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In this study, we conducted an analysis and evaluation of the heat affected zone (HAZ), which serves as a measure of surface processing quality in laser machining of Carbon Fiber Reinforced Plastics (CFRP). Carbon fibers have two axes, horizontal or vertical, in the alignment direction of the fibers. When the optical energy of the laser is primarily conducted along the alignment direction of the carbon fibers and diffused into heat, the HAZ occurs on the surface of the CFRP, exhibiting anisotropic characteristics. In laser processing by pulse, the accumulation of residual heat energy within the carbon fibers induces evaporation and thermal deformation of the polymer at the carbon fiber boundaries, ultimately resulting in a permanent change in the properties of the CFRP, defined as the HAZ. To confirm the influence of process variables on HAZ formation in laser machining, ray tracing was applied to predict the thickness and length of the layer in which the laser beam is absorbed by the CFRP. Generally, it was confirmed that more than 90% of the laser beam is absorbed by three layers of fibers from the surface. Based on this, the temperature distribution of carbon fibers due to residual laser energy during laser machining was predicted. Through these results, the size of HAZ according to the arrangement direction of carbon fibers could be numerically predicted. Experimental results confirmed that process variables such as laser power density and scan speed affect the formation of HAZ. Additionally, the size of HAZ due to conduction along the arrangement direction of carbon fibers was experimentally verified, and quantitative comparison and analysis were conducted with numerical results from previous modeling. Through this analysis, it was possible to predict the size of HAZ affecting surface quality during laser machining of CFRP and validate optimized laser process variables. [ABSTRACT FROM AUTHOR]

The softening of the heat affected zone (HAZ) remains a significant challenge in fusion welding of novel Al–Mg–Si–Cu alloy, and the underlying mechanisms vary across different aging states. However, limited research has been conducted on this topic. Therefore, this study investigates the influence of various aging states on the microstructure and mechanical properties within the HAZ of welded joints by selecting extrusions treated with T4, T5, and T6 heat treatments. The results indicate that the increase in hardness of HAZ I is attributed to solid solution strengthening. In the HAZ I, the precipitated phases are mostly dissolved into the matrix under the influence of a peak temperature of 464.6 °C, and no residual precipitated phase is detected in T4 and T5 alloy joints, while some undissolved Q phase is observed in T6 alloy joint. The decrease in hardness of HAZ Ⅱ is attributed to the limited precipitation of coarse β'' and Q' phases for the T4 alloy welded joints, which weakens the solid solution strengthening. However, the softening mechanisms in the HAZ Ⅱ of the T5 and T6 alloy joints are ascribed to the dissolution of β'' and subsequent precipitation of Q' and Q phases. HAZ Ⅲ, close to the base metal, exhibits a lesser degree of influence and thus experiences a gradual recovery in hardness. This study can provide theoretical guidance for the exploration of high-strength, heat-resistant aluminum alloys.

The laser additive hybrid manufacturing technology, which combines the precision of Laser Powder Bed Fusion (LPBF) and the flexibility of Laser Directed Energy Deposition (LDED), provides an effective solution for efficient forming and remanufacturing of large, complex components. The bonding zone (BZ) between LPBF and LDED forming regions is crucial for the final component performance. This study utilized LDED to remanufacture annealed LPBF substrates and investigated the microstructure and mechanical properties of TA15 alloy remanufactured parts. Results shows that a gradient microstructure forms at the bonding zone (BZ), where the bottom region exhibits a mixed structure including transitional β phase (βt), lamellar α and secondary α phase (αs). The top region shows a ''ghost structure'' of fine needle-like α phases. The mechanical property matched the microstructure well, as the hardness in the upper BZ reaches up to 463 MPa, whereas the LFZ exhibits the lowest hardness at 401 MPa. As the angle between the LDED region edge and tensile direction increases, the tensile strength first increases and then stabilizes, while elongation increases initially and then decreases. At a tilt angle of 60°, the strength peaks at 1098 MPa; at a 30° angle, the elongation reaches a maximum of 10.336%. All samples fracture at the LPBF zone, indicating that the formation of fine lamellar α phases in the BZ contributes to its higher strength compared to LPBF substrate and LDED deposition zones.

Carbon fiber reinforced polymer (CFRP) composed of carbon fiber and polymer matrix has been used in extensive applications due to its light weight and superior strength. However, the distinct difference in physicochemical properties between two constituents poses a significant challenge for laser homogeneous processing of heterogeneous CFRP. Herein, an aluminum/polyimide laminate is introduced onto CFRP as an assisting layer during femtosecond laser processing, which prevents CFRP from direct energy deposition of low-energy edge of the Gaussian laser. Moreover, a synergetic mechanism of horizontal heat conduction of aluminum foil and vertical heat insulation of polyimide film is proposed and confirmed through temperature measurements and simulation calculations. The heat is dissipated through the aluminum foil and obstructed by the polyimide film, alleviating the detrimental heat transfer and accumulation on CFRP. Therefore, it significantly inhibits thermal damage and entrance size expansion. Compared with traditional femtosecond laser direct processing, the maximum reduction ratio of HAZ and taper are up to 98% and 83%, respectively. High-quality CFRP homogeneous processing with an ultra-low HAZ (0.7 μm), minimal taper (0.07°) and intact smooth sidewalls can be achieved. The method shows great potential to dramatically improve processing quality and broaden applications of heterogeneous composites.

The sensitization behavior of the welding heat affected zone (HAZ) in austenitic stainless steels (SSs) was investigated through simulated thermal cycles emulating actual multi-pass welding processes using the Gleeble simulator. The tests were performed with austenitic SSs, considering carbon contents, heat input, and distance from the fusion line to determine the thermal cycle conditions of the HAZ. Higher carbon content led to increased sensitization (degree of sensitization, DOS) values, while the influence of the thermal cycle in the final weld pass was that even though it was rapidly heated to over 1000 °C and cooled at a rapid rate, the DOS value decreased due to partial carbide dissolution and chromium diffusion. Therefore, effective management of the final thermal cycle in the HAZ contributes to improved intergranular stress corrosion cracking resistance. Even with prolonged exposure of the HAZ to the sensitization region, the discovery that corrosion resistance improves when the final heating cycle reaches 1000 °C underscores the importance of HAZ heat cycle management and provides valuable insights for materials engineering and industrial applications. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to determine the performance of a commercial corrosion inhibitor (mixture of ethanediol, 2-butoxy ethanol, and fatty acid amine) in inhibiting weldment corrosion. The inhibitor's effect on parent metals (PM), heat affected zone (HAZ), and weld metal (WM) has been investigated on the corrosion behaviour of X65-welded structures in brine solution (10 m/s) using submerged jet impingement (SJI) flow loops. The results show that inhibitors can reduce the corrosion rate by 10 times to 0.36 mm/y for WM. Linear polarization resistance and electrochemical impedance spectroscopy (EIS) show that the WM exhibited the highest corrosion rate.

After 5 a of service, severe cracking occurred at the T-type weld seam between the tube sheet and shell of a low-pressure heater in a certain power plant. The causes of the weld cracking were analyzed by macroscopic inspection, fracture morphology analysis, metallographic structure analysis, energy-dispersive spectroscopy(EDS), chemical composition analysis and hardness testing. Results showed that due to the existence of a hardened martensite structure in the heat-affected zone(HAZ) of the welding, which was sensitive to alkali stress corrosion cracking, and the lack of stress reduction heat treatment of the welded joint, alkali embrittlement occurred in the welding heat affected zone of tube plate, and crack branches propagated and penetrated through the weld, causing equipment failure. The analysis of the failure causes of T-type welded joints is of great significance for the design, manufacture, operation of heat exchangers in similar situations under the same working conditions.

The high heat input welding (HHIW) can greatly enhance the welding efficiency of the steel plates. However, coarse grains and brittle microstructures will be formed in the heat‐affected zone (HAZ) during the HHIW process, which deteriorates the toughness of HAZ. In the present study, the effect of the Ti/N ratio on the size and distribution of titanium nitride (TiN) particles, microstructures, and toughness of HAZ after HHIW of 400 kJ cm−1 is investigated for the Ca‐treated steels with different Ti/N ratios of 1.61, 3.79, and 5.00 for TN16, TN38, and TN50 steels. The TN38 steel has the highest number density of the TiN particles with the sizes between 20 and 25 nm and the highest pinning force of the particles in three steels, resulting the smallest grain sizes in its HAZ. In addition, in three steels, the TN38 steel has the main microstructure of intragranular aciculate ferrites with the highest high‐angle grain boundaries density in its HAZ, thereby obtaining the highest value of low‐temperature impact toughness of the HAZ. [ABSTRACT FROM AUTHOR]

In this paper, a nanosecond laser was used to etch the surface of graphene nanoplatelets reinforced ZK60 (GNPs/ZK60) matrix composites, and the effects of different scanning speeds, pulse repetition frequency and laser power on the etched morphology of the machined surface were investigated. The experimental results show that the etched groove width and heat affected zone width of GNPs/ZK60 composites are significantly increased compared with ZK60 material due to the influence of graphene, and the growth rate of the difference in heat affected zone width between GNPs/ZK60 composites and ZK60 materials is most significantly affected by the pulse repetition frequency. In addition, the dross height increases with the increase of laser power, while the scaly dross structure becomes increasingly clear. [ABSTRACT FROM AUTHOR]

This research investigates the surface properties of 316L stainless steel machined by combining two wire electro manufacturing processes on a single machining platform, i.e., wire EDM roughing and wire ECM finishing. While the former is well known in industry, the latter has not yet seen much industrial use but can improve the surface integrity since it does not generate heat to achieve material removal, avoiding several EDM (semi)finishing passes at reduced sparking energies. With applications in the medical, energy, and aerospace fields, this research focuses on characterizing the machined surfaces with respect to the surface defects and the chemical composition. The studied surface properties include the (sub)surface morphology with respect to micro cracks and heat related damage introduced by wire EDM, and the mechanism of their removal by wire ECM finishing. The chemical composition of the surface is furthermore evaluated to characterize the contamination of the workpiece material by the tool electrode material. The manufactured samples are studied using a profilometer to quantify material removal and the resulting roughness. Metallographic analysis is carried out by optical microscopy and SEM with EDX. Initial results show an average surface roughness below 0.1 µm Ra by applying a wire ECM finishing pass after wire EDM. [ABSTRACT FROM AUTHOR]

Considerable scientific effort has been devoted to comprehending welding processes and establishing correlations between structure and properties in crystalline metals and alloys' welded joints. However, welding of bulk-metallic glasses (BMGs) presents unique challenges. The weldability of these glasses is complex due to their lack of long-range order and high propensity to crystallization. BMGs are joined through either supercooled-liquid-phase or liquid-phase welding techniques. To maintain the integrity of the glassy structure, it is imperative to meticulously control the welding temperature and duration during supercooled-liquid-phase welding to prevent crystallization or ensure a sufficiently rapid cooling rate in liquid-phase welding to suppress solidification. In most cases, the presence of crystalline phases adversely affects the mechanical and physical properties of the joints. This review article describes and critically analyzes the key aspects influencing BMG welding and the correlations between the welding conditions and BMG joint properties. The fundamental knowledge to understand the welding of BMGs is presented, and the many welding methods used are discussed. The review also offers recommendations for various opportunities and new directions for advancing the field of BMG welding. [ABSTRACT FROM AUTHOR]

During the major overhaul of a chemical plant, the pipelines were disassembled and cleaned. Upon reinstallation, an air-tightness test discovered that the flange of the tandem mixer had cracked at the 304 stainless steel (SS) welding joint, affecting normal production. In the present paper, the microstructure of the weld joint was analyzed using SEM equipped with an EDS detector, to explore the corresponding cracking mechanism. The results show that the cracks start on the inner surface of the flange and extend outside. The microstructure in the welding heat affected zone (HAZ) is coarse and carbides are occurring at the grain boundaries, which reduces the strength. The precipitation of carbides at grain boundaries also reduced the Cr content in the crystal, resulting in a decrease in the corrosion resistance of the passivation film on 304 SS. The HAZ showed lower elongation compared to the 304 SS substrate and the fused zone. Under the combined action of stress and corrosive media, the HAZ undergoes stress corrosion cracking. [ABSTRACT FROM AUTHOR]

The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite (IAF) using micron-sized inclusions and restricting the growth of prior austenite grains (PAGs) by nanosized particles during welding. The chaotically oriented IAF and refined PAGs inhibit crack initiation and propagation in the steel, resulting in high impact toughness. This work summarizes the combined effect of deoxidizers and alloying elements, with the aim to provide a new perspective for the research and practice related to improving the impact toughness of the heat affected zone (HAZ) during the high heat input welding. Ti complex deoxidation with other strong deoxidants, such as Mg, Ca, Zr, and rare earth metals (REMs), can improve the toughness of the heat-affected zone (HAZ) by refining PAGs or increasing IAF contents. However, it is difficult to identify the specific phase responsible for IAF nucleation because effective inclusions formed by complex deoxidation are usually multiphase. Increasing alloying elements, such as C, Si, Al, Nb, or Cr, contents can impair HAZ toughness. A high C content typically increases the number of coarse carbides and decreases the potency of IAF formation. Si, Cr, or Al addition leads to the formation of undesirable microstructures. Nb reduces the high-temperature stability of the precipitates. Mo, V, and B can enhance HAZ toughness. Mo-containing precipitates present good thermal stability. VN or V(C,N) is effective in promoting IAF nucleation due to its good coherent crystallographic relationship with ferrite. The formation of the B-depleted zone around the inclusion promotes IAF formation. The interactions between alloying elements are complex, and the effect of adding different alloying elements remains to be evaluated. In the future, the interactions between various alloying elements and their effects on oxide metallurgy, as well as the calculation of the nucleation effects of effective inclusions using first principles calculations will become the focus of oxide metallurgy. [ABSTRACT FROM AUTHOR]

P91 and P92 steels are widely used in nuclear and thermal power plant's high-temperature (650–700 °C) operating components. The welding procedure, base plate composition, filler material composition, and post-weld heat treatment (PWHT) significantly affect the metallurgical characterization of weldments at room temperature. This work focuses on joining P91 and P92 steel by the TIG welding with filler ER90S-B9. The study analyzes the materialization of coarse-grained HAZ (CGHAZ), inter-critical HAZ (ICHAZ), and fine grained HAZ (FGHAZ) under welded and PWHT. PWHT was conducted at 840 °C for 2, 4 and 6h. An optical microscopic (OM) scanning electron microscope (SEM) was employed to characterize the welded and PWHT samples. It was perceived that the tensile strength of PWHT increased as the heat treatment times increased from 2 to 6 h, while the hardness value decreased accordingly. The maximum tensile strength (594.71 MPa) was observed in PWHT_6 h, while the minimum tensile strength (537.52 MPa) was perceived in the as-welded sample. The PWHT_6h reveals the minimum hardness values (271.12 HV) at the fusion zone among all the conditions. The WFZ consisted of an untampered lath martensitic grain structure, demonstrating an average hardness value of 314.15 HV in the PWHT_2h condition. The hardness value in CGHAZ samples for as-welded, PWHT_2h, PWHT_4h, and PWHT_6h was observed at 456.85, 436.81, 368.63, and 327.41 HV, respectively. [ABSTRACT FROM AUTHOR]

The implementation of hard-facing alloy on the existing materials caters the need for high-performance surfaces in terms of wear and high temperatures. The present research explore the effect of Plasma Transferred Arc Welding (PTAW) parameters and powder composition on dilution, microstructure and hardness of the commonly used hard-facing alloy Ni–Cr–Si–B powder. The hard-facing alloy was deposited with three weight proportions of boron (2.5 %, 3 % and 3.5 %). The statistical-based Grey Relational Analysis (GRA) followed by a Machine Learning Algorithm (MLA) was implemented to identify the ideal parameters and degree of significance of each parameter and for the prediction of the responses. The dilution percentage, microstructure analysis, and phase detection were estimated through elemental analysis, Scanning electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD) respectively. The experimental and modelling results revealed that 400 mm/min of scanning speed, 8 gm/min of powder delivery, 14 mm of stand-off distance, and 120 A of current were the optimal parameters along with 3.5 wt% of boron powder composition to yield a better dilution, microstructure and hardness.

Bulk metallic glasses (BMGs) offer exceptional physical/mechanical properties enabling them to be highly desirable for a variety of applications. Laser powder bed fusion (LPBF) has great promise for producing large and intricate BMG structures. However, using non‐optimal energy distribution in current additive manufacturing machines leads to extensive reheating of previously solidified layers. As a result, the mechanical characteristics can be significantly impacted by structural relaxation and partial crystallization. Here, a tunable advanced laser beam shaping technology is employed to overcome the difficulties originating from non‐optimal energy distribution in current additive manufacturing machines. This study fabricates fully amorphous/dense BMG samples using the shaped laser beam and established optimized atomic‐scale short‐and medium‐range ordering along with improved yield/fracture compressive strength. Formation of a shallow and wide melting pool geometry using the beam shaping allows to increase hatching distances to better control the thermal history introducing improved amorphicity and rejuvenation. This higher rejuvenation and disordering allow for increased atomic mobility, which facilitates the creation and spread of shear bands, thus enhancing the mechanical strength and ductility of the material. The current work demonstrates that BMG parts can be fabricated using flexible beam‐shaping technology allowing to go beyond the capabilities of state‐of‐the‐art additive manufacturing techniques. [ABSTRACT FROM AUTHOR]

In recent years, demand for high-tensile strength steel sheets has been increasing from the viewpoints of energy conservation through weight reduction and the upgrading of product functions. However, since such high tensile strength steel sheets contain martensite, it has been reported that material strength is greatly reduced in the Heat Affected Zone (HAZ) due to tempering during laser welding. In other words, when laser welding is applied to high-strength materials, there is a possibility that rupture will be apparent in the HAZ softened zone. In this study, we evaluate the strength of a 1500 MPa steel sheet, which is subject to HAZ softening, by applying tension in any direction to the laser weld line and rupturing it. The results show that a welding angle of 20 ° significantly improves elongation and strength. If it is possible to minimize the strength loss due to HAZ softening by using these results, the welding portion of high-strength materials can be located where tensile deformation occurs during forming or collision, thereby increasing design flexibility. [ABSTRACT FROM AUTHOR]

The Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors, including the shipbuilding, automotive and aeronautics industries, as it expects to contribute to significant cost reduction associated with the production of high-quality welds. To comprehend the behavior of welded structures in regard to their damage tolerance, the application of fracture mechanics serves as the instrumental tool. However, the methods employed overlook the changes in the microstructure within the Heat-Affected Zone (HAZ), which leads to the degradation of the mechanical properties of the material. The purpose of this study is to simulate microhardness evolution in the HAZ of AA2198-T351 LBW. The material represents the latest generation of Al-Cu-Li alloys, which exhibit improved mechanical properties, enhanced damage tolerance behavior, lower density and better corrosion and fatigue crack growth resistance than conventional Al-Cu alloys. In this work, the microhardness profile of LBW AA2198 was measured, and subsequently, through isothermal heat treatments on samples, the microhardness values of the HAZ were replicated. The conditions of the heat treatments (T, t) were selected in line with the thermal cycles that each area of the HAZ experienced during welding. ThermoCalc and DICTRA were employed in order to identify the strengthening precipitates and their evolution (dissolution and coarsening) during the weld thermal cycle. The microstructure of the heat-treated samples was studied employing LOM and TEM, and the strengthening precipitates and their characteristics (volume fraction and size) were defined and correlated to the calculations and the experimental conditions employed during welding. The main conclusion of this study is that it is feasible to imitate the microstructure evolution within the HAZ through the implementation of isothermal heat treatments. This implies that it is possible to fabricate samples for fatigue crack growth tests, enabling the experimental examination of the damage tolerance behavior in welded structures. [ABSTRACT FROM AUTHOR]

Q690 steel is widely used as building steel due to its excellent performance. In this paper, the microstructure evolution of the heat-affected zone of Q690 steel under simulated high heat input welding conditions was investigated. The results show that under the heat input of 150–300 kJ/cm, the microstructures of the heat-affected zone are lath bainite and granular bainite. The content of lath bainite gradually decreased with the increase in heat input, while the content of granular bainite steadily increased. The proportion of large-angle grain boundaries decreased from 51.1% to 40.3%. Overall, the average size of original austenite increased, and the precipitates changed from Ti (C, N) to Cr carbides. During the cooling process, the nucleation position of bainitic ferrite was from high to low according to the nucleation temperature, and in order of inclusions at grain boundaries, triple junctions, intragranular inclusions, bainitic ferrite/austenite phase boundaries, twin boundaries, grain boundaries, and intragranular inclusions at the bainitic ferrite/austenite phase interface. The growth rate of bainitic ferrite nucleated at the phase interface, grain boundary, and other plane defects was faster, while it was slow at the inclusions. Moreover, it was noted that the Mg-Al-Ti-O composite inclusions promote the nucleation of lath bainitic ferrite, while the Al-Ca-O inclusions do not facilitate the nucleation of bainitic ferrite. [ABSTRACT FROM AUTHOR]

Glass-filled composites are used for overmolding of electrical components due to their good electrical isolation properties. Laser cutting is a preferred technology to remove excess mold material to achieve a low surface roughness and reduce tool wear. Hatching strategies improve the laser-cutting process of carbon fiber-reinforced polymers toward lower cutting times and a more homogeneous cut surface. The impact of hatching strategies on epoxy mold compounds has been so far unknown as the laser-cutting strategy was based on multiple single passes in previous studies. This work investigates the effects of hatching strategies such as perpendicular hatching, parallel hatching, and a single line, including the influence of material thickness and filler content regarding the cutting time, kerf taper angle, and heat-affected zone, using a 50 W short-pulsed fiber laser for different highly filled epoxy mold compounds. Results show that the use of a hatching strategy is required to cut workpieces at thicknesses of 4 mm or higher due to the sieving size of the filler. Perpendicular hatching needs to be chosen when the aim is a minimal cutting time. The kerf taper angle at the top of the cut is below 4° while hatching leads to a more pronounced kink of up to 25° occurring toward the bottom of the cut. Meanwhile, an increase in filler concentration leads to an increase in cutting time, because of higher thermal conduction, while no effect on the kerf taper angle or the heat-affected zone can be identified. [ABSTRACT FROM AUTHOR]

In this study, using flux cored wire, S235JR and S460MC structural steels with a thickness of 16 mm were joined by MAG welding method. Welding processes were carried out to join the same (S235JR-S235JR, S460MC-S460MC) and different types of materials (S235JR-S460MC). In the microstructure examinations, grain coarsening occurred in all conditions, from the base material to the weld metal. From the tensile test results, in all combinations, fracture occurred on the S235JR side. Since fractures are not from the weld zone (weld nugget and HAZ), the weld zone strengths are clearly understood to be higher than the main material tensile strengths. On microhardness tests, the highest microhardness was obtained from the welded metal in all combinations, followed by HAZ and base material. Also, the highest microhardness measured on dissimilar joints of S235JR-S460MC on weld metal was 269 HV (Vickers). The welded specimens were also subjected to fatigue tests; the failure occurred on the base material in all three joints. S460MC-S460MC joint had the highest fatigue strength at the most elevated stress, 625 MPa; however, S235JR-S235JR joint had the lowest fatigue strength at the lowest priority, 300 MPa. Although the fatigue strength results of the same and different combinations and the tensile test results have parallelism, the highest microhardness is seen in S460MC-S235JR dissimilar joints, and its fatigue strength is lower than S460MC-S460MC joints. [ABSTRACT FROM AUTHOR]

This review paper discusses the recent research work carried out in the frictional joining of dissimilar and similar alloys through the friction welding (FW) process with various parameters and modifications. It includes further the latest developments and advances in the research on FW and the influences of FW’s process parameters on the quality of joints and their properties. The specimens’ faying surfaces can also influence the joint properties as the surface modifications stimulate or change the metal joints’ bonding according to the welding parameters selected during FW. Though the rise of friction pressure (FP) during FW improves the strength of the joints, the improper selection of parameters leads to metal damage. It feels better if the axial shortening is less than 30 mm for FW of soft metals. The axial shortening values are less than 25 mm for the hemispherical bowl-type faying surfaces under 18 bar FP and it is noted that the bevel-type tapered faying surfaces increase the shortening. FW provided very narrow weld interfaces with around 5-10 µm width. With a low FP, it was possible to obtain a maximum of 100 % efficiency by modifying their faying surfaces. The small-diameter soft material needs less FP and friction time. The microstructure modification is possible and the weld joint is shown as U and V shapes for the bowl and tapered faying surfaces. It further increases the contact area and thus increases strength.

High hardness and wear resistance of bucket tooth are required in the face of abrasion and impact. High manganese steel is hard and ductile, making it more suitable for bucket tooth materials. Bucket tooth can wear out and need to be returned to their original size, so that bucket tooth that have been eroded must be coated with a hard material, using a hard facing process. In this study, the hard facing process was carried out in bucket tooth containing 10.4%, 11.60%, 12.70%, 13.60%, and 14.60% men (manganese) elements, using hard facing electrodes of the AWS A5.13 (JIS Z 3251). Hard facing process was using SMAW welding with an average heat input of 1087.43 J/mm. The hard facing process shown that the hardness of weld metal was always lower than of HAZ (Heat Affected Zone) and base metal. The hardness of the weld metal was almost the same for all types of bucket tooth, which was about 233.478 HVN.

A novel PID-type fuzzy logic controller (FLC) with an online fuzzy tuner was created to maintain stable in situ control of the cutting front temperature, aiming to enhance the laser process for thin non-oriented electrical steel sheets. In the developed controller, the output scaling factors and the universe of discourse were initially optimized using a hybrid of the particle swarm optimization and grey wolf optimization methods. The optimal parameters obtained were utilized in experiments involving the laser cutting of thin non-oriented electrical steel sheets, compared to an open-loop control system maintaining a constant cutting speed. The PID-type FLC with an online fuzzy tuner demonstrated a superior cutting quality, generating a smaller roundness and a reduced heat-affected zone (HAZ) through the in situ tuning of control parameters. Particularly, the HAZ width was significantly smaller than that reported in a previous study which used fuzzy gain scheduling for temperature control. Moreover, the cutting time was diminished by optimally adjusting the cutting speed using PID-type FLC with an online fuzzy tuner. Therefore, the accumulated heat in the steel sheet, particularly under high laser pulse frequencies, was effectively reduced, making it suitable for industrial applications. [ABSTRACT FROM AUTHOR]

A hybrid technique called spark assisted chemical engraving (SACE), also known as electro chemical discharge machining (ECDM) or electrochemical anode machining (ECAM), is used to efficiently and affordably miniaturise parts made of various non-conducting materials. In the micro-machining of these materials, ECDM has a wide range of applications in the nuclear, automotive, medical, etc. industries. ECAM is a hybrid method that combines the ability to remove material from electrochemical machining (ECM) and electro discharge machining (EDM) (EDM). The analysis of the material loss rate using finite element models is not widely studied (MRR). Testing is done to verify the FEA model and evaluate it against earlier research. The MRR was found to be 16.66% greater when simulated and contrasted to previous research results. It was also observed that existing experimental results error is larger in magnitude by 16.66% than experimental results error by 4.16% spark region is 400 microns by high speed camera. Furthermore, the temperature distribution has also analyzed. [ABSTRACT FROM AUTHOR]

Laser cutting of carbon fibre-reinforced plastics (CFRP) is a promising alternative to traditional manufacturing methods due to its non-contact nature and high automation potential. To establish the process for an industrial application, it is necessary to predict the temperature fields arising as a result of the laser energy input. Elevated temperatures during the cutting process can lead to damage in the composite's matrix material, resulting in local changes in the structural properties and reduced material strength. To address this, a three-dimensional finite element model is developed to predict the temporal and spatial temperature evolution during laser cutting. Experimental values are compared with simulated temperatures, and the cutting kerf geometry is examined. Experiments are conducted at 45° and 90° cutting angles relative to the main fibre orientation using a 1.1 mm thick epoxy-based laminate. The simulation accurately captures the overall temperature field expansion caused by multiple laser beam passes over the workpiece. The influence of fibre orientation is evident, with deviations in specific temperature data indicating differences between the estimated and real material properties. The model tends to overestimate the ablation rate in the kerf geometry, attributed to mesh resolution limitations. Within the parameters investigated, hardly any expansion of a heat affected zone (HAZ) is visible, which is confirmed by the simulation results. [ABSTRACT FROM AUTHOR]

The paper investigates the mechanical properties of the heat affected zone (HAZ) material near welds and compares the properties to those of the base metal and weld materials. A dedicated experimental set‐up was designed and manufactured to test miniature specimens with a cross‐section width in the range of 1 mm to 2.5 mm and a parallel gauge length of less than 10 mm. To identify the HAZ of the welded connections, a macro‐etching technique was adopted, and the shape and size of the HAZ were measured. Afterwards, miniature specimens were extracted from the base metal, weld and HAZ in both the longitudinal and transverse directions of the weld, and subsequently tested in the specialised experimental set‐up. The miniature specimens not only included the normal rectangular plate‐type specimen, but also the notched round bar and grooved plane strain types of specimens. Hence, the stress‐strain curve and fracture strains under various stress states were obtained from the tests. The validity of the Lode angle Modified Void Growth Model (LMVGM) was investigated using the experimental data, and the fracture loci of the base metal, weld and HAZ in both the longitudinal and transverse directions were identified. [ABSTRACT FROM AUTHOR]

Aluminium provides many advantages as a construction material in civil engineering, such as for example light weight, functionality by extruded profiles and corrosion resistance. It is obvious to use these advantages also for trusses. However, most aluminium alloys develop zones of weakening due to welding. The so called heat affected zones (HAZ) reduce the load‐bearing capacity of welded aluminium joints by up to 50%. Consequently, the design and execution of welded X‐joints within lattice girders are challenging. Indeed, the design of welded aluminium X‐joints is not specifically treated in EN 1999. Until now, the calculation of aluminium welded X‐joints relies on the steel standard EN 1993‐1‐8, which does not take into account the characteristic of aluminium. This results in errors and inefficient design. Thus, in this experimental research project the behavior of welded X‐joints in real‐scale models is explored. To this purpose, tests have been carried out on lattice girders made from aluminium alloy EN AW 6082 T6. In total, six girders with varying coefficient β and shape of the hollow section of brace members have been investigated. Thereby, the girders were loaded vertically until the failure of the X‐joints. Strains at the brace and chord members were measured by strain gauges and respective stresses were derived. In addition, a comparative analysis between experimentally and theoretically ‐ based on Eurocodes (EN 1993 part 1‐8 and EN 1999 part 1‐1) ‐ obtained results has been made. The analysis shows that the reduction of the load‐bearing capacity of welded aluminium X‐joints due to the HAZ is not constant but varies with the value of coefficient β and the shape of the cross‐section of the brace member. Obviously, the design of welded aluminium X‐joints based on EN 1993‐1‐8 applying a constant value for the HAZ does not reflect the true behavior of these joints as it leads to a quite conservative design approach. [ABSTRACT FROM AUTHOR]

The effect of cold deformation and annealing temperature on the microstructure evolution and mechanical properties is shown in this research together with a unique short strategy for manufacturing lean duplex stainless steel bars. Furthermore, the effects of post-weld heat treatment (PWHT) and cooling treatments on the microstructure and mechanical properties of LDX 2101 bars are being investigated. The results demonstrate that the austenite produces a large number of deformation twins and strain-induced martensite (SIM) as cold deformation increases, and the SIM and austenite follow the traditional K–S and N–W orientation relationships. The best mechanical properties overall are achieved in LDX 2101 bars that have been annealed at 1020 °C. Moreover, short-time PWHT improves the austenite proportion in the heat-affected zone and weld metal, and PWHT can greatly enhance the overall mechanical properties of the welded joints. Additionally, the optimal heat treatment temperature of the welded joints is 1050–1080 ℃. Furthermore, compared to those treated with air cooling, the mechanical properties of the welded joints treated with water quenching following flash butt welding are superior. As a result, it is recommended that following flash butt welding, the welded joints are given a water-quenching treatment. [ABSTRACT FROM AUTHOR]

Fatigue crack growth rates (FCGR) of multiple X100 pipeline steel welds and heat affected zones were measured in high-pressure hydrogen gas to investigate their behavior compared to lower strength pipeline welds. A total of five high strength welds and two heat affected zones (HAZ) were examined all of which were fabricated using the same X100 base material. Different welding wires and techniques were used to fabricate the welds to provide a variety of end products to evaluate susceptibility to fatigue in high pressure hydrogen gas. Residual stresses were measured for each weld and HAZ using the slitting method and the effect of residual stress on the stress intensity factor, Kres, was determined. Using Kres, the fatigue crack growth rate curves were corrected to remove the effects of residual stress by examining the influence of Kres on stress ratio, R. Comparisons were then made between the high strength welds, which were corrected for residual stress, and lower strength welds from the literature. It was found that the higher strength welds and heat affected zones exhibited comparable fatigue crack growth rates to lower strength welds, as the FCGR data of the high strength welds overlaid the lower strength welds. This suggests that despite distinct differences in strength and microstructure between the different welds, hydrogen-assisted fatigue crack growth susceptibility is similar. A comparison was made between the Kres measured in extracted coupons and residual stress estimates provided in relevant welded pipe assessment standards such as API 579-1/ASME FFS-1. It was found the residual stress values in the test coupons extracted from welded pipe were significantly lower than those expected in the intact welded pipes and highlights the importance in quantifying and removing coupon residual stresses when fatigue crack growth rates are measured and including expected weld joint residual stress when making structural assessments.

Fatigue crack growth rates (FCGR) of multiple X100 pipeline steel welds and heat affected zones were measured in high-pressure hydrogen gas to investigate their behavior compared to lower strength pipeline welds. A total of five high strength welds and two heat affected zones (HAZ) were examined all of which were fabricated using the same X100 base material. Different welding wires and techniques were used to fabricate the welds to provide a variety of end products to evaluate susceptibility to fatigue in high pressure hydrogen gas. Residual stresses were measured for each weld and HAZ using the slitting method and the effect of residual stress on the stress intensity factor, Kres, was determined. Using Kres, the fatigue crack growth rate curves were corrected to remove the effects of residual stress by examining the influence of Kres on stress ratio, R. Comparisons were then made between the high strength welds, which were corrected for residual stress, and lower strength welds from the literature. It was found that the higher strength welds and heat affected zones exhibited comparable fatigue crack growth rates to lower strength welds, as the FCGR data of the high strength welds overlaid the lower strength welds. This suggests that despite distinct differences in strength and microstructure between the different welds, hydrogen-assisted fatigue crack growth susceptibility is similar. A comparison was made between the Kres measured in extracted coupons and residual stress estimates provided in relevant welded pipe assessment standards such as API 579-1/ASME FFS-1. It was found the residual stress values in the test coupons extracted from welded pipe were significantly lower than those expected in the intact welded pipes and highlights the importance in quantifying and removing coupon residual stresses when fatigue crack growth rates are measured and including expected weld joint residual stress when making structural assessments.

The continuous cooling transformation (CCT) diagram of steels is very important in considering the phase transformation depending on the cooling rate of a material; however, it is difficult to obtain the diagram for each steel because of much experimental effort required. Therefore, it is important to establish a technique to predict the CCT diagram with good accuracy under arbitrary conditions such as composition and cooling rate. We have developed a prediction model of a CCT diagram for the weld heat affected zone (HAZ) using machine learning based on existing experimental data. The prediction accuracy was improved by separately considering critical cooling rate and temperature at which the transformation starts at various cooling rates, and by using double cross-validation (DCV) to effectively use a small amount of data.

The article presents the findings of a study on the machining of 10 mm thick Hardox 400 steel plates using the CO2 laser. The purpose of the investigation was to investigate the relationship between the entropy and the hardness of machined surfaces. For this purpose, a new mathematical model is established to estimate the entropy, and its influence on the hardness is determined. The mathematical model is statistically and experimentally validated. An entropy variation ΔS = −330 mJ/K between 2 K is found, causing a decrease in hardness compared to the standard value. The influences of input parameters (laser power, cutting speed, and auxiliary gas pressure) on hardness are determined. It is demonstrated that the surface hardness is strongly influenced by the auxiliary gas pressure. The combination of laser power P = 4200 W with gas pressure p = 0.45 bar at average cutting speed v = 1400 mm/min leads to a hardness of 38 HRC, extending the life and wear resistance of the cut parts. [ABSTRACT FROM AUTHOR]

In this study, the microstructure and performance of newly designed dual-phase steel (DP590) after joining by flash butt welding (FBW) for vehicle wheel rims was analysed and compared by two simulations, i.e., physical simulation and numerical simulation, due to the high acceptance of these two methodologies. Physical simulation is regarded as a thermal–mechanical solution conducted by the Gleeble 3500 simulator and which can distribute the heat-affected zone (HAZ) of the obtained weld joint into four typical HAZs. These are coarse-grained HAZ, fine-grained HAZ, inter-critical HAZ and sub-critical HAZ. A combination of ferrite and tempered martensite leads to the softening behaviour at the sub-critical HAZ of DP590, which is verified to be the weakest area, and influences the final performance due to ~9% reduction of hardness and tensile strength. The numerical simulation, relying on finite element method (FEM) analysis, can distinguish the temperature distribution, which helps us to understand the relationship between the temperature distribution and real microstructure/performance. Based on this study, the combination of physical and numerical simulations can be used to optimise the flash butt welding parameters (flash and butt processes) from the points of temperature distribution (varied areas), microstructure and performance, which are guidelines for the investigation of flash butt welding for innovative materials. [ABSTRACT FROM AUTHOR]