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Improvements in machinability by alloying of the workpiece often adversely impact the end user properties of a material. For example, the common use of non-metallic inclusions can lead to improved tool life during turning or milling, but often adversely affects weldability, corrosion, and wear resistance. A cutting tool material meets kilometers of workpiece material during a machining operation. Hence elements in small quantities in the workpiece may insignificantly affect the end user properties but may have large effects on tool wear. One such effect is the formation of refractory and wear resistant reaction products between the workpiece and tool. Such reaction products forming on tool surfaces may lead to improved machinability. This paper proposes the use of small amounts of alloying to induce such a Tool Protection Layer. Additionally, the paper develops a computational framework for designed alloying which balances formation of Tool Protection Layers, its in-process retention, and the functional properties of the alloy. The method has been validated for a case of manganese steel. The calculations were validated first by a wide range of diffusion experiments. Then by industrial turning of cast alloys, by comparing one reference and two newly designed alloys based on the alloying concept. The alloy with 0.003 mol fractions of Al resulted in more than 3 times increase in tool life, due to in-operando formation of Al 2 O 3 Tool Protection Layer. The designed manganese steel maintained its functional properties with respect to abrasive wear resistance and retained its ability to work harden. [Display omitted] • A thermodynamic modeling method for machinability improvement. • Microalloying leads to improved machinability, functional properties maintained. • The formation of alumina tool protection layers increases tool performance. [ABSTRACT FROM AUTHOR]

To meet the higher device vibration reduction requirements, novel porous Cu 71 Al 18 Mn 11 shape memory alloys (SMAs) with controllable porosity were prepared using Cu, Al, and Mn elemental powders as raw materials. To further enhance the strength and damping performance of SMAs, a low-temperature reactive synthesis combined with spark plasma sintering (LTRS+SPS) process was used. In this paper, the effects of LTRS+SPS process on pore structure and texture, compressive strength, and damping properties of porous Cu 71 Al 18 Mn 11 alloy were studied. The outcomes indicated that LTRS+SPS process can effectively improve both compressive strength and damping properties. The associated closed pore structure caused by this process and the second phase γ 2 phase formed by element diffusion result in a variety in compressive strength from 324.6 MPa to 617.9 MPa, which were 3.9 times that of the comparable porosity alloy with alloy powder as raw material by vacuum sintering. Meanwhile, the damping value changed from 0.27 to 0.10, which was 4.5 times that of the homogeneous dense alloy. The increase in damping property is caused by the increase of motionable interfaces in the matrix for the introduction of pores, which leads to the increase of energy dissipation. Besides. the interaction between the second phase γ 2 and dislocation contributes to the improvement of damping, as well as the compressive strength. These findings in this paper provide new insights and references for the structural design and microstructure design of high-performance Cu-based alloys. [Display omitted] • Segmented sintering process was developed to achieve synergistic improvement on ultimate strength and damping properties of novel porous Cu-Al-Mn alloys. • Influence mechanism of pore structure and microstructure induced by segmented sintering process on strength and damping was revealed. • The high strength is due to the unique closed pore structure and the interaction between the second phase and the large angle grain boundaries. • The high damping properties obtained by increase of phase interfaces and interaction of various defects and phases. [ABSTRACT FROM AUTHOR]

This study utilizes active control of welding clamping force through periodic additional force (PAF) to assist in fabricating ultrasonic spot-welded copper-aluminum joints. The microstructural characteristics and mechanical properties of the copper-aluminum ultrasonic spot welded with periodic additional force joints were systematically investigated. Periodic additional force was applied to the welding interface, facilitating plastic deformation and flow. This can transform the relatively smooth weld interface into a wave- and swirl-like surface with a maximum peak height of 12 μm. Simultaneously, the mutual diffusion length of copper and aluminum at the weld interface increased from 2 μm to 8 μm. Additionally, the weld interface of ultrasonic spot welded with periodic additional force exhibited typical {111}〈112〉 or {111}〈110〉 shear textures, confirming a strong interface bonding. The effect of the periodic additional force on the thermomechanically affected zone (TMAZ) was also examined. It was discovered that lower periodic additional forces enhanced dislocation density and decreased anisotropy, leading to improved mechanical characteristics. The utilization of periodic additional force in assisting ultrasonic spot welded can significantly enhance the lap shear failure force by up to 59.98%. The paper innovatively proposes a control method of reverse periodic additional force, offering a strategy for the preparation of reliable aluminum-copper joints. [Display omitted] • This paper proposed a novel bottom-up active force control ultrasonic spot welded method based on additional forces. • The active additional force was set periodic, providing control over the joint with minimal alteration of input energy. • The introduction of periodic additional force increased the plastic deformation at the Cu/Al interface. • {110}〈112〉 Brass and {110}〈111〉 P(B ND) textures were generated at low periodic additional forces. [ABSTRACT FROM AUTHOR]

Laser electrolytic hybrid machining methods still present a more significant challenge regarding material removal rates due to the high energy loss of the laser in the electrolyte column and the low conductivity electrolyte column between the electrodes. In this paper, a laser-induced plasma electrolyte jet machining method is proposed for the first time to overcome the above problems. Specifically, the short propagation distance of the laser beam in the electrolyte column in the laser-induced plasma electrolyte jet machining method reduces the laser energy loss. In addition, a plasma is formed between the cathode and anode to reduce the ohmic voltage drop between the electrodes. Compared to conventional laser-electrolytic hybrid machining, the introduction of plasma into electrolyte jet machining leads to a significant difference in machining performance. The evolution of laser-induced plasma channels and the enhancement of plasma shocks under the jet liquid film are demonstrated. The material removal mechanism and laser-induced plasma electrolyte jet machining characteristics are comprehensively investigated. The grooves were finally machined using the proposed laser-induced plasma electrolyte jet machining method, and a material removal rate of 2.23 mm3/min was obtained. This study significantly increased the material removal rates of the laser electrolytic hybrid machining technique. [Display omitted] • This paper presents a novel laser-induced electrolyte jet machining (LIPEJM) method. • The material removal mechanism of LIPEJM is investigated. • An equivalent circuit model is proposed to reveal the effect of plasma on EJM. [ABSTRACT FROM AUTHOR]

This paper presents force servo single point diamond cutting of freeform surfaces with nano-precision on a micro-precision machine. For nanometric machining accuracy, traditional diamond cutting based on position servo, requires accurate machine axial motions by ultra-precision machine with high cost, or utilizes a fast tool servo to compensate for machine slide vibration and motion error of common machines that is a complicated procedure. In this paper, nanometric machining accuracy was achieved on a micro-precision machine by force servo diamond cutting, in which the tool can be driven to trace the workpiece surface to compensate for the machine slide vibration, machine motion errors and workpiece incline errors accurately and automatically. For highly sensitive and stable force controlling, force servo nanocutting mechanism (FSNM) based on flexible structures was designed with force sensing resolution down to submillinewton level, and a damping controller was developed to suppress the resonant vibration of the FSNM. For extending application of force servo cutting from fabrication of only discontinuous microstructures to continuous freeform surfaces, referring force maps were developed by considering the real material removal volume of each cutting point. Force servo cutting was then validated by fabricating freeform surfaces with surface form errors of less than 10 nm on silicon spherical surfaces based on the micro-precision machine. The works discussed in this paper provide an effective technique for the fabrication of complex and continuous microstructured and freeform surfaces with nano-precision by common machines only with micron even tens of microns precision. [Display omitted] • Force servo nanocutting mechanism was designed with force sensing resolution of submillinewton level. • Machine slide vibration and motion errors were automatically compensated in force servo cutting process. • Fabrication of nano-precision complex freeform surfaces was achieved on a machine with only micro-precision. [ABSTRACT FROM AUTHOR]

Electron beam powder bed fusion (EB-PBF) is a key metal additive manufacturing (AM) technology known for its high energy absorption and low heat stress. However, the high surface roughness of EB-PBF parts has limited its broader application. To address this issue, this paper proposes a dashed-scan contouring strategy to obtain lower surface roughness in EB-PBF. This strategy involves melting the contour in the form of segmented staggered scans and employing high-frequency jumping of the electron beam (EB) to melt multiple positions synchronously. A comprehensive analysis, combining experimental investigations and multi-physical simulations, elucidates the intrinsic connection between control processes and melt pool stability. Results show that by controlling the length-to-width ratio of the melt pool, regulating overlap distances between melt pools, and fine-tuning cooling times, balling phenomena and Plateau-Rayleigh instabilities can be suppressed. Additionally, these measures effectively mitigate irregularities in track formation when compared to the traditional process. Experimental validation demonstrates the efficacy of the approach, achieving reduced surface roughness (Ra) of thin-walled Ti-6Al-4 V parts from over 25 μm to below 12.6 μm, while enhancing dimensional accuracy and reducing melt anomalies at corners. The proposed dashed-scan contouring strategy opens new avenues for AM of highly reliable and intricate structures, such as lattice sandwich structures, thin walls, and internal flow passages. [Display omitted] • A new contouring strategy enables lateral surface roughness of Ra10 μm on parts. • Dashed-scan strategy overcomes irregular fluctuations caused by long scanning. • Defects were greatly eliminated by remelting and solidification between dashes. • Dashed-scan strategy reduces heat accumulation and improves dimensional accuracy. [ABSTRACT FROM AUTHOR]

The main challenge in electrochemical machining (ECM) of titanium alloys is not processing efficiency, but the difficulty in achieving high-quality machined surfaces. Titanium alloys are particularly susceptible to pitting, and there are obvious dissolution differences among different phases in ECM, which greatly affect the machining accuracy and surface quality. This paper aims to eliminate the dissolution disparity between different phases and enhance the surface quality of titanium alloys through the synergistic effect of a similar normal distribution current waveform and passivation film. A new experimental phenomenon was found that the presence of a passivation film resulted in a remarkably smooth pit during the initial pitting stage, with no discernible dissolution differences among different phases. A superior surface quality can be achieved when the surface of the titanium alloy sample is composed of these smooth pits. From this perspective, the effect of frequency and passivation film on pitting process and surface quality of titanium alloys in pulse ECM was systematically investigated. In particular, at the frequency of 100 Hz, high surface quality was achieved on Ti-6.5Al-2Zr-1Mo-1 V (TA15) alloy with a surface roughness of Ra 0.69 μm while the dissolution disparity between different phases was significantly eliminated. The rate of material thickness removal was 0.09 mm/min. Successful applications on other titanium alloys, such as Ti-6Al-4 V (TC4), Ti-25 V-15Cr-0.3Si (Ti40), and Ti-5.8Al-4Sn-3.58Zr-0.7Mo-0.5 Nb-1.1Ta-0.4Si (Ti60), further validated that high-quality surfaces can be obtained with surface roughness values of Ra 0.31 μm, Ra 0.44 μm and Ra 0.92 μm respectively. [Display omitted] • The synergistic effect of current waveform and passivation film improve the surface quality of titanium alloys in ECM. • The current waveform and frequency affect the corrosion morphology and repassivation process. • High quality surfaces of titanium alloys are achieved under optimized frequencies. [ABSTRACT FROM AUTHOR]

Flatness plays a crucial role in determining the quality of products in strip cold rolling. Data driven methods have shown promise in flatness prediction by effectively capturing the nonlinearities and strong coupling present in cold rolling processing, surpassing the capability of conventional methods. However, existing data driven models remain restricted by a lack of rolling theory guidance, a black-box nature of predictive processes, and gradient conflict of multi-channel flatness. To overcome these limitations, this paper proposes an interpretable mechanism guided multi-channel distributed meta learning framework for flatness prediction. Initially, significant physic-based parameters, such as theoretical rolling force deviation and tension deviation, and controller parameters are calculated to guide data driven modeling. Subsequently, a distributed meta learning framework is modeled for multi-channel flatness to eliminate gradient conflict. Furthermore, eXplainable Artificial Intelligence (XAI) technique is implemented to ensure the transparent predictive processes of multi-channel flatness. The analysis results present that theoretical parameters and controller parameters effectively improve the performance of flatness prediction. In addition, the comparative results demonstrate that the proposed framework outperforms the existing flatness prediction methods and other state-of-the-art machine learning methods by 4.24%. Importantly, the XAI-based explanation of the proposed framework effectively enhances the credibility of data driven flatness prediction. [Display omitted] • An interpretable distributed meta learning framework is proposed for flatness prediction. • The interpretability and performance of data driven model is enhanced by integrating rolling mechanism. • Distributed learning framework is effective in eliminating gradient conflict of multi-channel flatness in training procedure. • The predictive process of data-driven model in cold rolling is first explained by eXplainable Artificial Intelligence (XAI). [ABSTRACT FROM AUTHOR]

Copper (Cu) particle sintering is widely regarded as one of the most ideal interconnect technologies for wide band gap semiconductors owing to its potential for low-temperature curing while withstanding a higher working temperature. Nevertheless, the strict requirements for sintering conditions and high costs limit the widespread application of Cu sintering technology. In this paper, a simple vehicle was introduced into Cu paste formulation to achieve an effective sinter bonding even using commercially available sub-micron or even micrometer Cu particles (C-Cu particles) with the in-situ generation of composite Cu particles. This innovative vehicle comprises Cu salt, a combination of capping agents and reducing agents. The addition of the hybrid capping agent binds Cu atoms to the surface of the C-Cu particles and allows the generated Cu particles (G-Cu particles) produced from the vehicle to grow on their surface, resulting in the in-situ generation of composite Cu particles. Based on the in-situ generated composite Cu particles, sintering experiments were conducted at designated temperatures (200 °C, 225 °C, 250 °C) for various durations (3 min, 5 min, 10 min) in a N 2 atmosphere under different pressures (10 MPa, 15 MPa, 20 MPa). A reliable Cu sintered joint with a high shear strength of 41.3 MPa can be achieved at a low temperature (200 °C) using 500 nm C-Cu particles. Moreover, the joints sintered with large size (>3 μm) particles at 250 °C could also reach 43.3 MPa. The in-situ generated composite Cu particles accomplish the transformation of low-energy interfaces of C-Cu/C-Cu to high-energy interfaces of G-Cu/G-Cu, which in turn facilitates low-temperature sintered connection of C-Cu particles and reliable sintered joints formed of large size C-Cu particles. These findings improve the feasibility of Cu sinter bonding in practical applications. [Display omitted] • Composite micron-nano Cu particles were prepared by an in-situ synthesis strategy. • The high surface energy of synthesized nano-Cu contributes to the sintering. • 41.3 MPa were obtained for joints sintered at 200 °C using submicron Cu particles. • 43.3 MPa were obtained for joints sintered at 250 °C using 3.5 μm Cu particles. [ABSTRACT FROM AUTHOR]

Welding solidification cracks are considered as critical defects in narrow gap laser welding, and it is of utmost importance to develop reliable measures to suppress them. The fundamental approach to curbing solidification cracks lies in controlling the solidification behavior of the weld. A novel narrow gap laser welding technology is proposed to address this issue by controlling the solidification of the weld with double laser beam in this paper. The influence of process parameters on the suppression of welding solidification cracks is explored. Additionally, the mechanism behind the dual-beam laser's ability to suppress solidification cracks are comprehensively examined through weld formation, molten pool solidification behavior and microstructure evolution. The findings demonstrate that the energy matching of the dual-beam and the spacing between the beams are crucial factors that impact the effectiveness of welding crack suppression. When the beam spacing is greater than 6 mm, this method begins to work on suppressing welding solidification cracks. Three distinct effective modes of crack suppression are identified, namely molten pool expansion, gradient solidification, and weld remelting. Among these, the gradient solidification mode proves to be the most reliable method for suppressing welding solidification cracks, as it facilitates a transformation in the molten pool's solidification mode from "enclosed" solidification to "sequential" solidification. Compared to conventional single-beam Narrow Gap Laser Welding, this approach not only effectively suppresses welding solidification cracks but also improves welding efficiency by nearly doubling the filling speed. [Display omitted] • Inventing a narrow gap laser welding method based on dual-beam gradient control of weld solidification (NGDBLW). • Developing an in-situ observation method for molten pool solidification in weld cross-section. • NGDBLW has three effective modes to inhibit welding solidification cracks. • NGDBLW changes the growth mode of columnar crystals and enhances the tendency of growth along the y-axis. • NGDBLW significantly improves the efficiency of deposited metal. [ABSTRACT FROM AUTHOR]

Drilling temperature has always been a hot issue in the drilling process of CFRP/Ti stacks. Accurately predicting drilling temperature is necessary for reliable optimization of drilling parameters. However, since the drilling process involves two materials and may affect each other, the prediction of temperature during drilling is still a challenge. In this paper, a novel drilling temperature model is established to predict the temperature distribution in CFRP workpiece during the drilling process of CFRP/Ti stacks, considering the minor cutting edge and titanium alloy chip ejection process. Specifically, according to different drilling phases, in addition to considering the heat source of the cutting zone of different materials, the heat source generated by the interaction of minor cutting edge and rebound hole wall of CFRP and the heat source formed by the thermal-mechanical effect of Ti chip ejection process are also considered. The results show that the prediction errors of peak temperature in CFRP entrance and stack interface region during drilling are within 15.8 % and 10.9 %, respectively, which indicates the validity of the model. Finally, the green cooling strategy (High and low frequency compound vibration-assisted drilling) is adopted to significantly reduce the peak temperature in the drilling process by controlling the chip morphology and ejection process, which further proves that the thermo-mechanical action of Ti chips on CFRP cannot be ignored, and provides reference for temperature modeling and low-damage processing of CFRP/metal stacks. [Display omitted] • A novel drilling temperature model is established for CFRP/Ti stacks. • The interaction between minor cutting edge and CFRP was considered. • The thermal-mechanical effect of Ti chips ejection process on CFRP was considered. • The presented green cooling strategy can effectively reduce the drilling temperature. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites (CMCs) are highly promising for the hot components of the high thrust-to-weight ratio aeroengines because of their excellent high-temperature resistance and lightweight. Submillimeter cooling holes are necessary cooling structures for the extremely high working temperature of a CMCs hot component. However, CMCs are hard, brittle, and poorly conductive. Current machining is trapped in severe tool wear, poor hole quality, and low efficiency in machining such small size holes. This paper proposes high-frequency ultrasonic vibration-assisted drilling (UAD) to machine submillimeter holes of CMCs. It reveals that increasing vibration frequency during machining can enlarge the cutting edge's effective rake angle and reduce drilling forces. Correspondingly, the tool life and hole quality are improved. The machinability of high-frequency UAD is rationalized by both theoretical analysis and experiments. Results show that compared with low-frequency UAD and Conventional drilling (CD), the drilling force in high-frequency UAD is reduced by 47 % and 81 %, the tool life is more than three times, and the hole quality is improved by 12 % and 35 %, respectively. Therefore, the study paved the way for the machining of submillimeter cooling holes in CMCs, which is important to the industrial application of CMCs. [Display omitted] • The change of effective rake angle in drilling is revealed • Effects of ultrasonic vibration frequency on effective rake angle are clarified. • A drilling force model of submillimeter holes is built. • Performance of UAD in drilling small holes in CMC is demonstrated. • Effects of ultrasonic vibration frequency on drilling performance are revealed. [ABSTRACT FROM AUTHOR]

Metal-bond diamond tools find extensive use in the grinding of hard and brittle materials. The mechanical properties and wear resistance of the metal bond are crucial for the grinding performance and life of diamond tools. However, Fe bonds exhibit insufficient hardness, strength, and wear resistance, and existing reinforcement methods are difficult to simultaneously improve the self-sharpness and wear resistance of diamond tools, leading to a trade-off between grinding performance and life. In this paper, a novel AlCoCrFeNi HEA particles reinforced Fe (HEA/Fe) alloy was proposed as the bond for diamond tool to address the aforementioned issue. The work considers materials science fundamentals related to the element diffusion mechanism and particle reinforcement mechanism in the design of the HEA/Fe bond. Through the mutual element diffusion between the HEA and Fe matrix, expanded HEA regions are formed, which not only enhance the strength and overall wear resistance of the HEA/Fe bond but also generate a composite structure with varying hardness. The distinct mechanical properties of composite structure form wear-resistant and non-wear-resistant areas within the diamond tool, effectively balancing the challenging trade-off between wear resistance and self-sharpness. This allows HEA/Fe bond diamond tools to achieve both prolonged service life and high grinding performance. The results reveal that the HEA/Fe bond diamond tool exhibits a lower grinding force, a superior surface finish, and a nearly equivalent grinding ratio compared to the commercial Fe-based alloy bond diamond tool in grinding of sapphire. [Display omitted] • The element diffusion and phase formation mechanisms of HEA/Fe alloys were investigated. • The influence of HEA content on the mechanical property of HEA/Fe alloys was investigated. • The HEA/Fe bond diamond tool exhibited a lower grinding force, a superior surface finish, and a nearly equivalent grinding ratio compared to the commercial Fe-based alloy bond diamond tool in grinding of sapphire. [ABSTRACT FROM AUTHOR]

This paper presents an improved method for achieving controllable preparation of the composition and size of the monotectic alloy core-shell structure microspheres. This advancement is expected to enhance the commercial application of monotectic alloy core-shell structure microspheres. By installing a heating device at the top of the drop tube in the pulsated orifice ejection method setup, we achieved in-situ heat treatment of falling droplets, resulting in the successful preparation of Al 45 (Sn 42 Bi 58) 55 core-shell structure microspheres. Furthermore, we investigated the formation mechanism of the Al@Sn-Bi core-shell structure. Nine sets of Al-Sn-Bi microspheres with varying in-situ heat treatment temperatures were prepared. Analysis via X-ray diffraction and transmission electron microscopy revealed that the microspheres consisted of Al-rich, Sn-rich, and Bi-rich phases, without any intermetallic compounds. Scanning electron microscopy results indicated that as the in-situ heat treatment temperature increased, the structure of the Al-Sn-Bi microspheres transitioned from irregular to regular core-shell configurations. This suggests that higher heat treatment temperatures prolong liquid phase separation time, leading to increased repetition of Marangoni motion within the droplet, Ostwald ripening of the minor phase droplets, and Soret effect of the matrix phase. However, at temperatures exceeding 700 °C, the solidification rate of alloy droplets decreased, causing the Al-rich phase core to deviate from the center and form a crescent structure due to Stokes motion. [Display omitted] • A method is provided for the controllable production of monotectic alloy microspheres which have a core-shell structure. • Core-shell structure Al@Sn-Bi microspheres were prepared by the pulsated orifice ejection plus in-situ heat treatment. • Performing the microstructure evolution process of the core-shell structure Al@Sn-Bi microsphere. • Using TEM to observe the interface between Al and Sn, which composed of amorphous and nanocrystalline. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) has been attracting increasing interests for customised manufacture of thermoplastics, but the application in high-performance and hard-to-form thermoplastics is still a challenge. This paper develops a new heat-assisted friction stir incremental sheet forming (HAFS-ISF) process to form polyether ether ketone (PEEK) and polymethyl methacrylate (PMMA, acrylic). Flexible heating tapes and tool rotational friction heat the thermoplastic sheet on both bottom and top surfaces, which maintain the sheet material at high temperature and reduce the through-thickness temperature gradient. Results are given for the effect of key parameters on forming temperature, force, accuracy and thickness distribution. Spindle speed has the most significant effect on all the studied aspects, followed by the pre-heating temperature, while feed rate and step size have less effect. With lower spindle speed of 100 rpm, the through-thickness temperature gradient is improved. Compared with PEEK parts, more uniform forming temperature and smaller forming force can be observed for PMMA parts. But the material brittleness causes worse formability, and the severer twist and stretching effect affect the forming accuracy of PMMA parts. Forming accuracy, fracture and twist are discussed by developing analytical models. The model for forming accuracy considers the initial bending effect and springback. The fracture is discussed by modelling the stress triaxiality and equivalent strain distribution under contact. While the model for twist considers effect of the applied torque on shear strain energy and continuous accumulation of twist along the tool path. By comparing analytical models and testing observations, the effectiveness of the models is confirmed to understand the underlaying mechanisms and to address a few challenges. [Display omitted] • A new heat-assisted friction stir incremental sheet forming for thermoplastics. • Improved temperature uniformity by friction heat and flexible heating tapes. • Significant effect of spindle speed on the forming temperature, force and accuracy. • Analytical understanding and prediction of forming accuracy, fracture and twist. [ABSTRACT FROM AUTHOR]

In this paper, a detailed analysis of the rheological behaviour and segregation mechanisms within twin-roll casting (TRC) processes for 2060 Al-Cu-Li alloys is presented. Building on previous research where fixed roll gaps limited the adjustability of cast-rolling speed, this study expands the scope by adjusting roll gaps from 3 mm (TRC-3), to 6 mm (TRC-6), to 10 mm (TRC-10). This approach yields three typical process ranges with gradually increasing roll gaps and a wide range of decreasing cast-rolling speeds, allowing us to investigate the inherent nature of segregation and identify conditions conducive to segregation-free processing. A significant contribution of this study is the development of a novel multi-scale simulation model that integrates the thermal, flow, mechanical, solute and phase fields. This advanced simulation framework enhances our understanding of TRC processes and aids in exploring the interplay between the various factors affecting alloy fabrication. This study identified two primary stress-induced inverse segregation mechanisms: the reflux of the semi-solid phase due to rolling stress and expansion of the solidifying shell under shearing stress. Using these insights, a low-stress, low-segregation process, termed TRC-6, was established, which showed notable improvements in the mechanical properties. Specifically, TRC-6 demonstrated a remarkable strength of 562.9 MPa post-T8-treatment, surpassing those of TRC-3 and TRC-10 by 9.0 % and 5.2 %, respectively. These findings offer valuable insights for future TRC process designs with the aim of eliminating segregation defects and enhancing the sustainable and efficient production of Al-Cu-Li alloys. [Display omitted] • First-ever integrate model of heat-flow-mechanical-solute, providing enhanced insights into TRC processes. • Unveiled two unique stress-induced segregation mechanisms, offering clearer views on TRC challenges. • Introduced a revamped TRC process design strategy, indicating a potential pathway for advancing TRC production. [ABSTRACT FROM AUTHOR]

In this paper, a novel flat-top laser-aided cold metal transfer additive manufacturing (F-LCAM) method is proposed for titanium alloys to restrict internal defects and anisotropy of mechanical properties in large-scale additive-manufactured titanium structures. The proposed method uses a flat-top laser to stabilise the drifting cathode spot and suppress the irregular shape of the weld deposit by promoting thermionic emission on the molten pool surface. Compared to the cold metal transfer additive manufacturing (CMT-AM) process, the auxiliary flat-top laser promotes the wettability of the molten pool and increases the contact angle of deposition from 95° to 142° in an F-LCAM sample. The non-destructive X-ray testing (NDT) results of multi-bead multilayer deposition showed that the defects caused by the pool weld bead morphology were effectively suppressed. Attributed to fluid flow in the melt pool enhanced by the flat-top laser, the dendritic arms were broken, columnar β grains in the F-LCAM sample were finer than in CMT-AM sample, and the aspect ratios of prior-β grains decreased from approximately 6 to 1. The F-LCAM sample exhibited a higher elongation and lower anisotropy than the CMT-AM sample. Defects were observed on the fracture surfaces of the CMT-AM vertical samples, which reduced the elongation of the CMT-AM samples to lower than that of the F-LCAM sample. The ultimate tensile strength, yield strength, and elongation of the multi-bead multilayer deposition met the standards of as-forged Ti6321 titanium alloy, indicating that the Ti6321 titanium alloy structure fabricated by the F-LCAM process has acceptable tensile properties for engineering applications. [Display omitted] • A novel flat-top laser was introduced in cold metal transfer additive manufacturing (CMT-AM) process for titanium alloys. • The flat-top laser could stabilise the drifting arc cathode spot and suppress the irregular shape of the weld deposit. • Due to the flat-top laser, Marangoni flow was significantly enhanced, and the wettability of the molten pool was promoted. • The internal defects were effectively eliminated and coarse columnar grains were refined in the F-LCAM samples. • The tensile properties of F-LCAM samples met the standards of as-forged Ti6321 titanium alloy for engineering applications. [ABSTRACT FROM AUTHOR]

Optical aspherical lenses are widely used in the aerospace, electronics, and optical communication industries. Grinding is the primary processing method used to ensure their precision. It is difficult for traditional evaluation indexes to fully reflect the optical properties of optical surfaces after grinding. This paper presents a novel method for characterizing surface quality of optical aspherical surface oriented to the application of optical properties. The proposed evaluation indicators include the profile error, surface roughness, slope error, and projection-area scale-deviation value, which can be used to comprehensively evaluate the surface quality. Subsequently, a novel grinding compensation method for the optical aspherical surface is proposed, and its compensation precision is evaluated using the abovementioned evaluation indicators. The results show that the maximum surface-shape error decreases to less than 150 nm; additionally, the central cusp point is restrained. The precision and efficiency of error compensation for the optical aspherical surface are significantly better than those of the conventional method. The proposed evaluation indicators can be applied to reflect the features of optical aspheric surface directly. The high efficiency and precision compensation of optical aspherical surface can be achieved with the proposed evaluation method and modified error compensation algorithm. [Display omitted] • The reason of the central cusp point in the grinding process of the optical aspheric surface is revealed. • A method is proposed for characterizing the surface quality of the optical aspherical surface oriented to the application of optical properties. • The proposed evaluation indicators include the profile error, surface roughness, slope error, and projection-area scale-deviation value. • A grinding compensation method for the optical aspheric surface is proposed. [ABSTRACT FROM AUTHOR]

Due to the limitations of tool size, field assisted polishing methods are often employed for polishing the internal surfaces of slender holes with large aspect ratios. However, in existing polishing methods, fields are often applied in isolation, which limits the ability to obtain high surface quality. Furthermore, it is rare for polishing method studies to fully leverage the advantages of multiple fields to create a synergistic effect. Therefore, developing a polishing method that harnesses the synergistic interaction of multiple fields, and revealing the polishing mechanism, is crucial for achieving high-quality internal surfaces of quartz slender holes. To address this problem, a novel magnetic enhanced chemical mechanical polishing method was proposed in this paper and a systematic process study was carried out to analyze the synergistic effects of magnetic and chemical fields. To evaluate the effects of process parameters on material removal and forecast MRR, the material removal process was modeled and validated based on the consistency between experimental and theoretical values. Suitable process parameters are determined through experiments and analysis on magnetic field distribution and process parameters. By conducting EDS mapping and XPS analyses on the reaction product, the enhancement mechanism of magnetic field on material removal in the chemical mechanical polishing process was identified. Under the assistance of a magnetic field, the magnetic abrasive particles encircle the Ce O 2 particles to fully contact the workpiece surface. The contact force between the polishing tool and the workpiece surface increase. Both of the effects promote the chemical reaction and enable the reaction layer on the surface to be removed in time to obtain higher surface quality. As a result, this method achieves high-efficiency and high-quality polishing, significantly reducing the surface roughness Sa of slender holes from 0.3 μm to 77 nm, with a material removal rate of 141 μm/h. [Display omitted] • A new magnetic enhanced chemical mechanical polishing method for inner surface was proposed. • The synergistic effect of magnetic and chemical fields was identified. • The inner surface roughness of quartz slender hole was reduced from 300 nm to 77 nm, with a material removal rate of 141 μm/h. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of laser-beam intensity distribution (LBID) on the performance of the annular laser-beam directed energy deposition (DED) process with axial powder delivery. Three different LBIDs: Gaussian-like (G-LBID), top-hat-like (TH-LBID) and ring (R-LBID) at two LBID diameters were used. The process performance was characterised qualitatively in terms of the melt-pool shape and the process stability and quantitatively by powder-catchment efficiency, selected geometrical and metallurgical properties of the clad. The observed influence of LBID on process performance, as determined by the relationship between LBID and powder stream density distribution (PSDD), decreased with increasing mean surface-energy density and was more significant at larger LBID diameter. The highest powder-catchment efficiencies (90% and 87%) were achieved with the G-LBID and TH-LBID, whose high-intensity centre is aligned with the peak of the Gaussian-like PSDD. A lower powder-catchment efficiency of 77% was achieved with the R-LBID, whose high-intensity region is located at the edge of the melt pool with minimum powder density. However, this also results in the highest and most uniform dilution, the highest metallurgical bond ratio and the lowest lack of fusion porosity at the clad-substrate interface. In addition, the process was stable at the lower values of mean surface-energy density with R-LBID, while balling instability was observed with G-LBID and TH-LBID. It can be concluded that the use of R-LBID at lower values of mean surface-energy density improves the performance of the DED process with axial powder feed in terms of process stability and metallurgical properties of the clad. [Display omitted] • Influence of laser-beam intensity distribution in metal-powder DED was investigated. • Gaussian-like, top hat, and ring laser-beam intensity distributions were considered. • Effect of intensity distribution was more pronounced at a low surface-energy density. • Gaussian-like distribution provided the highest powder-catchment efficiency. • Ring-intensity distribution improved process stability and clad properties. [ABSTRACT FROM AUTHOR]

As an established tool-based micro-machining technique, micro electrical discharge machining (μ EDM) has received widespread attention from academia and industry for its capability of producing intricate micro-scale structures and features on various difficult-to-cut materials. However, assurance of the as-built surface quality and consistency has been a challenge due to the complex interactions among machining parameters and the unpredictable variability of material properties and the discharge process. In this paper, an efficient closed-loop control methodology based on an innovative application of on-machine metrology (OMM) and in-process roughness prediction (IPRP) is proposed for automatically ensuring the μ EDM surface quality. The work takes into consideration process fundamentals related to size and distribution of craters by means of single crater experiments and pulse discrimination studies in order to analyze the influence of actual energy parameter on the evolving surface roughness. The OMM enables accurate in situ surface characterization while the IPRP, which is built on an online Bayesian regression model, allows for the prediction of surface quality according to the monitored process features. This IPRP model presents an increased predictive performance and confidence when more OMM data become available. Depending on the acquired quality outputs, a two-step quality control strategy involving energy adaptation and discharge stability regulation is implemented. This novel control strategy has proven to achieve a consistent areal surface roughness with variations smaller than 0.1 μ m for a specific material and dielectric combination in μ EDM milling. [Display omitted] [ABSTRACT FROM AUTHOR]

During the "β-forging" of Ti-6Al-4V structural aircraft components that follows pre-heating above the β-transus, the skin zone of the blank actually cools down to below the β-transus whilst being deformed, as a result of heat losses towards the atmosphere or the dies. The core areas of the bulkiest sections of the blank, however, can be deformed above the β-transus during the whole processing time. This paper focuses on the development of an innovative rheological model to support the numerical modelling of the forging process, suitable for both the equilibrium conditions above the β-transus and the non-equilibrium conditions below. For that purpose, small-scale hot compression tests were performed with the thermomechanical simulator Gleeble 3500, after pre-heating in the β-field of Ti-6Al-4V at 1100 °C and rapid cooling to the compression temperature under the β-transus, which was varied between 750 °C and 950 °C. In some cases, a lag time -or stabilization time- at constant temperature was introduced between the cooling step and the deformation step. Effects of lag time and deformation temperature on microstructural evolutions and rheological properties of Ti-6Al-4V were investigated. Results show that the lack of stabilization time leads to a significant reduction of the flow stress at low strain. Such a behavior is associated with non-equilibrium thermodynamic conditions at the beginning of deformation and the progress of phase transformation during deformation. Based on that observation, an analytical formulation for the targeted rheological model is proposed. It includes a sub-model for the kinetics of phase transformation derived from the literature. [Display omitted] • constitutive model for off-equilibrium Ti-6Al-4 V deformed below the beta transus. • constitutive model for in-equilibrium Ti-6Al-4 V deformed above the beta transus. • includes a physics-based model for the kinetics of beta phase transformation. • the constitutive model is derived from non-isothermal hot compression tests. • suitable for the finite element modelling of beta forging with cool dies. [ABSTRACT FROM AUTHOR]

The asymmetric spinning in the middle-tube is a field that has not yet been thoroughly explored. An approach for this process using generic rollers is first proposed that introduces a novel method for forming irregularly shaped tubes suitable for industrial production. This paper delves into the precise forming of the novel spinning process under tool-less controlled axial and radial metal flow conditions, and methodically examines its forming mechanism. Asymmetric tubes with various shape factors are spun via derived roller-path equations, where two roller feeding methods are appropriately designed. The effects of three spinning schemes (Scheme A, Scheme B, and the one using the profile roller) with three forming depths on the shape accuracy and wall thickness distribution, are contrastively examined. The obtained results reveal that the shape accuracy based on the generic roller is enhanced by 14.6% compared to the case of utilizing the profile roller. Additionally, the spun wall thickness distribution based on the generic roller is generally more uniform than that of the using-profile-roller. In the generic-roller working conditions, Scheme A presents a more reasonable forming approach and exhibits a more uniform wall thickness distribution. This reveals the forming mechanism of the middle-tube asymmetric spinning using the generic roller. [Display omitted] • A novel approach to middle-tube asymmetric spinning via generic rollers is developed. • The asymmetric tubes with different shape parameters are spun by using the derived roller-path equations. • Three spinning schemes are adopted to investigate the forming accuracy and wall thickness distribution of the novel approach. • The shape accuracy and wall thickness uniformity is improved significantly by using the generic roller. • The forming mechanism of asymmetric spinning in the middle-tube via a generic roller is revealed. [ABSTRACT FROM AUTHOR]

Injection molding is a significant means of producing high-quality plastic parts. In the injection molding process, the microstructure of the product is directly determined by two factors: the melt front and flow velocity. However, it is challenging to penetrate the steel mold and monitor the cavity inside, where the melt process happens. In this paper, the ultrasonic phased array is firstly introduced to visualize and monitor the melt front and flow velocity during the injection molding process. The phased array is mounted on the back of the moving mold and collects the FMC datasets online during the forming process. A mapping relationship between radiation angle and target point is established to fast determine the time delays, and total focusing method (TFM) is used to obtain the image of the melt bottom, where the melt front is located. Furthermore, the experiments verify the effectiveness of the proposed method. Short shot experiments show that the location accuracy of melt front position of the proposed method is within 0.5 mm. In addition, the proposed method is capable of measuring the melt flow velocity, and the linear correlation coefficient between the measurement results and injection speed is 0.9994. In the packing experiments, the melt bottom history can intuitively reflect the melt flow process and the velocity-pressure (V-P) switchover point. Moreover, the proposed method can determine the optimal V-P conversion point online, and also has strong potential in simulation improvement, injection velocity control and injection molding process control. [Display omitted] • Ultrasonic phased array is firstly introduced to monitor injection molding process. • Efficient imaging method is developed to process the full-matrix datasets online. • Location accuracy of melt front position of the proposed method is within 0.5 mm • The melt flow velocity is measured with a correlation coefficient of 0.9994 to injection speed. • Melt bottom history reflects flow process and velocity-pressure switchover point. [ABSTRACT FROM AUTHOR]

Aiming at the problems of poor structural stability and low service life caused by the traditional forming method of round tube wrapped with iron wire and fixed by spot welding at both ends, this paper proposes to use multi-pass cold drawing and intermediate annealing process to realize the integral forming and precision forming of ribbed tube for nuclear fuel cladding, and microstructure evolution of the ribbed tube during the process is investigated. The stress and strain distribution during cold drawing showed that there were severe stress concentrations at the junction of the rib and tube on the outer surface, which restricted the radial and circumferential metal flow and thus inhibited rib filling. The excessive radial and circumferential metal flow on the inner surface leads to serious rib groove defects, which are more likely to appear during cold drawing compared to rib filling. The effects and mechanisms of process parameters and geometric parameters on the cold drawing forming accuracy of ribbed tube were investigated and applied to multi-pass cold drawing to obtain defect-free ribbed tube. In the multi-pass cold drawing and intermediate annealing process, stainless steel tube produces grain refinement, which is due to the martensite produced in the cold drawing process reverses to austenite in the annealing process resulting in grain split, and the multi-pass cold drawing increase the degree of grain refinement. [ABSTRACT FROM AUTHOR]

Based on the application of snake-spine-like structures, this paper proposes a roller-type multi-point flexible 3D profile bending process with snake-spine-like structures (Flexible stretch-bending with roller dies - driven by snake-like mechanism, FSBRD-S), and establishes a finite element model. Taking the L-shaped cross-section profile as the research object, different working modes and contact modes are defined to study their impact on crease defects during the vertical bending step, and the new structure is designed to improve the forming quality of the products' surface. The research results show that changing the contact mode leads to a change in the relative angle between the die and the billet. In the process of larger angle vertical bending, the FSBRD-S process can effectively reduce the crease defects generated by the traditional FSBRD process, especially in the area near the clamp. Furthermore, this article proposes the FSBRD-S shape-adjusting technology, which allows for adjustments to the FSBRD-S process based on actual needs, to obtain products with different surface qualities. [Display omitted] • Adaptive multi-point flexible-bending technology driven by snake-spine-like motion mechanism has been proposed. • The dispersed molds with multi-degrees of freedom changes the contact mode between the profile and the molds. • Finite element simulation combines with microscopic analysis and forming experiments to verify the accuracy of the shape adjustment mechanism. [ABSTRACT FROM AUTHOR]

Laser-based spatial manipulation for welding, surface modification, and additive manufacturing presents challenges centred around controlling the thermal field's impact on material response. Traditional wobbling methods often struggle with weld pool stability and fluence profile control. This paper presents a novel wobbling approach aimed at precisely managing the thermal field during laser processing. The proposed approach leverages controllable parametric equations—Lissajous equations—coupled with speed modulation to eliminate turning points. This strategy stabilizes the weld pool effectively but also enables the creation of diverse fluence profiles through laser beam oscillations. The study showcases the consequences of this method on the energy delivered by the laser on the material. Its successful implementation with Ti-6Al-4 V have demonstrated changed in the weld geometry and microstructural integrity. The approach yields consistent α' microstructures within prior-β grain, free from welding defects. Further development of galvanometric systems could allow the implementation of the described method to navigate between control methods and scan patterns to permit microstructural manipulation. On a broader range, the use of the scan strategies explored here presents significant advantage which allows new solutions to traditional approaches in energy beam processing for any kind of metallic alloys. [Display omitted] • Presentation of a new method to realize wobbling by implementing a control on the speed instead of the frequency. • Explored the effect of this new method on laser oscillation speed and fluence distribution. • This method has produced superior results to competitor approaches. • The effect of energy distribution and speed variations on the weld shapes and microstructure is explored. [ABSTRACT FROM AUTHOR]

In order to solve the irregular surface morphology introduced by laser shock processing, actively control the spot boundary effect and effectively reduce surface roughness. In this paper, a laser shock imprinting technology for actively designing surface morphology was proposed, and the effects of different laser shock processes on the surface morphology and roughness of TC4 titanium alloy were investigated by simulation and experiment. In the simulation, ABAQUS software was used to simulate the dynamic deformation behavior of the workpiece surface under single point impact, so as to reveal the mechanism of surface morphology forming. Meanwhile, the surface morphology under 33% and 50% spot overlapping impacts were investigated. In the experiment, the surface morphology was verified under single point and overlapping impacts, and the surface roughness was measured. The results showed that compared with laser shock processing, both laser shock wave planishing and laser shock imprinting can reduce surface roughness, which was significantly reduced when 33% spot overlapping impact was used; compared with laser shock processing and laser shock wave planishing, laser shock imprinting can achieve the active design of surface morphology under the premise of guaranteeing the reduction of surface roughness, effectively controlling the spot boundary effect, and 50% spot overlapping impact can make the surface morphology more uniform under laser shock imprinting. The special plastic rheological behavior of laser shock imprinting technology will provide a new way for metal surface morphology to be transformed in a direction conducive to improving its fatigue properties. [Display omitted] • The plastic rheological behavior of different laser shock processes on the material surface is studied comparatively. • The laser shock imprinting technology can effectively reduce surface roughness and actively design surface morphology. • The rebound effect of contact film is the key to reduce surface roughness. • Both laser shock wave planishing and laser shock imprinting with 33% overlapping mode can greatly reduce surface roughness. • The sample treated by laser shock imprinting with 50% overlapping mode can make the surface morphology more uniform. [ABSTRACT FROM AUTHOR]

The extend of tool wear significantly affects blanking processes and has a decisive impact on product quality and productivity. For this reason, numerous scientists have addressed their research to wear monitoring systems in order to identify or even predict critical wear at an early stage. Existing approaches are mainly based on indirect monitoring using time series, which are used to detect critical wear states via thresholds or machine learning models. Nevertheless, differentiation between types of wear phenomena affecting the tool during blanking as well as quantification of worn surfaces is still limited in practice. While time series data provides partial insights into wear occurrence and evolution, direct monitoring techniques utilizing image data offer a more comprehensive perspective and increased robustness when dealing with varying process parameters. However, acquiring and processing this data in real-time is challenging. In particular, high dynamics combined with increasing strokes rates as well as the high dimensionality of image data have so far prevented the development of direct image-based monitoring systems. For this reason, this paper demonstrates how high-resolution images of tools at 600 spm can be captured and subsequently processed using semantic segmentation deep learning algorithms, more precisely Fully Convolutional Networks (FCN). 125,000 images of the tool are taken from successive strokes. Selected images are labeled pixel by pixel according to their wear condition and used to train a FCN (U-Net). The approach presented offers the possibility of spatially monitoring wear in high-speed blanking operations in real-time. [ABSTRACT FROM AUTHOR]

For an accurate numerical simulation of springback behavior and control of shape and dimensional accuracies of the manufacture component under warm and hot precision plastic forming, the use of an appropriate material model dependent with strain, strain rate and temperature describing the nonlinear unloading process is vital, which is remained to be developed. The thermo-mechanical coupling effect in difficult-to-form material deformed at elevated temperature makes the unloading process more complicated and thus more difficult to model. In this paper, by using face-centered cubic (FCC) aluminum alloys as case study materials, loading-unloading experiments with different strains and strain rates at warm and elevated temperatures of 300 – 500 °C were conducted, the effects and contributions of strain, strain rate and temperature on unloading chord modulus (elastic modulus) and nonlinear unloading stress-strain response were quantified. A unique strain-, strain rate- and temperature-dependent nonlinear unloading coupled model was established. By validating and applying the nonlinear unloading coupled model in the both monotonous loading-unloading and cyclic loading-unloading warm and hot compression deformation, the calculation results agree well with experimental results, indicating that the model can describe perfectly the nonlinear unloading stress-strain responds and springback behavior. From the discussion on calculated results and capabilities of model, it was found that the proposed unified equation incorporating strain rate and temperature is also able to be coupled with the existing strain-dependent chord modulus model such as modified Yoshida-Uemori (Y-U) model. The capability of predicting nonlinear unloading curves and springback strains of aluminum alloys deformed at various strains, strain rates, and temperatures demonstrates the potential applicability of the model to a wide range of warm and hot forming process conditions. [Display omitted] • Thermal-mechanical coupling effect were considered in modeling of nonlinear unloading. • Nonlinear variation relationship of unloading chord modulus with strain, strain rate and temperature, and their coupled model are studied. • A new strain, rate and temperature-dependent nonlinear coupled model was proposed to describe nonlinear unloading stress-strain response and predict springback strain during warm and hot deformation. • The model can be applicable to monotonous loading-unloading and cyclic loading-unloading hot deformation. [ABSTRACT FROM AUTHOR]

Aluminum (Al) and copper (Cu) metal foils of thickness 6–20 µm are employed as current collectors for the production of Li-ion battery cathodes and anodes. Greater demand for this product is driving up production rate requirements, especially in the field of car manufacturing. Laser-based cutting processes for trimming and cutting electrodes are considered suitable for meeting this demand as they can achieve very high throughput while maintaining process quality. In order to meet market requirements, laser manufacturers are developing new laser sources, optics, and scanning heads that will improve process productivity and quality. Establishing the relationship between the laser system and cut quality will lead to competitiveness, increased productivity, and sustainability production. This paper presents a thorough analysis of the cutting performance of pulsed and continuous-wave lasers with scanning speeds of up to 28 m/s for processing thin Al and Cu current collectors. Comparisons between process outcomes are made in terms of maximum and minimum cutting speed and power, kerf geometry, cut quality, and presence of defects. Identification of configurations leading to high and low cut quality enables detailed process parameter windows to be defined for both laser system systems employing continuous-wave and pulsed sources. By analyzing correlations between the materials, laser source, and process variables, the main outcome is that continuous-wave single-mode fiber lasers enable highest cut quality in the high-productivity regime, surpassing the current state-of-the-art in laser cutting of metal foils. [ABSTRACT FROM AUTHOR]

Residual stress, a pivotal indicator for assessing surface quality, represents significant thermomechanical stresses encountered during material removal processes. The precision of machining and workpiece performance is of paramount importance in the industries such as aerospace and tool manufacturing. Besides the mitigating residual stresses, the persistent challenge particularly lies in grinding operations. While the mechanisms of grinding-induced residual stresses deserve attention. This paper seeks to bridge this knowledge gap by conducting a thorough analysis of the factors contributing to residual stress generation, taking into account the characteristics of mechanical, thermal, and thermodynamic coupling stresses. Firstly, an exploration of the mechanisms behind residual stress generation leads to a deeper understanding of the factors initiating these stresses. Additionally, this analysis provides insights into auxiliary accuracy adjustment methods for integrated models. Subsequently, the microstructural mechanisms and stress modeling of typical materials are discussed when subjected to the combined effects of heat, force, and their coupling effect. Moreover, common detection techniques for real-time analysis and prediction are summarized. Notably, the resulting combined prediction models indicate an error range in residual stress prediction spanning from 3% to 6%, with an average error of approximately 3%. Finally, the principles governing residual stress generation find practical application in actual production scenarios, wherein different perspectives of ultra-precision grinding processes are considered. These findings not only enhance our comprehension and control of residual stresses but also establish a robust foundation for future advancements in this field. • Summary of grinding residual stress generation mechanism and its future research outlook. • Elaboration of grinding residual stress modelling and summary of material removal mechanisms. • Summary of research on the mechanism of change in microscopic material processing and its research significance. • Application of residual stress detection methods and regulation techniques. [ABSTRACT FROM AUTHOR]

Ultrasmooth surface of soft metals is required in the field of advanced technology. However, the strong plasticity of soft metals makes it hard to achieve high surface finishing in ultraprecision machining. In this paper, the ultraprecision machining experiments of polycrystalline tin are carried out, and the factors including tool nose radius, cutting parameters, and material properties affecting the surface roughness in single-point diamond turning are investigated. Side flow, anisotropy, and grain boundary step are identified as the main causes of increasing of surface roughness, with grain boundary step demonstrating the largest impact. A surface roughness prediction model of tin in single-point diamond turning is established, which takes the minimum undeformed chip thickness, side flow, anisotropy and grain boundary step into consideration. The experiments show that the maximum prediction error of this prediction model is 6.51%. [ABSTRACT FROM AUTHOR]

The curved Fresnel lens array on the spherical surface owns exceptional optical performance and meets the growing demand for smart home and security alarm systems. However, the intricate three-dimensional microstructure of such optical component is typically considered impossible to be directly fabricated by diamond machining. In this paper, a novel 6-axis diamond ruling method is proposed to fabricate the complex optics utilizing a commercial 6-axis ultra-precision machine tool. The kinematic principle and tool path generation algorithm of this method are presented. A varying-angle sampling strategy is employed in the proposed algorithm to reduce the acceleration and following error in the rotation of the A-axis. Novel trial cutting processes are introduced to figure out the tool setting errors induced by visual inspection, which need to be compensated in the tool path. Based on the proposed tool path generation algorithm and cutting processes, this method enables the efficient processing of precise curved Fresnel lenses. There is no interference between the diamond tool and the curved microstructure in the 6-axis synchronized motions. Finally, the feasibility and superiority of this method are experimentally verified by analyzing the surface roughness and shape accuracy of the machined component. It can indeed generate high-quality curved Fresnel lenses on the spherical surface by the proposed 6-axis diamond ruling method. • A 6-axis diamond ruling method is proposed to fabricate the curved Fresnel lens array on the spherical surface. • The nonlinear kinematic principle of the method is presented. • The tool setting errors are eliminated by the novel trial cutting processes. • A vary-angle sampling strategy is employed to disperse the spatial Archimedean spiral. • The tool path generation algorithm for the 6-axis diamond ruling is introduced and validated. [ABSTRACT FROM AUTHOR]

Spinning is a common processing method for ultra-thin-walled tube. However, it is susceptible to surface ruptures in the deformation zone due to point-by-point contact, which affects the quality of products. In response to this issue, a ring-roller spinning (RRS) process is proposed, where the spinning roller makes tangential inner contact with the tube blank. This expands the triaxial compressive region, reducing ruptures tendency. And the tangential compressive stress is strengthened on the basis on triaxial compression of the conventional spinning (CS) process, which provides shear stress state in deformation zone. This paper conducts a comprehensive investigation into the RRS for thin-walled tubes made of 304 austenitic stainless steel. The study combines theoretical and experimental approaches and employs the finite element method (FEM) to evaluate the stress state within the tangential region. Various characterization methods are applied to examine the microstructural evolution under ultra-low stress triaxiality (ULST). The results confirm that the deformation zone is primarily characterized by tangential pressure under ULST, which significantly influence the metal microstructure, plastic behavior, and cumulative large deformation. This innovative process facilitates the continued deformation of the tubes, even under the saturated conditions of work hardening with the martensitic plasticising behaviour promotes grain refinement to 124 nm, resulting in an increase in the yield strength of the tubes from -1060 MPa to 1550 MPa. Continuous processing of ultra-thin-walled tube with a cumulative thinning rate of 90% was achieved by conducting RRS five-pass spinability experiments. [ABSTRACT FROM AUTHOR]

The microstructural characteristics and mechanical properties of forged parts differ significantly from those of additively manufactured parts, which results in different machinability. In this paper, the microstructure effect on the machinability of Inconel 718 parts obtained by different manufacturing processes, laser directed energy deposition (LDED), laser powder bed fusion (LPBF) and forging, is evaluated and critically discussed in terms of milling forces, surface morphology, surface roughness, chip morphology and subsurface microstructure. The results show that due to having the smallest grain size, high dislocation density, and precipitation hardening provided by the reinforcing phases, the milling force is maximized when cutting LPBF Inconel 718 parts. In addition to grain size and dislocation density, the texture also has an effect on the plastic deformation of the subsurface after milling. Furthermore, LDED and forged Inconel 718 parts undergo a continuous dynamic recrystallization process characterized by sub-grain rotation transforming low angle grain boundaries into high angle grain boundaries during milling. This study provides some theoretical guidance for the integration of additive and subtractive processes in the machining of complex structural parts with Inconel 718 alloy. [ABSTRACT FROM AUTHOR]

Electrical Arc Machining (EAM) is a high-efficiency, cost-effective method for machining electrical conductive materials especially difficult-to-cut ones. Because this thermal process relies on high-density energy to melt and remove material, effective arc control is crucial to maintain stable machining without overheating the workpiece. However, due to the limited discharge gap, it is difficult for the existing arc breaking methods to manage the arc plasma in a timely and uniform manner. This paper proposes a novel method named Magnetic Field Assisted Blasting Erosion Arc Machining (M-BEAM). This method introduces a magnetic field to enhance the control effect on arc plasma by directly influencing charged particles. Initially, the arc control and material removal mechanisms were revealed through an analysis and experiments of single arc discharge. Both simulated particle trajectory and high-speed photographs demonstrated that the arc plasma deflects much earlier in the magnetic field than that of traditional BEAM. Moreover, the expulsion effect of molten metal was significantly improved, resulting in a larger volume crater. Building on this, the magnetic-assisted arc control mechanism was utilized to enhance the performance of BEAM. Experimental results indicate that compared with traditional BEAM, Magnetic Field assisted BEAM increases its Material Removal Rate (MRR) by 10.09% while significantly reducing the Tool Wear Ratio (TWR) by 29.02%. Additionally, surface roughness (Sa) is decreased by 47.73%, and the thickness of the recast layer is decreased by 78.54%. Therefore, M-BEAM can further improve the machining performance and build a good foundation for subsequent machining. [ABSTRACT FROM AUTHOR]

Irregular lenses are commonly employed in various beam shaping, imaging, and other optical applications. They require secondary processing to meet specific design and assembly criteria. Bessel beam lasers have gained popularity for their ability to efficiently separate hard-brittle materials owing to their high processing quality and speed. However, the complex surface of irregular lenses creates challenges such as refraction and scattering, which impede the laser beam's ability to form a laser center lobe inside the material. This paper proposes an innovative technique called immersion laser separation (ILS), where an irregular lens is immersed in a refractive index matching medium to create a compound with a uniform refractive index. This approach mitigates the impact of surface complexity on the optical path of the Bessel beam. The separation of a fast axis collimator (FAC) by ILS is used as an example to test the proposed technique. The distribution characteristics of the Bessel beam light field inside the lens material under different refractive index were investigated to find that the laser consistently forms a laser center lobe inside the material during cutting when the matching deviation is small. This results in a modified area that covers the entire surface. The maximum cutting speed can reach 50 mm/s, the cutting surface roughness is less than 700 nm, and the technique produces no chips or micro-cracks, ensuring uniformly high-quality separation. Experimental and simulation results are in close agreement, suggesting that the proposed technique is effective for the efficient, high-quality cutting of irregular lenses. [ABSTRACT FROM AUTHOR]

Material extrusion additive manufacturing of metals has found widespread application and is typically thought of as a facile technique to create metal components. This can be undertaken without the need for energy sources typically used in direct energy deposition and powder bed fusion processes. Despite recent advances in achieving net shape and improvements to material/component integrity, these processes are characterized by performance limiting defects which often emerge as a result of deposition strategy and are retained post sintering. Although the debinding and sintering steps have been investigated for metal injection molding technology, quantitative studies of defect evolution are lacking. This work proposes an approach to study the pore evolution behavior from deposition to sintering through X-ray Computed Tomography (XCT) image processing. Quantitative results of pore shrinking, partial and full closure through backtracking of individual pores from the sintered to the green state are presented. It is shown that where pores are larger than 4 × 10-6 mm3, equals to the D 90 of the feedstock metal particles, these cannot be fully closed upon sintering and will survive to limit the performance of the final part. The average pore shrinkage is by a factor of 5.6 and partial closure happens in pores with minimum Feret diameter of 33 μm, equals to 160% of the D 90 powder particle, or less. The utilization of overfill as a proposed technique in the literature for the elimination of macro pores is investigated, yielding disparate and unsatisfactory results. This discrepancy can be attributed to the insufficient formation of micro-channels within the pore structure during the deposition process of the aqueous feedstock, leading to regions of weak grain bonding. To evaluate the contribution of these to undermining material integrity, tensile tests of linear and circular deposition strategies are undertaken. Experiments show that track interface length plays a major role in determining elongation to failure and tensile strength. It is concluded that the limitation to the mechanical properties of metal paste extrusion components originates from the emergence of defects and their characteristics after the completion of the processing, as opposed to being influenced by the metallurgy prior or post sintering. [Display omitted] • A new approach to metal paste extrusion characterization post sintering is presented. • The authors show how inbuilt defects evolve as a result of thermal cycling. • Key defect metrics are defined and characterized. • The performance characteristics of material and process combination are reported and failures examined. [ABSTRACT FROM AUTHOR]