Search Results (231)

Rapid pavement repair demands materials that combine accelerated strength gains, dimensional stability, long-term durability, and sustainability. However, finding materials or formulations that offer these balances remains a critical challenge. This study systematically evaluates two polymer-modified belitic calcium sulfoaluminate (CSA) concretes—CSAP (powdered polymer) and CSA-LLP (liquid polymer admixture)—against a traditional Type III Portland cement (OPC) control under both laboratory and realistic outdoor conditions. Laboratory specimens were tested for fresh properties, early-age and later-age compressive, flexural, and splitting tensile strengths, as well as drying shrinkage according to ASTM standards. Outdoor 5 × 4 × 12-inch slabs mimicking typical jointed plain concrete panels (JPCPs), instrumented with vibrating wire strain gauges and thermocouples, recorded the strain and temperature at 5 min intervals over 16 weeks, with 24 h wet-burlap curing to replicate field practices. Laboratory findings show that CSA mixes exceeded 3200 psi of compressive strength at 4 h, but cold outdoor casting (~48 °F) delayed the early-age strength development. The CSA-LLP exhibited the lowest drying shrinkage (0.036% at 16 weeks), and outdoor CSA slabs captured the initial ettringite-driven expansion, resulting in a net expansion (+200 µε) rather than contraction. Approximately 80% of the total strain evolved within the first 48 h, driven by autogenous and plastic effects. CSA mixes generated lower peak internal temperatures and reduced thermal strain amplitudes compared to the OPC, improving dimensional stability and mitigating restraint-induced cracking. These results underscore the necessity of field validation for shrinkage compensation mechanisms and highlight the critical roles of the polymer type and curing protocol in optimizing CSA-based repairs for durable, low-carbon pavement rehabilitation. Full article

This study investigated into how different current input levels during cold metal transfer (CMT) welding affected the characteristics of the weld bead. For the current variation, three input values were taken: 80 A, 90 A, and 100 A. Weld beads fabricated from all three current inputs were compared by analysing their microstructure, microhardness, tensile strength, and residual stress. The microhardness of the weld bead decreased when the current parameter was increased from 80 A to 100 A. The average tensile strength increased from 80 A to 90 A. The lowest residual stress calculated was −135 MPa with 100 A current. Full article

This study explores the feasibility of generating a globular microstructure in situ during the thixotropic 3D printing of the EN AW-4043 alloy, starting from a conventional cold-rolled wire. Thermodynamic simulations using Thermo-Calc software were first conducted to identify the semi-solid processing window of the alloy, based on the evolution of liquid and solid fractions as a function of temperature. Guided by these results, thermal treatments were performed on cold-rolled wires to promote the formation of a globular microstructure. A laboratory-scale printing head prototype was then designed and built to test continuous heating and deposition conditions representative of a thixotropic additive manufacturing process. The results showed that a globular microstructure could be achieved in the cold-rolled EN AW-4043 wires by heating them at 590 °C for 5 min in a static muffle furnace. A similar effect was observed when continuously heating the wire while it flowed through the heated printing head. Preliminary deposition tests confirmed the viability of this approach and demonstrated that thixotropic 3D printing of EN AW-4043 alloy is achievable without the need for pre-globular feedstock. Full article

Low-carbon micro-alloyed steel has become a wire material with great potential for further development due to its excellent comprehensive performance; however, there is still a lack of insight into the evolution of its electrical conductivity during annealing treatment after undergoing deformation. In this present contribution, we systematically explored the intrinsic correlation between the microstructural characteristics (including grain size evolution, dislocation density change, etc.) and performance indexes of cold-rolled high-conductivity high-strength steels and their mechanisms, using the annealing temperature, a key process parameter, as a variable. Characterization methods were used to comprehensively investigate the variation rule of the electrical conductivity of low-carbon micro-alloyed steels containing Ti-Nb elements under different annealing temperatures, as well as their influencing factors. The results show that for the ultra-low-carbon steel (0.002% C), the dislocation density continuously decreases with the increasing annealing temperature. Both experimental steels underwent complete recrystallization at 600 °C, with grain growth increasing at higher temperatures (with ultra-low-carbon steel being finer than low-carbon steel (0.075% C)). Dislocation density in ultra-low-carbon steel decreased steadily, whereas low-carbon steel exhibited an initial decline followed by an increase due to carbon-rich precipitate pinning. The yield ratio decreased with the annealing temperature, with optimal performance being at 700 °C for ultra-low-carbon steel (lowest resistivity: 13.75 μΩ/cm) and 800 °C for low-carbon steel (best conductivity: 14.66 μΩ/cm). Yield strength in ultra-low-carbon steel was dominated by grain and precipitation strengthening, while low-carbon steel relied more on precipitation and solid solution strengthening. Resistivity analysis confirmed that controlled precipitate size enhances conductivity. Full article

Straw as a building material alternative is in line with sustainable development goals. To make effective use of straw resources such as rice and corn stalks in rural areas, a kind of steel wire mesh-reinforced straw concrete sandwich panel (SCSP) was developed. The SCSP was composed of cold-drawn low-carbon steel-wire mesh (SWM), fine gravel concrete (FGC), and straw. The used type of FGC was shotcrete. A cold-drawn low-carbon SWM was arranged on the upper and lower sides of the SCSP, and a vertical wire tie was arranged between the upper and lower cold-drawn low-carbon SWMs. The FGC was sprayed on the SWM to make the SCSP layer work together. The loading process of the SCSP could be divided into three stages: elastic working state, cracking state, and failure state. The results of the four-point loading test show that the maximum flexural moment of the SCSP can be up to 7.5 kN·m in the elastic range. The ultimate bearing capacity of SCSP reaches 10.9 kN·m, and the maximum crack width can reach 3~4 mm. At the same time, based on the assumption of the flexural section of SCSP, two simplified calculation models of SCSP bearing capacity were established. The average error was 2.99% and 9.41%, respectively, by comparing the experimental values with the two calculated values. The results obtained by using the two models were in good agreement with the experimental results. Full article

The primary objective of this study is to explore how machine learning techniques can be incorporated into the analysis of material deformation. Neural network algorithms are applied to the study of mechanical properties of wire rods subjected to cold plastic deformations. Specifically, this study explores how pre-trained neural networks with appropriate architecture can be exploited to predict apparently distinct but internally related features. Tentative predictions are made by observing only an insignificant cropped fraction of the material’s profile. The neural network models are trained and calibrated using 6400 image fractions with a resolution of $120\times 90$ pixels. Different architectures are developed with a focus on two particular aspects. Firstly, different possible architectures are compared, particularly between multi-output and multi-label convolutional neural networks (CNNs). Moreover, a hybrid model is employed, essentially a conjunction of a CNN with a multi-layer perceptron (MLP). The neural network’s input constitutes combined numerical and visual data, and its architecture primarily consists of seven dense layers and eight convolutional layers. By proper calibration and fine-tuning, observed improvements over the standard CNN models are reflected by good training and test accuracies in order to predict the material’s mechanical properties, with efficiency demonstrated by the loss function’s rapid convergence. Secondly, the role of the pre-training process is investigated. The obtained CNN-MLP model can inherit the learning from a pre-trained multi-label CNN, initially developed for distinct features such as localization and number of passes. It is demonstrated that the pre-training effectively accelerates the learning process for the target feature. Therefore, it is concluded that appropriate architecture design and pre-training are essential for applying machine learning techniques to realistic problems. Full article

Metal inert gas (MIG) brazing was used to join galvanized thin sheets with thicknesses in the range of 0.8 to 2 mm in a lap joint configuration using CuAl₈ wire as filler. The process was used to manufacture built-up cold-formed steel beams composed of corrugated steel webs and flanges made from thin-walled cold-formed steel lipped channel profiles. The effect of heat input and sheet thickness on joint properties, such as macro- and microstructure, wettability, and mechanical characteristics such as microhardness and tensile strength were investigated. The bead geometry was assessed by studying the wettability of the filler material. The microstructure was investigated by digital and scanning electron microscopy, and the composition in the heat-affected zone (HAZ), interface, and bead was determined by energy dispersive spectroscopy. Formation of Fe–Al intermetallics was observed in the bead at the bead–base material interface. Some pores were noticed that formed due to the evaporation of the zinc coating. The bead shape and mechanical properties were found to be the best when 1.2 and 2 mm sheets were brazed using a heat input of 121.4 J/mm. This suggests that not only the heat input but also the thickness of the sheet metal play a crucial role in the production of MIG brazed joints. Full article

The development of microelectronics results in higher demand for copper microwires and thin foils. Higher demand requires conducting research to obtain knowledge on the influence of extreme plastic deformation on materials’ susceptibility to plastic processing without the loss of coherence. One of the key factors contributing to rupture during the plastic deformation of copper is the presence of micrometer-sized, eutectic Cu₂O oxides, which are weakly bound to the copper matrix. These oxides are formed during the metallurgical stage of wire rod copper manufacturing. Copper wire rod of the ETP (electrolytic tough pitch) grade was subjected to wire drawing followed by cold-rolling. Applying different states of stress during plastic deformation (wire drawing, cold-rolling, and upsetting) made it possible to specify the conditions required for Cu₂O oxides’ fragmentation due to the extreme total deformation. Qualitative and quantitative analyses of the Cu₂O oxides’ evolution and fragmentation as the plastic deformation progressed were the main focus of this paper. It was determined that major fragmentation occurred during the initial stages of plastic deformation. Applying further extreme deformation or changing the state of stress during plastic deformation did not facilitate the continuation of fragmentation. It was only their shape that was becoming elongated. Full article

This paper focuses on the study of the tensile fracture behaviour of prismatic notched specimens of cold drawn pearlitic steel, providing a macro- and micro-approach. Two types of notched samples with very different notch radius (sharp and blunt notches, PAA and PCC) and the same notch depth were studied, thereby allowing a study of the fracture behaviour under different levels of stress triaxiality (constraint) in the experimental specimen. The studied samples are machined from pearlitic steel wires taken from a real cold drawing chain, analysing the entire drawing process, from the initial base material (hot rolled bar; not cold drawn at all) to the final commercial product (prestressing steel wires; heavily cold drawn), including two intermediate stages in the manufacture chain. The aforesaid specimens were subjected to tensile fracture tests and analysed at macroscopic and microscopical level using the scanning electron microscope (SEM), thereby obtaining micrographs of the different areas appearing in the specimens under study and assembling full micro-fracture maps (MFMs) of the fractured area. The aim of the research is to analyse the macro- and microscopic changes produced by the variation in stress triaxiality state (constraint), along with the different fracture processes. The first relevant finding is the increase in fracture path deflection for higher drawing degrees, and for greater triaxiality levels associated with sharp notches. Another finding is the variation in area of the different fracture zones, i.e., outer crown (OC), fracture process zone (FPZ) and intermediate zone (Z_INT), which are characterised by their specific micro-mechanisms, micro-void coalescence (MVC), cleavage (C) and special (large) micro-void coalescence (MVC*). The higher the stress triaxiality level, the larger the area occupied by the Z_INT in the fracture process. The fracture behaviour tends to unify along with the degree of drawing, with less dependence on the state of triaxiality imposed on heavily drawn wires. Results have been obtained in which the increase in triaxiality, imposed by the smaller radius of curvature of the notch (sharp notch), as well as the greater degree of drawing of the wires, cause the fracture process to place the FPZ at the notch tip. It is demonstrated that the variation in stress triaxiality and the drawing degree can generate different locations of the fracture initiation zone (FPZ). Full article

The drawability and microstructural homogeneity of twinning-induced plasticity (TWIP) steel were improved during the wire drawing process by utilizing a temperature gradient along the wire’s radial direction. The surface temperature of the wire increased by applying heat to the die during the drawing process, thereby creating a temperature gradient across the wire during wire drawing. The drawability of the wire subjected to the temperature gradient with warm die (WD) increased by approximately 33% compared to that of conventional wire drawing with cold die (CD). The higher temperature of about 300 °C at the surface region of the wire with the WD suppressed the twinning rate at the surface region owing to the increase in the stacking fault energy (SFE) from 34 to 55 mJ/m², leading to a uniform twinning rate along the wire’s radial direction compared with the CD wire, finally resulting in the improvement of the homogeneity in the microstructure and mechanical properties of TWIP steel. As a result, the drawability of the TWIP steel improved. Therefore, the general conclusion was derived that controlling the SFE within the area of the workpiece by tailoring the temperature can improve the formability in TWIP steels during the plastic forming process. Full article

The thermal history of a part deposited via wire arc additive manufacturing (WAAM) and hence its as-built properties can vary significantly depending on the thermal management applied, especially for metallurgically complex materials. Thus, this work aimed to assess the feasibility of processing thin-walled Scalmalloy^® (Al-Mg-Sc-Zr) structures by WAAM while examining the effects of arc energy and heat dissipation on their response to direct age-hardening heat treatment (without solution annealing). As a complement, the geometry, porosity, and processing time of such parts were also analyzed. The walls were built via the cold metal transfer (CMT) deposition process with different arc energy levels in combination with near-immersion active cooling (NIAC) settings (as thermal management solution), as well as with natural cooling (NC), resulting overall in both low surface waviness and porosity levels. Based on hardness testing, the resultant Scalmalloy^® direct-aging response (relative increase in hardness after direct age-hardening from WAAM as-built state) depended more on the arc energy per unit length of deposit applied. In contrast, the other thermal management approaches (NIAC or NC) helped in maintaining Sc in a supersaturated solid solution during deposition. Thus, Scalmalloy^® strengthening was demonstrated as feasibly triggered by means of a post-WAAM direct age-hardening heat treatment solely. Additionally, in comparison with a thermally equivalent (same interpass temperature) condition based on NC, the NIAC technique allowed the achievement of such a positive result on direct-aging response with much shorter WAAM processing times, therefore improving productivity. Full article

This article presents the results of experimental studies on the dynamic and static strength of commercial aluminum alloy 5056 manufactured by wire-arc additive manufacturing (WAAM). The main objective is to evaluate the utilization potential of this technology for manufacturing parts for operation under shock loads. The dynamic tensile strength of the material was investigated with a modified Kolsky method, implemented by a split Hopkinson pressure bar. A comparative analysis of the strength characteristics of materials manufactured by WAAM and conventional cold-rolling methods was carried out using a structurally temporal approach with the incubation time criterion. The results showed that the aluminum alloy obtained by WAAM demonstrates comparable strength levels to that of cold-rolled material. The findings suggest that WAAM can be a competitive alternative for producing high-strength aluminum alloys for operation under shock loads. Full article

NiTi shape memory alloys (SMAs) are widely studied for their potential applications, and atomic layer deposition (ALD) is an effective technique for coating them due to its precise control over coating thickness. This study investigates the impact of Al₂O₃ coating on the fatigue behavior of cold-drawn NiTi wires with a 0.125 mm diameter. The wires were coated using atomic layer deposition (ALD) with 100 ALD cycles. Fatigue tests were conducted in tensile mode at room temperature, applying cyclic loading between 0–50, and 700 MPa (700 MPa is almost 40% of ultimate tensile strength). The results show that the cold-drawn NiTi wires failed after an average of 7500 tensile loading cycles, while the lifetime of the coated and stretched NiTi wires with a preload of 1.7–2.8 kg significantly improved, with an average of 293,000 cycles before failure. Full article

The present study was carried out using a cold-drawn wire of Ni_50.8Ti at.% subjected to post-deformation solution treatment at 700 °C for 1 h to obtain a fine-grained recrystallized structure. Subsequent aging was carried out at a temperature range of 300, 430, and 500 °C for 1, 10, and 20 h. The time–temperature aging mode strongly affects the aging-induced microstructure. Variation of the aging-induced microstructure (using various aging modes) permits precise tuning of the characteristic temperature of the martensitic transformations and their specific temperature ranges upon cooling and heating. The latent heat and hysteresis exhibit different evolution vs. aging durations; this finding remains fair when using different aging temperatures. The aging mode strongly affects the stress–temperature behavior: (i) a dramatical expansion of the temperature range of realization of the transformation yield stress (σ_tr); and (ii) the magnitude of σ_tr at a chosen test temperature is generally determined by the position of the M_s temperature. An additional contribution of competing factors is discussed. The efficiency of the aging temperature under isochronous aging is significantly higher than the efficiency of the aging time under isothermal aging. Aging at 430 °C for 10–20 h provides the highest resource for the recovery strain. The strain–temperature behavior strongly depends on the relative position of the R_s and M_s temperatures (onset of B2→R and R→B19′ transformations, respectively). The regularities obtained can be used to predict the set of functional and mechanical properties of titanium nickelide. Full article

This article conducts wire bonding tests and cold/hot-cycle tests using φ 0.025 mm Ag-Au alloy wires and Ag-Au-Pd alloy wires with different specifications. The results show that, due to the addition of the alloying element Pd, under the same bonding parameters, the fracture strength and ball-bonded point shear force of the Ag-Au-Pd alloy wires are significantly higher than those of the Ag-Au alloy wires. After the cold/hot-cycle tests, the failure probability of the Ag-Au-Pd alloy wires is approximately half that of the Ag-Au alloy wires. Among Ag-Au-Pd alloy wires, 92% break at the ideal positions, while 77% of the Ag-Au alloy wires break at the necks. As the Au content increases, the Free Air Ball (FAB) morphology of the Ag-Au-Pd alloy wires becomes more and more regular, gradually transitioning from a pointed ball to an ellipsoid and finally presenting a spherical shape. Full article