Search Results (123)

This study investigates the compound surface modification of 7075 aluminum alloy through the High-Speed Cutting-Solid Projectile Embedded Water Jet (HSC-SPEWJ) method. The research employed SEM, XRD, TEM, and HRTEM techniques to assess how process parameters such as jet pressure, nozzle distance, and nozzle traverse speed influence surface properties, including surface quality, roughness, microhardness, residual stress, and microstructural evolution in the alloy. The results indicate that the surface of the alloy treated with the SPEWJ process primarily exhibits features such as “craters,” microcracks, and micropores, with the lowest surface roughness recorded at 0.6214 μm. The modification leads to the formation of a plastic deformation layer with depths varying between 28 and 78 μm, with the maximum depth of 78 μm achieved at a jet pressure of 15 MPa. This treatment results in an 8.8% increase in the maximum microhardness when compared to the untreated sample. The greatest work-hardened layer observed extended to a depth of 100 μm. Furthermore, the surface residual compressive stress reached −210.37 MPa, with the stress field extending to 356 μm below the surface. The HSC-SPEWJ treatment also facilitated the formation of high-density dislocations and grain refinement in the alloy, while the size of the Precipitate-Free Zone (PFZ) was reduced by 5 to 10 nm relative to the untreated sample. Full article

In this study, CoCrFeNiMn high-entropy alloys (HEAs) with different aluminum (Al) contents were fabricated, and the effects of Al content on the microstructure evolution and mechanical properties were systematically explored. The microstructural characterization results indicated that the Al content exerted a crucial regulatory effect on the crystal structure of the alloy. With increasing Al content, shifts in the characteristic XRD peaks indicate lattice expansion of the alloy. Meanwhile, the phase structure continuously evolved from a single face-centered cubic (FCC) structure to an FCC/body-centered cubic (BCC) dual-phase structure, and then finally transformed into a BCC-dominated structure. Appropriate Al element addition could produce localized stress fields near dislocations and achieve prominent solid-solution strengthening, which effectively inhibited dislocation movement and further improved the yield strength, tensile strength, and hardness of the alloy. In contrast, excessive Al addition would break through the solid solubility limit of the alloy matrix, causing obvious phase separation and the precipitation of brittle B2-ordered NiAl-type intermetallic secondary phases. These brittle secondary phases easily induced crack initiation in the plastic deformation process, which significantly deteriorated the ductility, work-hardening ability, and impact toughness of the alloys. Full article

In this study, the effects of friction stir welding (FSW) parameters on the mechanical properties and formability of pre-hardened (PH) 2219 aluminum alloy welds were systematically investigated through tensile testing and Erichsen tests. Energy dispersive spectrometry (EDS), electron back scatter diffraction (EBSD), and a transmission electron microscope (TEM) were employed to characterize the microstructure of the PH alloy weld joints, revealing the strength–ductility synergy mechanism of the PH welded sheets. Experimental results indicated that with respect to mechanical properties, when the welding rotational speed was fixed at 1000 rpm, increasing the forward speed from 50 mm/min to 150 mm/min reduced the ultimate tensile strength (UTS) by 6.3% and decreased the EL by 21.4%. When the forward speed was fixed at 50 mm/min, increasing the rotational speed from 500 rpm to 1500 rpm resulted in only a 0.4% variation in UTS and maintained a stable EL, demonstrating that forward speed is the dominant parameter affecting mechanical properties. In terms of formability, at a lower forward speed (50 mm/min), the Erichsen value exhibited a single-peak trend with increasing rotational speeds. At higher forward speeds (100 or 150 mm/min), the Erichsen value was insensitive to changes in rotational speed. When the rotational speed was fixed at 1500 rpm, increasing the forward speed from 50 mm/min to 150 mm/min reduced the Erichsen value by 21.3%. Microstructural strengthening mechanism: In the weld zone, the cooperative precipitation of the θ″ and θ′ phases effectively hindered dislocation motion. Simultaneously, the high geometric compatibility factor promoted the activation of multiple slip systems, and dislocation rearrangement subsequently led to the formation of sub-grain boundaries, thereby achieving strength–ductility cooperation. These findings provide theoretical support for the performance-driven welding process design of high-strength aluminum alloy components in aerospace applications. Full article

Aluminum alloys, particularly those in the Al-Cu and Al-Mg-Si series, are extensively employed in aerospace, automotive, and structural applications owing to their favorable strength-to-weight ratio. However, optimizing their mechanical and surface properties to meet advanced performance requirements remains a critical challenge. Over the past three decades, extensive research has explored thermochemical treatments, precipitation hardening, and thermomechanical processing, yet most studies have examined these methods in isolation. This review systematically analyzes the influence of each treatment route on microstructural evolution, precipitation behavior, and mechanical performance, with emphasis on grain refinement, precipitation kinetics, surface hardening, and fatigue resistance. Particular attention is given to severe plastic deformation, advanced surface modification techniques, and aging behavior under different conditions. The review also highlights gaps in the current literature, including limited integration of hybrid treatment cycles, insufficient understanding of coupled diffusion-precipitation mechanisms, a lack of high-temperature performance data, and minimal industrial-scale validation. Future research directions are proposed to develop optimized hybrid processing strategies, predictive computational models, and scalable treatment cycles. This consolidated review provides a comprehensive foundation for advancing aluminum alloy design, aiming to achieve tailored surface-to-core property gradients suitable for next-generation aerospace and automotive applications. Full article

This study examines the through-thickness microstructure and crystallographic texture evolution in friction-stir-welded (FSWed) AA5052-H32 and AA6061-T651 aluminum alloys using a tri-flats threaded pin tool. Optical microscopy and electron backscatter diffraction (EBSD) were employed to characterize grain morphology, boundary misorientation, and texture components across the weld thickness. Both alloys exhibited progressive grain refinement and increased high-angle grain boundary fractions from the top to the bottom of the stir zone due to combined thermal and strain gradients. The FSWed AA5052 displayed dominant {111}<110> and Y + γ fiber components at the upper and mid regions, whereas AA6061 showed more randomized textures. At the bottom region, both alloys developed rotated Goss {011}<01-1> and weak A ({112}<110>) and α fiber components. These results clarify how alloy strengthening mechanisms—solid-solution versus precipitation hardening—govern texture evolution under different strain-path and heat input conditions. The findings contribute to optimizing process parameters and material selection for structural-scale FSW aluminum joints in industrial applications such as bridge decks, transportation panels, and marine structures. Full article

This research systematically investigates the influence of multi-microalloying with Sn, Mn, Er, and Zr on the homogenized microstructure, aging behavior, and mechanical properties of a 6082 Al-Mg-Si alloy. The optimization of the homogenization treatment for the alloy was based on isochronal aging curves and conductivity measurements. The results show that the addition of Mn, Er, and Zr can precipitate thermally stable Al(Fe,Mn)Si dispersoids and Al(Er,Zr) dispersoids. The three-stage homogenization treatment resulted in the precipitation of more heat-resistant dispersoids, thereby achieving the best thermal stability. During direct artificial aging, the initial hardening rate of the Mn-containing alloy was slightly delayed, but its peak hardness was significantly increased. This is due to the dispersoids offering additional heterogeneous nucleation sites for the strengthening precipitates. Meanwhile, the Sn atoms release their trapped vacancies at the aging temperature, thereby promoting atomic diffusion. However, short-term natural aging before artificial aging accelerated the early-stage aging response of the Sn-containing alloy but resulted in a reduced peak hardness. Notably, the co-microalloying with Mn and Sn led to a higher peak hardness during direct artificial aging, while it caused a more significant hardness loss when a natural aging preceded artificial aging, revealing a distinct synergistic negative effect. The reason for the negative synergy effect might be related to the weakened ability of Sn to release vacancies after natural aging. This study clarifies the process dependence of microalloying effects, providing a theoretical basis for optimizing aluminum alloy properties through the synergistic design of composition and processing routes. Full article

Aluminum alloys require improved surface performance to satisfy the demands of today’s aerospace, automotive, marine, and structural applications. This paper compares three key surface hardening methods: diffusion-assisted microalloying, thermomechanical deformation-based treatments, and composite/hybrid reinforcing procedures. Diffusion-assisted Zn/Mg enrichment allows for localized precipitation hardening but is limited by the native Al₂O₃ barrier, slow solute mobility, alloy-dependent solubility, and shallow hardened depths. In contrast, thermomechanical techniques such as shot peening, surface mechanical attrition treatment (SMAT), and laser shock peening produce ultrafine/nanocrystalline layers, high dislocation densities, and deep compressive residual stresses, allowing for predictable increases in hardness, fatigue resistance, and corrosion performance. Composite and hybrid reinforcement systems, such as SiC, B₄C, graphene, and graphite-based aluminum matrix composites (AMCs), use load transfer, Orowan looping, interfacial strengthening, and solid lubrication effects to enhance wear resistance and through-thickness strengthening. Comparative evaluations show that, while diffusion-assisted procedures are still labor-intensive and solute-sensitive, thermomechanical treatments are more industrially established and scalable. Composite and hybrid systems provide the best tribological and load-bearing performance but necessitate more sophisticated processing approaches. Recent corrosion studies show that interfacial chemistry, precipitate distribution, and galvanic coupling all have a significant impact on pitting and stress corrosion cracking (SCC). These findings highlight the importance of treating corrosion as a fundamental design variable in all surface hardening techniques. This work uses unified tables and drawings to provide a thorough examination of strengthening mechanisms, corrosion and fatigue behavior, hardening depth, alloy suitability, and industrial feasibility. Future research focuses on overcoming diffusion barriers, establishing next-generation gradient topologies and hybrid processing approaches, improving strength ductility corrosion trade-offs, and utilizing machine-learning-guided alloy design. This research presents the first comprehensive framework for selecting multifunctional aluminum surfaces in demanding aerospace, automotive, and marine applications by seeing composite reinforcements as supplements rather than strict alternatives to diffusion-assisted and thermomechanical approaches. Full article

This review systematically synthesizes the research progress on θ-series precipitates. It traces the historical evolution of θ-series precipitate research, from the accidental discovery of age hardening in Duralumin to the atomic-scale insights enabled by advanced electron microscopy and computational methods. The precipitation sequence (supersaturated solid solution → GP zones → θ″ → θ′ → θ), transformation mechanisms, and interfacial characteristics of θ′/Al are comprehensively analyzed, with special attention to ongoing controversies such as the structure of GP zones and the pathways of θ″ → θ′ transition. Furthermore, the review discusses how alloying elements regulate θ′ stability through interfacial segregation, vacancy interactions, and co-precipitation effects. Critical unresolved challenges are highlighted, including the kinetic limitations of θ′ coarsening and the need for mechanistic studies on multi-element microalloying. This synthesis aims to provide a foundation for future research toward designing high-performance age-hardenable aluminum alloys. Full article

High-silicon, low-magnesium aluminum alloys are important for lightweight electrical applications, yet they face a typical strength–conductivity trade-off. This study investigates Al-0.2Mg-xSi alloys with Si ranging from 0.4 to 1.0 wt%. The wires underwent homogenization, solution treatment, cold working, and controlled annealing. In the cold-worked (Y) state, increasing Si raised tensile strength from 190 MPa to 291 MPa but reduced conductivity from 57.6% IACS to 52.1% IACS, with limited ductility. After annealing (R state), strength dropped by half (105–137 MPa), while elongation recovered beyond 22% and conductivity exceeded 62.1% IACS. Notably, the 1.0% Si alloy showed superior overall performance: its strength (137 MPa) was 32 MPa higher than the 0.4% Si alloy, with only a 0.2% IACS conductivity loss. This reveals that under low Mg content, increasing Si enhances strength via work hardening and, more critically, promotes annealing-induced precipitation that relieves lattice distortion, enabling significant strength improvement at minimal conductivity cost. These findings offer a useful strategy for optimizing strength and conductivity in such alloys. Full article

The mechanical properties of 6082 aluminum alloy under different aging conditions were investigated in this study. Precipitation behavior leading to an increase in strength was confirmed by the observation of the microstructure using TEM. The β″ precipitate, which is coherent with the Al matrix, contributes to the high tensile strength and hardness of the alloy. The transformation of the β″ phase into the β′ phase observed under TEM was proven to be responsible for the decrease in strength and hardness. The hardness curves indirectly reveal that a higher aging temperature could accelerate the transformation of β″ into β′. The coherent strain field introduced by the β″ precipitate was clearly observed and is discussed. In addition, an ideal artificial aging window is proposed, with a combined performance of a TS of 360 MPa, hardness of 105 HB and elongation over 10%. Full article

The addition of reinforcement particles can considerably improve the mechanical properties of 7xxx series aluminum alloy. In this work, the effects of TiB₂ reinforcement particles on the microstructure, mechanical properties, strengthening mechanisms, and aging precipitation of TiB₂/Al-Zn-Mg-Cu composites were systematically investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile testing machine. The results indicate that when the TiB₂ content is 1 wt.%, the composite achieves a tensile strength of 831 MPa while maintaining an elongation of 6.7%, meeting the research objectives of this experiment. When the aging heat treatment temperature is set at 120 °C, the peak aging time is shortened to 20 h. The interfacial phase composed of solute elements preferentially nucleates near the TiB₂ particles during the cooling process. With the increase in TiB₂ content, clustering in localized regions slows down the diffusion rate of interfacial phases into the matrix, thereby increasing the required duration of the solution treatment. Excellent interfacial relationships exist between TiB₂ particles and both the aluminum matrix and the MgZn₂ phase. It is also found that with the increase in TiB₂ content, the aging-hardness response of TiB₂/Al-Zn-Mg-Cu composites is accelerated and the work hardening rate is reduced. In addition, a multi-component strengthening model for the yield strength of the composite was established based on various strengthening mechanisms, including second-phase strengthening, dislocation strengthening, age-precipitation strengthening, and fine-grain strengthening. The results indicate that age-precipitation strengthening and dislocation strengthening are the most significant contributors to strength in the composite. Full article

The aim of this work is to investigate the effect of annealing (at temperatures ranging from 260 °C to 530 °C) of thin-walled Al-Mn-Mg-Ti-Zr samples manufactured by selective laser melting (SLM) on their tensile mechanical properties, hardness, and surface roughness. The results of this study may contribute to the development of post-processing modes for thin-walled products made of corrosion-resistant aluminum alloys with increased strength, manufactured using SLM technology. Hierarchical clustering methods allowed us to identify three groups of thin-walled samples with different strain-hardening mechanisms depending on the annealing temperature. The greatest hardening is achieved in the first group of samples annealed at 530 °C. Metallographic analysis showed that at this heat treatment temperature, there are practically no micropores (macrodefects) and microcracks. X-ray phase analysis showed the precipitation of Ti and Zr, as well as the formation of an intermetallic phase with a composition of Mg8Al16. At lower heat treatment temperatures, from 260 °C to 500 °C, the observed hardening is statistically significantly lower than at 530 °C. This phenomenon, combined with the formation of intermetallic phases and the precipitation of titanium/zirconium, contributes to the hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM. The main results of this study show that the optimal strain hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM is achieved by heat treatment at 530 °C for 1 h. The strengthening mechanism has two characteristics: (1) dispersion strengthening due to the formation of precipitates and (2) reduction in macrodefects at high temperatures. Full article

This preliminary study investigates the optimization of the mechanical properties of the zinc wrought alloy ZEP1510 with the objective of assessing its potential to approach the hardness, strength, and toughness of the brass alloy, CuZn21Si3P. Enhancing both toughness and hardness was targeted to improve the durability of potential replacement components. Heat treatment was the primary method, applying annealing, air cooling, water quenching, and artificial aging to modify material properties. Mechanical characterization was performed through Brinell hardness, as well as tensile and Charpy impact testing, complemented by metallographic analysis. Air cooling from temperatures near the transformation point at 275 °C produced a visually refined and homogeneous microstructure (qualitative assessment by OM/SEM), resulting in simultaneous increases in hardness and toughness. Water quenching from this range yielded a metastable state with high toughness but low hardness, while subsequent natural aging significantly increased strength and reduced toughness. Artificial aging indicated precipitation hardening behavior similar to that of aluminum alloys. Although property improvements were achieved, the targeted combination of high toughness and high strength was not fully realized. The findings suggest that controlled artificial aging, alternative quenching media and grain refinement strategies could further enhance performance, providing a basis for tailoring ZEP1510 for demanding engineering applications. Full article

Laser welding, a vital process in modern industry, offers significant technical and economic benefits, including improved part quality, precision, productivity, and cost reduction. This study significantly enhances our understanding of heat-treatable weldability (AA2024, AA2017, AA6061) and non-heat-treatable AA5083 aluminum alloys. It establishes a “weldability window” based on power density and interaction time, identifying three key domains: insufficient penetration, full penetration with regular weld, and irregular weld or cutoff. The study’s findings reveal that heat-treatable alloys soften in the fusion zone due to the dissolution of reinforcing precipitates during welding. In contrast, non-heat-treatable alloys exhibit hardening due to a fine dendritic microstructure. The fusion zone features fine dendrites, and in the heat-affected zone (HAZ), coarse particles and liquation at the fusion line are observed, particularly in AA6061 and 2024 alloys. The study also shows that the joint efficiency, a measure of the weld’s load-bearing capacity, is approximately 90% for the AA5083 alloy and 80% for the heat-treatable alloys. These findings significantly contribute to our understanding of welding processes. They can be used to optimize laser welding processes, thereby ensuring the production of high-quality and reliable joints in industrial applications. Full article

This article investigates the precipitation behavior of the phases in metastable β-type titanium alloys (Ti-38644) and their significant impact on the mechanical properties. By manipulating various solid solution aging parameters, the morphology, quantity, and distribution of the αs phase can be optimized. After one hour of solid solution treatment at 760 °C, the alloy is predominantly composed of the β phase, with a higher concentration of aluminum at the grain boundaries compared to the interior of the grains. Subsequently, after ten hours of aging treatment at 450 °C and 470 °C, the needle-shaped αs phase preferentially precipitated at the grain boundaries. As the aging temperature increased to 470 °C, the area percentage of the αs phase rose from 42.36% to 57.34%, while its yield strength (σs) increased from 967 MPa at 450 °C to 1211 MPa at 470 °C. This increase in σs results from the combined effects of dislocation strengthening (${\sigma }_{\rho }$) and precipitation hardening. This article provides a comprehensive theoretical analysis of the various factors that influence σs, offering valuable theoretical support for the development of heat treatment processes for the Ti-38644 titanium alloy. Full article