To investigate the effects of multiple-element rare earth addition on U75V steel, this study produced three types of steel: sample 1 steel without rare earths, sample 2 steel containing 0.0035% La and 0.018% Ce, and sample 3 steel containing 0.02% La and 0.0023% Ce. Microstructural analysis showed that the addition of rare earth elements modified the MnS and silicoaluminate inclusions into RE2O2S and RE2O2S–oxide complexes, which reduced the number and size of inclusions while simultaneously refining the microstructure, including the grain size and the spacing of pearlite layers. Concurrently, RE addition enhanced the steel’s mechanical properties, with the degree of enhancement dependent on RE content; sample 2 exhibited the most balanced improvement. Compared to sample 1, the hardness of samples 2 and 3 increased by 15.3% and 3.6%, respectively, and their tensile strength increased by 7.9% and 6.8%, respectively. Meanwhile, their coefficients of friction decreased significantly, by 69.5% and 22.1%. The impact toughness was also enhanced by RE addition, with both samples 2 and 3 showing higher values than sample 1 at room temperature and moderate low temperatures. Nevertheless, a distinct reversal was observed at −60 °C, where the impact energy of sample 3 was 23.5% lower than that of sample 2. This result implies that while moderate RE addition is beneficial, an excessive amount can adversely affect the toughness under cryogenic conditions.

This work compares the mechanical properties of the surface and root regions of high-strength weld metals deposited by the spin arc process using a metal-cored wire as filler metal under various gaseous atmospheres using a narrow gap joint. Weld metals were deposited using two welding passes in the flat position over carbon steel plates with a thickness of 10 mm, a preheat temperature of 100 °C, a rotation frequency of 1,500 rpm, a rotation diameter of 3 mm, and an average heat input of 2 kJ/mm. Mixtures of Argon containing 5, 10, and 25% CO2 were used as shielding gas. After welding, metallographic examination by electron microscopy and electron backscattering diffraction at the weld metal centerline was conducted. Vickers microhardness tests and Charpy-V impact tests were performed at the positions examined by metallography. The results revealed that the weld metals obtained by the GMAW-RE process with different shielding gases present equivalent microstructure and mechanical properties both at the root and surface regions studied, thus indicating that the root pass is not significantly affected by dilution due to the joint geometry. In addition, the reheated region exerts a strong effect on the impact toughness of weld metal.

Strength and impact toughness of Q690CFD welded joints under varied heat input

Variant-pairing-enhanced dislocation plasticity — A key mechanism governing impact toughness in low-alloy steels

Superior impact toughness achieved in an austenitic steel through sustained TWIP-assisted TRIP effect

Effect of heat input on microstructure and impact toughness of X80 FCAW-S weld joint

In the present research, the investigation of the heat-affected zone behavior and weld metal characteristics in API 5L X70 pipeline steel welded using robotic Metal Inert Gas (Robo-MIG) process is studied. The microstructural evolution and its influence on mechanical properties are also analyzed for the same metal. Nine weld samples were fabricated using a Taguchi L9 orthogonal array experimental design. The input parameters, such as current (140-180 A), voltage (24-28 V), and welding speed (2.7-3.6 mm/s), varied systematically to perform various testing and characterization. This mechanical characterization consists of tensile testing, Vickers microhardness measurements, and Charpy V-notch impact testing at both room temperature and sub-zero conditions (-40°C to -100°C). Microstructural analysis is done using optical microscopy. This shows that the distinct phase transformations occur across the base metal, HAZ, and weld zone. It was observed that welding current exerts the most significant influence on mechanical properties. With an increase in the welding current from 140 A to 180 A, the hardness increases from 161 HV to 190 HV. The result shows that a current of 180 A, voltage of 26 V, and speed of 2.7 mm/s are the optimal input parameters, which yield output parameters as maximum tensile strength of 478 MPa and average hardness of 190 HV at a heat input of 2.9 kJ/mm. Due to the formation of Widmanstätten ferrite, bainite, martensite, and Martensite-Austenite (MA), the HAZ shows the highest hardness among all zones. Impact toughness evaluation revealed that the HAZ maintained adequate toughness (28 J average) at -40°C, meeting ASME requirements for cold-service applications. It is observed from the Microstructural analysis that lower heat input conditions produced finer grain structures with higher bainite content and pronounced acicular ferrite. This optimizes the strength-toughness balance. Higher heat input resulted in coarser grains with predominant Widmanstätten ferrite and elevated MA content. These findings reveal the detailed information for optimizing robotic MIG welding parameters to ensure structural integrity and reliable performance of API 5L X70 steel pipelines in oil and gas transmission applications.

Polymer skeleton porous concrete (PSPC) is an innovative type of pavement material combining the high strength of cement concrete with the high toughness of asphalt concrete. It is also characterized by excellent water permeability, noise reduction, construction efficiency, and driving comfort, leading to extensive practical applications. The authors found that incorporating rubber powder greatly enhances the mechanical properties of PSPC, including flexural strength, deformation resistance, and impact toughness. This paper investigated influences of five different proportions of rubber powder on PSPC. Results show that polymer skeleton porous rubber concrete (PSPRC) exhibits exceptional deformation capacity and toughness. When the rubber content is 10% of the cement mass, compared with PSPC without rubber content, the deformation performance of PSPRC increased by 49.4% and the impact toughness increased by 156.6%. Scanning Electron Microscopy (SEM) was also employed to elucidate how rubber power enhances the overall mechanical properties of PSPC.

This study demonstrated the fundamental feasibility of producing a crankshaft using electric-arc wire 3D growth of metal parts on the WI 1500 process system. Specifically, the feasibility of manufacturing a crankshaft using Sv-08KhN2GMTA wire, which complies with GOST 2246–70, was investigated.Testing determined the chemical composition, mechanical properties, hardness, non-metallic inclusion content, grain size, micro- and macrostructure, and microhardness of the test sample.The results showed significantly higher relative elongation, relative contraction, and impact toughness compared to a hot-rolled blank, demonstrating the high strength and ductility of the material. The sample's microstructure is represented by bainite with clearly defined layers, ensuring excellent mechanical properties. The sample's macrostructure is free of defects such as porosity, pinholes, and cracks, and has a dense, uniform structure with typical characteristics of 3D printing. The sample is characterized by a high purity level of non-metallic inclusions, which also positively impacts its mechanical properties. The hardness of the samples produced by the weld deposition method exceeds that of hot-rolled blanks, making them promising for use under high loads and wear.Analysis of the obtained results convincingly demonstrates that additive manufacturing using the fused adhesion method (WAAM) ensures isotropic physical and mechanical properties. Moreover, this sample production method ensures the required quality of macro- and microstructural parameters, which is critical for ensuring the performance characteristics of the final product.

This review highlights conventional forging steels and advanced medium-Mn steels containing retained austenite (RA), emphasizing their potential for industrial forging applications. Modern steels intended for forgings are required to combine strength, ductility, toughness and fatigue resistance with good hardenability and machinability at minimal cost. Medium-Mn multiphase steels fulfill these requirements by the strain-induced martensitic transformation (SIMT) of fine, lath-type RA, which can create a strength-ductility balance. Ferritic-austenitic steels provide high ductility with moderate strength, martensitic-austenitic steels show very high strength at the expense of ductility, and bainitic-austenitic steels achieve intermediate properties. Impact toughness and fatigue resistance are strongly influenced by the morphology of RA. The lath-type RA enhances energy absorption and delays crack initiation, while blocky RA may promote intergranular fracture. Low carbon (0.2-0.3 wt.%) combined with elevated manganese (3-7 wt.%) contents provides superior hardenability and machinability, enabling cost-effective air-hardening of components with various cross-sections. Advanced medium-Mn steels provide a superior mechanical performance and economically attractive solution for modern forgings, exceeding the limitations of conventional steel grades.

Abstract Polymer matrix composites are prospective for automotive component applications, such as roof frames, cabinets, and seat frames, due to their lightweight, better tensile, and compression strength behaviour. However, the mono-fibre-reinforced polymer matrix exhibited variations in mechanical behaviour due to poor interfacial bonding strength. In this research, nano-boron nitride (BN) particles are introduced during the fabrication of low-density polyethene (LDPE) composites with 15 wt% chopped hemp fibre (chemically treated hemp fibre, or chemically treated HF) through the hot compression moulding technique. Influences of nitride-fiber actions on microstructural and mechanical properties of the synthesized composite were investigated, and X-ray diffraction analysis confirms the crystalline peaks. From transmission electron microscopy analysis, nitride fibres are identified as being widely dispersed within the base LDPE matrix, resulting in enhanced mechanical properties of the composites. The LDPE/15 wt% HF/9 wt% BN composite exhibits a high tensile strength of 25 MPa, an impact toughness of 6.1 J/mm 2 , and a flexural strength of 28 MPa, with a notable enhancement in microhardness value (44 HV). Moreover, lightweight, improved moisture absorption (0.82 %), and higher onset degradation temperature of 356 °C (Higher thermal stability). This composite sample is proposed for automotive roof applications.

Ti-6Al-4Zr-3Nb-1.1Mo-1Sn-1V (Ti90) alloy is widely used in marine engineering and oil and gas extraction due to its excellent strength, impact toughness, and corrosion resistance. The corrosion behavior of Ti90 alloy after solution treatment at 750 °C, 900 °C, 940 °C, and 960 °C in 5 M hydrochloric acid (HCl) solution was investigated using open-circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), static immersion tests, and surface characterization. The results of electrochemical tests indicate that the corrosion resistance of Ti90 alloy increases with rising solid solution temperature. The static immersion tests show that the variation trend of the annual corrosion rate at different solid solution temperatures in 5 M HCl solution is consistent with the electrochemical test results. The corrosion morphology of Ti90 alloy reveals that the α phase is more prone to decomposition than the β phase. The corrosion behavior of Ti90 alloy in 5 M HCl solution is mainly influenced by the volume fraction of the β phase and the size of the α phase.

Abstract This study investigates the behaviour of high-chromium stainless steel 304/high-carbon grey cast iron (HCSS 304/HCGCI) bimetallic metal matrix composite alloys (MMCAs) produced via green sand mold casting. The work focuses on the interaction between the molten HCGCI layer and the solid HCSS 304 functional layer during solidification. Elevated pouring temperature promoted effective metallurgical bonding by enabling substantial heat transfer from the liquid HCGCI to the solid HCSS 304 plate. During the uphill casting process, carbon and silicon diffused toward the steel, while chromium migrated from the HCSS 304 into the HCGCI. Ultrasonic non-destructive testing and destructive characterization confirmed the formation of a permanent diffusional bond at the bimetal interface. The interface was observed to be free of defects and exhibited a well-developed dual-phase microstructure comprising α-ferrite, γ-austenite, and minor martensite/carbide constituents. Post-solidification mechanical and microstructural analyses revealed that tensile strength, ductility, hardness, and impact toughness decreased with increasing HCGCI layer thickness. Overall, the findings demonstrate that HCGCI layer thickness significantly influences the mechanical performance and interfacial integrity of HCSS 304/HCGCI bimetallic systems, providing important guidance for optimizing bimetal casting processes.

An Inherently Flame-retardant Bio-based Poly(ethylene 2,5-furandicarboxylate) Copolyester with High Impact Toughness and UV Shielding

The effect of high-temperature annealing on the Charpy fracture properties of 316L stainless steel manufactured via Selective Laser Melting (SLM) was studied at ambient (25 oC) and cryogenic (–196 oC, LNT) temperatures. Charpy V-notched specimens (5×10×55 mm) were built along the Z-axis and annealed (5 h) at 900oC, 1050oC, or 1200oC, followed by water quenching. Impact tests were performed with the force-displacement curves recording. Microstructure was analysed using OM, SEM, EBSD, and EDX. The SLM-316L exhibited impact toughness (KCV) of one-third that of rolled 316L due to SLM’s cellular structure and specific micro-defects. Annealing at 900 oC removed the cellular structure, slightly improving impact toughness, while annealing at 1200 oC reduced it by a factor of 1.5 due to (MnCrSiAl)O3 precipitation. At –196 oC, absorbed energy decreased compared to 25 oC by a factor of 1.7-2.2. At 25oC, crack propagation energy (KVprop) exceeded crack initiation energy (KVini) across all conditions. At –196 oC, the KVprop fraction in annealed samples decreased because of deformation-induced martensitic transformation. The cellular structure of as-printed steel promoted a higher KVprop fraction at –196 oC. Ratio KCVLNT/KCVRT (0.46-0.59) indicates no ductile-brittle transition threshold, supporting the suitability of SLM-316L steel for cryogenic applications.

Shielded Metal Arc Welding (SMAW) is widely used in steel construction, where welding current variation strongly affects weld quality, surface defects, and mechanical performance. This study examines the influence of 60A and 110A currents on weld defects, hardness, and impact toughness of ST 60 carbon steel. The methodology includes welding specimens with both current levels, evaluating surface defects using dye penetrant testing, measuring Brinell hardness in the base metal, weld metal, and heat-affected zone (HAZ), and conducting Charpy impact tests. Penetrant results show that 60A produces dominant defects such as excessive spatter and porosity, while 110A generates excessive spatter with one porosity indication. The average weld metal hardness increases from 151.67 HB at 60A to 164 HB at 110A, indicating that higher heat input promotes the formation of a harder microstructure. In contrast, impact toughness decreases from 0.91 J/mm² (60A) to 0.53 J/mm² (110A), demonstrating an inverse relationship between hardness and absorbed energy. Overall, low current triggers porosity due to rapid solidification, whereas high current increases spatter and reduces toughness through microstructural modification. These results emphasize the need for optimal current selection to minimize defects and obtain balanced mechanical properties in ST 60 steel welds

This study investigated the influence of niobium additions on ductile iron through the production of four alloys containing 0 wt.%, 0.11 wt.%, 0.23 wt.% and 0.32 wt.% Nb. Microstructural phases were characterized, and mechanical properties were evaluated through hardness, impact toughness, tensile and wear tests. Niobium promoted carbide formation, which increased from 0.53 % to 2.48 %, and reduced graphite nodularity from 256.1 nod/mm² to 156.4 nod/mm². Hardness increased from 13.72 HRC to 26.6 HRC, while the ultimate tensile strength and yield strength reached 746 MPa and 449 MPa, respectively, in Alloy 4. In contrast, impact toughness decreased from 10.45 J to 5 J. Overall, niobium improved wear resistance but reduced the toughness of the material.

A clean and sustainable environment is essential for all living beings, yet large-scale industrialization often compromises this balance. Boilers and pressure vessels, critical to many industries, produce significant waste and residues, raising serious environmental concerns. This study explores the development of submerged arc welding (SAW) flux by transforming industrial waste materials, specifically boiler fly ash and sugarcane bagasse ash, into a high-performance, cost-effective welding solution. The resulting flux not only reduces reliance on virgin mineral resources but also addresses waste management challenges. Comprehensive evaluations, including chemical composition analysis, mechanical property testing, and microstructural and fractographic analysis using FESEM, confirmed the flux’s adherence to ASME SFA 5.17 standards. Welds produced with the developed flux exhibited superior performance, with higher ultimate tensile strength (548.49 MPa) and impact toughness (133.33 J) compared to commercially available flux, alongside stable arc characteristics and a high-quality weld bead surface. Moreover, the developed flux offered a 64% cost savings over commercial alternatives, demonstrating both economic and environmental benefits. This research enhances welding efficiency and mechanical reliability while promoting sustainability through innovative waste repurposing.

The effect of Ni content on the improvement of low-temperature impact toughness and microstructure refinement in a simulated coarse-grained heat-affected zone (CGHAZ) of high-strength steel was studied. The impact toughness tests revealed that as the heat input increased from 20 to 50 kJ/cm, both low-nickel (L-Ni) steel and high-nickel (H-Ni) steel exhibited a rapid decline in the impact toughness of their coarse-grained heat-affected zones (CGHAZ), though the H-Ni steel consistently demonstrated significantly higher impact toughness than the L-Ni steel. Microstructural characterization showed that the microstructure of L-Ni steel gradually transitioned from lath bainite (LB) to granular bainite (GB) with increasing heat input, which accounted for its reduced impact toughness. Conversely, H-Ni steel underwent a phase transformation from lath martensite (LM) to LB with increasing heat input, showing an unexpected trend opposite to the conventional understanding of toughness enhancement. Notably, the martensitic structure obtained in H-Ni steel at 20 kJ/cm exhibited substantially higher impact energy (59.6 J) than both the LB structures of L-Ni steel (44.6 J) and those of H-Ni steel (37.8 J) observed at 20 and 50 kJ/cm heat inputs. This phenomenon is attributed to the increased Ni content significantly refining the packet of LM, thereby enhancing its resistance to brittle crack propagation. Although LB structures obtained under different conditions exhibited refined blocks, their parallel arrangement within coarse packets resulted in less effective obstruction of brittle crack propagation compared to the refined packet with interlocking arrangement.

The technological operation of expansion in the range of e = 0–1.2% has a negligible effect on the standard mechanical characteristics of the base metal of straight-seam welded pipes made of L450M steel. The tensile strength practically does not change, and the yield strength decreases by approximately 6% in comparison to the base metal of the unexpanded pipe. At the same time, the relative elongation and relative area reduction decrease by 6–8% with an increase in the expansion level. It is found that the impact toughness KCV of the base metal in straight-seam welded pipes is more sensitive to changes in the expansion level, and at e = 1.2% it increases by approximately 11% compared to the unexpanded pipe.