiency of nano-reinforcements and additional multilevel HDI strengthening. Ductility was improved through the synergistic effects of multilevel HDI strain hardening, multi-slip induced strain delocalization, and crack blunting by the ductile alloy region. Importantly, pyramidal -dominated multi-slip in both the alloy region and ECGs alleviated deformation incompatibility and promoted dislocation interactions/substructure formation, contributing to extra strain hardening. Our work confirmed the effectiveness of an innovative dual-heterostructured design with nano-reinforcements in developing high-performance TMCs. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The strength and ductility trade-off in titanium matrix composites (TMCs) is a critical factor limiting their widespread application. In this study, a (TiB + TiC)/Ti-6Al-4V composite with an optimal balance between strength and ductility was engineered via multi-directional forging. Compared to the matrix alloy, the ultimate tensile strength increased by 10.4% without reducing the plasticity (14.5%). The mechanisms for overcoming the strength-ductility trade-off were systematically investigated. TiB promotes the activation of dislocations with high critical resolved shear stress (CRSS) and facilitates the activation of multiple slip systems. Meanwhile, a novel TiB-mediated grain refinement mechanism during deformation is found: differences in dislocation motion among various regions within grains adjacent to TiB induce grain subdivision, thereby leading to grain refinement in the TiB-surrounding region. Based on the aforementioned effects of TiB on the surrounding grains during deformation, the tailored multi-pass multidirectional forging promotes extensive grain refinement during deformation. Moreover, it facilitates the refinement and dispersion of TiB, thereby enhancing the activation of multiple slip systems and coordinated deformation. The new discovery of the deformation mechanism of TiB on the surrounding grains provides valuable insights for evading the strength and ductility trade-off. (sic)(sic)(sic)(sic)(sic)(sic)(TMCs)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (TiB + TiC)/Ti-6Al-4V(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)10.4%,(sic)(sic)(sic)(sic)(14.5%)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(CRSS)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)TiB(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Achieving synergistic enhancement of strength, plasticity, and heat resistance remains a major challenge for titanium matrix composites. In this study, a beta TRIPLEX heat treatment (beta 3HT) process was adopted to tailor the matrix microstructure of (TiB + La2O3)/IMI834 composite, achieving a synergistic improvement in both room-temperature strength-plasticity and high-temperature strength. EBSD and HRTEM analyses revealed that the second stage alpha + beta solution coarsened the primary alpha lamellae within acicular structure formed during the first stage beta solution, while the final annealing promoted uniform silicide precipitation. Furthermore, beta 3HT enhanced the alpha-variant selection effect of TiB, promoting the formation of coherent or semi-coherent TiB/alpha interfaces, with their fraction increasing from 2.3 % to 22.5 %. Compared with untreated-TMCs, the treated composite retained similar room-temperature strength (1222 +/- 1 MPa vs. 1215 +/- 4 MPa) but showed higher uniform ductility, with uniform elongation rising 91 % (3.5 % +/- 0.5 % to 6.7 % +/- 0.2 %). The high-temperature strength rose nearly 15 %, reaching 860 +/- 4 MPa at 600 degrees C, 757 +/- 4 MPa at 650 degrees C, and 625 +/- 2 MPa at 700 degrees C. This strength improvement arose from the synergistic effects of dislocation pinning by the lamellar microstructure, silicide precipitation strengthening, and load-transfer by TiB.

Advances in aerospace technology have fueled a substantial demand for titanium matrix composites (TMCs), as promising candidates for structural load-bearing components. Traditional TMCs, however, encounter the persistent trade-off between strength and ductility due to strong stress concentration induced by micron-phases. Substituting micron-phases with nano-phases (e.g., ceramic nano-phases or carbon nanomaterials) has been demonstrated to effectively improve mechanical properties in TMCs. Nevertheless, severe interfacial lattice mismatch between nano-phases and Ti matrix, coupled with the agglomeration behavior caused by inherent van der Waals forces of nano-phases pose notable challenges to attaining maximum strengthening efficiency. Thus, this review systematically summarizes recent advancements in addressing the aforementioned dilemma in nano-phases reinforced TMCs (NRTMCs). It begins with an overview of various nano-phases and fabrication methodologies employed in NRTMCs. Subsequently, the discussion focuses on the multiscale design strategies of NRTMCs, encompassing interfacial engineering in nanoscale, and configuration strategies in microscale, mechanical properties and associated strengthening mechanisms in NRTMCs. Finally, this review provides comprehensive insights into current development trends and future application prospects, outlining the advantages/disadvantages alongside underlying issues of NRTMCs. It serves as a valuable guideline for researchers pursuing the next-generation of high-performance TMCs, highlighting the considerable potential of NRTMCs to revolutionize aerospace and other industries.

Traditional titanium alloys with microstructural inhomogeneities presented lower workability due to limited heterogeneous deformation compatibility, particularly the intrinsic α precipitates easily induced the interfacial stress concentration and strain incompatibility, resulting in severe fracture. Good workability remains the hot topic in high-strength titanium alloys. Here, this work deeply reveals the activation of multi-slip systems and dual-functional α phases that enhance the workability, including {110}<111>, {112}<111>, and {123}<111>, and discusses the effect of α phases on the double-softening stages in the novel Ti-1500G alloy. The dual-functional α phases could synergistically serve both as dislocation barriers and softening agents. The activation of intragranular multiple slips, dominated by dynamic recovery, promote the dynamic softening. This accelerates the orientational transition from sub-grains to continuous dynamic recrystallization (CDRX) grains. The presence of α phases hinders the migration of dislocations and sub-grain boundaries (sub-GBs). This obstruction can lead to the bulging of primary β grain boundaries (β-GBs), facilitating the formation of discontinuous DRX (DDRX) grains separated from the primary β matrix. Furthermore, pinned sub-GBs by α phases promote the development of CDRX. Notably, we demonstrate that these α phases exert a distinctive influence on DRX behavior by activating stress-induced dynamic phase transformation (DPT) from α to β, which enhances DRX grain formation. Additionally, complex interactions between the α phases and dislocation motion mobilize mechanisms such as α spheroidization and particle-stimulated nucleation (PSN), further enhancing the softening effect. These α phases exhibit a dual functional role. Their interaction interfaces transition from coherent α/β boundaries with low lattice misfit to incoherent interfaces characterized by local strain and high-density stacking faults, governed by interface-controlled mechanisms. This new multiple softening integration shows an efficient approach for improving the hot-workability of ultrahigh-strength titanium alloy components at large industrial scales.

A clear understanding of strengthening mechanisms and creep behavior is crucial for optimizing performance and advancing the application of titanium matrix composites (TMCs). In this study, a (TiB + La2O3)/α-Ti composite was fabricated via melting and forging, followed by a three-step heat treatment to regulate the matrix microstructure and the crystallographic matching at TiB/α interfaces. The heat-treated composite exhibits strength-ductility synergy at room temperature (1228 ± 10 MPa and 7.9% ± 0.2%), with nearly doubled uniform elongation (from 3.7% to 6.1%). The tensile strength shows a 17.7% increase compared to the as-forged TMCs, exceeding previously reported thermo-mechanically processed TMCs. Meanwhile, the composite exhibits an exceptionally low steady-state creep rate of 1.05 × 10−9 s−1 and a minimal creep strain of 0.106% during a creep test at 650 °C/100 MPa for 100 h. First-principles calculations reveal that coherent TiB/α-Ti interfaces exhibit highest work of separation and smallest interfacial energy. The three-step heat treatment increases the fraction of coherent interfaces, thereby improving load-transfer efficiency and delaying damage accumulation at high temperatures. Meanwhile, the creep mechanism exhibits stress dependence, with diffusion dominating at low stress (100 MPa) and dislocation activity coupled with dynamic recrystallization at high stress (240–300 MPa).

Heat treatment plays a crucial role in tailoring the microstructure and mechanical properties of AMed TMCs, while the role of reinforcements remains insufficiently understood. In this study, TiB/IMI834 composites were fabricated via laser-directed energy deposition and subjected to alpha + beta solution treatments with varying cooling rates. Rapid cooling retained fine lamellae, while slower cooling promoted coarsening and partial equiaxialization. Meanwhile, metastable TiB underwent dissolution and coarsening via Ostwald ripening, fragmenting the network into whiskers. Crucially, TiB-induced alpha variant selection occurs during both additive manufacturing and subsequent heat treatment, particularly under the AC condition, with the presence of three preferred misorientations (0 degrees/[001], 58.57 degrees/[010], and 90 degrees/[010]). Selected alpha variants exhibited larger grain areas and equiaxed morphologies. Mechanistic analysis reveals that alpha variants satisfying 0 degrees/[001] and 58.57 degrees/[010] preferentially nucleate on (100)TiB and (101)TiB facets, while the 90 degrees/[010] variant originated from microstructural heredity. Therefore, AC composite achieved a peak compressive strength of 2020 + 34 MPa and fracture strain of 22.9% + 0.3%. High-temperature tensile strength reached 920 + 4 MPa at 600 degrees C and 690 + 5 MPa at 700 degrees C. These findings offer novel insights into TiB-induced alpha variant selection and a theoretical basis for optimizing AMed TMCs via heat treatment strategies.

Microscale laser shock peening without coating (& micro;LSPwC) was applied to (TiB + La2O3)/IMI834 Ti-matrix composite. The effects of & micro;LSPwC on surface integrity and wear behavior, particularly under varying impact numbers, were systematically investigated. The results identified 1 impact as the optimal condition, where the average coefficient of friction (COF) decreased from 0.40 to 0.348, and the wear rate decreased from 0.81 & times; 10-5 to 0.62 & times; 10-5 mm3/N center dot mm. The wear mechanism shifted from severe abrasive-adhesive wear to predominantly mild abrasive wear. This improvement was associated with & micro;LSPwC-induced surface integrity modification, including surface morphology, microstructure, residual stress, and microhardness.

High-temperature fatigue performance is one of the key hurdles for successful application of titanium matrix composites (TMCs) in aerospace. However, most strategies have primarily focused on the role of ceramic reinforcements, neglecting the twins' nucleation in matrix microstructure. This study investigated the influence of {1 0 1(sic) 2} twin nucleation on the fatigue crack growth behavior of TMCs. Compared with the composite loaded along the drawing direction (DD), the composite loaded along the transverse direction (TD) exhibited a significantly higher {1 0 1(sic) 2} twin density (increased by similar to 376.72%) and a lower fatigue crack growth rate (FCGR, reduced by similar to 5%). The high stress concentration induced by hybrid TiB and TiC reinforcements in the crack tip plastic zone (CTPZ) activated pyramidal < c + a > slip in grains with hard orientations for prismatic/basal slip, and facilitated the decomposition of < c + a > dislocations into < a > dislocations, thus becoming dislocation sources of {1 0 1(sic) 2} twin nucleation. Additionally, twin nucleation sites and stepped structures acted as additional obstacles that promoted fatigue crack deflection at twins, thereby reducing the high-temperature FCGR. Our work provided novel insights into enhancing high-temperature fatigue crack resistance via inducing {1 0 1(sic) 2} twin nucleation, offering a viable strategy for developing higher fatigue-resistant TMCs.

Combining nano-reinforcements with heterogeneous grain structure is a promising strategy for overcoming the strength-ductility trade-off in titanium matrix composites (TMCs). In this study, we developed a unique heterostructure with alternating alloy and composite bands, containing equiaxed fine grains (FGs) embedded with nano-(TiB + La2O3) particles and lamellar coarse grains (CGs), using an innovative powder-assembly and thermal-deformation strategy. The hetero-structured (TiB + La2O3)/IMI834 composite achieved remarkable mechanical properties, exhibiting an ultimate tensile strength (UTS) of 1292 MPa and a fracture elongation of 9.8 % at room temperature, and a UTS of 860 MPa at 600 degrees C. The strength enhancement was attributed to the hetero-deformation induced (HDI) strengthening caused by geometrically necessary dislocations density gradients near the CGs/FGs interfaces and the obstruction of dislocation motion by nano-reinforcements. Meanwhile, multiple slip in CGs, arising from the interaction between basal/prismatic < a > slip and HDI stress-induced pyramidal < c + a > slip, together with the activation of extra < c + a > dislocations in FGs, effectively coordinated deformation and generated extra strain hardening. Additionally, CGs with high deformability deflected and shielded cracks, and absorbed more strain, enhancing crack resistance and maintaining good ductility. This work provides a feasible strategy for designing and fabricating novel hetero-structured TMC with superior strength-ductility synergy.

Understanding deformation mechanisms can effectively guide the improvement of material mechanical properties. In this work, the tensile and creep properties of (TiB + La2O3) reinforced titanium matrix composites (TMCs) were evaluated, and the deformation mechanisms during tensile and creep was systematically investigated. The composite exhibited an ultimate tensile strength (UTS) of 1134 MPa at room temperature. At elevated temperatures, the UTS reached 724 MPa at 650 °C and 663 MPa at 700 °C. Meanwhile, the composite exhibited an exceptionally low steady-state creep rate of 1.0 × 10−9 s−1 and a minimal creep strain of 0.20% during a 650 °C/100 MPa/100 h creep test. Microstructures evolution during tensile and creep deformation at different temperatures and stresses was systematically studied and the deformation mechanism as well as role of reinforcements were analyzed in depth. The tensile deformation mechanism exhibited a strong temperature dependence. As the temperature increases, dislocation activation intensified, promoting dynamic recovery. For creep, the influence of stress was even more pronounced. Creep in low-stress regimes was governed primarily by diffusion coordinated with dislocation movement, while the dislocation motion dominated in high-stress regimes accompanied by dynamic recrystallization and diffusion. The microscale TiB whiskers play a load-bearing strengthening effect and exert a significant influence on dynamic recrystallization while nanoscale La2O3 particles hinder dislocation motion. These findings provide guidance for the microstructure design aimed at synergistically improve tensile and creep performance of TMCs.

Titanium matrix composites exhibit higher elastic modulus, strength, and hardness; however, interfacial bonding issues between the reinforcements and the matrix limit their application in engineering tribological components. In this study, microscale laser shock peening without coating (μLSPwC) was applied to the surface of (TiB + La2O3)/IMI834 Ti-matrix composite to enhance their tribological performance. The surface integrity and tribological performance before and after treatment were evaluated. The results show that μLSPwC treatment produced a unique periodic “peaks” and “valleys” surface morphology, induced compression of the near-surface β dendrites, and introduced a compressive residual stress (CRS) layer and a hardened layer to a certain depth, resulting in an increase in surface microhardness of up to 17.86

Thermomechanical processing (TMP) is of critical importance for tailoring microstructures and properties of high-strength titanium alloys and their composites. In this study, mechanical response and microstructural evolution mechanisms of 2 vol.% TiB/Ti-5Al-5Mo-5V-3Cr-1Zr (Ti-55531) matrix composites during isothermal compression at varied deformation temperatures (785-925 °C) and strain rates (0.001-1 s-1) are comprehensively investigated by kinetic calculation and microstructural characterization. Strain-compensated constitutive equations in α + β and β phase regions were established. Results show that deformation temperature and strain rate influence flow behavior and microstructure through dynamic recovery (DRV) and dynamic recrystallization (DRX) of the β phase as well as dynamic spheroidization of the α phase. Crucially, three DRX mechanisms of β phase were identified, wherein TiB-induced β-DRX dominates, with α-assisted β-DRX and continuous dynamic recrystallization (CDRX) as secondary mechanisms. Dynamic spheroidization mechanisms of the α phase, including β-wedge penetration as well as α interaction and kinking, were elucidated. A comprehensive microstructural evolution mechanism map was constructed, and an optimized hot-processing window was proposed. Notably, the introduction of TiB significantly promotes β-DRX, which tends to randomize crystallographic orientations of the β phase, and enhances microstructural stability. This study provides theoretical complement and practical guidance for hot processing and microstructure control of metastable β titanium matrix composites.

The strength-ductility trade-off and the suboptimal processability of titanium matrix composites are important factors limiting their widespread application. In this study, by employing hot isostatic pressing (HIP) and an embedded network-structured reinforcement powder, we successfully fabricated (TiB + TiC)/Ti-6Al-4V composites with a novel powder-inherited characteristics. The powder-inherited microstructural characteristics exhibit heterogeneous dislocation density distributions between the powder-edge and powder-core regions, which contribute to the enhanced strength of the composite. In addition, TiB is present at both the micron scale and the nanometer scale within the powder-inherited microstructure. Nano-sized TiB inhibits grain growth. Meanwhile, TiB at both the nano- and micro-scales promotes pyramidal dislocation slip. Concurrently, in the HIPed (TiB + TiC)/Ti-6Al-4V composite, the elevated geometric compatibility factor (m ') between basal , prismatic and pyramidal systems enable efficient dislocation transmission, jointly underpinning the superior tensile ductility. At a sintering temperature of 980 degrees C, the HIPed (TiB + TiC)/Ti-6Al-4V composite demonstrates superior mechanical performance, achieving an ultimate tensile strength of 1095.8 MPa and an elongation of 14.9%. The present study offers a new perspective on optimizing the fabrication processes of TMCs and enhancing its performance.

Lightweight titanium alloys with ultra-high strength and reasonable ductility are desirable for aerospace applications. However, titanium alloys typically require cumbersome heat treatment to achieve excellent mechanical properties. Here, ultra-high strength Ti-55531-based composites were fabricated by introducing TiB whiskers using a short process, i.e. melting and isothermal forging. The microstructure evolution during isothermal forging was investigated, TiB whiskers would promote the discontinuous dynamic recrystallization and impede abnormal grain growth, resulting in significant beta grain refinement, equiaxialization, and crystal orientation randomization. In addition, uniformly distributed nano-scaled alpha s lamellae were formed. 2.5 vol% TiB/Ti-55531 achieved a superior strength-plasticity synergy with the ultra-high strength of 1525 +/- 4 MPa and elongation of 6.4 %+/- 0.2 %, which were 9.2 % and 12.3 % higher than that of Ti-55531, respectively. The strengthening mechanisms were thoroughly analyzed, providing further insight to simplify the preparation and advance the application of ultra-high strength TMCs via short-process technology.

Strength-ductility trade-off in additively manufactured titanium alloys has been a critical bottleneck, significantly limiting their engineering applications. Our work demonstrated that this dilemma was overcome by tailoring a hierarchical heterostructure (HHS) in laser-directed energy deposited titanium alloy (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si). The designed HHS consisted of coarse micro-sized alpha phases (alpha p, soft region) and ultrafine nano-sized alpha precipitates (alpha s, hard region), generating hierarchical heterointerfaces including microscale alpha p/beta t and nanoscale alpha s/beta r interfaces. The HHS enhanced the total elongation to failure by 476.2 % without sacrificing strength compared to the conventional alpha-beta lamella structure, achieving exceptional strength-ductility synergy. Micro/nano-scale mechanical deformation analyses showed that hetero-deformation between coarse alpha p and ultrafine alpha s regions caused noticeable accumulation of geometrically necessary dislocations (GNDs) at heterointerfaces, inducing the pronounced hetero-deformation induced (HDI) strengthening effect on the soft alpha p, and the HDI hardening effect improving ductility. The HDI stress facilitated the formation and growth of dislocation networks in soft alpha p, promoting the accumulation of interfacial GNDs, enhancing the HDI hardening effect. Compared to single-level alpha/beta interfaces, hierarchical heterointerface generated higher GND density with a dual-gradient distribution, further improving the HDI stress and producing multiscale HDI hardening. This resultant high HDI stress activated high-proportioned pyramidal (c + a) slip modes with significant increment of GND density, overcoming deformation incompatibility. Moreover, hierarchical heterointerface exhibited a multi-scale crack buffering effect, synergistically contributing to the excellent ductility. Finally, a two-level homogenization model was established to comprehensively elucidate the intrinsic strengthening-toughening mechanism of the HHS. This work provided theoretical guidance for developing additively manufactured titanium alloys with high-performance.

The columnar to equiaxed transition (CET) of grain structures presents significant challenges in titanium alloy additive manufacturing (AM), especially in wire arc additive manufacturing (WAAM) with highly localized heat input and large temperature gradient. In this work, the strategy of decoupling the relationship between heat source and remelting depth was proposed, which was achieved by altering the electrode connection type with arc discharge between the tungsten electrode and the welding wire (IPAW-Wire method). Compared to the conventional WAAM methods based on tungsten inert gas welding (Conventional-TIG method), the IPAW-Wire method reduces the average beta grains width from 2 mm to around 200 mu m and the maximum texture intensity by approximately three times. The decoupling strategy combined with thermal undercooling and periodic solidification effect of low-frequency pulse arc promotes CET results. The IPAW-Wire method increases tensile strength by 50-80 MPa without altering the alloy composition or making external equipment modifications, and significantly weaken the anisotropy of mechanical properties, both in terms of ultimate strength and plasticity. The strength enhancement and anisotropy reduction are attributed to the coupling of beta grains refinement, weakened alpha crystallographic texture, fine needle-like alpha ' martensite, and high-density dislocation with multiple types of dislocations, dislocations and dislocations. This innovative IPAW-Wire method effectively mitigates coarse columnar grains and anisotropy by decoupling the relationship between heat source and remelting depth. This control strategy can inspire other heat sources and material additive manufacturing process, addressing hotspot challenges such as programmable microstructure, metamaterials structure, multimaterial, and bioinspired printing.