Key Engineering Materials Vol. 1037

Abstract: Solution quenching and aging are used to thermally treat Ti-6Al-4V, an α+β titanium alloy. Three Ti-6Al-4V alloy plates were subjected to high temperatures and quenched in water, 5% HCL, and 15% HCl in this investigation. As a comparison, a fourth untreated sample was employed. When compared to the untreated samples, the microstructure and strength of the quenched plates revealed an increase in elongation and a decrease in yield strength. An equiaxed increase of α+β was recorded in all post-quenched samples.

Abstract: This study investigates the deformation behaviour of the CM247LC superalloy through a combination of physical experimentation and computational analysis. High temperature deformation was conducted at 600°C, 800°C, and 1000°C with a strain rate of 0.001 s⁻¹ and 50% of deformation. This research integrates microstructural analysis and mathematical equations to enhance understanding of the alloy's response under varying conditions. The findings reveal that at 600°C, the superalloy exhibits high flow stress and significant ultimate strength due to limited dynamic recovery (DRV) and restricted dynamic recrystallization (DRX). The increase in yield strength from 708 MPa at 600°C to 814 MPa at 800°C is attributed to effective precipitation strengthening from the γ' phases, corroborated by FEM simulations that show higher average yield strength values ranging from 875 MPa to 900 MPa at 800°C. Microstructural analysis indicates the role of finely dispersed carbides at lower temperatures and their coarsening at higher temperatures, which affects the material's strain-hardening behaviour and softening mechanisms. While physical simulations provide empirical data on mechanical properties and microstructural changes, FEM simulations predict stress-strain distributions and identify potential instability regions.

Abstract: Tungsten Inert Gas Welding (TIG) is a welding process that has low weld penetration and low heat intensity of the electric arc. This affects the low productivity of processes. To overcome this drawback, Activated Tungsten Inert Gas Welding has been developed. This study investigates Al-7 series plates using the A-TIG welding process. Different kinds of fluxes, TiO2 and Al2O3 are used with a ratio of 1:1 mixture of both these powders. This mixture was applied on Al-7075 plates to enhance weld characteristics. Activated flux has been used to improve the weld depth. The effects of various process parameters (welding current (I), welding speed(V), and gas flow rate were analysed and compared with the TIG welding method. Activated Tungsten Inert Gas (A-TIG) welding canincrease the joint penetration and weld depth width ratio compared to conventional TIG welding. The main objective of this work is to enhance weld penetration, improve mechanical properties (tensile strength and elongation), and assess metallurgical changes in Al-7075 joints using A-TIG welding with TiO₂ and Al₂O₃ mixed fluxes.

Abstract: This study investigates the effects of fiber type and hybridization on the tensile properties of epoxy composites produced using the temperature-controlled vacuum-assisted resin transfer molding (VARTIM) method. Tensile strengths and fracture behaviors are examined by fabricating 6-layer glass fiber-reinforced composites [G6], 6-layers carbon fiber-reinforced composites [C6], and hybrid composites consisting of six layers of glass and carbon fibers [H1] and [H2]. The microstructures of the composites are analyzed using an optical microscope, and tensile tests are conducted in accordance with ASTM standards. Tensile tests are performed at a constant speed and room temperature, and the fracture surfaces after tensile testing are analyzed using a Stereo Microscope. The results showed that the highest tensile strength is achieved in the carbon fiber-reinforced composite (CFRP), with an increase of approximately 123% compare to the glass fiber-reinforced composite (GFRP). Hybrid composite exhibits the reduced tensile strength compare to CFRP, with decreases of 23% for H2 and 29% for H1, respectively, whereas, increased the fracture toughness of the tested samples. Additionally, fracture surface analysis reveals that GFRP exhibits incomplete separation of the fractured surfaces, while CFRP shows a brittle and clean fracture surface. This study highlights the significant impact of fiber type and hybridization on the tensile property and fracture behavior of epoxy composite, demonstrating the better tensile performance of CFRP, while improving the fracture toughness and manufacturing cost of both GFRP and Hybrid composite.

Abstract: Cracks significantly affect the structural integrity and functionality of mechanical components. While most existing studies focus on identifying straight cracks using dynamic response (DR) data, the characterisation of crack paths, especially curved ones, remains limited. This gap is critical, as the path of crack propagation plays a vital role in determining the severity of structural damage, particularly in critical regions of plate structures. The large number of possible crack paths has made systematic research in this area difficult. Therefore, this study proposes a novel methodology for modelling both straight and curved crack paths in plate structures to analyse their DR using the Finite element method (FEM). Straight cracks are represented by coordinate pairs, while curved cracks are defined using second-order polynomial equations. A combination-based approach is employed to generate feasible curved paths within a bounded region, allowing variation in crack shapes, lengths, and geometries. The results demonstrate that the proposed methodology effectively reduces the total number of crack path configurations from 7140, an impractically large set for detailed analysis, to a manageable subset of 288. This reduction facilitates more efficient implementation in both numerical simulations and experimental investigations without compromising the representational diversity of crack path geometries. They also show that the crack path has a greater influence on the dynamic response than crack length, offering a more comprehensive framework for crack path identification and evaluation.

Abstract: This study investigates the mechanical degradation of nylon 6,6 under tensile stress, induced by accelerated aging via ultraviolet (UV) radiation [1-3]. Specimens were fabricated and exposed to controlled UV doses, simulating outdoor weathering conditions. Tensile properties were evaluated, revealing a significant reduction in tensile strength and elongation at break with increasing UV dose. The predominant degradation mechanism was photo-oxidation, evidenced by polymer chain scission and the formation of functional groups altering the material's molecular structure[4,5]. Specimen surfaces exhibited cracks and fissures, contributing to mechanical strength loss. These findings are critical for nylon 6,6 applications in telecommunications and energy industries, where UV exposure is unavoidable. Understanding this degradation is essential for optimizing the durability and reliability of critical infrastructure. This study lays the foundation for developing advanced protective materials and coatings, enhancing the safety and efficiency of outdoor systems.

Abstract: Carbon fiber reinforced polymer (CFRP) bonded structures are widely used for their lightweight and high specific strength. However, research on durability of adhesively bonded lap joints under hygrothermal conditions remain insufficient. Therefore, the aging process and residual strength of CFRP-bonded lap joints with different adhesives were studied. Condition of hygrothermal aging tests were set, then moisture absorption behavior of CFRP plate and adhesive layer were analyzed, respectively. Based on the same aging period, residual tensile strength of acrylic-based specimens and epoxy-based specimens were compared. To evaluate their performance and clarify the failure mechanisms, Finite element method (FEM) simulations were conducted. Load-displacement curve was recorded and morphology of the failure surfaces was analyzed by using a microscope.

Abstract: The microstructure of phenolic resin undergoes significant transformation under high-temperature pyrolysis, affecting its mechanical performance and fracture behavior. By combining Convolutional Neural Networks (CNN) and Conditional Variational Autoencoders (CVAE), a generative modeling framework was proposed. Then its suitability to predict microstructure evolution of phenolic resin under varying pyrolysis temperatures was studied. Finite Element Method (FEM) simulations were conducted to analyze stress distributions. Results indicate a significant increase in the area of high stress concentration zones with rising pyrolysis temperature, with pore bridges, sharp edges, and clustered porosity identified as potential fracture initiation sites.

Abstract: This comprehensive review examines the intersection of biodegradable polymer science and advanced additive manufacturing technologies, synthesizing current knowledge across material development, processing techniques, property enhancement, and applications. The urgent need to address plastic pollution through sustainable alternatives has accelerated research into biodegradable polymers, particularly polylactic acid (PLA) and polyhydroxybutyrate (PHB), which offer promising combinations of mechanical performance and environmental benefits. This article analyzes production methodologies, composite formation strategies, and novel functionalization approaches that enhance mechanical, thermal, and functional properties of these materials. The review explores how additive manufacturing techniques—from material extrusion to vat photopolymerization—have revolutionized the processing of biodegradable polymers, enabling complex geometries and tailored properties unachievable through conventional methods. Advanced manufacturing approaches including field-assisted printing, ultrasonic enhancement, and low-pressure processing are evaluated for their ability to overcome inherent limitations in printed parts. Starting with technologies like 4D printing, the article pays serious attention to the use of shape-memory and stimuli-responsive materials to fabricate dynamic structures that undergo predetermined transformations. The article further explores various applications in the fields of biomedical devices, food packaging, structural components, and consumer goods, discussing both present-day applications and possible future ones. This review covers mechanical performance, biodegradation phenomena, and processing alternatives to provide a broad perspective of the present and future trajectory of biodegradable polymer research to aid researchers, engineers, and industry practitioners aiming toward truly sustainable material solutions.