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In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS.

To mitigate the adverse ecological impacts of inorganic solidified materials on modified red clay and address the issues of low bearing capacity and extensive cracking under hydraulic erosion, this study investigates the use of low-environmental-impact materials to improve the mechanical fracturing of red clay. In this context, this study focuses on modifying red clay using an environmentally friendly biopolymer, xanthan gum (XG). Through a series of laboratory mechanical and microstructural tests, the effects of XG on the mechanical fracturing, California Bearing Ratio (CBR), and microstructural characteristics of red clay are examined. The results indicate that the shear strength of XG-modified red clay increases approximately linearly with the increase in normal stress. The cohesion and internal friction angle of the modified soil first increase and then decrease with the increasing XG dosage. The compressive strength of the modified soil initially increases and then decreases with the addition of XG, with the most rapid growth occurring between 14 and 28 days. The deformation modulus of the modified soil initially increases and then decreases with increasing XG dosage, achieving a 7.71% increase after 28 days. As the number of cycles increases, the development of fractures in the modified soil slows down, primarily due to the transformation of secondary fractures into primary fractures. The internal friction angle of the modified soil decreases with the increasing number of cycles, while the cohesion and compressive strength exhibit a decreasing trend. The CBR of the modified soil first increases and then decreases with the increasing XG dosage, reaching a peak value of 24.1%. The addition of XG promotes the formation of flake-like and needle-like polymer bonding products that cover the soil particles, fill the pores, and form dense aggregates. After 28 days, the hydrophilic minerals in the modified soil decreased by 53.99%. Pore analysis reveals a decrease in the average porosity and total pore volume of the XG-modified soil. The research results provide a novel modification approach to address the ecological environmental issues associated with the treatment of red clay using inorganic solidifiers, offering valuable numerical references for similar engineering projects.

Being solid in nature, friction stir processing (FSP) is considered as most efficient and effective tool to eradicate the shortcomings associated with cast products. In the present investigation, FSP has been utilized to refine the cast alloy (A356) and see its effect on mechanical properties. It carries a non-consumable tool which rotates at high RPM, creating a lot of stirring action that breaks up dendritic structure (α-Al). It also smooths out acicular Si-particles. This procedure guarantees that silicon particles are evenly distributed over the treated plate’s stirred zone. The treated alloy exhibits a significant improvement in hardness and tensile strength due to the breaking of dendritic structure (α-Al) and even sputtering of particles.

This study investigates the performance of alkali-activated mortar incorporating slag, fly ash, and desert sand, with a focus on flowability, mechanical properties, sulfate resistance, and microstructural characteristics. A four-factor, three-level orthogonal experimental design was used to analyze the effects of the fly ash substitution rate, alkali content (Na2O/b), activator modulus, and desert sand replacement rate for natural sand. The results indicate that increased slag and desert sand contents reduce mortar flowability. Despite this, the mortar exhibits excellent mechanical strength, with compressive strength reaching 77.7 MPa at 28 days and increasing to 89.34 MPa under sulfate exposure. However, after 120 days of sulfate erosion, a decline in strength is observed due to the formation of expansive products such as gypsum and caliche, leading to cracking. Microstructural analyses (XRD, SEM/EDS, MIP) reveal partial dissolution of desert sand under alkali activation, enhancing gel formation and reducing cumulative porosity. The pore structure predominantly consists of harmless pores. These findings demonstrate the potential of slag–fly ash–desert sand alkali-activated mortar as a durable and sustainable material for structural and construction engineering applications, especially in sulfate-rich environments or arid regions where desert sand is abundant.

This paper studies the effect of the laser melting process (LMP) on the microstructure and hardness of a new modified AlCuMgMn alloy with zirconium (Zr) and Yttrium (Y) elements. Homogenized (480 °C/8 h) alloys were laser-surface-treated at room temperature and a heating platform with in situ heating conditions was used in order to control the formed microstructure by decreasing the solidification rate in the laser-melted zone (LMZ). Modifying the AlCuMgMn alloy with 0.4 wt% Zr and 0.6 wt% Y led to a decrease in grain size by 25% with a uniform grain size distribution in the as-cast state due to the formation of Al3(Y, Zr). The homogenization dissolved the nonequilibrium intermetallic phases into the (Al) matrix and spheroidized and fragmentized the equilibrium phase’s particles, which led to the solidification of the crack-free LM zone with a nonuniform grain structure. The microstructure in the LMZ was improved by using the in situ heating approach, which decreased the temperature gradient between the BM and the melt pool. Two different microstructures were observed: ultrafine grains at the boundaries of the melted pool due to the extremely high concentration of optimally sized Al3(Y, Zr) and fine equiaxed grains at the center of the LMZ. The combination of the presence of ZrY and applying a heating platform during the LMP increased the hardness of the LMZ by 1.14 times more than the hardness of the LMZ of the cast AlCuMgMn alloy.

This paper aims to investigate the dielectric properties, i.e., dielectric constant (ε′), dielectric loss factor (ε″), dielectric tangent loss (tan δ), electrical conductivity (σ), and penetration depth (Dp), of the porous nanohydroxyapatite/starch composites in the function of starch proportion, pore size, and porosity over a broad band frequency range of 5 MHz–12 GHz. The porous nanohydroxyapatite/starch composites were fabricated using different starch proportions ranging from 30 to 90 wt%. The results reveal that the dielectric properties and the microstructural features of the porous nanohydroxyapatite/starch composites can be enhanced by the increment in the starch proportion. Nevertheless, the composite with 80 wt% of starch proportion exhibit low dielectric properties (ε′, ε″, tan δ, and σ) and a high penetration depth because of its highly interconnected porous microstructures. The dielectric properties of the porous nanohydroxyapatite/starch composites are highly dependent on starch proportion, average pore size, and porosity. The regression models are developed to express the dielectric properties of the porous nanohydroxyapatite/starch composites (R2 > 0.96) in the function of starch proportion, pore size, and porosity from 1 to 11 GHz. This dielectric study can facilitate the assessment of bone scaffold design in bone tissue engineering applications.

Owing to the unparalleled advantages in repairing of high value-add component with big size, fabricating of functionally graded material, and cladding to enhance the surface properties of parts, the laser material deposition (LMD) is widely used. Compared to the continuous wave (CW) laser, the controllability of the laser energy would be improved and the temperature history would be different under the condition of pulse wave (PW) laser through changing the pulse parameters, such as duty cycle and pulse frequency. In this paper, the research status of temperature field simulation, surface quality, microstructural features, including microstructures, microhardness, residual stress, and cracking, as well as corrosion behavior of metallic coating created by pulsed laser material deposition have been reviewed. Furthermore, the existing knowledge and technology gaps are identified while the future research directions are also discussed.

Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation and waste disposal issues, respectively. While these materials are affordable and display good thermal insulation, their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns. Alternative insulation materials with enhanced sustainable characteristics are therefore being explored, and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre. Among the few review studies conducted on Natural Fibre Reinforced Composite (NFRC) insulation boards, the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered. This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs. Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs, namely the fibre lumen size, α, and the fibre-matrix thermal conductivity ratio, β, respectively, were found to largely affect the Transverse Thermal Conductivity (TTC) in NFRC boards. Extrinsic factors, which were found to indirectly affect NFRCs’ thermal conductivity, such as fibre pre-processing, composite manufacturing and environmental factors, were also covered. Some of the noteworthy NFRC features which were found to affect their thermal conductivity are volume fraction of fibres, bulk density and porosity. The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres, composition and fabrication techniques. The fabrication of high-grade NFRC boards, which will display an optimum balance between enhanced thermal insulation and long-term durability performance, could further replace conventionally used thermal insulation boards in the modern building and construction industry.

This paper reviews the status of nanoparticle technology as it relates to the additive manufacturing (AM) of aluminum-based alloys. A broad overview of common AM processes is given. Additive manufacturing is a promising field for the advancement of manufacturing due to its ability to yield near-net-shaped components that require minimal post-processing prior to end-use. AM also allows for the fabrication of prototypes as well as economical small batch production. Aluminum alloys processed via AM would be very beneficial to the manufacturing industry due to their high strength to weight ratio; however, many of the conventional alloy compositions have been shown to be incompatible with AM processing methods. As a result, many investigations have looked to methods to improve the processability of these alloys. This paper explores the use of nanostructures to enhance the processability of aluminum alloys. It is concluded that the addition of nanostructures is a promising route for modification of existing alloys and may be beneficial to other powder-based processes.