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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 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.)

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]

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]

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]

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]

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]

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]

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]

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 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]

This study was carried out in order to fill the gap in the literature and to increase the usability of welded joints as electrical connectors. For this purpose, shielded electrode metal arc welding and gas metal arc welding methods, which are frequently used in the industry, were used. In addition to mechanical tests such as microstructure, tensile and hardness of the joints made at different heat inputs, electrical conductivity tests were also performed and the results were evaluated together. According to the results obtained, electrical conductivity is lower in arc welding joint with shielded electrode, in other words, the weld metal has reduced conductivity. In the gas arc welding, the electrical conductivity five times more than in the electrode welding. In MAG welding, at the highest heat input 0.78 kJ/mm, 186.33 HV hardness was measured, while 191.33 HV hardness was measured at 0.60 kJ/mm, the lowest heat input. While 386.5 MPa tensile strength was obtained at 0.78 kJ/mm, 377 MPa tensile strength was measured at 0.60 kJ/mm heat input. In SMAW, 163 HV hardness was obtained at the highest heat input as 1.47 kJ/mm, while the tensile strength of the weld metal was measured as 343.5 MPa and the electrical resistance was measured as 21.5 Ohm. The electrical resistance was measured as 11.86 Ohm, with a 384 MPa tensile strength and a 174 HV hardness at the lowest heat input 1.17 kJ/mm. It was determined that as the weld metal hardness increased, the electrical conductivity decreased. The relation between the test findings and their interpretation are detailed in the study. [ABSTRACT FROM AUTHOR]

Welding is one of the major assembly processes employed in most common aeronautical applications. However, the consequences of the thermal cycle might be detrimental to the material's fatigue resistance depending strongly on the resulting microstructure. The 4340 steel is known to present temper embrittlement, which greatly reduces its fatigue life and weldability. This work proposes plasma nitriding as an alternative solution to tempering as a post-weld treatment and investigates its effects on material's hardness and fatigue life. This analysis was complemented by microstructural and fracture surface characterization. Plasma nitriding resulted in the formation of a double layer consisting of a smaller white micrometric nitride layer at the surface and a more diffuse sub-superficial region which led to better fatigue behaviour when compared with the conventional tempering treatment. The achieved higher surface hardness might also be interesting in other applications such as those involving high erosion and wear. [ABSTRACT FROM AUTHOR]

Concerning the increasingly widespread utilization of the finite element method (FEM), the concept of the so-called virtual factory is also gaining ground, and not only in the engineering industry. This approach does not use numerical simulations of individual production technologies separately but treats the entire production process as a chain of interrelated technologies. Thus, the output data from one technology is taken as input data for the following technology. The resulting thermal and mechanical effects are then not only dealt with within one technology but always comprehensively within the production process. In the consideration of the loading and subsequent service lives of manufactured components, values of residual stresses are one of the very important characteristics. For these reasons, this paper deals with the effect of residual stresses' magnitude and distribution during the formation and the final springback of the seamed pipe end section with and without respect to the influence of the preceding welding. The resulting residual stress values from numerical simulations are subsequently compared with the actual values of residual stresses experimentally measured using X-ray diffraction. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of cutting speed and flank wear on the depth profile of residual stresses, as well as the fraction of retained austenite after hard turning of quenched bearing steel 100Cr6. Residual stress and retained austenite profiles were studied for the white layer, heat-affected zone thickness, and XRD sensing depth. It was found that the influence of flank wear on the white layer and heat-affected zone thickness predominates. On the other hand, residual stresses are affected the cutting speed and the superimposing contribution of flank wear. Moreover, these aspects also alter microhardness in the affected regions. The study also demonstrates that information concerning residual stresses and the austenite fraction is integrated into the white layer, and the heat-affected zone in the surface is produced by the insert of low flank wear since the XRD sensing depth is more than the thickness of the white layer. On the other hand, the pure contribution of the white layer or the heat-affected zone to residual stress and the austenite fraction can be investigated when the affected surface region is thick enough. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to investigate the influences of key processing parameters of water jet guided laser processing on the grooves's cross-sectional morphology and heat affected zones of CFRPs. Therefore, based on the water jet guided laser processing equipment, a single factor experiment was designed to explore the effects of multiple key processing parameters, including laser power, water jet pressure, feed speed and laser repetition frequency. On this grooving experiment, the morphology of the groove sections and the formation mechanism of the heat affected zones were also analyzed. The following experimental results show that: the laser power has the greatest influences on the groove ablation depths and heat affected zones; the water jet pressure has the greatest influences on the groove ablation width; feed speed and laser repetition frequency has little effects on the groove ablation depth and ablation width, but has great effects on the heat affected zones. In addition, it is found that the removal area of groove cross sections displays V shape, and the heat affected zones are in the shape of sawtooth. A better groove section morphology is obtained by single factor analysis, the ablation depth and ablation width are as 772.8 µm and 894.7 µm, respectively. The heat affected zones of the carbon fiber layers is as 326.5 µm for the direction of 90° and 102.4 µm for the direction of 0°. [ABSTRACT FROM AUTHOR]

Quenching is a swift way of returning metal back to ambient temperature in order to acquire a certain property. Although it is often used to enhance the hardness of metals and their microstructure, it equally causes a serious variation in the mechanical and physical properties of the metals. This research focuses on quenching media's effect on the microstructure and mechanical properties of a 150mm x 80mm x 8mm welded mild steel plate through microscopic examination, metallography mounting, surface grinding, and surface polishing. Microstructural analysis with hardness and impact test was carried out on the steel plate using water, air, and oil as the quenching media. The results of the test show the Vickers Pyramid Number (HV) for water, oil, and air to be 284.2, 270.9, and 262.2 HV for the base metal, heat affected zone (HAZ), and weld metal (WM), respectively. The amount of energy absorbed by the three specimens during fracture is 23.12, 25.27, and 26.83 J, respectively. The test further indicates that the water-quenched media exhibited mostly martensitic structures and held back austenite with many structures of cementite while the oil and air media exhibited martensite phase and refined grains structures individually. It is therefore concluded that air is more suitable to cool the weld metal for damping applications in engineering. [ABSTRACT FROM AUTHOR]

In the present study, fabrication of micro-channel on glass fiber reinforced plastic (GFRP) sheet has been performed through micro-electrochemical spark machining process. Box-Behnken design has been followed to conduct experiments and the influence of machining parameters and their ranges that is, applied voltage (50 V–60 V), duty factor (35%–45%), electrolyte concentration (20–30 wt%), and pulse frequency (6–10 kHz) on the micro-channel quality has been investigated. The width of micro-channel (WMC), delamination extent (DE), and heat-affected zone (HAZ) are considered as the responses. Response surface method (RSM) with desirability analysis and multi-objective optimization are utilized to optimize the process. The minimum observed WMC, DE, and HAZ are 532.81, 1.09, and 50.52 μm respectively which are obtained at machining voltage: 50 V, duty factor: 35%, concentration: 20 wt% of NaOH, and pulse frequency: 10 kHz. The fiber breakage and re-deposition/adhesion of broken fiber and matrix materials are observed at the edges of the micro-channel. [ABSTRACT FROM AUTHOR]

The Gas Tungsten Arc Welding (GTAW) between P22 (2.25Cr-1Mo) and P91 (9Cr-1Mo) steels are quite common in heavy vehicle structures like; railway locomotives and war (or combat) vehicles. After welding, high hardness values of the Heat-Affected Zones (HAZs) of these dissimilar weld joints are possibly obtained. The uneven hardness in HAZ comes from the austenite transformation to Martensite, because of highly uncontrolled cooling rates. The considerable difference in hardness among various zones leads to prior cracking and is bound to failure during high-temperature operations. Therefore, there is a dire need to establish an appropriate Post Weld Heat Treatment (PWHT) to temper the dissimilar weld joints for required durability. The study investigates the microstructure and mechanical properties of various erupted zones of steel, before and after the application of PWHT. Before and after PWHT, weld zone and HAZ in P22 and P91 are mechanically tested and metallurgically examined. Further PWHT is tried to be optimised strategically and statistically, for the least variation in hardness among different zones. So that any failure due to thermal stresses or strains, during normal running conditions can be avoided. [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. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced composites are widely used in automobile, aerospace and military lightweight manufacturing due to their excellent mechanical properties such as light weight, excellent fracture resistance, corrosion resistance and wear resistance, etc. However, because of their high hardness, anisotropy and low interlayer strength characteristics, there are many problems with machine carbon fiber-reinforced composites with traditional methods. As a non-contact processing technology, laser machining technology has lots of advantages in carbon fiber-reinforced composites processing. However, there are also some defects produced in laser machining process such the heat affected zone, delamination and fiber extraction due to the great difference of physical properties between the carbon fibers and the resin matrix. To improve the quality of carbon fiber-reinforced composites laser machining, lots of works have been carried out. In this paper, the research progress of carbon fiber-reinforced composites laser machining parameters optimization and numerical simulation was summarized, the characteristics of laser cutting carbon fiber-reinforced composites and cutting quality influence factors were discussed, and the developing trend of the carbon fiber-reinforced composites laser cutting was prospected. [ABSTRACT FROM AUTHOR]

The research represents the ongoing investigation of the welded joints behavior made of low-carbon low-alloyed steel in the presence of different multiple defects. Following the initial experimental and numerical analyses performed on low-grade steel, a set of experiments were performed with specimens made of steel EN 1.0044 (commercial designation S275JR), along with development of new numerical models. Four combinations were made, including defects like undercuts, excess weld metal, misalignment, weld face sagging and incomplete root penetration, considering that these defects are often encountered in practice, and can appear simultaneously. The finite element method (FEM) was used to simulate the experiments. Tensile properties of the HAZ and weld metal were calculated using strain measurements by the digital image correlation (DIC) method. The finite element method (FEM) results were in good agreement with the experimental ones. [ABSTRACT FROM AUTHOR]

Dissimilar Friction Stir Welding (DFSW) is a process by which different metals such as aluminium, copper, steel, titanium, magnesium, etc., are combined without melting. It is a solid-state joining technique in which workpieces fuse due to thermo-mechanical deformation. The conventional joining of dissimilar materials is not feasible due to several issues such as changes in mechanical, thermal, chemical, and physical properties. In this paper, a comprehensive review of dissimilar FSW techniques presents state-of-the-art research in joining dissimilar materials. Latest developments in joining technologies are reviewed according to the mechanisms of joint formation, i.e. mechanical, chemical, thermal, or hybrid processes. Emphasis is given to essential aspects that determine the quality of the weld, microstructural analysis, weld joint characteristics, joining of dissimilar materials, the welding tools, welding defects experienced during DFSW, and industrial applications. [ABSTRACT FROM AUTHOR]

Magnesium Alloy is gaining momentum now a days as it is light in weight and possess moderate strength. Automotive and aerospace industries and electronics companies looking for light and strong and smart materials to save fuel and emission free environments, which magnesium alloy can meet. As Tailor welded magnesium alloy sheets are in demand, AZ31B -H24 magnesium alloy sheet with 2 mm thickness is selected in this research work. Laser welding is used to join magnesium alloy sheets in butt configuration. The samples are analyzed, and observations and challenges are addressed with help of micrographs for further scope of work. Effect of laser welding on grain or microstructure changes are also outlined. Thorough micro structural analysis is carried out with an objective to capture grain structure near parent metal, left and right-hand sides of heat affected zone and weld line. Impact and hardness tests are conducted to assess the mechanical behavior of laser welded samples. [ABSTRACT FROM AUTHOR]

Toughness and fatigue resistance of welds and associated heat-affected zones (HAZs) in high-strength steels are important design parameters in structural applications. Acicular ferrite microstructures, which can be achieved through control of weld process and nucleant (inclusions or precipitates) characteristics, are often regarded as key to enhancing weld metal and HAZ properties of welded steels. This paper addresses the transformation characteristics of acicular ferrite related to alloying and weld processing as well as the specific role of acicular ferrite in weld performance, along with future research needs to identify weld processes suitable to specific alloying strategies. [ABSTRACT FROM AUTHOR]

In addition to traditional chip methods, performance lasers are often used in the field of wood processing. When cutting wood with CO2 lasers, it is primarily the area of optimization of parameters that is important, which include mainly laser performance and cutting speed. They have a significant impact on the production efficiency and cut quality. The article deals with the use of an artificial neural network (ANN) to predict spruce wood cut characteristics using CO2 lasers under several conditions. The mutual impact of the laser performance (P) and the number of annual circles (AR) for prediction of the characteristics of the cutting kerf and the heat affected zone (HAZ) were examined. For this purpose, the artificial neural network in Statistica 12 software was used. The predicted parameters can be used to qualitatively characterize the cutting kerf properties of the spruce wood cut by CO2 lasers. All the predictions are in good agreement with the results from the available literary sources. The laser power P = 200 W provides a good cutting quality in terms of cutting kerf widths ratio defined as the ratio of cutting kerf width at the lower board to the cutting kerf width at upper board and, therefore, they are optimal for cutting spruce wood at 1.2·10−2 m·s−1. [ABSTRACT FROM AUTHOR]

In this study, the effect of the Ti/N ratio on the coarsening behaviour of (Ti, Nb)(C, N) precipitates and prior austenite grain size (PAGS) in the coarse-grained heat-affected zone (CGHAZ) during the welding process was investigated. Oscillation and tandem electro-gas welding (EGW) were simulated using the finite element method to calculate the thermal history of the CGHAZ. The calculated thermal history was applied to the Gleeble specimens to simulate the CGHAZ of tandem EGW. As the Ti/N ratio decreased to ~1.5, and the amount of N increased, finer and more (Ti, Nb)(C, N) precipitates existed in the as-rolled and CGHAZ specimens (peak temperature ~ 1335 °C), thereby producing a small PAGS. Comparing with the previous studies regarding to the isothermal kinetics conducted by isothermal heat treatment of Ti(C,N), the athermal kinetics (simulation of tandem EGW) of (Ti,Nb)(C,N) showed the insignificant growth of PAGS. Furthermore, Nb-rich precipitates were dissolved in the matrix above 1000 °C, and they did not contribute to the PAGS growth of the CGHAZ. [ABSTRACT FROM AUTHOR]

The carbon fiber-reinforced composite (CFRP) has the properties of a high specific strength, low density and excellent corrosion resistance; it has been widely used in aerospace and automobile lightweight manufacturing as an important material. To improve the CFRP cutting quality in the manufacturing process, a nanosecond laser with a wavelength of 532 nm was applied to cut holes with a 2-mm-thick CFRP plate by using laser rotational cutting technology. The influence of different parameters on the heat-affected zone, the cutting surface roughness and the hole taper was explored, and the cutting process parameters were optimized. With the optimized cutting parameters, the minimum value of the heat-affected zone, the cutting surface roughness and the hole taper can be obtained, which are 71.7 μm, 2.68 μm and 0.64°, respectively. [ABSTRACT FROM AUTHOR]

We consider the features of using modern nondestructive methods for assessing structural degradation in the process of elastic-plastic cyclic loading of normalizing (average grain size 10 μm) and overheating (average grain size 45 μm) zones of the heat affected zone of St3 steel. In this case, the approaches of digital image processing of microstructures, fractal analysis, and ultrasonic and magnetic testing were used. The features of the stages of degradation of the structure under fatigue and the corresponding behavior of the numerical microstructure parameters such as fractal dimension and the concentration and fraction of defects and slip bands are analyzed, as well as changes in the elastic properties of the material under study (determining an acoustic parameter that takes into account the complex change in the velocities of longitudinal and transverse waves) and the coercive force. It has been established that cyclic loading of samples from the sections of the heat affected zone leads to the formation of a large number of structural defects in the form of deformation bands, discontinuities, and microcracks, the occurrence of which is accompanied by a considerable change in the numerical microstructure characteristics (a decrease in the value of fractal dimension) as well as elastic (a decrease in the values of acoustic parameters) and magnetic (an increase in coercive force) properties. It is also shown that cyclic loading of the material under study leads to an increase in microhardness. However, the nature of such an increase for overheating and normalizing zones is different. The results of the research can be applied to the problems of diagnosing premature destruction and monitoring the most loaded zones of St3 steel structures to determine the residual resource. [ABSTRACT FROM AUTHOR]

Cold‐working can occur during the production of flat sheet products and the fabrication of structural cross‐sections. In both cases, when the material is cold‐worked, plastic deformations result in material strength enhancements. These strength enhancements are particularly significant for materials such as stainless steel, which exhibit rounded stress‐strain behaviour and pronounced strain hardening, and for hollow cross‐sections, where the strength increases arise in both the corner and flat regions of the cross‐section. Numerous studies have shown the importance of utilising this strength enhancement in design, and expressions to predict the strength enhancements have been established. However, if cold‐worked material is welded, some enhanced strength can be lost due to partial annealing in the heat affected zone (HAZ). The extent of this strength loss is investigated experimentally herein. The experimental programme comprised ten tensile coupon tests, with central welds parallel and transverse to the direction of cold‐rolling, as well as twelve full cross‐section tensile tests. Digital imaging correlation was utilised to determine the local constitutive properties of the base metal, the HAZ, and the weld metal. The microhardness and microstructure of the welded coupons, along with the widths of the weld and HAZ, were also characterised. [ABSTRACT FROM AUTHOR]

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The heat generated during welding induces a large temperature gradient in and around the welded area. In the arc welding process, three main different zones have been recorded in the welded joint: the fusion zone, the heat affected zone and the base metal. The objective of this article is to present the thermal cycle simulation technique and its usefulness for the study of the heat-affected zone. Rapid heating and cooling treatment was applied in specific simulation equipment. The most published research on using thermal cycle simulation to understand the heat affected zone is presented. A case study is also presented. An X70 steel was chosen to undergo thermal treatment cycles using the simulation equipment. It has been shown the importance of this technique for the study of HAZ. It was found that the microstructure of HAZ depends on the heating temperature. [ABSTRACT FROM AUTHOR]

The cutting process of materials with the use of laser techniques is now widely used in industry. Coupled thermomechanical phenomena occur in the laser cutting zone as a result of the concentrated heat source activity. Due to the high dynamics of the cooling process, the formation of the martensitic transformation is of great importance. This has a significant impact on the local increase in residual stress and hardness. The paper presents a numerical analysis of the laser beam cutting process, where the main research is focused on the cutting zone. A three-dimensional numerical model is developed on the basis of experimental research. The performed experimental tests allow to determine the structural properties in the cutting zone, i.e., microstructure and microhardness. The influence of the laser beam power change on the created cutting zone is analyzed. The material parameters of S235Jr steel changing with temperature are taken into account. The width of the cutting zone is determined numerically on the basis of performed calculations. The range of the heat affected zone and the hardening depth of the cutting zone are determined numerically. [ABSTRACT FROM AUTHOR]

Residual stresses and strains, distortions, heat-affected zone (HAZ), grain size changes and hardness variation during gas metal arc welding (GMAW), are fundamental aspects to study and control during welding processes. For this reason, numerical simulations of the welding processes represent the more frequently used tool to better analyse the several aspects characterizing this joining process with the aim to reduce lead time and production costs. In the present study, an uncoupled 3D thermo-mechanical analysis was carried out by two commercial finite element method (FEM) software to model an experimental single bead GMAW of AISI 441 at different processes set-up. The experimental HAZ and measured temperatures were used to calibrate the heat source of both the used numerical codes, then a validation phase was done to test the robustness of the two developed analytical procedures. One software was used to predict the residual stresses and strains and the distortions of the welded components, while in the second software, a user routine was implemented, including a physical based model and the Hall-Petch (H-P) equation, to predict grain size change and hardness evolution, respectively. The results demonstrate that the predicted mechanical and microstructural aspects agree with those experimentally found showing the reliability of the two codes in predicting the thermal phenomena characterizing the HAZ during the analysed welding process. [ABSTRACT FROM AUTHOR]

Maraging steels are ultra-high strength iron nickel-based alloys which are used in military applications like rocket motor casings, missiles, and ship hulls. In the current work, maraging steels of 250 grade butt joints with 2 mm thickness are welded by using Nd:YAG laser. The experiments were designed and conducted using the L16 orthogonal array. Various welding parameters selected for the current work are laser power, welding speed, and focal position, whereas tensile strength, hardness and depth of penetration were considered as the output responses. The influence of process variables on weld bead morphology was analysed experimentally. The microstructure, mechanical characteristics and numerical analysis of the optimum joint were also investigated. Analysis of variance (ANOVA) was used to determine the effect of different variables on tensile strength and depth of penetration. According to the results, laser power and welding speed are essential factors for tensile strength. The depth of penetration is strongly influenced by welding speed, focal position, and laser power. In order to predict the weld bead, finite element analysis was performed on ABAQUS 3D finite element software. The results reveal that finite element simulation and experimental observations are matched. [ABSTRACT FROM AUTHOR]