Achieving a synergistic enhancement of hardness and electrical conductivity in Cu-Ni-Si alloys requires precise modulation of nanoprecipitation. Although Co and Cr microalloying are established strategies, their underlying mechanisms, particularly the role of chemical short-range order (CSRO), remain unclear. Contrary to expectations, introducing Co and Co-Cr into a Cu-Ni-Si alloy increased hardness but decreased electrical conductivity. Atomic-scale characterization and computational analysis revealed, for the first time, that Co induces a distinct Cu-Co CSRO. This CSRO traps Si solutes, impeding the nucleation and growth of the primary strengthening delta-Ni2Si nanoprecipitates. The retained disordered Ni and Si atoms, along with the CSRO itself, degrade conductivity. Furthermore, Co and Cr regulate nanoprecipitates differently: Co stabilizes the precipitate-matrix interface, refining delta-(Ni,Co)2Si and suppressing coarsening, while Cr segregates at the precipitate core, exerting a kinetic drag effect. Both elements synergistically enhance coarsening resistance. This work clarifies the dual, strengthening-yet-conductivity-limiting role of Co-induced CSRO and the distinct, synergistic mechanisms of Co and Cr in nanoprecipitate modulation.

Mg-11Gd-4Y-2Zn-0.5Zr alloy with long-period stacking ordered (LPSO) phases exhibits excellent high-temperature strength and ductility. In this paper, the influence of compressive stress (hot compression) and shear stress (hot torsion) on the deformation of LPSO phases and dynamic recrystallization (DRX) behavior was investigated at 450 °C and 0.01s−1. Microstructural evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD). The results revealed distinct stress-mode dependencies: DRX area fractions were notably higher under shear stress than under compressive stress. Moreover, the LPSO phases exhibited noticeably different deformation behaviors: intragranular lamellar LPSO phases exhibited weaker kinking deformation with lower kink angles during torsion, while intergranular block LPSO phases suffered more severe fragmentation under shear stress. Theoretical analysis confirmed that the enhanced fragmentation under torsion promotes DRX via particle-stimulated nucleation (PSN) mechanism. Analysis of in-grain misorientation axes (IGMA) and effective Schmid factors (ESF) demonstrated that more pyramidal II slips were preferentially activated under shear stress. Such increased activation of pyramidal II slip facilitates DRX nucleation by generating a higher density of low-angle grain boundaries and sub-grains compared to that under compressive stress.

Laser heat treatment (LHT) was employed to achieve rapid quenching of an Al-Cu-Mg alloy. The mechanical properties, microstructural evolution, and precipitate characteristics under different LHT conditions were systematically investigated. The results showed that LHT with peak temperatures above 450 °C significantly improved the mechanical strength of the alloy but not exceeding 580 °C to avoid grain boundary melting. With increasing laser temperature, no obvious changes in grain orientation, texture, or grain size were observed, whereas the morphology and distribution of precipitates evolved considerably. Unlike conventional furnace heat treatment, which predominantly produced uniformly dispersed nanoscale S′ precipitates within grains, LHT generated fewer intragranular S′ precipitates but induced a unique continuous chain-like S′ phase along grain boundaries, accompanied by the formation of precipitation-free zones. The volume fraction of these grain-boundary precipitates increased markedly with rising laser temperature. This distinctive precipitation behavior contributed to a novel strengthening mechanism. Quantitative analysis based on theoretical models revealed that the chain-like S′ phases contributed up to approximately 18.3

As a light rare earth element, La element is primarily selected microalloying element in aging strengthened copper alloy. In this study, the La added Cu-Ni-Si alloy is studied for clarifying structure and type of the second phase formed by La element and other elements. The Cu-Ni-Si alloy with addition of La exhibits different texture types and stronger interaction between Ni2Si phase and nano-twins compared to the alloy without La element. Such difference contributes the excellent resistance to over-aging of the La contained Cu-Ni-Si alloy. Meanwhile, the structure of the La-rich phase was explored using a transmission electron microscope with multiple probes and a fast imageable X-ray energy spectrum analysis probe as well as first-principle calculations. The addition of La element in the alloy formed two kinds of rich La phases, LaNi9Si4 and LaNi2Si2, which both show incoherent relationship with the matrix. Specially, a new kind of core-shell structure is found with shell of LaNi9Si4 and core of LaNi2Si2. This characteristic can be used as a dispersion strengthening phase in the subsequent design of Cu-Ni-Si alloys, providing a new idea for the research and development of new high-performance Cu-Ni-Si alloys.

A novel method called thermomechanical treatment based on impact hydroforming (TTIHF) was proposed. The pre-deformation was achieved by using impact hydroforming (IHF) loading. The strengthening effect and mechanism of 2195 Al−Li alloy were investigated under various loading pre-deformation conditions. The results showed that the time for the alloy to reach peak aging was shortened under TTIHF. Compared with those of the pre-deformation method of stamping forming, the yield strength and tensile strength of the Al−Li alloy under TTIHF increased by 18.6% and 18.0%, respectively. The deformation caused by IHF loading resulted in a high density of dislocations, which served as nucleation sites for the precipitation of the T1 phase during aging. After TTIHF, the average diameter and thickness of the T1 phase in the alloy were smaller than those under other experiment conditions. Moreover, the density and distribution of the T1 phase were the highest and the most uniform.

Internal defect is a general problem in cross wedge rolling, which usually diminishes mechanical properties and even leads to the failure of rolled workpieces. In this study, variation of characteristics (stress state, strain path, etc.) in rolled workpieces during deformation was investigated through numerical simulation. Then, microstructural evolution of internal defects was clarified by quasi-in-situ experiments. Finally, process parameter intervals forming rolled workpieces with internal defect-free and good mechanical properties were confirmed. Results show that rolled workpieces with good surface quality can be produced although they experience complex strain paths and stress states during deformation. Further, quasi-in-situ experiments revealed that evolution process of internal defects. Namely, defect nucleates at interface between inclusion and matrix, and grows into a micro-pore. As section shrinkage increases, micro-pores gradually expand and coalesce, forming larger micro-holes and potentially leading to macro-cracks. Among them, propagation process is accelerated by fine carbide particles served as expansion channels. In addition, rolled workpieces with good internal and external quality can be formed at a heating temperature of 970–1 020 °C and a rolling velocity of 400 mm/s. Specially, area proportion of defects was counted quantitatively to characterize damage degree. At a fixed velocity of 400 mm/s, as temperature increased from 950 °C to 1 050 °C, area proportion changed from 1.4

The forming limit behavior of ultra-thin TA2 titanium sheets under microchannel hydroforming is critically affected by the ratio of sheet thickness (t) to grain size (d). In this study, the impact of varying t/d ratios on formability was systematically evaluated using an integrated experimental and finite element (FE) methodology. Forming limit curves (FLCs) were determined for sheets with t/d ratios spanning 1 to 5.21. The results indicate a pronounced decrease in the plane-strain forming limit for t/d values below 5.21, correlating with heightened susceptibility to localized thinning and fracture, particularly at microchannel bends and corners. To address the limitations of direct FLC measurement at low t/d, a hybrid experimental-numerical framework was introduced, enabling virtual FLC prediction. Strain path analysis and FE simulations identified the upper corner regions of the microchannel as most prone to failure, characterized by thickness-direction thinning exceeding 20% under plane strain conditions. The proposed approach establishes a direct relationship between microstructural state, deformation mode, and failure, offering a robust strategy for optimizing process parameters and structural integrity. These findings advance the design and manufacture of ultra-thin titanium components for energy and microfluidic applications, including fuel cell bipolar plates.

Taking half-tube part with curvature as an example,the Impact Hydroforming(IHF)characteristics were studied by combining the actual forming experiment and numerical simulation.The IHF experiment showed that wrinkles appeared at the bottom of the part during single-step forming,but no wrinkles were observed during double-step forming.The thinning rate and devia-tion of the wall thickness of the part in each area were less than 20％and 2.7 mm,correspondingly,and the drawing depth of the part reached 45.8 mm.The effect of double-step forming was better than that of single-step forming,which was related to the IHF forming law.Besides,the character-istics of the IHF process were studied by numerical simulation.The results indicated that when double-step forming was utilized,there was almost no velocity field in the opposite direction of deformation after the bottom of the part contacted the die,and the existence of stress state at the bottom would restrain and eliminate the wrinkles.The inertia effect evolved with the driving pressure.Specially,the inertia effect can improve the flow of metal and reduce the deviation of the wall thickness of the part under double-step forming.

An unexpected increase in the electrical conductivity of Cu-Cr-Zr alloy was identified during solid solution treatment, with the conductivity rising from the typical 42.11 % IACS to as high as 88.95 % IACS. Such a significant enhancement in conductivity is driven by oxygen diffusion at 950 °C, where oxygen primarily reacts with dissolved Cr in the matrix, not with primary Cr phases. Specifically, oxygen-driven dissolution of primary Cr phases forms a ring-like structure that further promotes reactions. These reactions result in formation of nano-sized Cr₂O₃ precipitates, thereby contributing to the improved conductivity. These findings suggest a potential method for optimizing copper alloys' microstructure and properties by controlling oxygen content.

Little is known about the mechanical property and formability of CZ1 zirconium alloy sheet. In this study, tensile tests of CZ1 sheet were carried out along rolling direction (RD), diagonal direction (DD) and transverse direction (TD). Nakazima tests were conducted to construct the forming limit diagram (FLD) for CZ1 sheet. Three anisotropic yield criteria including Hill48, Barlat89 and BBC2003 were chosen to calibrate the anisotropic coefficients in order to compare the accuracy for anisotropy description. The classical Marciniak-Kuczynski (M-K) model and different yield criteria are applied to predict the forming limit strains theoretically. After comparison, BBC2003+M-K model predicted FLD is in good agreement with the experimental result. Then the effects of material parameters including hardening exponents (n value) and Lankford coefficients (r-values) on the FLD are analyzed with this approach. Furthermore, the relationship between material parameters and formability can be unveiled aiming at providing an optimized direction for formability.

The Zr-1.0Sn-1.0Nb-0.1Fe alloy sheet with a typical double-peak basal texture was rolled up to 70 % thickness reductions at room temperature to follow its textural evolution. An unusual weakened basal texture under increasing rolling strain is found for cold rolled Zr alloy sheets. Specifically, basal pole is changing from transverse direction (TD) to normal direction (ND) resulting in a stronger basal texture under small deformation amount. For heavy deformation, the maxima of texture components spread from ND to TD. This spreading of the texture change is primarily related to a certain amount activation of pyramidal (c + a) slip, which inhibited the formation of basal texture. In-grain misorientation axes analysis and visco-plastic self-consistent simulation jointly suggested that the distinctive tendency of texture evolution is mainly derived from the competition between basal (a) slip and pyramidal (c + a) slip.

This study focuses on the key failure issues of rolls in the three-roll planetary rolling process. Firstly, through the analysis of failure morphology, it is inferred that the main failure mechanisms are the initiation and propagation of thermal fatigue cracks and severe friction and wear. On this basis, the thermal fatigue and friction wear tests of the roll material were designed and carried out. The research results show that the failure behavior of the rolls is jointly dominated by the synergistic effects of thermal fatigue and friction wear. By systematically analyzing the evolution law of cracks, a thermal fatigue damage model with crack length and crack area as core parameters was established, thereby effectively evaluating the crack propagation behavior of rolls. Further research indicates that coating the surface of the rolls with diamond-like carbon (DLC) coatings can significantly enhance their thermal fatigue resistance and friction and wear performance, providing theoretical support and experimental basis for greatly extending the service life of the rolls.

To solve the difficulty of forming complex parts of aluminium alloy, a method was proposed using local hardening by laser heat treatment (LHT) to improve the formability of the Al alloy sheet. In order to explore the influence of laser local hardening on deep drawing forming performance, the temperature field of laser treatment was simulated based on the measured data, and a sheet model coupled with mechanical property gradient was established. In addition, the mechanism of the improvement of material formability by the change of constitutive parameters was revealed by the combination of simulation and experiment. The results show that laser scanning can generate a stable gradient temperature field with little influence on the surrounding area. Furthermore, the multi-pass scanning allows for the design of property gradient differential sheets with varying ranges. It is proved that the LHT can effectively improve the plastic strength and the local hardening ability of Al alloy. The results of deep drawing simulations and tests show that the LHT mainly affects the forming ability of differential aluminium alloy sheets by regulating the gradient distribution of strain hardening exponent n and strain hardening coefficient k. The gradient decreasing distribution of n value from the heat treatment center to the surrounding area can not only improve the forming ability of the core area, but also alleviate the strain concentration in the periphery, so as to achieve a more uniform strain distribution in the large deformation zone. The gradient distribution of k can change the position and order of the yield behavior of the plate, and then change the material flow sequence, thus slowing down the material flow at the bottom fillet with higher k value and reducing the tendency of thinning and cracking. In particular, it is found that the gradient distribution of k value is the dominant factor to improve the forming ability of poor aluminium alloy sheet. When the gradient of k value distribution between the laser strengthening area and the surrounding material reaches the critical value, the fracture position of the deep drawing part will shift, which greatly delays the occurrence of necking and cracking processes and improves the overall forming ability of the sheet.

Cross wedge rolled Ti-6Al-4V(TC4)titanium alloy workpieces with a large cross-section reduction,often display surface necking and internal defects during the forming process.True stress-strain(ɛ)curves for TC4 titanium alloy are derived from hot compression tests conducted within a deformation temperature range of 800-950℃and a strain rate((ε̇))range of 0.1-30 s-1.An Arrhenius constitutive model,which includes strain compensation,and DMM(dynamic material model)-type processing maps are developed to analyze the deformation and defect evolution in cross-wedge rolling.The influence of rolling temperature and heating methods on process defects is thoroughly investigated.The results indicate that both the necking and internal defects of the rolled workpieces diminish as the experimental temperature rises,corroborating the precision of the processing maps and finite element simulations.Microstructure characterization and mechanical property tests reveal that the better surface and internal quality of rolled workpieces can be obtained by induction heating compared with resistance furnace heating.Workpieces rolled using induction heating at 900℃show a tensile strength of 1073.18 MPa,while retaining a hardness of approximately 400HV.The mechanism for internal defects formation in rolled workpieces is the preferential nucleation of microscopic voids at β phase regions or α/β phase interfaces.These voids then undergo axial extension under applied stress,leading to a banded distribution of microscopic cracks.

The structural integrity of welded joints is critical to the safety and long-term durability of aluminum alloy components in automotive and aerospace applications, where fatigue failure frequently initiates at localized stress concentrations. This study investigates the fatigue performance of representative welding configurations in 6061 aluminum alloy. The fracture mechanisms and underlying microstructural evolution, particularly dislocation behavior, in the welded joints were characterized to elucidate the failure origins. Additionally, this study proposes a high-precision fatigue life prediction method for welded components, leveraging finite element numerical simulations, empirical fatigue performance data of 6061 aluminum alloy base material, and key correction parameters from the Forschungskuratorium Maschinenbau guideline. The method establishes fatigue life predictions based on stress characteristics at critical locations—specifically, those corresponding to characteristic points on the fatigue S-N curve. While validated for aluminum alloy welded joints, the approach is broadly applicable to engineering components, offering a novel and robust framework for fatigue performance assessment.

This study systematically investigates the strain-rate-dependent deformation mechanism and microstructure evolution of Ti-6Al-4V alloy over a broad range of strain rates (0.001-4000 s_ 1). Uniaxial tensile testing, combined with advanced electron microscopy techniques (SEM, EBSD, and TEM), was employed to study the behavior of the alloy. At low strain rates, the alloy exhibits conventional monotonic strain hardening accompanied by stable ductile fracture. However, as the strain rate increases, a noticeable transition in hardening behavior occurs, marked by a shift to more dynamic strain hardening and the emergence of a secondary hardening stage. This stage is dominated by localized deformation and intensified slip activity, reflected in the evolution of the microstructure. High-resolution EBSD mapping reveals that elevated strain rates increase alpha/(3 phase interactions and the density of geometrically necessary dislocations (GNDs), which facilitates dynamic recovery and the formation of ultra-fine subgrains. This helps delay necking and improves tensile elongation (up to 18 % at 3828 s_ 1). While rate-sensitive mechanisms primarily govern the enhancement in ductility, the adiabatic temperature rise further aids dynamic recovery. Fractographic analysis corroborates these findings, showing a shift from uniform dimples to layered delamination in the fracture surface. These results provide a comprehensive mechanics-microstructure framework for understanding strain-rate-dependent plasticity in dualphase Ti alloys, offering valuable insights for engineering applications involving dynamic loading, such as aerospace impact-resistant structures, automotive crashworthy components, defense systems, and high-speed metal forming processes.

Bipolar plate is one of the most important components of proton exchange membrane fuel cells, which has the basic functions of conducting electricity, supporting membrane electrode assemblies, uniformly distributing and isolating reactant gas, circulating coolant, and rapid heat dissipation. In this article, taking the micro runner flexible forming process of 316L stainless steel sheet as the research object, the influence of process parameters on the forming quality of micro flow runners is analyzed. The results show that an increase of the equipment pressure and a decrease of the soft film hardness are conducive to the improvement of the forming depth of a bipolar plate, while the holding time has a minor effect on the forming depth. Under the same loading conditions, the forming depth of a 0.1 mm thick sheet is smaller than that of a 0.075 mm sheet. An increase of the grain size reduces the difficulty of forming, and the larger the grain size, the larger the forming height and runner filling rate. However, with an increase of the grain size, the surface roughness of the bipolar plate increases and the wall thickness of some parts of the runner becomes uneven.

Zircaloy-4 (Zr-4) sheets used in fuel assembly structural parts are subjected to high temperatures, stresses, corrosive environments, and radiation. Due to the poor formability of Zr-4, cracks usually occur during the fabrication of spacer grids at room temperature. In this research, annealed Zr-4 sheets with two distinct initial textures were studied during stamping. Experimental results showed that the sheet with higher normal Kearns factors exhibited weaker formability, leading to cracking at the punch radius under the same punching depth. Electron backscatter diffraction (EBSD) observations revealed discrepancies in texture evolution under different strain paths during plastic deformation. A multi-scale simulation was conducted to elucidate the deformation mechanisms. Modeling accuracy was validated by comparing crack locations, thickness distributions, and post-deformation textures with experimental results. The contribution of slip and twinning to crack formation was quantified. The simulation indicated that Zr-4 sheets with weaker textures exhibited better deformation compatibility, primarily due to enhanced activation of prismatic slip, whereas sheets with stronger textures showed dominant basal slip activity, which promoted cracking.

This study investigated the influence of aggregate powder compositions (Ti-Al-Graphite/Ti-Al-TiC) and processing variables on microstructure, phase composition, and tribological properties of atmospheric plasma sprayed Ti-Al-C coatings. The coatings exhibited a distinct layered structure, with variations in phase composition and microstructure attributed to differences in agglomerated powder and spraying conditions. Incorporating TiC in the agglomerated powder significantly improved the hardness and bonding strength of the coatings. High-temperature friction and wear tests demonstrated superior wear resistance of the TiC-containing coatings compared to those with graphite. The formation of a protective oxide layer, consisting of TixAly and Ti2AlC phases, during frictional sintering oxidation led to enhanced wear resistance at elevated temperatures. The mechanisms of friction and wear in these coatings involved oxidative wear, adhesive wear, and fatigue wear. The results suggest that the composition of the Ti-Al-C coatings can be tailored to optimize their high-temperature tribological performance for various applications.