Additive Friction Stir Deposition (AFSD) was employed to deposit an aluminum alloy onto a copper substrate, and the bonding mechanism at the resulting Al/Cu interface was thoroughly investigated. The results indicate that two intermetallic compounds (IMCs), Al4Cu9 and Al2Cu, were formed at the interface, with a total IMCs layer thickness ranging from 0.38 to 0.72 mu m. Specifically, the copper-rich Al4Cu9 layer measured 0.14-0.42 mu m, while the aluminum-rich Al2Cu layer measured 0.26-0.49 mu m. Dynamic recrystallization occurred in the aluminum deposit, and twinning was observed in the copper substrate due to severe plastic deformation. When the rotation speed increased to 800 rpm, the Al/Cu interface achieved a high shear strength of 88.3 MPa, with a mixed brittleductile fracture mode observed.

Friction stir deposition of Al-Zn-Mg-Cu alloys often suffers from abnormal grain growth (AGG) during subsequent solution treatment, negating the fine-grain advantage and impairing toughness. This study addresses this challenge by introducing 1.5 wt% Mn into an Al-10Zn-2Mg-1Cu alloy. The added Mn led to the formation of thermally stable Al6Mn phase, which effectively pinned grain boundary during a 470 degrees C/1h solution treatment, successfully inhibiting AGG and maintaining a fine-grained microstructure (similar to 1.8 mu m). Following a 150 degrees C/4h peak-ageing treatment, a high density of nanoscale eta ' precipitate (similar to 15 nm diameter, similar to 4 nm thickness) formed, providing substantial precipitation strengthening. Consequently, the friction stir deposited Al-Zn-Mg-Cu-Mn alloy achieved a high ultimate tensile strength of 625 MPa with an elongation of 10.2%. This strength surpasses most reported friction stir deposited precipitation-strengthened aluminum alloys and is comparable to morph + heat-treated AA7085. The strategy of utilizing stable Al6Mn phase to suppress AGG enables the retention of a fine-grained, high-strength, and ductile microstructure in friction stir deposited ultra-high-strength aluminum alloys, enhancing their potential for large aerospace components.

This study investigates the repair of blind-hole defects in Al-Mg-Li alloy using Additive Friction Stir Deposition (AFSD). The effects of hole geometry (diameter and depth) on filling behavior, interfacial bonding, microstructure evolution, and mechanical properties were systematically examined. Results reveal a distinct “reparable window”: holes with a diameter of 8 mm and depth ≤ 4 mm could be fully filled due to matched frictional heating and material flow. Beyond this range, incomplete filling and interfacial defects occurred. Microstructural analysis showed that the near-center region developed a 111 <110 > shear texture with coarse grains, while the periphery formed a fine-grained < 111> fiber texture with a directional banded structure under constrained flow. The bottom edge region (BEBR) exhibited the weakest bonding due to insufficient heat input, pressure attenuation, and localized Al2O3 formation. The repair zone displayed refined nano-scale δ′-Al3Li precipitates via dissolution–reprecipitation, leading to recovered hardness. Tensile strength reached 379 MPa at well-bonded shallow regions but dropped sharply to 54 MPa at poorly bonded deep regions, where fracture occurred along the interface. This work provides a fundamental understanding of AFSD-based repair of constrained 3D defects in high-strength Al alloys.

This study investigates a novel strengthening strategy for FCC-structured high-entropy alloys (HEAs) through the combined effects of Cu-rich precipitation and NbC-mediated grain refinement. The FeCoNiCrMn-based alloys with 5 % Cu and 0.2 % NbC additions were processed through optimized thermal-mechanical treatments, achieving a unique microstructure with nanoscale precipitates and refined grains. Microstructural characterization revealed that NbC addition reduced grain size from 27.4 mu m to 8.8 mu m, while aging treatments generated coherent Cu-rich precipitates (50-200 nm) that evolved through distinct nucleation and growth stages. Mechanical testing demonstrated exceptional property combinations: peak ultimate tensile strength of 858.4 MPa with 51.4 % elongation in HEA-5Cu-0.2NbC, representing a 28 % strength increase over the base alloy while maintaining > 45 % ductility. Quantitative analysis identified grain boundary strengthening (73 MPa), precipitation strengthening (145-170 MPa), and solid solution effects (23-27 MPa) as key contributors. Deformation mechanism studies revealed a transition from dislocation-twinning interactions in the base alloy to dislocation-dominated plasticity in Cu/NbC-modified variants, with precipitate-dislocation interactions playing a critical role in mechanical performance.

Al-Li alloys, known for their low density and high specific strength, are promising materials for aerospace applications. Spray forming, a rapid solidification technique, offers distinct advantages in fabricating these alloys. This study systematically examines the effects of various elemental compositions on the microstructure and mechanical properties of low density spray formed Al-Li alloys for the first time. The results reveal that Mg, Cu, and Sc elements can reduce the average grain size, with Sc having the most pronounced impact on grain refinement. Increasing Mg content leads to coarser precipitates at grain boundaries, while Cu and Sc refine these precipitates. The incorporation of Mg and Sc significantly improves the microhardness, while Mg, Cu, and Sc together enhance the alloys' maximum tensile strength. Mg reduces elongation, whereas Cu and Sc improve it, with Cu providing the most substantial increase in strength. In alloys containing Cu and Sc, small amounts of the coherent Al3Li phase precipitate within the matrix. Sc also promotes the formation of nanoscale Al3(Sc, Zr) particles. No significant large scale precipitation free zones (PFZ) are observed in the alloys. These findings provide valuable insights into the optimal formulation of elemental compositions for the future development of spray formed Al-Li alloys.

Controlling microstructural evolution and texture to improve mechanical properties and weld seam integrity in Mg-RE hollow profiles is a generic challenge in materials processing. To address this, a novel Rotational Strain Porthole Die Extrusion (RSPDE) technique was developed, introducing circumferential shear strain during extrusion to refine texture and enhance dynamic recrystallization. Using Mg-8.8Gd-3.8Y-1.0Zn-0.7Mn hollow profiles as a case study, the RSPDE process achieved finer grains in the matrix zone, narrowed the precipitation- free zone in the welding seam, and reduced basal texture intensity compared to conventional porthole die extrusion (CPDE). Although the weld seam remained somewhat weaker due to larger grain sizes and absence of beta' and gamma' precipitates, subsequent aging treatments improved tensile strength. These improvements, however, came with reduced ductility due to precipitate-dislocation interactions. Despite this trade-off, RSPDE produced more homogeneous microstructures, weaker basal textures, and superior weld seam quality than CPDE. Fundamentally, this work establishes a transferable framework that links controlled shear deformation to predictable microstructural refinement and texture control, enabling more informed process optimization and alloy design strategies. This generic approach thus offers predictive guidelines for structural design and optimization across a broad range of high-strength magnesium alloys.

Friction Stir Welding (FSW) is widely used for joining high-strength aluminum alloys in aerospace and transportation applications. However, the impact of welding speed on the microstructural evolution and fatigue behavior of 7085 aluminum alloy joints remains underexplored. In this study, FSW joints were fabricated at three welding speeds (150, 200, and 250 mm/min) to systematically investigate their effects on grain structure, precipitate characteristics, hardness distribution, and fatigue performance. SEM, EBSD, TEM, and ultrasonic fatigue testing (20 kHz) were employed. Results revealed that increasing welding speed refined the SZ grains from similar to 3.4 mu m to similar to 2.3 mu m and enhanced hardness from 170 HV to 183 HV. The fatigue life improved significantly at low stress (69 MPa), from 10(6) to nearly 10(7) cycles, as crack propagation was impeded by fine intermetallic particles and higher intragranular strength. Fractographic analysis showed a shift in crack initiation from the TMAZ to the SZ under different stress regimes. These findings provide quantitative guidance for optimizing FSW parameters to improve fatigue reliability of 7085 alloy joints.

This study systematically investigates the effects of solution treatment (S. S.) temperature (450-500 °C) on the microstructure, mechanical properties, and Portevin-Le Chatelier (PLC) effect of Al-5Mg-2.5Li alloy. At lower S. S. temperatures (450-470 °C), the alloy retained a fine grain size ( 9 µm) with minimal Li oxidation, whereas higher temperatures (480-500 °C) induced grain coarsening (>50 µm) and severe Li oxidation, forming 10 µm-wide Li2O bands. Precipitation strengthening dominated the mechanical performance: aging at 450 °C after S. S. produced dense δ′-Al3Li precipitates. Its hardness can reach 142 HV, and its tensile strength is 502 MPa. High-temperature S. S. (500 °C) suppressed δ′-Al3Li formation due to Li oxidation. The PLC effect exhibited temperature-dependent behavior: aged alloys at 450-470 °C showed higher stress drops (Δσ: 3.9 MPa in aging) and B/C-type serrations, attributed to δ′-Al3Li shearing and solute-dislocation interactions. At 480-500 °C, reduced Li content shifted PLC to Mg-dominated C-type serrations with lower stress drops (Δσ: 2.3 MPa in aging) and higher critical strain (εC: 5.3

Additive Friction Stir Deposition (AFSD) is an effectively method to deposit AA7075 alloy. In this investigation, the strengthening and toughening mechanisms have been systematically discussed. The results indicate that a higher rotation speed of 1450 r/min leads to an elevated peak temperature during AFSD. The deposited AA7075 with this higher rotation speed exhibited less coarse grain boundary's eta phase and a finer intragranular eta phase as the dissolving and precipitating of more Mg, Zn, and Cu atoms from original eta phase at a higher peak temperature. Therefore, the AA7075 deposited with a high rotation speed of 1450 r/min exhibited higher yield strength and ultimate tensile strength. For the plastic deformation, the higher rotation speed also resulted to larger Schmid factor (SF) and less coarse Al2CuMg phase. The larger SF reduced the deformation resistance. The less Al2CuMg phase declined the brittle cracking tendency. As a result, the AA7075 deposited at 1450 r/min exhibited an elongation between 25 % and 35 %.

Additive friction stir deposition （AFSD） is a technology with several advantages for aerospace manufacturing. It is particularly valuable because it can deposit materials at low temperatures while retaining high quality and efficiency. This article introduces the operations of AFSD in detail and investigates its effect on three types of precipitation-reinforced aluminum alloys. Key challenges hindering the production of high-strength aluminum alloy components through AFSD are highlighted. AFSD utilizes solid-phase deposition to avoid problems like porosity and thermal cracking that can occur with other types of deposition， such as laser and arc depositions. However， the slow cooling of the deposited metal and the long residence time in the sensitive temperature range can cause issues. Subsequent layers exert a thermal effect on the previous layers during the AFSD process. This can lead to coarsening of the precipitates in the middle and lower regions， resulting in decreased strength in these areas. The top layer remains unaffected， but has poorer mechanical properties compared to the base material. To improve performance， aging treatment can be used to cause reprecipitation of some elements dissolved during AFSD， but it does not reach the values achieved by solid solution and aging （T6） treatment. T6 treatment after AFSD can renew uniformly distributed fine-strengthening precipitates， but it triggers abnormal grain growth （AGG） in the deposited material. Therefore， it is generally not recommended to subject solution treatment to metals deposited with AFSD. Further research should focus on alloy design， composite reinforcement and innovative techniques， which are essential to obtain high-strength precipitation-reinforced aluminum alloy components through AFSD.

This study systematically investigates the anisotropic failure behavior of extruded Al-Cu-Li alloys under very high cycle fatigue (VHCF) conditions. Ultrasonic fatigue testing reveals that, after aging, specimens loaded along the extrusion direction (ED) exhibit significantly longer fatigue lifetimes than those along the transverse direction (TD) and normal direction (ND), with all orientations achieving VHCF performance. A detailed analysis of < 100 > and < 111 > fiber textures demonstrates their pronounced influence on fatigue crack initiation sites, propagation paths, and fracture modes. Finite element analysis and microstructural characterization are combined to establish a mechanism chain linking texture evolution, slip behavior, stress localization, and fatigue crack growth. The results show that the < 111 > texture promotes orientation-dependent slip constraint and stress accumulation at grain boundaries and unfavorably oriented slip systems, thereby governing the formation of anisotropic fatigue failure modes. These findings provide key mechanistic insight into the fatigue failure behavior of Al-Cu-Li alloys and lay a theoretical foundation for their reliable structural application.

The dissolution of strengthening precipitates and high susceptibility to hot cracking are the primary causes of the joint failure in 7xxx series aluminum alloys. In this study, in-situ (ZrB2+ Al2O3) nanoparticle-reinforced AA7N01 aluminum matrix composites were welded using Laser Beam Oscillation Welding (LBOW) to optimize microstructure and mechanical performance. The in-situ nanoparticles, with average sizes of approximately 35 nm for ZrB2 and 25 nm for Al2O3, effectively eliminated the dendritic structure in the fusion zone (FZ), promoting the formation of equiaxed grains with a refined average size of 6.74 mu m, thereby mitigating hot cracking. The composite with 3 vol% nanoparticles exhibited the best performance in the pre-weld deformed condition, achieving an ultimate tensile strength (UTS) of 555.29 MPa and an elongation of 13.62 %. After welding, the UTS and elongation reached 446.27 MPa and 6.45 %, respectively, corresponding to the highest joint efficiency of 80.4 %. This improvement is attributed to grain refinement, dislocation pinning, and crack deflection induced by the thermally stable dual-phase nanoparticles, which also compensated for the loss of precipitation strengthening caused by welding thermal input. Furthermore, the nanoparticles acted as crack-bridging agents, promoting ductile fracture behavior. This study reveals the grain nucleation and refinement mechanisms induced by the dual-phase nanoparticles and elucidates the synergistic enhancement in joint strength and toughness.

This study investigates the microstructure, mechanical properties, and tribological behavior of Cu-Ag-Al alloy coatings with varying Ag/Al ratios. The coatings exhibit a dual-layer structure comprising a Cu-Ag-Al ternary surface layer and an Ag interlayer, where increasing Ag interlayer thickness (210-610 mu m) directly enhances the eutectic phase fraction (27-73 %). Phase evolution is composition-dependent: high-Al Cu-19Ag-20Al forms R' phases via R -> R' ordering, while lower-Al alloys (Cu-34Ag-15Al, Cu-45Ag-12Al) stabilize Cu solid solutions (Cu S. S.) with nanotwins due to suitable stacking fault energy (SFE). Mechanical performance is governed by dual-phase interactions: the R' phase in Cu-19Ag-20Al achieves high hardness (4.71 GPa) and work-hardening rates (2699 MPa) via coherent (128)-plane interfaces, whereas nanotwin-strengthened Cu S.S. phases dominate in low-Al alloys. Tribological analysis reveals that increasing Ag content reduces friction coefficients (0.72 -> 0.33) through the formation of Ag-rich nanocrystalline tribolayers. However, wear resistance peaks in Cu-34Ag-15Al (397 mu m scar width), balancing 42 vol% hard Cu S.S. phases with 58 vol% friction-reducing eutectic structures. Excessive eutectic content in Cu-45Ag-12Al compromises wear resistance despite low friction, underscoring the necessity of optimizing phase hardness and tribolayer efficacy. These findings highlight the critical role of Ag/Al ratio in tailoring phase selection, strengthening mechanisms, and wear performance in Cu-based coatings.

Dispersed nanoparticles are expected to improve the weldability of 7085Al alloy for load-bearing structure of aerospace vehicles. In this work, Er elements were added to enable ZrB2 nanoparticle dispersion through the modified interface and then the well-designed in-situ ZrB2/7085Al-Er nanocomposites were joined by friction stir welding (FSW). The results showed that the coherent (10 1 0)ZrB2//(111)Al3Er//(111)Al interface constructed by primary Al3Er improved the interfacial wettability between ZrB2 and Al, enabling the dispersion of ZrB2 nano- particle during solidification. After FSW, finer equiaxed recrystallized grains were formed in the nugget zone (NZ) thanks to the particle stimulated nucleation (PSN) mechanism and Zener pinning effect from ZrB2 and Al3(Er, Zr), which was in favor of alleviate welding hot cracking. The coarsen process of precipitates in the heat- affected zone (HAZ) was weaken. The coarse grain boundary precipitates were modified into fine precipitates with discrete distribution by ZrB2 and Al3(Er, Zr). The ultimate tensile strength and elongation of ZrB2/7085Al-Er joint were 484 MPa and 14.8 %, which were enhanced by 36.3 % and 45.1 % compared with 7085Al joint. The joint efficiency reached up to 75.2 %. The strength-ductility synergy of ZrB2/7085Al-Er joint came from grain refinement, avoidance of strain localization at grain boundary and activation of high density of intragranular dislocations brought by dispersive ZrB2 and Al3(Er, Zr).

Additive Friction Stir Deposition (AFSD), an emerging solid-state additive manufacturing technique, has shown great promise in processing single aluminum alloys. However, its applicability to dissimilar aluminum alloys remains unclear. In this study, the feasibility of additive friction stir deposition for fabricating dissimilar 7075-2024 aluminum alloy structures was investigated for the first time. The effects of tool rotational speed (800-1400 rpm) on interfacial bonding, microstructural evolution, and mechanical properties were systematically studied. All deposited samples exhibited defect-free macrostructures within the studied range. Increasing the rotational speed resulted in grain refinement in the mid-layer regions of both 7075 and 2024, reaching minimum average grain sizes of 1.14 mu m and 1.40 mu m, respectively. The fraction of high-angle grain boundaries (HAGBs) increased significantly, reaching 86.1 % and 67.0 %, along with recrystallization fractions of 91.04 % and 84.39 % in 7075 and 2024 layers, respectively. At 1100 rpm, a uniform distribution of strengthening precipitates was observed, with the hardness reaching 75 % of the base materials and the highest tensile strength (181.9 MPa) and elongation (6.3 %) obtained. Further increases in rotational speed led to partial dissolution of precipitates due to excessive heat input, reducing hardness. While additive friction stir deposition was proven effective for fabricating dissimilar aluminum alloys, the tensile properties in the build direction (BD) were noticeably inferior to those in the longitudinal direction (LD). This study demonstrates that large-area joining of dissimilar aluminum alloys can be achieved via the AFSD process, providing a novel approach for the bonding of dissimilar alloys and laying a theoretical foundation for the AFSD fabrication of such materials.

The strength-ductility trade-off has long challenged FCC-typed HEAs. This paper presents a NbC-reinforced FeCoNiCrMn HEA with ultra-fine grain and nano NbC particle. Its ultimate tensile strength and elongation are 853.7 +/- 7.3 MPa and 57.8 +/- 1.9 %, respectively. The combination of high temperature solid solution at 1180 degrees C, cold rolling, and low temperature annealing at 1050 degrees C contributes to the generation of nano-sized NbC particles on the high-density grain boundary (GB) and sub-GB of rolled microstructure. The almost uniformly distributed nano-sized NbC particles deeply hinders the grain growth and contributes to the ultra-fine grain of NbCreinforced HEA. It sheds new insights into understanding the way to refine grain and precipitate of NbCreinforced FCC-typed HEA and its effect on strength-ductility trade-off.

Taking the new and old P92 pipes as the object,the rod samples of fine grain heat affected zone(FGHAZ)was prepared by using rapid heat treatment process.The microstructure and properties of the two FGHAZ samples were compared through observation by SEM,TEM,microhardness and creep tests,and the effect of the pipe original state on the microstructure and mechanical properties of FGHAZ of P92 steel was revealed.The results show that compared with that of the FGHAZ of new P92 pipe,the dislocation density of the FGHAZ of old P92 pipe is lower,the size of the precipitates is bigger,which decreases the hardness and creep resistance.During creep test,the FGHAZ of the old P92 pipe has higher precipitating tendency of Laves phase,which promotes the formation of creep void,accelerates the creep fracture and shortens the creep rupture life.

Super 304H has been a crucial material for ultra-supercritical boilers. However, the relationship between microstructure evolution, strengthening mechanism, and embrittling behavior during long-term aging was lacking investigation. This investigation aimed to reveal the strengthening and embrittling mechanism from precipitates in Super 304H. The results showed that the hardness increment came from the grain boundary’s M23C6 (GB’s M23C6) and intragranular nano Cu-rich particles. After being aged for 5000 h, the GB’s M23C6 and nano Cu-rich particles provided a hardness increment of approximately 10 HV and 30 HV, respectively. The impact toughness gradually decreased from 213 J/cm2 to 161 J/cm2 with the extending aging time. For the aged Super 304H, the GB’s M23C6 provided a higher cracking source. In addition, the nano Cu-rich particle restricted the twin-induced plastic deformation of austenitic grain and depressed the absorbed energy from austenitic grain deformation.