Search Results (729)

C276 Hastelloy/Q235 Steel cladding plates were prepared by vacuum-sealed hot rolling (VSHR) with a small hole. The effects of different Ni interlayers on the macro-morphology, microstructure, mechanical properties and corrosion resistance of the cladding plates were systematically investigated. The results indicated that without an interlayer, a large number of Mo-rich white M₆C particles formed near the C276 Hastelloy side, along with the formation of black Cr-Mn oxides at the interface. The addition of the Ni interlayer suppressed the diffusion of the C element from the Q235 Steel toward the C276 Hastelloy, consequently reducing the precipitation of M₆C carbides and Cr-Mn oxides. When the Ni interlayer thickness was 0.5 mm, the M₆C carbides on the Hastelloy side disappeared completely. The incorporation of a Ni interlayer increased the hardness of the C276 Hastelloy side and the interface layer, as well as the shear strength of the cladding plate. This was mainly because the Ni interlayer acted as a barrier to suppress the development of a Mo/Cr-depleted zone adjacent to the C276 Hastelloy and decrease interfacial Cr-Mn oxides, thus enhancing interfacial bonding. Under all three conditions, the cladding plates were bent without cracking. Moreover, the addition of a Ni interlayer also improved the corrosion resistance of the cross-section of the C276 Hastelloy. XPS analysis of the passive film revealed that the corrosion resistance was primarily attributed to the formation of Mo- and Cr-containing oxides on the surface. The corrosion resistance reached the optimal with the Ni interlayer thickness of 0.5 mm, in which Mo and Cr played a crucial role. Full article

High nitrogen austenitic stainless steels are an important engineering structural material. Under annealing conditions, the addition of interstitial solid solution element nitrogen can improve the yield strength and tensile strength of the alloy without reducing its plasticity. In addition, nitrogen can partly or completely replace the more expensive nickel element at a relatively cheap element cost to improve economic benefits, while maintaining or even enhancing the excellent corrosion resistance of stainless steels. However, the cracks and defects caused by high nitrogen austenitic stainless steels during hot working in high temperature ranges have always been the pain points in the engineering field. High nitrogen elements bring high temperature strength, but also narrow the hot working temperature range, the possibility of nitride precipitation and the tendency of heat induced cracking, which limit the further engineering application of high nitrogen austenitic stainless steels. It is urgent to analyze and study the hot deformation law of high nitrogen austenitic stainless steels in engineering. This article commences with an examination of the developmental trajectory of high nitrogen austenitic stainless steel, elucidates the role and strengthening mechanism of nitrogen, and delineates the factors influencing the mechanical behavior of high nitrogen austenitic stainless steel during hot working. These factors include the impact of nitrogen content and manufacturing processes, hot-working parameters, grain size distribution, and the presence of precipitated phases. This article synthesizes various studies, analyzes the causes of thermal cracking, and proposes potential solutions. Ultimately, it summarizes the practical applications and future prospects of high nitrogen austenitic stainless steel, highlighting its substantial potential. Full article

This study aims to develop a sustainable fibre-reinforced, high-strength mortar (UHSM) using Rice Husk Ash (RHA), cement, and steel fibres, with a view to developing a high-strength mortar that can be utilized for repair work in major industries where cracks occur due to vibrations and thermal conditions. RHA was used in 20%, 30%, and 40% replacement levels of cement. Steel fibres were used at a constant dosage of 1.5%, and a very low w/c of 0.25 was adopted. Five different types of curing conditions, namely 1-day hot water curing, 1-day oven curing and 7-day normal water curing, 1-day oven curing and 28-day normal water curing, and 7-day normal water curing and 28-day normal water curing, were adopted. The mechanical behaviour of the mortar was evaluated using a compressive strength test and a split tensile test, and a statistical analysis was done using two-way ANOVA. Results revealed that the replacement levels up to 30% yielded better strength results, and there was indeed a significant effect of the curing conditions. Full article

2219 aluminum alloy is widely used in aerospace components because of its high specific strength, excellent fracture toughness, and resistance to stress corrosion cracking. Accurate characterization of its hot deformation behavior is important for the numerical simulation and process design of ring rolling. In this study, isothermal compression tests were carried out on a thermal–mechanical simulator at temperatures of 380–460 °C and strain rates of 0.01–10 s⁻¹ to investigate the hot deformation behavior of 2219 aluminum alloy. The effects of deformation temperature and strain rate on flow stress evolution were analyzed based on the experimental results. A strain-compensated Arrhenius-type constitutive model was developed to describe the flow stress behavior over a wide strain range. The material constants, including the stress exponent, stress level parameter, activation energy for hot deformation, and structure factor, were determined by regression analysis, and their strain dependence was expressed as polynomial functions of true strain. The model was evaluated by comparing predicted and experimental flow stress values, giving an average absolute error of 4.78%. The results indicate that the developed model can describe the combined effects of temperature, strain rate, and strain with good accuracy, and can be used for numerical simulation and process optimization in hot ring rolling. Full article

Liquid metal embrittlement (LME) during hot stamping of Zn-coated high-strength steels poses significant challenges to the long-term durability of automotive components. This study investigates how ~30 μm deep LME cracks affect the mechanical behavior of Zn-coated high-strength boron steel. LME-free flat specimens were compared with hat-shaped specimens containing LME cracks. While tensile strength and ductility exhibited minimal changes, the high-cycle fatigue limit (R = −1, 10⁷ cycles) decreased by 10.9% from 550 MPa to 490 MPa in hat-shaped specimens. Fractographic examination revealed distinct stress-dependent crack initiation mechanisms: at high stress amplitudes (≥690 MPa), LME cracks competed with intrinsic substrate defects but did not dominate fatigue failure. In contrast, at moderate-to-low stress amplitudes (≤630 MPa), LME cracks dominated fatigue degradation through a multi-site crack initiation tendency. El Haddad analysis positioned these cracks at the short-to-long crack transition boundary (l ≈ l₀). Preliminary fracture mechanics analysis reveals that conventional single-crack LEFM models systematically overestimate the fatigue threshold stress for LME-affected specimens, a discrepancy qualitatively attributed to the high surface density and morphological complexity of LME crack networks and to chemically assisted grain boundary weakening induced by liquid Zn infiltration—effects not captured by standard fracture mechanics frameworks. These results establish the stress-dependent mechanisms governing LME crack-induced fatigue degradation and provide a mechanistic basis for the development of more accurate fatigue life prediction methods for Zn-coated hot-stamped high-strength steels. Full article

Laser powder bed fusion (LPBF) of AA7075 is severely constrained by a narrow process window and susceptibility to defect formation (hot cracking and porosity), which often dominates performance. In this study, 5 wt.% AlCoCrFeNi_2.1 high-entropy alloy (HEA) particles, volumetric energy density (VED = 74–222 J·mm⁻³), and subsequent T6 heat treatment were systematically investigated to reveal their combined effects on defect structure, crystallographic texture/substructure, and tensile behaviour. Quantitative EBSD shows a measurable grain refinement in the as-built state (average grain size 13.44 → 11.80 µm, ~12%) accompanied by a pronounced weakening of the <001> fibre texture (maximum MRD 4.94 → 2.38), indicating disrupted epitaxial growth and a more dispersed orientation distribution. After T6, the reinforced alloy retains a higher low-angle boundary fraction (31.62% vs. 24.17% in unreinforced AA7075) and a higher kernel average misorientation (0.80° vs. 0.60°), consistent with particle-stabilised substructure retention and retarded recovery. Across all VEDs, AA7075-HEA exhibits higher microhardness (compared with AA7075, the addition of HEA increases the hardness by roughly 20–50 HV) and tensile strength, with the intermediate VED (140.74 J·mm⁻³, T6 states) yielding the best performance. While macroscopic cracking is not fully eliminated, the results clarify that HEA-enabled texture/substructure modifications can contribute to enhanced defect tolerance and are more effectively translated into tensile performance when the as-built defect severity is controlled. These findings provide quantitative insights into defect–microstructure–property coupling in LPBF AA7075-HEA composites from as-built to T6 states. Full article

In this work, compatibilized poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were developed and characterized, to be potentially utilized as biodegradable self-healing matrices for composite laminates. Blends containing 10, 20 and 30%wt of PBAT and 0.5 phr of an epoxy-based compatibilizer were prepared by melt compounding and hot pressing. Rheological measurements showed that moduli and complex viscosity generally increased with PBAT content, while maintaining viscosity levels suitable for conventional melt-processing operations. FT-IR and FESEM analyses confirmed the formation of an immiscible but well-compatibilized morphology, characterized by a homogeneous dispersion of PBAT domains within the PLA phase. Mechanical tests revealed a decrease in tensile modulus (up to 44%), strength (up to 45%) and fracture toughness (up to 40%) with a PBAT content up to 30%wt. Self-healing was evaluated by measuring the fracture toughness (K_IC) recovery after thermal treatment at 140 °C. After healing, the blend containing 20%wt of PBAT exhibited a self-healing efficiency of 64% under impact conditions, which was attributed to the smoother fracture surface generated at an elevated strain rate that facilitated a more effective flow of the molten PBAT phase across the crack interface during healing. The formulation containing 20%wt of PBAT featured the best balance between mechanical performance and self-healing efficiency. Full article

TC4/Al₃Ti metal–intermetallic laminated (MIL) composites were fabricated by the vacuum hot-pressing process at 650 °C. The microstructure characteristics, i.e., grain boundary distribution, crystallographic orientation and Kernel Average Misorientation (KAM) map, were analyzed using EBSD. Meanwhile, the distribution of local strain and the fracture behavior of TC4/Al₃Ti MIL composites during tensile process were determined by Digital Image Correlation (DIC) and in situ tensile experiments, respectively. Results show that the TC4/Al₃Ti interfaces are well bonded and exhibit a distinct wavy morphology. The obvious Kirkendall pores and centerline are observed within the central region of the Al₃Ti layer. The texture components of (10-10) <0001> and (11-20) <10-10> are predominant in the TC4 layers; (100) <001> and (110) <001> are observed in the Al₃Ti layer. Additionally, the average geometrically necessary dislocation (GNDs) density is 2.53 × 10¹⁴ m⁻² in the TC4 layer, whereas it is 1.74 × 10¹⁴ m⁻² in the Al₃Ti layer. In the tensile test, the fracture resistance of TC4/Al₃Ti MIL composites is significantly improved by the plastic deformation of the TC4 layers and the suppression of crack-tip instability. It is found that the extrinsic toughening mechanisms contain crack deflection, crack blunting, crack bridging, multiple cracking modes, and the plastic deformation of ductile TC4 layers in TC4/Al₃Ti MIL composites. The real-time observation technique may provide more complete insights into the relationship between fracture behavior and enhanced toughness. Full article

The corrosion behavior of hot-press-formed (HPF) B-pillar components fabricated from Al–Si-coated boron steel was investigated with an emphasis on the forming-induced crack morphology. The specimens were extracted from the inner and outer surfaces of the top, flat, and radius regions. Microstructural characteristics and coating cracks were examined using optical microscopy, as well as field-emission scanning electron microscopy (FE-SEM) in combination with energy-dispersive spectroscopy (EDS), and corrosion behavior was evaluated using cyclic corrosion immersion and potentiodynamic polarization tests in a 3.5 wt.% NaCl aqueous solution. The Al–Si coating exhibited a multilayered structure composed of alternating Al- and Fe-rich layers. The crack morphology strongly depended on the local stress state: wide macrocracks were mainly formed on the outer surface of the radius region under tensile deformation, whereas the narrow microcracks predominated on the inner surface subjected to compressive deformation. Cyclic corrosion immersion tests showed that the corrosion propagated preferentially along the coating cracks and was more severe on the inner surfaces, where narrow microcracks promoted aggressive crevice corrosion owing to chloride ion accumulation and local acidification. By contrast, wider macrocracks on the outer surface mitigated crevice corrosion by allowing electrolyte exchange. Potentiodynamic polarization tests indicated similar corrosion rates for all regions; however, the outer radius region exhibited a relatively noble corrosion potential owing to oxide film formation on the locally exposed substrate areas. These results demonstrate that the crack morphology induced by curved forming is a key factor governing the corrosion behavior of HPF B-pillar components. Full article

The reuse of milled pavement material, known as RAP (Reclaimed Asphalt Pavement), represents one of the major current challenges in highway engineering worldwide. There is no doubt that the most valuable application of this residue is its use in the production of new hot asphalt mixtures, incorporating the highest possible RAP content, a process that requires adaptations in residue processing at asphalt plants. In Brazil, the RAP content added to these mixtures is limited to a maximum of 25%. Consequently, alternative applications have gained prominence in the country to increase RAP utilization in pavement engineering, such as its use in cold premixed asphalt mixtures. This study aimed to evaluate the performance of cold asphalt mixtures containing different RAP contents through mechanistic-empirical analyses of a reference pavement structure, using the modelling framework adopted in the Brazilian Asphalt Pavement Design Method (MeDiNa). After Marshall mix design and volumetric and mechanical characterization of mixtures containing 0%, 10%, 20%, 30%, and 40% RAP, stiffness and fatigue parameters were used to estimate the evolution of cracked area in the reference pavement, with each mixture applied as the surface layer under different traffic levels. The results demonstrated that pavement performance improved for all RAP contents evaluated compared to the mixture without RAP, with the mixture containing 30% RAP showing the best overall performance. Full article

The influence of base plate temperature (25, 100, 200, and 400 °C) on the laser powder bed fusion processing of EN AW 7075 was systematically investigated using microstructural characterisation (LM, SEM, EBSD, GROD), chemical analysis, hardness testing, and thermal simulations across a broad range of process parameters. Moderate preheating at 100 °C and 200 °C showed no significant reduction in crack density or changes in grain morphology compared to processing without preheating. At the highest studied temperature—400 °C—a transition to columnar crack networks was observed, accompanied by modified grain orientation, pronounced stress relaxation, and reduced hardness. Independent of preheating temperature, consistent evaporation of Zn (~1 wt.%) and Mg (~0.3 wt.%) occurred during processing. Thermal simulations qualitatively supported the experimental observations, indicating increased thermal retention and displacement with increasing preheating temperature. The results demonstrate that base plate preheating alone is insufficient to suppress hot cracking in EN AW 7075 and may promote alternative crack-growth mechanisms at elevated temperatures, highlighting the need for alternative alloy or process design strategies. Full article

A low-temperature tempering staged drying process was proposed in this study to minimize quality degradation and improve drying efficiency during waxy corn drying. Experiments of continuous drying, low-temperature tempering drying, and low-temperature tempering staged drying were conducted to investigate the drying characteristics and quality of waxy corn. The results showed that the low-temperature tempering drying process could shorten the effective drying time and increase the drying rate during the latter stage of the drying process. Under the same hot air temperature, increasing the tempering temperature from 30 °C to 40 °C reduced the effective drying time by 20 min. The Modified Henderson and Pabis model exhibited the best fit to the experimental drying data (R² ≥ 0.9864). The microstructural images of the waxy corn flour showed no significant changes among the experimental groups. The color difference (ΔE) of the continuous drying group was higher than that of the other experimental groups. Both the low-temperature tempering drying process and the low-temperature tempering staged drying process caused less damage to the waxy corn with a relatively lower crack ratio, thereby leading to a reduced electrical conductivity value. The starch content of the 80 °C–60 °C–40 °C group was higher than that of the other experimental groups. Based on comprehensive evaluation of the drying characteristics, the color parameters, and the quality of the dried waxy corn, the 80 °C–60 °C–40 °C group represents a favorable alternative. Full article

The main goal of this study is to evaluate the feasibility of designing high-performance MASAI mixtures produced at ambient temperature. For this purpose, the impacts of certain variables, such as the type and amount of asphalt emulsion and the use or non-use of RAP, on its performance are evaluated. Subsequently, its stiffness modulus, tensile strength, permanent deformation, and resistance to thermal cracking were evaluated and compared against a conventional dense-graded asphalt concrete (AC 16) and an open-graded (BBTM11B) hot-mix asphalt used for wearing courses. The results showed that these materials could represent more sustainable and good solutions for the rehabilitation of some types of pavements. Full article

The disposal of waste tyres presents a significant environmental challenge, necessitating sustainable, high-value recycling solutions. This study explores the incorporation of waste tyre metal fibre (WTMF) into hot mix asphalt (HMA) to enhance mechanical performance while reducing landfill burden. WTMF-modified mixes containing 0%, 0.375%, 0.75%, 1.125%, and 1.50% fibre were evaluated through Marshall and volumetric testing, indirect tensile strength (ITS) and tensile strength ratio (TSR) for moisture damage, stiffness modulus at varying temperatures, and fatigue life under cyclic loading. Microscopic analysis revealed WTMF’s irregular, rough surface with microcracks and pits, aiding crack-bridging and stress transfer. Marshall testing showed that the optimum binder content of WTMF-modified mixtures was approximately 5% higher than that of the control (conventional HMA without WTMF); however, stability decreased while flow increased, resulting in a reduced Marshall quotient due to fibre conglomeration affecting porosity and bulk specific gravity. ITS results indicated that the control mixture exhibited the highest cracking resistance, whereas WTMF-modified mixtures demonstrated improved moisture resistance (TSR > 80%). The maximum improvement was observed at 0.75% WTMF-induced HMA, with an 11% increase in TSR, while a slight reduction of 2.4% occurred at 1.50% WTMF-induced HMA. Stiffness testing showed that the mixture containing 0.375% WTMF achieved the highest modulus, exhibiting up to a 70% increase at 5 °C and more than a twofold increase at elevated temperatures compared to the control mixture. With increasing temperature, stiffness decreased by approximately 84% for the control mixture and 80% for the 0.375% WTMF-modified mixture. Fatigue analysis showed that the control mixture achieved a fatigue life of 115,529 loading cycles at low stress, followed by substantial reductions in fatigue life with increasing stress levels, whereas moderate WTMF contents improved strain performance; however, excessive fibre content increased permanent deformation under high stress. Stress- and strain-based empirical power-law relationships were established for predicting the fatigue life of each investigated mixture. Results demonstrate that WTMF’s controlled dosage within the optimum range of 0.375 to 0.75% has the potential to improve HMA’s performance indicators, offering a sustainable recycling pathway for waste tyres. Full article

During reservoir stimulation and long-term operation of Enhanced Geothermal Systems (EGSs), repeated injection of cold fluids induces cyclic thermal shock in the surrounding rock mass, leading to progressive modification of mechanical properties and fracture behavior. However, the combined effects of cyclic thermal shock and true-triaxial stress conditions on granite strength and failure characteristics remain inadequately quantified. In this study, a series of true-triaxial compression tests were conducted on granite specimens subjected to cyclic thermal shock at 400 °C. Thermal shock cycles of 0, 1, 5, 10, and 15 were considered in conjunction with intermediate principal stress levels of 5, 20, 30, and 50 MPa to systematically evaluate their coupled influence on characteristic stresses and macroscopic failure behavior. The results show that the peak intensity increases with the rise of the intermediate principal stress, but with the increase in the number of thermal shocks, it first increases and then decreases. Macroscopic failure is dominated by asymmetric V-shaped fracture surfaces, roughly oriented along the ${\sigma }_2$ direction. As the intermediate principal stress increases, the failure mode transitions from tensile–shear mixed failure to shear-dominated failure, whereas thermal cycling promotes the persistence of tensile–shear cracking even under relatively high ${\sigma }_2$ conditions. Based on these observations, a modified Mogi–Coulomb strength criterion that accounts for thermal shock-induced damage is proposed to describe granite strength under true-triaxial stress conditions. The research results can provide a theoretical basis for optimizing the design of hydraulic fracturing in hot dry rock and evaluating reservoir stability. Full article