Metals, Volume 11, Issue 1 (January 2021) – 176 articles

The Master-alloy (MA) alloy route to promote a liquid phase during sintering has great potential to reduce costs in low alloyed sintered steels, meanwhile enabling the introduction of innovative alloy systems with Cr, Mn and Si. However, in order to successfully modify the performance of steels, multi requirements must be met, including, for example, solubility with the base material, compatibility with the usual sintering atmospheres, homogeneous distribution of the powdered master alloy in the material and the control of secondary porosity. Efforts have been made to properly design the composition of MA, to identify the reducing agents and to understand how they affect the wetting and liquid spreading all over the sintered part. This work reviews these key aspects for the efficient development of steels and explores the possibility to achieve a composition that can act as liquid former or as sinter braze adapting its use to the component requirement. Full article

The concept of Industry 4.0 is defined as a common term for technology and the concept of new digital tools to optimize the manufacturing process. Within this framework of modular smart factories, cyber-physical systems monitor physical processes creating a virtual copy of the physical world and making decentralized decisions. This article presents a review of the literature on virtual methods of computer-aided manufacturing processes. Numerical modeling is used to predict stress and temperature distribution, springback, material flow, and prediction of phase transformations, as well as for determining forming forces and the locations of potential wrinkling and cracking. The scope of the review has been limited to the last ten years, with an emphasis on the current state of knowledge. Intelligent production driven by the concept of Industry 4.0 and the demand for high-quality equipment in the aerospace and automotive industries forces the development of manufacturing techniques to progress towards intelligent manufacturing and ecological production. Multi-scale approaches that tend to move from macro- to micro- parameters become very important in numerical optimization programs. The software requirements for optimizing a fully coupled thermo-mechanical microstructure then increase rapidly. The highly advanced simulation programs based on our knowledge of physical and mechanical phenomena occurring in non-homogeneous materials allow a significant acceleration of the introduction of new products and the optimization of existing processes. Full article

The Fe-rich intermetallic phases have a broadly detrimental effect on the mechanical properties of Al–Cu alloy. In this paper, the continuous evolution of Fe-rich intermetallics and their effects on mechanical properties, especially the tensile fracture behavior of 2219 wrought Al–Cu alloys as a function of Fe content against different processing approaches (i.e., as-cast, homogenization, multidirectional forging, and solution-peak aging treatment) were investigated using optical microscopy, scanning electron microscopy, and tensile tests. The results indicated that needle-like Al₇Cu₂Fe or Al₇Cu₂(Fe, Mn) intermetallics mainly presented in the final microstructures of all alloys with various Fe contents. The size and number of Al₇Cu₂Fe/Al₇Cu₂(Fe, Mn) intermetallics increased with the increase of Fe content. The increase of Fe content had little influence on the ultimate tensile strength and yield strength, while obvious deterioration in the elongation, because fracture initiators mainly occurred at the Al₇Cu₂Fe/Al₇Cu₂(Fe, Mn) particles or particles–matrix interface. Therefore, the 2219 Al–Cu alloy with 0.2 wt.% Fe content presented relatively low tensile ductility. The tensile fracture mechanism has been discussed in detail. Full article

Bimetallic materials are important in many industries (aerospace, medicine, etc.) since they allow the creation of constructions that combine specific functional properties, for example, low density (aluminum alloy) and high corrosion resistance (stainless steel), due to layering fabrication of the bimetallic joint. On the other hand, the difference in thermophysical properties of the dissimilar material layers leads to residual stresses, which cause deformation and destruction of such a bimetallic joint produced via the methods of surfacing or additive technologies. This article discusses the methods based on the gray relational analysis and generalized desirability function for the quality assessment of Al–10Si–Mg aluminum alloy and Cr18–Ni10–Ti stainless-steel bimetal fabricated via selective laser melting (SLM). There are four main parameters (quality indices) of the quality generalized assessment, which determine the degree of Al penetration into the steel substrate and Fe into the deposited layer, the difference in microhardness values on both sides of the interface boundary, and the resistance to mechanical destruction of the bimetallic joint. According to the results obtained, the best set of quality indices corresponds to the SLM technological modes with an energy density of 105 and 147 J/mm³. The greatest functionality of the bimetals is determined by the quality index associated with its strength. Therefore, methods of gray relational analysis and desirability function make it possible to form a generalized assessment for the bimetallic joint quality and, consequently, to select the best technological mode. Full article

Binary and ternary Mg-1%Er/Mg-1%Er-1%Zn alloys were rolled and subsequently subjected to various heat treatments to study texture selection during recrystallization and following grain growth. The results revealed favorable texture alterations in both alloys and the formation of a unique ±40° transvers direction (TD) recrystallization texture in the ternary alloy. While the binary alloy underwent a continuous alteration of its texture and grain size throughout recrystallization and grain growth, the ternary alloy showed a rapid rolling (RD) to transvers direction (TD) texture transition occurring during early stages of recrystallization. Targeted electron back scatter diffraction (EBSD) analysis of the recrystallized fraction unraveled a selective growth behavior of recrystallization nuclei with TD tilted orientations that is likely attributed to solute drag effect on the mobility of specific grain boundaries. Mg-1%Er-1%Zn additionally exhibited a stunning microstructural stability during grain growth annealing. This was attributed to a fine dispersion of dense nanosized particles in the matrix that impeded grain growth by Zener drag. The mechanical properties of both alloys were determined by uniaxial tensile tests combined with EBSD assisted slip trace analysis at 5% tensile strain to investigate non-basal slip behavior. Owing to synergic alloying effects on solid solution strengthening and slip activation, as well as precipitation hardening, the ternary Mg-1%Er-1%Zn alloy demonstrated a remarkable enhancement in the yield strength, strain hardening capability, and failure ductility, compared with the Mg-1%Er alloy. Full article

This study establishes a vertical–horizontal coupling vibration model of hot rolling mill rolls under multi-piecewise nonlinear constraints considering the piecewise nonlinear spring force and piecewise nonlinear friction force constraints of the hydraulic cylinder in the vertical direction of the rolls, the piecewise stiffness constraints in the horizontal direction, and the influence of the nonlinear dynamic rolling force in the rolling process. Using the average method to solve the amplitude–frequency response equation of the coupled vibration system and taking the actual parameters of a 1780 mm hot rolling mill (Chengde Steel Co., Ltd., Chengde, China) as an example, we study the amplitude–frequency characteristics of the mill rolls under different parameter settings. The results show that the amplitude and resonance region can be reduced by appropriately reducing the external disturbance force and the nonlinear spring force of the hydraulic cylinder, appropriately increasing the nonlinear friction force, and eliminating the gap between the bearing seat and the mill housing, to avoid the amplitude jump phenomenon due to piecewise variation. Furthermore, using the singularity theory to study the static bifurcation characteristics of the coupled vibration system, we establish a relationship between the vibration parameters and the topological bifurcation solution of the coupled system. The transition sets and their corresponding bifurcation topological structure in three cases are given, and the steady and unsteady process parameter regions of the rolls are obtained. The dynamic behavior of the coupled vibration system can be controlled by varying the bifurcation parameter. This study provides a theoretical basis for restraining the vibration of hot rolling mill rolls and optimizing the process parameters. Full article

In this study we present a series of light-weight (6.24 to 6.42 g/cm³), Ti-rich Mo-Si-Ti alloys (≥40 at.% nominal Ti content) with the hitherto best combination of pesting and creep resistance at 800 and 1200 °C, respectively. This has been achieved by fine-scaled eutectic-eutectoid microstructures with substantial fractions of primarily solidified (Mo,Ti)₅Si₃. (Mo,Ti)₅Si₃ was found to be oxidation-resistant in these alloys and also beneficial for the creep resistance. The enhanced solidus temperature is of specific relevance with respect to the latter point. The creep resistance is competitive to the non-pesting resistant, but most creep-resistant (among the Mo-Si-Ti alloys) eutectoid alloy Mo-21Si-34Ti developed by Schliephake et al. [Schliephake et al., in Intermetallics 104 (2019) pp. 133–142]. Moreover, it is favourably superior to the commercially applied Ni-based single crystal alloy CMSX-4 for the applied compressive loading conditions under vacuum. Full article

Determining the intrinsic indices of sheet metals under compression states at high temperatures is vital to accurately predict the behavior of the material in warm/hot forming processes. Nevertheless, the literature contains little previous experimental data in this regard due to the difficulty of carrying out specific test methodologies in sheet metals. The authors of the present manuscript previously developed an approach to evaluate the in-plane compression behavior under a wide range of test conditions, which was applied here to characterize pure titanium and Ti6Al4V alloy until 750 °C. This procedure allowed us to quantify the asymmetric and anisotropic tension–compression (T-C) response of the materials involved and their evolution with temperature and strain rate. The asymmetry detected at room temperature showed a higher compression response in all cases, mostly reaching differences of around 10%. For the lowest strain rate studied, the typical assumed symmetric T-C behavior was observed from 300 and 450 °C onwards, for the rolling and transverse direction, respectively. In addition, stepped compression tests led us to deduce the anisotropy indices, which were different from those found under tension, in contrast to the r-values applied by most authors. Using the experimental results, a factor related to the asymmetry found was proposed to formulate an extended constitutive model. The asymmetry and anisotropy data supplied for compression under warm/hot conditions are the main novelty of this research. Full article

Surface roughness and burr formation are among the most important surface quality metrics which determine the quality of the fabricated parts. High precision machined microparts with complex features require micromachining process to achieve the desired yet stringent surface finish and dimensional accuracy. In this research, the effect of cutting speed (m/min), feed rate (µm/tooth), depth of cut (µm) and three types of tool coating (AlTiN, nACo and TiSiN) were analyzed to study their effect on surface roughness and burr formation during the micromachining of Inconel 718. The analysis was carried out using an optical profilometer, scanning electron microscope and statistical technique. Machining tests were performed at low speed with a feed rate (µm/tooth) below the cutting-edge radius for 10 mm cutting length using a carbide tool of 0.5 mm diameter on a CNC milling machine. From this research, it was determined that the depth of cut was the main factor affecting burr formation, while cutting velocity was the main factor affecting the surface roughness. In addition, cutting tool coating did not significantly affect either surface roughness or burr formation due to the difference in coefficient of friction. The types of burr formed during micromilling of Inconel 718 were mainly influenced by the depth of cut and feed rate (µm/tooth) and were not affected by the cutting velocity. It was also concluded that the results for the surface finish at low-speed machining are comparable to that of transition and high-speed machining, while the burr width found during confirmation experiments at low-speed machining was also within an acceptable range. Full article

The paper considers a three-stage technology for angular rolling of the pipe workpiece. This technology facilitates the expansion of the range of flange parts available by eliminating a number of drawbacks of the known methods of metal forming. In the presented paper, we analyze the results of numerical calculations and experiments, as well as the effective deformation values in blank material, using computer simulation in the DEFORM-3D software package. The results of the computer simulation were reached taking into account experimental studies of the rheological properties of copper alloy L68 in the form of a strain hardening curve using the Instron-8850 complex. The results of the ratio of basic geometric dimensions expanded the range of flange parts under investigation and allowed us to consider angular rolling technology with a variable angle of inclination of the rolling roll from a three-stage perspective, especially in small-scale production. Full article

In order to study the effect of BaO or B₂O₃ on the absorption of Ti inclusions, the effects of mold fluxes with different contents of BaO (0~15%) or B₂O₃ (0~15%) on the mass transfer coefficients of TiO₂ or TiN were studied with the rotating cylinder method. The experimental results show that with the addition of BaO in the mold flux, the mass transfer coefficient of TiO₂ increases from 4.58 × 10⁻⁴ m/s to 6.08 × 10⁻⁴ m/s, that of TiN increases from 3.09 × 10⁻⁴ m/s to 4.41 × 10⁻⁴ m/s, 2CaO·MgO·2SiO₂ is transformed into BaO·2CaO·MgO·2SiO₂, and the Ti inclusions combine with CaO to form CaTiO₃. With the addition of B₂O₃ in the mold flux, the mass transfer coefficient of TiO₂ increases from 4.58 × 10⁻⁴ m/s to 7.46 × 10⁻⁴ m/s, that of TiN increases from 3.09 × 10⁻⁴ m/s to 5.50 × 10⁻⁴ m/s, CaO and B₂O₃ combine to 2CaO·B₂O₃, and Ti inclusions exist in the form of TiO₂. During the experiment, TiN will be transformed into titanium oxide. Full article

The bonding of metallic alloys and composite materials in the form of a hybrid structure is a line of great interest for the current industry. The different machinability of both materials requires a specific machining process. Abrasive water-jet machining (AWJM) is an excellent technology for the simultaneous machining of both materials. However, defects at the micro and macro-geometric level have been detected in several scientific articles. In this review, a detailed study of the two main defects in metals, composite materials and hybrid structures has been developed. The conclusions of several scientific articles have been exposed for a better understanding of the topic in articles between 1984 and 2020. The influence of the cutting parameters on the reduction in kinetic energy of the water jet and the order of stacking of the materials in the hybrid structure is the main objective in order to minimize these defects. Cutting parameter optimization studies, predictive model proposals, process-associated defects and evaluation methodologies have been discussed. The aim of this article is to set a solid background on AWJM machining in hybrid structures and on the influence of cutting parameters on generated defects and machining strategies to obtain the best results at a macro and micro-geometric level. Full article

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix. Full article

The article presents the results of Hardox Extreme steel tests in the as-delivered state from a steel mill (after quenching and tempering), and also in the normalized state. The research procedures included a microstructure analysis using light microscopy; and a static tensile test at ambient temperature to determine its Young’s modulus, yield strength, tensile strength, elongation and reduction in area after fracture. During the tensile tests, both the longitudinal and transverse orientation of rolling direction were taken into account. The Charpy impact test was also carried out in the temperature range of the ductile–brittle transition in connection with the fractographic analysis carried out with the use of a scanning microscope (SEM). The impact tests were carried out on samples in both directions on the plate, using the following temperatures: −40, −20, 0, +20 °C. Based on the structural and strength characteristics of Hardox Extreme steel determined on the basis of the research, in a further part of the paper the possibility of its use in machine construction elements operating in selected industrial sectors is considered/discussed, with a particular emphasis on reducing the level of energy consumption in the manufacturing and operation of the above technical facilities. Full article

This work aimed to design an undermatched lap joint that has an equal load-carrying capacity (ELCC) with a traditional equalmatched joint under out-of-plane bending. A weld strength calculation method was proposed based on the similarity of a lap joint and a T joint, as shown using linear elastic finite element (FE) analysis, and then applied in the analysis of a lap joint and the design of an ELCC lap joint. A single lap joint of HQ785 steel was chosen for experimental verification. The bending force limit of the ELCC joint was 93.35% of the theoretical prediction and 96.90% of the traditional equalmatched joint. The results show that the weld strength calculation method and the ELCC design method are reasonable and feasible. Full article

In the present paper, new heat treatment was performed on 10 vol.% TiC/Ti-6Al-3Sn-9Zr-1.5Mo composite fabricated by an in situ casting technique. The aim is to obtain fully lamellar structure in matrix, control the lamellar structure quantitatively and understand the variation of the tensile properties of as-cast and heat-treated composites. For as-cast composite, matrix exhibited fully lamellar structure with some extent of basket-weave characteristics, and reinforcement was mainly in fine rod and strip shape. After β heat treatment, matrix microstructure was refined visibly. As the new cooling method was employed, wider α lath in matrix was obtained. The composite with very fine lamellar structure showed better yield strength (YS) in comparison with that with coarse lamellar microstructure below 650 °C. At 700 °C, fine grain strengthening cannot exert effective influence on tensile strength. It is proved that the enhanced YS is mainly ascribed to the refinement of α lath at ambient temperature. The heat-treated composites with wider α lath displayed excellent ductility at ambient temperature. Above 600 °C, the effect of α phase size on tensile elongation was negligible in the heat-treated composites, since matrix was softened. Full article

In this paper, the investigation of chip formation of aluminum alloy in different machining strategies (i.e., micro and macro cutting) is performed to develop a holistic view of the chip formation phenomenon. The study of chip morphology is useful to understand the mechanics of surface generation in machining. Experiments were carried out to evaluate the feed rate response (FRR) in both ultra-precision micro and conventional macro machining processes. A comprehensive study was carried out to explore the material removal mechanics with both experimental findings and theoretical insights. The results of the variation of chip morphology showed the dependence on feed rate in orthogonal turning. The transformation of discontinuous to continuous chip production—a remarkable phenomenon in micro machining—has been identified for the conventional macro machining of Al alloy. This is validated by the surface crevice formation in the transition region. Variation of the surface morphology confirms the phenomenology (transformation mechanics) of chip formation. Full article

This research evaluates the effectiveness of using a roller-type base isolation device with tensile strength in reducing the dynamic response of industrial steel storage racks. These were subjected to a seismic input acting separately in both directions of the structure. The seismic record obtained from the earthquake that occurred in Llolleo, Chile, on 3 March 1985, was used as input. This earthquake was scaled in the frequency domain, adjusting its response spectrum to coincide with the design spectrum required by NCh2745. In the calculations of this spectrum, the most hazardous seismic zone (zone 3) and soft soil (soil III) that amplifies the effect of the low frequencies of the earthquake were considered. These frequencies are the ones that have the most affect on flexible structures such as high racks and systems with base isolation. Numerical time-history analyses were performed in fixed base racks and base isolation racks. In both cases, the models include semi-rigid connections with capacity for plastic deformation and energy dissipation. Parametric analyses were carried out considering the most relevant variables, using an algorithm programmed in MATLAB software. The maximum relative displacement, maximum basal shear load, and maximum absolute floor acceleration were considered as responses of interest. The results showed the effectiveness of using the base isolation device by reducing the absolute accelerations between approximately 75% and 90%, compared to the same fixed rack at its base. This makes it possible to reduce the vulnerability of the stored load to overturn under the action of a severe earthquake. Full article

Stress–strain behavior of a low carbon low alloy multiphase steel with ferrite, tempered bainite, and retained austenite was studied at different cryogenic temperatures. Results indicated that both strength and ductility were enhanced with decreasing tensile testing temperature. The enhancement of both strength and ductility was attributed to the decreased mechanical stability of retained austenite with decreasing temperature, resulting in sufficient transformation induced plasticity (TRIP) effect for increasing work hardening rate. Full article

In this paper, fiber waviness, as one of the most frequently occurring defects in fiber reinforced composites, is numerically investigated with regard to the formation of residual stresses in fiber metal laminates. Furthermore, the prediction of the residual stress state in the thickness direction by means of the simulated hole drilling method is studied. To this regard, a global-local finite element analysis based on the submodel technique is presented. The submodel technique essentially consists of two governing steps: In the first step, a global model is first utilized to calculate and analyze the residual stress distribution and deformation in the intrinsically joined hybrid structure. Effective cure-dependent thermo–elastic properties predicted by a numerical homogenization procedure were used to simulate the curing-process and analyze the residual stresses state. However, the dimension of the intrinsically manufactured hybrid plate is large compared to the diameter of the drilled hole (2 mm), so that a local model is necessary, which provides only a geometric partial portion of the global model. The local model takes the global stress state into account and is subsequently used to simulate the incremental hole drilling method with a refined mesh discretization. The production-related fiber waviness is modeled by an element-wise orientation approximating a sinus function. In order to validate the global-local modeling approach, a comparison between numerical results and experimental data from literature is presented. The comparison between global residual stress state (global model) and the simulated hole drilling method (local model) is used to assess the applicability and reliability of the hole drilling method in case of fiber waviness. It is found that an in-plane fiber waviness leads to a rather low variance of residual stresses over thickness. In case of an out-of-plane fiber waviness, oscillating residual stress fields occur over the entire thickness along the fiber direction. Moreover, the current limits of the incremental hole drilling method could be pointed out by the presented investigations. It is seen that the simulated results of the incremental hole drilling method are sensitive to waviness, even if the amplitude-wavelength-ratio is small. Without further adjustment of the calibration coefficients the oscillating stress and strain fields lead, in particular fiber waviness in thickness direction, to unreliable predictions. For the experimental application it can be concluded that the specimens have to be carefully examined with regard to fiber waviness. Full article

The aim of the present work is to contribute to the characterization of the biaxial tensile behavior of commercially pure titanium, under various in-plane loading conditions at room temperature, by a non-contact digital image correlation system. Several loading conditions, with load ratio ranging from 4:0 to 0:4 and displacement rate ranging from 0.001 to 0.1 mm/s, are examined. It is found that the yield strength and ultimate tensile strength of biaxial sample are greater than that of uniaxial sample, where the equi-biaxial sample shows the highest strength. It is also observed that increase in strain rate leads to remarkable improvement of tensile strength. Fractographic analysis indicates that the shape and size of dimples are load ratio and strain rate dependent. Additionally, a modified Johnson–Cook constitutive model was proposed to account for the effect of strain rate on biaxial tensile deformation. The experimental results are in good agreement with the simulated results, indicating that the proposed model is reliable to predict biaxial tensile deformation of commercially pure titanium at different strain rates. Full article

Interaction of migrating $\left\{10\overline{1}2\right\}$ twin boundary with obstacles was analyzed by atomistic and finite elements computer simulations of magnesium. Two types of obstacles were considered: one is a non-shearable obstacle and another one is the void inside bulk material. It is shown that both types of obstacles inhibit twin growth and increased stress is necessary to engulf the obstacle in both cases. However, the increase of critical resolved shear stress is higher for the passage of the twin boundary through raw of voids than for interaction with non-shearable obstacles. Full article

One of the most important routes for obtaining Al-Bi-x monotectic alloys is directional solidification. The control of the thermal solidification parameters under transient heat flow conditions can provide an optimized distribution of the Bismuth (Bi) soft minority phase embedded into an Al-rich matrix. In the present contribution, Al-Bi, Al-Bi-Zn, and Al-Bi-Cu alloys were manufactured through this route with their microstructures characterized and dimensioned based on the solidification cooling rates. The main purpose is to evaluate the influence of typical hardening elements in Al alloys (zinc and copper) in the microstructure, tensile properties, and wear of the monotectic Al-Bi alloy. These additions are welcome in the development of light and more resistant alloys due to the growing demands in new sliding bearing designs. It is demonstrated that the addition of 3.0 wt.% Cu promotes microstructural refining, doubles the wear resistance, and triples the tensile strength with some minor decrease in ductility in relation to the binary Al-3.2 wt.% Bi alloy. With the addition of 3.0 wt.% Zn, although there is some microstructural refining, little contribution can be seen in the application properties. Full article

Cast nickel-based superalloys INC713 LC, B1914 and MAR-M247 are widely used for high temperature components in the aerospace, automotive and power industries due to their good castability, high level of strength properties at high temperature and hot corrosion resistance. The present study is focused on the mutual comparison of the creep properties of the above-mentioned superalloys, their creep and fracture behaviour and the identification of creep deformation mechanism(s). Standard constant load uniaxial creep tests were carried out up to the rupture at applied stress ranging from 150 to 700 MPa and temperatures of 800–1000 °C. The experimentally determined values of the stress exponent of the minimum creep rate, n, were rationalized by considering the existence of the threshold stress, σ₀. The corrected values of the stress exponent correspond to the power-law creep regime and suggest dislocation climb and glide as dominating creep deformation mechanisms. Fractographic observations clearly indicate that the creep fracture is a brittle mostly mixed transgranular and intergranular mode, resulting in relatively low values of fracture strain. Determined main creep parameters show that the superalloy MAR-M247 exhibits the best creep properties, followed by B1914 and then the superalloy INC713 LC. However, that each of the investigated superalloys can be successfully used for high temperature components fulfils the required service loading conditions. Full article

In many applications that use high strength steels, structural integrity depends greatly on weld quality. Imperfections and the weld bead geometry are influencing factors on mechanical properties of the welded joints but, especially in the fatigue strength, they cause a great decrease. The proper knowledge of these two factors is important from the nominal stress approach to the fracture mechanics approaches. Studies concerning the profile and imperfections of the weld bead in laser welding for thin plates of high strength steels are scarce. In this work, these two aspects are covered for five series single and double-welded joints, butt joints in a 3 mm thick HSLA steel, welded in a small range of welding parameters. The actual profiles captured with profilometer were modeled with proposed geometric parameters achieving an adequate fit with values of the coefficient of determination ℜ² greater than 0.9000. Description of imperfections includes the distributions of porosity and undercuts. The evaluation of the weld quality, taking as guide the ISO 13919-1 standard determined B and D levels for the welded series while based on the stress-concentrating effect, showed a greater detriment in those series with undercuts and excessive penetration. The analysis of variance validated the results of the different combinations of laser welding parameters and showed, for the factorial experimental design, a more significant effect of the welding speed. Full article

At present, copper smelting slag is not effectively recycled and is wasted. Copper smelting slag contains Fe_xO at more than 40 mass%. For the utilization of copper slag as a Fe resource, it is necessary to separate the Cu in the slag. For copper recycling from slag, FeS-based matte can be introduced to use sulfurization to concentrate Cu from the slag into the sulfide and finally recover the copper. In a previous paper, a kinetic model was developed to simulate the coupled reactions between the multicomponent slag and FeS-based matte by using previously reported thermodynamic data. Building on this work, we carried out equilibrium experiments to supplement the thermodynamic data used in the previously developed model. An empirical formula for the Cu₂O activity coefficient of Cu₂O-FeO_X-CaO-MgO-SiO₂-Al₂O₃ system slag was obtained. In addition, the effect of alumina content in the slag on the Cu₂O activity coefficient in the slag was investigated. The model was also supplemented to account for MgO solubility. By the developed model and the industrial conditions, we investigated the effect of slag composition on the behavior of Cu between matte and Cu₂O-FeO_X-CaO-MgO-SiO₂-Al₂O₃ system slag for the copper loss. Full article

The bottleneck of recycling chains for spent lithium-ion batteries (LIBs) is the recovery of valuable metals from the black matter that remains after dismantling and deactivation in pre‑treatment processes, which has to be treated in a subsequent step with pyrometallurgical and/or hydrometallurgical methods. In the course of this paper, investigations in a heating microscope were conducted to determine the high-temperature behavior of the cathode materials lithium cobalt oxide (LCO—chem., LiCoO₂) and lithium iron phosphate (LFP—chem., LiFePO₄) from LIB with carbon addition. For the purpose of continuous process development of a novel pyrometallurgical recycling process and adaptation of this to the requirements of the LIB material, two different reactor designs were examined. When treating LCO in an Al₂O₃ crucible, lithium could be removed at a rate of 76% via the gas stream, which is directly and purely available for further processing. In contrast, a removal rate of lithium of up to 97% was achieved in an MgO crucible. In addition, the basic capability of the concept for the treatment of LFP was investigated whereby a phosphorus removal rate of 64% with a simultaneous lithium removal rate of 68% was observed. Full article

This research investigates the effect of machining parameters on material removal rate, electrode wear ratio, and gap clearance of macro deep holes with a depth-to-diameter ratio over four. The experiments were carried out using electrical discharge machining with side flushing and multi-aperture flushing to improve the machining performance and surface integrity. The machining parameters were pulse on-time, pulse off-time, current, and electrode rotation. Response surface methodology and the desirability function were used to optimize the electrical discharge machining parameters. The results showed that pulse on-time, current, and electrode rotation were positively correlated with the material removal rate. The electrode wear ratio was inversely correlated with pulse on-time and electrode rotation but positively correlated with current. Gap clearance was positively correlated with pulse on-time but inversely correlated with pulse off-time, current, and electrode rotation. The optimal machining condition of electrical discharge machining with side flushing was 100 µs pulse on-time, 20 µs pulse off-time, 15 A current, and 70 rpm electrode rotation; and that of electrical discharge machining with multi-aperture flushing was 130 µs, 2 µs, 15 A, and 70 rpm. The novelty of this research lies in the use of multi-aperture flushing to improve the machining performance, enable a more uniform GC profile, and minimize the incidence of recast layer. Full article

The interaction of biofilms with metallic surfaces produces two biologically induced degradation processes of materials: microbial induced corrosion and bioleaching. Both phenomena affect most metallic materials, but in the case of noble metals such as gold, which is inert to corrosion, metallophilic bacteria can cause its direct or in direct dissolution. When this process is controlled, it can be used for hydrometallurgical applications, such as the recovery of precious metals from electronic waste. However, the presence of unwanted bioleaching-producing bacteria can be detrimental to metallic materials in specific environments. In this work, we propose the use of single-layer graphene as a protective coating to reduce Au bioleaching by Cupriavidus metallidurans, a strain adapted to metal contaminated environments and capable of dissolving Au. By means of Scanning Tunneling Microscopy, we demonstrate that graphene coatings are an effective barrier to prevent the complex interactions responsible for Au dissolution. This behavior can be understood in terms of graphene pore size, which creates an impermeable barrier that prevents the pass of Au-complexing ligands produced by C.metallidurans through graphene coating. In addition, changes in surface energy and electrostatic interaction are presumably reducing bacterial adhesion to graphene-coated Au surfaces. Our findings provide a novel approach to reduce the deterioration of metallic materials in devices in environments where biofilms have been found to cause unwanted bioleaching. Full article