Search Results (84)

This study investigates the fabrication and residual stress behavior of a 0.5 wt.% graphene-reinforced AA2195 aluminum matrix composite, developed for advanced aerospace structural applications. The composite was synthesized via squeeze casting, followed by a multi-pass hot rolling process and subsequent T8 heat treatment. The evolution of residual stress was systematically examined after each rolling pass and during thermal treatments. The successful incorporation of graphene into the matrix was confirmed through Energy-Dispersive Spectroscopy (EDS) analysis. Residual stress measurements after each pass revealed a progressive increase in compressive stress, reaching a maximum of −68 MPa after the fourth hot rolling pass. Prior to the fifth pass, a solution treatment at 530 °C was performed to dissolve coarse precipitates and relieve internal stresses. Cold rolling during the fifth pass reduced the compressive residual stress to −40 MPa, and subsequent artificial aging at 180 °C for 48 h further decreased it to −23 MPa due to recovery and stress relaxation mechanisms. Compared to the unreinforced AA2195 alloy in the T8 condition, which exhibited a tensile residual stress of +29 MPa, the graphene-reinforced composite in the same condition retained a compressive residual stress of −23 MPa. This represents a net improvement of 52 MPa, highlighting the composite’s superior capability to retain compressive residual stress. The presence of graphene significantly influenced the stress distribution by introducing thermal expansion mismatch and acting as a barrier to dislocation motion. Overall, the composite demonstrated enhanced residual stress characteristics, making it a promising candidate for lightweight, fatigue-resistant aerospace components. Full article

Electrolytic copper foil is one of the core materials in the fields of electronics, communications, and power. The cathode roller is the key component of the complete set of electrolytic copper foil equipment, and the quality of the titanium cylinder of the cathode roller directly determines the quality of the electrolytic copper foil. There typically exists a longitudinal weld on the surface of the cathode roller’s titanium cylinder sleeve manufactured by the welding method, which leads to the degradation of the quality of the electrolytic copper foil. Refining the grains in the weld zone and the heat-affected zone to close to those of the base material is a key solution for the manufacturing of welded cathode rollers. In order to effectively modify the microstructure and obtain an optimal refining effect in the weld zone of a TA1 cathode roller, a novel composite technology consisting of low-energy and fewer-pass welding combined with multi-pass rolling deformation and vacuum annealing treatment was primarily explored for high-purity TA1 titanium plates in this study. The microstructure of each area of the weld was observed using the DMI-3000M optical microscope, and the hardness was measured using the HVS-30 Vickers hardness tester. The research results show that the microstructure of each area of the weld can be effectively refined by using the novel composite technology of low-energy and fewer-pass welding, multi-pass rolling deformation, and vacuum annealing treatment. Among the explored experimental conditions, the optimal grain refinement effect is obtained with a V-shaped welding groove and four passes of welding with a welding current of 90 A and a voltage of 8–9 V, followed by 11 passes of rolling deformation with a total deformation rate of 45% and, finally, vacuum annealing at 650 °C for 1 h. The grain size grades in the weld zone and the heat-affected zone are close to those of the base material, namely grade 7.5~10, grade 7.5~10, and grade 7.5~10 for the weld zone, heat-affected zone, and base material, respectively. Meanwhile, this technology can also refine the grains of the base material, which is conducive to improving the overall mechanical properties of the titanium plate. Full article

To accurately and reliably characterize the degradation trend of rolling bearings and predict their life cycle, this paper proposes a bearing life prediction model based on an improved transformer encoder layer and multi-scale convolution. First, time-domain, frequency-domain, and time-frequency domain features are extracted from the vibration data covering the entire lifespan of the rolling bearings and passed through the transformer encoder layer. A novel dual-layer self-attention mechanism network structure is proposed to capture global information on the lifecycle progression of rolling bearings. Next, to further extract local temporal features within the bearing’s life cycle, a multi-scale convolution module is proposed to reinforce the local information across the entire lifespan. This method fully exploits both the long-term trends and short-term dynamic variations in the health status of rolling bearings, effectively enhancing the accuracy of life predictions. Experimental results show that, even under conditions with interference features, the TransCN model outperforms mainstream advantage model in terms of prediction accuracy and generalizability. This approach offers a new solution for managing the fault risk of rotating machinery and reducing maintenance costs. Full article

Modeling hot rolling remains a major challenge in computational solid mechanics. It demands the simultaneous consideration of geometric and material responses. Although the finite element method (FEM) is widely used, multi-pass simulations often treat each pass independently, leading to error accumulation, particularly in flat product rolling, where inter-pass interactions are crucial. Advanced models and remeshing techniques have been developed to address these issues, but substantial computational resources are required. In this study, a previously validated and simplified 3D FEM model was employed to simulate the initial stages of the hot rolling of large-scale AISI 430 ferritic stainless-steel slabs, using data from an industrial rolling schedule. Specifically, the simulations encompassed preheating and descaling, and seven passes of the roughing stage. Through these simulations, a transfer bar with an approximate length of 16,100 mm was obtained. The simulated thickness and rolling load values were compared with experimental data, demonstrating good agreement in most passes. Subsequently, the temperature, effective plastic strain, and equivalent stress distributions along the rolled material were extracted and analyzed. The results highlighted that the employed model adequately predicted the variations in the analyzed parameters throughout the volume of the rolled material during the different stages of the process. However, discrepancies were identified in the rolling load values during the final passes, which were attributed to the presence of phenomena not considered in the constitutive model used. This model will be refined in future studies to reduce the error in the rolling load estimation. Full article

To resolve the challenges of weak bonding interface and to avoid expensive and time-consuming trials, integrated computational materials engineering (ICME) was applied to study the hot roll bonding and forming of ultra-thick 45 steel stacked assemblies (>60 mm) and to optimize the rolling processes. Microstructure and properties of the continuous cast slabs of 45 steel subjected to heating and forming were acquired from JMatPro V13.2 calculations and essential experimental validations. Interfacial bonding criteria were established from hot compression tests and were applied to the finite element simulations of the multi-pass rolling processes of a two-slab stacked assembly and a three-slab stacked assembly to predict the bonding of interior interfaces and the deformation of the plates. Unlike previous studies, the aim of this research is to apply the concept of integrated computational materials engineering to shorten the development cycle and reduce re-search costs. The results revealed that the compressive strain of 0.05 is sufficient to form metallurgical bonding at the interface for machined 45 steel in a vacuum. Finite element simulation results indicate that complete bonding of the interfaces is established after two passes for the two-slab stacked plate and four passes for the three-slab stacked plate. Optimized rolling process parameters from analyzing the finite element simulation results are applied to design the hot rolling process of the stacked slab assemblies to produce ultra-thick plates. By applying the concept of integrated computational materials engineering, the development cycle of product processes can be significantly shortened, and financial investment can be reduced. Full article

In order to meet the demand for structural/functional integrated materials in the field of electromagnetic shielding, a graphene nanosheets (GNSs) reinforced magnesium matrix composite was fabricated using an electrophoretic deposition and subsequent accumulative roll bonding process (ARB). The microstructure, mechanical properties, and electromagnetic interference (EMI) shielding effectiveness (SE) of the GNSs/Mg composites were characterized systematically. The results showed that synergistic strengthening of the mechanical properties and EMI shielding performance of the composites was realized. The strengthening mechanisms for the mechanical and EMI shielding performance of the GNSs/Mg composites were analyzed thoroughly. After five passes of ARB, the ultimate tensile strength and elongation were 271.79 MPa and 12.9%, respectively. For the laminated structure, the strengthening is related to the thickness of the graphene layer, the dispersion, and the interfacial bonding with the metal matrix. In electromagnetic shielding aspects, after ARB-5, the SE is 93.36–105.15 dB. The introduction of well-organized multivariate multi-scale macro–micro interfaces increased the electromagnetic wave propagation paths and multiple reflection loss absorption in the internal propagation paths. Moreover, the addition of carbon nanomaterials led to an increase in the number of interfaces, which was conducive to the expansion of the internal reflection paths; carbon nanomaterials at the interfaces also improved the electromagnetic wave absorption. Full article

This paper is focused on the rolling finite element simulation and experimental study of 20CrNiMo/Incoloy 825 composite materials. Firstly, single-pass rolling finite element simulations of the composite materials were conducted. The effects of rolling pass reduction and rolling speed on the warpage, interface strain difference, and stress of the 20CrNiMo/Incoloy 825 composite materials were evaluated, highlighting an ideal first-pass reduction of 30% and a rolling speed of 0.117 m/s. Based on these results, rolling finite element simulations under total reduction–pass conditions of 65%–3 passes, 75%–4 passes, and 85%–5 passes were conducted on 20CrNiMo/Incoloy 825 composite materials. The rolling process was found to be optimal for a total reduction of 85%–5 passes based on the ratio of the vertical compressive stress experienced by the Incoloy 825-side metal to the yield strength of Incoloy 825 at 1150 °C. Based on the results of single- and multi-pass finite element simulation experiments, microstructural observations and interface analyses were then conducted on the 20CrNiMo/Incoloy 825 composite materials after rolling. The bonding interface of the composite materials was found to be undulating, indicating good composite effects. In addition, Cr, Ni, and Fe at the interface of the composite materials exhibited a steep gradient of change, indicating trace element diffusion with a distance of 8.27 μm in the 20CrNiMo/Incoloy 825 composite materials. Finally, the interfacial bonding mechanism of the 20CrNiMo/Incoloy 825 composite materials was studied, and the results indicate that this mechanism is based on a combination of diffusion and recrystallization bonding mechanisms. Full article

By coordinating the rolling direction and mode, a multi-rolling plastic deformation process for an aluminum (Al) sputter target is proposed to achieve multiple excellent properties, including a uniform and fine grain structure and low defect risk, which are significant in producing high-quality sputtered films. In this work, therefore, DEFORM 3D 10.2 software is adopted to establish three strategies, clock-synchronous rolling, cross-synchronous rolling, and clock–snake rolling. The effect of different rolling routes and modes on the metal flow velocity (MFV), effective strain distribution (ESD), grain size distribution (GSD), damage, and rolling force (RF) are comparatively investigated. The simulation results show that clock–snake rolling can increase the MFV and effective strain by producing a deeper deformation than the others. It provides sufficient energy for dynamic recrystallization to promote grain refinement. In combination with the microstructure homogeneity promoted by the clock rolling route, the GSD from 6.5 to 44.3 μm accounts for about 80.5% of all the grains because of the fact that a randomly oriented grain region is full of high-angle grain boundaries. Compared with the synchronous rolling mode, the decrement in RF maximum reaches up to 51% during the asynchronous rolling process because component energy is consumed to form cross-sheering stress. It remarkably reduces the risk of defects, with a damage value of less than 73%, and simultaneously improves energy efficiency owing to smaller and uniform grains caused by less RF. The results obtained in this work are of great significance as they can guide practical production in the metal target industry. Full article

Material design and preparation based on constructing heterogeneous microstructures can break the conventional performance limitations of fine-grained magnesium alloys. In this study, AZ61 alloys processed via multi-pass equal channel angular pressing (ECAP) were subjected to single-pass rolling (SPR) with increased rolling reductions. The effect of rolling reduction on the formation of heterogeneous microstructure and the mechanical properties of the alloy was investigated. Microstructural examinations revealed that a heterogeneous microstructure was formed in the alloy at varied rolling reductions, but the desired heterostructure with higher fine grain contents could only be achieved at increased rolling reduction. This was mainly due to the fact that the alloy underwent partial dynamic recrystallization (PDRX) under SPR, and PDRX more easily occurred with higher rolling reduction. The tensile test results showed that with increased rolling reduction, the strength of the alloy first increased and then decreased slightly, with the ductility steadily increasing. Improved mechanical properties were achieved in the alloy rolled at increased rolling reductions owing to the heterogeneous microstructure with a greater content of fine grains. Full article

In the present study, the hot roll bonding process of 7000 series aluminum alloy laminated materials was numerically simulated and investigated using the finite element method, and the process parameters were experimentally verified by properties testing and microstructure analysis after hot roll bonding. In the roll bonding process of aluminum alloy laminated materials, the effects of the intermediate layer, pass reduction ratio, rolling speed and thickness ratio of component layers were studied. The results of finite element simulations showed that the addition of a 701 intermediate layer in the hot roll bonding process could effectively coordinate the deformation of the 705 layer and 706 layer and prevented the warping of the laminated material during hot rolling. It is recommended to use a multi-pass rolling process with small deformation and high speed, and the recommended rolling reduction ratio is 20%~30%, the hot rolling speed is 1.5~2.5 m/s and the thickness ratio of the 705 layer and 706 layer is about 1:5. Based on the above numerical results, five-layer and seven-layer 7000 series aluminum alloy laminated materials were prepared by the hot roll bonding process. The results showed that metallurgical bonding was realized between each component layer, and no delamination was observed from the tensile fracture between the interfaces of component layers. The tensile strength of the prepared laminated materials decreased with the increase in the thickness ratio of the 705 layer, and the bonding strengths of the laminated materials were in the range of 88–99 MPa. The experimental results verified the rationality of the process parameters recommended by the numerical simulations in terms of warping and delamination prevention. Full article

The azimuth track is an important component of the radio telescope wheel–rail system. During operation, the azimuth track is inevitably subject to phenomena such as track wear, track fatigue cracks, and impact damage to welded joints, which can affect observation accuracy. The 110 m QiTai radio telescope (QTT) studied in this paper is the world’s largest fully steerable radio telescope at present, and its track will bear the largest load ever. Since the welded joint of an azimuth track is the weakest part, an innovative welding method (multi-layer and multi-pass weld) is adopted for the thick welding section. Therefore, it is necessary to study the contact mechanical properties between the wheel and the azimuth track in this welded joint. In this study, tensile tests based on digital image correlation technology (DIC) and Vickers hardness tests are carried out in the metal zone (BM), heat-affected zone (HAZ), modified layer, and weld zone (WZ) of the welded joint, and the measured data are used to fit the elastic–plastic constitutive model for the different zones of the welded joint in the azimuth track. Based on the constitutive model established, a nonlinear finite element model is built and used to simulate the rolling mechanical performance between the wheel and azimuth track. Through the analysis of simulated data, we obtained the stress distribution of the track under different pre-designed loads and identified the locations most susceptible to damage during ordinary working conditions, braking conditions, and start-up conditions. The result can provide a significant theoretical basis for future research and for the monitoring of large track damage. Full article

Two plates of nanostructured ferritic alloy NFA-1 were processed by ball milling atomized Fe-14Cr-3W-0.4Ti-0.2Y (wt.%) with FeO powders, canning, and hot-extrusion at 850 °C, followed by annealing and multipass cross-rolling at 1000 °C. This produces a severe (001) brittle cleavage texture on planes running parallel to the plate faces. In the first plate (P1), pre-existing microcracks (MCs) formed on the cleavage planes during cross-rolling. The second plate (P2) contained far fewer, if any, MCs. Here, we compare the tensile data for out-of-plane (S) and in-plane (L) tensile axis orientations, at temperatures from −196 °C to 800 °C. We also assess the tensile property differences between P1 and P2, and the effect of specimen size. The L-orientation strength and ductility were excellent; for example, the room temperature (RT) yield stress, σ_y ≈ 1042 ± 102 MPa, and the total elongation, ε_t ≈ 12.9 ± 1.5%. In contrast, the S-orientation RT σ_y ≈ 708 ± 57 MPa, and ε_t ≤ 0.2%. These differences were due to cleavage on the brittle (001) planes. Cleavage leads to beneficial delamination toughening, but is deleterious to deformation processing and through-wall heat transfer. Therefore, it is important to quantitatively characterize the pronounced NFA-1 strength anisotropy due to severe crystallographic texturing and cleavage fracture. Full article

The evolution of microstructure, phase composition and physico-mechanical properties of the biocompatible Ti-39Nb-7Zr alloy (wt.%) after severe plastic deformation by rotary forging (RF) was studied using various methods including light optical microscopy, scanning and transmission electron microscopies, X-ray diffraction, microindentation, tensile testing and investigation of thermophysical properties during continuous heating. The hot-rolled Ti-39Nb-7Zr with initial single β-phase structure is subjected to multi-pass RF at 450 °C with an accumulated degree of true deformation of 1.2, resulting in the formation of a fibrous β-grain structure with imperfect 500 nm subgrains characterized by an increased dislocation density. Additionally, nano-sized α-precipitates formed in the body and along the β-grain boundaries. These structural changes resulted in an increase in microhardness from 215 HV to 280 HV and contact modulus of elasticity from 70 GPa to 76 GPa. The combination of strength and ductility of Ti-39Nb-7Zr after RF approaches that of the widely used Ti-6Al-4V ELI alloy in medicine, however, Ti-39Nb-7Zr does not contain elements with limited biocompatibility and has a modulus of elasticity 1.5 times lower than Ti-6Al-4V ELI. The temperature dependences of physical properties (elastic modulus, heat capacity, thermal diffusivity) of the Ti-39Nb-7Zr alloy after RF are considered and sufficient thermal stability of the alloy up to 450 °C is demonstrated. Full article

A series of plane strain compression tests were carried out in order to simulate the thermomechanical controlled processing of a 0.09wt% Nb low carbon steel, in a scheme of multipass finish rolling at 950 °C with interpass times of 10 s. It was observed that after the first two finishing passes a remarkable grain refinement can be achieved, since the recrystallisation was fully suppressed and abundant ultrafine ferrite was transformed dynamically during the deformation. The addition of a third finishing pass however, led to partial recrystallisation. A deep characterisation of the dynamic ferrite was carried out by diverse methods conducting to relevant findings that contribute to a better elucidation of the dynamic transformation. The results obtained indicated that the dynamic formation of a colony of Widmanstätten ferrite plates during deformation, initiates with the formation of a pair of self-accommodating plates followed by face-to-face sympathetic nucleation of new plates at one of the faces of the pairs of plates already formed. Furthermore, the crystal orientation within the dynamic ferrite phase was analysed with EBSD, it was observed that during the coalescence of plates, prior to the full polygonisation of grains, the ferrite adopts a transitory morphology which possesses particular crystallographic characteristics. Full article

The study refers to the application of numerical modeling for the improvement of the currently realized precision forging technology performed on a hammer to produce connecting rod forgings in a triple system through the development of an additional rolling pass to be used before the roughing operation as well as preparation of the charge to be held by the robot’s grippers in order to implement future process robotization. The studies included an analysis of the present forging technology together with the dimension–shape requirements for the forgings, which constituted the basis for the construction and development of a thermo-mechanical numerical model as well as the design of the tool construction with the consideration of the additional rolling pass with the use of the calculation package Forge 3.0 NxT. The following stage of research was the realization of multi-variant numerical simulations of the newly developed forging process with the consideration of robotization, as a result of which the following were obtained: proper filling of the tool impressions (including the roller’s impression) by the deformed material, the temperature distributions for the forging and the tools as well as plastic deformations (considering the thermally activated phenomena), changes in the grain size as well as the forging force and energy courses. The obtained results were verified under industrial conditions and correlated with respect to the forgings obtained in the technology applied so far. The achieved results of technological tests confirmed that the changes introduced into the tool construction and the preform geometry reduced the diameter, and thus also the volume, of the charge as well as provided a possibility of implementing robotization and automatization of the forging process in the future. The obtained results showed that the introduction of an additional rolling blank resulted in a reduction in forging forces and energy by 30% while reducing the hammer blow by one. Attempts to implement robotization into the process were successful and did not adversely affect the geometry or quality of forgings, increasing production efficiency. Full article