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To improve the fatigue performance of turbine blade tenon， the effect of shot peening on the surface integrity and high temperature fatigue performance of DD412 single crystal alloy was investigated. The surface morphology， roughness， hardness gradient and microstructure after shot peening were characterized by white light interferometer， roughness tester，microhardness tester， scanning electron microscope and transmission electron microscope respectively. The results show that after shot peening， the surface grinding tool marks are eliminated， and the surface micro stress concentration factor is significantly reduced. Severe plastic deformation occurr in the surface layer of the specimen， and a hardened layer with a depth of about 0.10-0.32 mm is formed.The mean fatigue life of the optimal shot peening specimens at 600 ℃/500 MPa is increased by more than 21.7 times， and the median fatigue limit at 600 ℃ is increased by 17.3%. The favorable change of surface integrity is the main reason for the improvement of high temperature fatigue properties of DD412 alloy after shot peening.

In the global pursuit of energy conservation, reduction in consumption and emissions, as well as lightweighting, 5xxx-series aluminum alloys have emerged as a promising lightweight and high-strength material with a wide range of applications in aerospace, transportation, building structures, medical devices, and more. However, it is worth noting that 5XXX-series aluminum alloys belong to a category of non-heat-treatable reinforced aluminum alloys with limited means of enhancing their properties through heat treatment. Consequently, the development of high-performance 5XXX-series aluminum alloys poses a significant challenge. This paper provides an overview of the research progress on 5xxx-series aluminum alloys while discussing the current state of research regarding the influence of microalloying elements on their microstructure and properties. Furthermore, it elucidates the emerging trends in synergistic regulation between deformation processes and heat treatment processes for enhancing organizational refinement and improving alloy properties. Additionally, this study analyzes the reinforcement mechanism responsible for the exceptional properties exhibited by 5xxx-series aluminum alloys. Lastly, it discusses the exceptional properties exhibited by 5xxx-series alloys along with their primary areas of application. The findings presented herein can serve as a valuable reference for future advancements in advanced high-performance 5xxx-series aluminum alloys.

Powder Plasma Arc Additive Manufacturing (PPA-AM) technique has tremendous potential for the practical application in medium-entropy alloys (MEAs). In this study, we investigated the effect of heat treatment on microstructural evolution, mechanical properties, and the work hardening behavior in the PPA-AM processed (CoCrNi)90Al5Ti5 MEA. The results show that the As-built specimen is a single-phase FCC structure, displaying strong FCC texture in the deposition direction. The stacking faults (SFs) and dislocations were observed in the alloy, which formed the stacking fault networks and the Lomer-Cottrell locks structure. The plasticity of the alloy increased significantly after the high-temperature heat treatment, which can be attributed to the modifications of the microstructure, such as the weakening of the texture strength and the reduction of the stresses. Low-temperature heat treatment decreases the density of dislocations in the alloy, but promotes the generation of the co-lattice phase. The evolution of the dislocation density, texture strength, and precipitates significantly influenced the strain hardening behavior and mechanical properties. The tensile results showed that the strength and plasticity of the samples were increased after two-step heat treatment. The yield strength, ultimate tensile strength, and elongation to failure were 733 MPa, 1080 MPa, and 22.3%, respectively, which were 16.2%, 20.3%, and 15.5% higher than the As-built samples. This work elucidates the underlying mechanisms of heat treatment on the microstructure and mechanical properties of the alloy.

The food concept of "healthy low-fat" had attracted significant public attention in recent years. Oxidized konjac glucomannan (OKGM) was introduced as a fat replacer to address the issue of low gel strength in low-fat yoghurt. The effects of different oxidation degrees of OKGM on the quality of yoghurt were investigated by analyzing the physicochemical properties, texture, rheological properties and microstructure of yoghurt. The research demonstrated that yoghurt containing high oxidation degrees of OKGM (OK-60, OK-90, OK-120) increased the hardness from 375.90 g to 436.67 g and the water holding capacity from 28.03% to 31.89% compared to yoghurt without added OKGM. In addition, it improved the rheological properties of yoghurt including apparent viscosity and viscoelasticity. The results of scanning electron microscopy and confocal laser microscopy revealed that high oxidation degrees of OKGM reduced integral pores in yoghurt, promoted casein micelles aggregation, and increased average particle size from 88.27 nm to 125.33 nm. In contrast, natural konjac glucomannan (KGM) and lower levels of OKGM oxidation (OK-30) reduced texture, apparent viscosity, and viscoelasticity of the yoghurt, disrupted yoghurt gel structure and compromised its stability. The results of sensory evaluation showed that high oxidation levels improved the glossiness, uniformity, and overall taste of yoghurt, providing a theoretical basis for the development of high-quality, low-fat, and healthy yoghurt products.

316L stainless steel (316L SS) is easy to be damaged due to poor corrosion and wear resistance, the preparation of composite coating with excellent corrosion and wear resistance properties on the surface can lengthen its service life. In this aspect, Fe-based amorphous CoCrFeNi high entropy alloy (HEA) composite coating was prepared on 316L SS by laser cladding. The microstructure, phase, microhardness, wear and corrosion resistance of the coatings were analyzed by scanning electron microscope (SEM) equipped with energy disperse spectroscopy (EDS), X-ray diffraction (XRD), Vickers hardness tester, electrochemical workstation, and the friction and wear tester. The results show that the phase composition of the coatings was FCC solid solution. The microstructure of the coatings gradually evolved from regular cellular crystals to irregular amorphous structures, while the microhardenss of each coating changed little. The wear and corrosion resistance of the coatings was better than that of the substrate. When the content of Fe-based amorphous is 8%, the properties of the coating are the best.

The present study tested the effect of addition of whole common buckwheat flour on the rheological properties of wheat dough, and the textural characteristics, water distribution, secondary structure and molecular mass distribution of proteins, microstructure, and color of fresh noodles. The results demonstrated that the dough with 30% whole common buckwheat flour had a higher G’ (5.3 × 105 Pa) and a minimum tan δ value of 0.50. The resulting noodles had a maximum elasticity of 0.97, a maximum α-helix content of 28.30%, and a denser and more homogenous microstructure. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) data, the band intensities of buckwheat protein subunits increased with increasing addition of whole common buckwheat flour. Compared with the control group, the addition of whole common buckwheat flour caused partial transformation of tightly bound water to weakly bound water and free water. As the addition of common buckwheat flour increased, the L* value of noodles decreased significantly, the a* and b* values increased to varying degrees, and as a result the overall color turned reddish and yellow. In conclusion, the addition of 30% whole common buckwheat flour can improve the mechanical properties and processing quality of fresh noodles.

Magnesium alloys, acknowledged as the environmentally-friendly engineering material of the 21st century, are ideally suited to fulfill the requirements of lightweight manufacturing. However, the poor plasticity of magnesium alloys hampers their further application. Subsequently, development of nanoparticle-reinforced magnesium matrix composites has been proven to be a promising way to enhance the comprehensive performance of magnesium alloys. The exceptional performance achieved even by very small number of reinforcements stimulated innovation in preparation techniques and in-depth analysis of reinforcement mechanisms. This paper provides a review on key challenges related to their processing, the profound impact of different micro-nanoparticle reinforcements on the microstructure and properties of magnesium matrix composites during solidification and subsequent deformation machining. Additionally, the reinforcement mechanisms of the excellent mechanical performance of the composites are also discussed. This study can provide valuable insights for the understanding of the selection of appropriate reinforcements and processing to optimize the performance nanoparticle-reinforced magnesium matrix composites.

In this study, a hot isostatic pressing (HIP) manufactured SiC particles (SiCp) reinforced high alloyed Al–Zn–Mg–Cu–Zr–Ti aluminum matrix composite was fabricated through ball-milling, HIP, homogenization, hot extrusion, solution treatment, and aging treatment. The results showed the presence of an interfacial reaction layer, MgAl2O4, around the SiCp, which enhanced the bonding between the particles and the matrix. The aging treatment resulted in the formation of different aging precipitates, which were featured by GP zone for T4, GP zone + η' (metastable MgZn2) + η (stable MgZn2) for T6 and GP zone + η' (metastable MgZn2) for T6I4. The composite samples of T4, T6, and T6I4 exhibited different mechanical properties. Specifically, the elastic modulus was measured as 102.9, 103.4, and 102.3 GPa, the yield strength was 685.3, 598.1, and 619.7 MPa, the ultimate tensile strength was 713.6, 618.9, and 633.3 MPa, and the elongation was 2.2%, 1.8%, and 2.8%, respectively. Furthermore, the corrosion behavior of the composite was evaluated through electrochemical, intergranular corrosion, and exfoliation corrosion. The corrosion current density was found to be 3.17 × 10−7, 4.97 × 10−7, and 3.67 × 10−7 A cm−2, the corrosion potential was measured as −0.70, −0.81, and −0.56 V, and the maximum intergranular corrosion depth was 139.9, 167.8, and 106.2 μm for T4, T6, and T6I4, respectively. The severity of exfoliation corrosion varied, with T4 showing severe pitting, T6 exhibiting moderate pitting, and T6I4 displaying slight pitting. The strengthening mechanism and load transfer strengthening of the composites were discussed in detail based on theoretical calculations, and the anti-corrosion mechanisms were also analyzed.

Magnesium (Mg) matrix composites (Mg-MMCs) with high strength and ductility properties are crucial for the development of lightweight automobiles. In this study, a novel method is proposed for fabricating Mg-MMCs by incorporating nanocopper (Cu) decorated titanium (Ti) particles (Cu@Ti) to reinforce AZ91 alloys. The in-situ generation of the AlCuMg phase at the interface between the Ti particles and the Mg matrix enhances interface integration and promotes the formation of massive twins. The 5.0 wt% Cu@Ti/AZ91 composite exhibits notable mechanical properties, with a yield strength of 238 MPa, ultimate tensile strength of 368 MPa, elongation of 12%, and modulus of elasticity of 46 GPa. These values represent increases of 8.9%, 5.3%, 50.0%, and 2.0%, respectively, compared to those of AZ91 alloys. The strengthening mechanism is mainly attributed to grain refinement strengthening, thermal expansion coefficient mismatch strengthening, Orowan strengthening, and load transfer strengthening. The plasticity improvement benefits from the optimization of the interface structure, grain refinement and twin formation.

Herein, we investigate the influence of heat treatment on microstructure and thermo-physical properties of Al-50wt%Si alloy fabricated by selective laser melting (SLM). Microstructure characterizations reveal that SLM and heat-treated Al-50wt%Si alloys are all characterized by the primary Si and eutectic structure consisting of dominant Al matrix and tiny eutectic Si. However, the size of primary Si monotonously increases with increasing the heat treatment holding time at 550 °C. In addition, the SLM Al-50wt%Si alloy displays a highest coefficient of thermal expansion (CTE) among all examined alloys. As the heat treatment holding time increases, the Si precipitates from the Al(Si)-supersaturated solid solution, leading to the formation of a skeleton-like Si phase, which effectively alleviates the thermal expansion. Furthermore, the SLM Al-50wt%Si alloy exhibits a lowest coefficient of thermal conductivity (CTC), since the significantly increased size of primary Si with increasing the heat treatment holding time leads to a substantial reduction in the number of grain boundaries, which severely restricts the scattering of heat transfer phonons. Moreover, theoretical models are employed to calculate the CTE and CTC. Results indicate that the Schapery lower model provides a better prediction of CTE, and the actual CTC values of Al-50wt%Si alloys after heat treatment are closer to theoretical values. These findings can provide new insights into designing Al matrix composites with low CTE and high CTC through microstructural optimization.

The presence of high-density defects is rarely observed in bulk 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics obtained through conventional pressureless sintering. In the present work, fine-grained dense 147 nm 3Y-TZP ceramics were prepared by pressureless sintering of commercial 0.25 wt% alumina-doped zirconia powders at 1300 ℃. A novel discovery was reported in which large amounts of defects were present in the grain interiors of the sample. The phenomenon was further examined using three types of powder samples, and the reasons for defect formation were investigated by microstructural characterization using high-resolution transmission electron microscopy (HRTEM) analysis and Rietveld refinement. The results confirmed the essential dependence of the defect formation on the alumina addition. The authors attributed the defect formation to the significant difference in ionic radii of the solvent and solute during the dissolution of alumina into the zirconia lattice. The sintering kinetics were proposed to be enhanced by the presence of substantial defects, which consequently favored the low-temperature sintering of the alumina-doped zirconia ceramics.

NiTiTa ternary shape memory alloy is a potential biomedical material, and wire arc additive manufacturing (WAAM) technology has been widely used in the research of NiTi alloys. It is of great significance to study the effect of Ta addition on the microstructure and properties of WAAM NiTi alloys. In this paper, 5-layer NiTi and NiTiTa alloy walls were fabricated by WAAM technology, and the effects of Ta addition on the microstructure, phase transformation behavior, mechanical properties and corrosion resistance of NiTi alloys were systematically studied. The results show that the grains of the NiTiTa alloy are remarkably refined compared with NiTi alloys, and the precipitation phase of NiTiTa alloy changes from Ni3Ti of NiTi alloy to Ni(Ti, Ta)2. In addition, the phase transition temperature of the NiTiTa alloy is significantly increased, which makes the phase at room temperature change from the complete austenite phase (B2) to a mixed phase of austenite (B2) and martensite (B19'). Tensile tests show that the tensile strength of NiTiTa samples is increased by 9.5% compared with NiTi samples, but the elongation is decreased by 6.8%. The polarization curve results show that the NiTiTa alloy has a higher corrosion potential and a lower corrosion current density, which means a significantly improved corrosion resistance. This paper lays a theoretical foundation for promoting the application of NiTiTa alloys fabricated by WAAM technology in the biomedical field.

Compacted graphite iron (CGI) is an engineering material with the potential to fill the application gap between flake- and spheroidal-graphite irons thanks to its unique microstructure and competitive price. Despite its wide use and considerable past research, its complex microstructure often leads researchers to focus on models based on representative volume elements with multiple particles, frequently overlooking the impact of individual particle shapes and interactions between the neighbouring particles on crack initiation and propagation. This study focuses on the effects of graphite morphology and spacing between inclusions on the mechanical and fracture behaviours of CGI at the microscale. In this work, 2D cohesive-zone-element-based models with different graphite morphologies and spacings were developed to investigate the mechanical behaviour as well as crack initiation and propagation. ImageJ and scanning electron microscopy were used to characterise and analyse the microstructure of CGI. In simulations, both graphite particles and metallic matrix were assumed isotropic and ductile. Cohesive zone elements (CZEs) were employed in the whole domain studied. It was found that graphite morphology had a negligible effect on interface debonding but nodular inclusions can notably enhance the stiffness of the material and effectively impede the propagation of cracks within the matrix. Besides, a small distance between graphite particles accelerates the crack growth. These results can be used to design and manufacture better metal-matrix composites.

To cater to the diverse requirements of industrial applications, it is crucial to conduct a comprehensive investigation into the influence of laser shock peening (LSP) with and without coating (LSPwC) on the microstructure and mechanical properties of materials. This study employs various methods to compare and analyze the effects of LSP and LSPwC on the microstructure and mechanical properties of GH4169 alloy. One notable contrast between LSP and LSPwC lies in the formation of oxide layers and microcracks on the surface of LSPwC-treated samples. Tensile tests subsequently reveal that LSP enhances the tensile strength, whereas LSPwC diminishes it. The reduced strength in LSPwC-treated samples can mostly be attributed to the oxide layer and microcracks resulting from laser-induced heat, as determined through failure analysis. After the removal of the oxide layer, the strength undergoes a significant improvement with LSPwC treatment, surpassing both the strength and ductility levels observed in GH4169 treated with LSP alone. These improvements can be attributed to a combined effect involving the removal of the oxide layer and microcracks, the formation of a gradient hardened layer, and the presence of dense slip bands.

To facilitate and even complete the peritectic transformation, the ultrasonic vibration (USV) and isothermal treatment were applied to the solidification process of Cu–70Sn alloy. It was found that the peritectic transformation was difficult to carry out due to the limited atomic diffusion under the normal solidification condition. With the single isothermal treatment, the peritectic transformation could be enhanced to some extent, with a small amount of η phase (Cu6Sn5) formed relying on the coarse elongated primary ε phase (Cu3Sn), but the further prolongation of isothermal time led to the abnormally coarsening of microstructure. When the molten alloy was subjected to 1500W USV and 30 min isothermal treatment, the peritectic transformation was dramatically facilitated. The ultrasonic-induced effects of cavitation and acoustic streaming play an important role in the remarkable reduction in the curvature radius of primary ε phase, thereby enhancing the diffusion of Sn solute atoms from the liquid phase to the interior of ε phase at the following isothermal stage. Accordingly, the transformation degree of ε phase to η phase was increased up to 77 %, and there was a high volume fraction of primary ε phase could thoroughly complete the peritectic transformation.

Effect of duplex grain size distributions on long-term stress-rupture life of Nimonic 80A had been investigated. Non-homogeneous duplex grain size distributions greatly reduce stress-rupture life. Regional distribution of coarse grains is not good for acquiring high stress-rupture life, the formation of micro-void and propagation of cracking can easily occur at coarse grain boundary especially when plate-like Cr23C6 precipitates at grain boundary. But relatively homogeneous duplex grain size distributions are of great significance in improving stress-rupture life, the samples even possess the life value up to more than 13000 h especially when hardly any plate-like Cr23C6 precipitates at grain boundaries. Slightly increased Ti/Al ratio from 1.65 to 1.80 is also beneficial to obtain a significantly longer stress-rupture life value. The γ′ phase is very stable and always exhibits a coherent orientation relationship with γ on {100} and {111} atomic planes. The grain boundary cracking will not easily appear at the early stage of stress-rupture test in the samples with relatively homogeneous grain size distribution, the coarse and adjacent fine grains possess better deformation adjustability, and the grain boundary cracking is apparently wider and the number of cracking is also getting more after fracture for the sample with longer stress-rupture life.

Lithium slag (LS) is a waste residue generated during lithium extraction, posing significant environmental challenge due to its extensive accumulation. This study proposes a method of utilizing thermally activated LS as the sole precursor for geopolymer synthesis. The thermal activation mechanism of LS was investigated using XRD, FTIR, ICP, and SEM techniques, while exploring the optimal composition for LS geopolymers(LSG). The research revealed that heating at 700 °C increased the amorphous content of LS from 15.9 % to 48.1 %, altering the chemical structure of its aluminosilicates and enhancing its leaching capacity in alkaline environments, thereby boosting its reactivity. The activator modulus and alkali equivalent were found to significantly influence the strength and microstructure of LSG. As the modulus increased from 1.0 to 1.4, geopolymer strength initially rose before declining, whereas strength progressively increased with alkali equivalent from 0.10 to 0.16. The geopolymer synthesized with a modulus of 1.2 and alkali equivalent of 0.16 exhibited the highest compressive strength of 53.1 MPa after 28 days. Test results indicated that the internal structure of LSG primarily comprised unreacted particles, N(C)-A-S-H gel, and microcracks. The increased alkali equivalent facilitated the dissolution of Si4+ and Al3+ within LS, intensifying geopolymerization to produce more N(C)-A-S-H gel, thereby densifying the structure and significantly enhancing compressive strength. This study elucidates the mechanism by which high-temperature calcination enhances LS reactivity, as well as the impact of activator on compressive strength and microstructural properties of LSG, offering new insights into the engineering applications of LS in high-performance cementitious materials.

Neutralization slag (NS) of copper smelting is a waste residue mainly composed of calcium sulfate, which is produced during the process of metal smelting. The large accumulation and storage of NS poses a significant threat to the environment. Therefore, it is imperative to explore a new economically and environmentally friendly approach for recycling NS. This study proposes a method for preparing a new eco-friendly geopolymer material by utilizing NS. A geopolymer with satisfactory mechanical properties was created by employing a hybrid solid activator consisting of CaO-Na2SiO3. The effects of hybrid solid alkali activators calcium oxide (CaO)/sodium silicate (Na2SiO3) ratio on the hydration properties of the NS-based geopolymer were studied, and its curing mechanism was discussed. The results show that, when the hybrid solid activator CaO/Na2SiO3 ratio was 3:1, the maximum 28 d compressive strength of the geopolymer reached 27.8 MPa. The solid activator at a suitable ratio can accelerate the hydration reaction, form higher amounts of C-A-S-H gel and ettringite, reduce the proportion of harmful macropores in the geopolymer, and improve the microstructure of the geopolymer. Toxicity characteristic leaching procedure (TCLP) test confirmed that the NS-based geopolymer had a solidification effect on heavy metals. The leaching concentration of elemental Pb from the neutralised slag feedstock was 7.241 mg/L, while the lowest concentration was 0.286 mg/L in the NS based geopolymer. As a green cementitious material, the NS-based geopolymer is expected to be applied in engineering practice.

Rapidly growing urbanization and industrialization drive the continued development of soil stabilization and ground improvement techniques. Rice husk ash (RHA) is widely regarded as a highly promising construction material in civil engineering due to its excellent pozzolanic properties and has garnered significant attention from researchers. This paper presents an experimental study and a micro-mechanical discussion on the role of RHA in the mechanical improvement of soil. RHA was mixed with the native soil in varying proportions, ranging from 0% to 12%. Several laboratory tests were conducted, including standard proctor compaction tests, Atterberg limit tests, freeze-thaw tests, unconfined compression tests, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The results indicated that the optimal moisture content (OMC) of the soil mixture increased while the maximum dry density (MDD) decreased with higher RHA dosage. The Atterberg limits of the soil mixture exhibited a positive correlation with the RHA content. A substantial enhancement in the soil's strength, stiffness, and ductility was observed upon the incorporation of RHA. It was noted that the strength loss of the untreated samples and those with 12% RHA was 34.91% and 12.89%, respectively, following 12 freeze-thaw cycles. Furthermore, XRD test results revealed that the treated specimen had an identical mineral composition to the control specimen, with no generation of hydration products. SEM analysis also highlighted that the filling effect of RHA significantly reduced pore content and pore connectivity within the soil, accompanied by a shift in the specimen's pores from mesopores to small and micropores. The excellent thermal insulation and heat retention properties of RHA, along with its pore-refining effect, make a positive contribution to enhancing the frost resistance of the specimens. These findings contribute to guiding the effective application of RHA in civil engineering, offering eco-friendly solutions for biomass waste management, and promoting the sustainable development of construction materials.

The copper crystal cone-shaped micro-nanostructure is used as the substrate, and the Ni–W alloy layer and Au nanolayer are plated sequentially. Instantaneous soldering with lead-free solder is realized under ultrasonic assistance at room temperature. This solves the residual stress and thermal damage caused by high melting point lead-free solder on thin chips and thermal components, and ensures the safety and reliability of electronic components. Copper-based microstructures are deposited by electrochemical methods. An amorphous Ni–W alloy layer with a thickness of 180 nm is deposited on the Cu-based microstructures by adjusting the atomic ratio of the plating solution. The Ni–W layer is further coated with a 50 nm Au layer to prevent oxidation. Solid-phase transient soldering is realized by combining the Au/Ni–W multilayer thin-film-modified Cu substructures with commercial solder (SAC305) for a holding time of 3 s at a soldering pressure of 10,000 gf (20 MPa) while ultrasonically assisted. The soldered samples are aged at 180 °C for 10 min, 30 min, and 60 min, respectively. Copper substructures with different surface modifications are subjected to destructive shear experiments with solder balls. Scanning electron microscope and X-ray fluorescence thickness gauge are used to study the microstructure, intermetallic compound (IMC) composition thickness and properties of the soldered interface and section. The cone height of the Cu-based structure is 2–4 μm, and the diameter of the bottom is 800 nm–1200 nm, which has a sharp tip and an excellent L/D ratio. The interface between the Au/Ni–W modified Cu substructure and the solder ball is almost free of holes. The average shear strength at the soldering interface is about 43.06 MPa. The fracture surface after the shear experiment basically occurs inside the solder ball matrix, which belongs to the pure toughness fracture. The interface between the Au/Ni–W-modified Cu-based structure and the solder ball is subjected to long aging treatment at 180 °C. The soldering interface showed a “bright layer”. New phases are generated on the solder side above the “bright layer”, while no new phases appear on the Cu substructure side below the “bright layer”. The copper-based microstructure is inserted into the inside of the solder ball to form an inlay and produce mechanical interlocking. Au/Ni–W alloy modification layer can effectively improve the surface hardness of copper-based structures. This creates a large hardness difference with soft solder and enables the formation of fewer holes in the insertion solder. Amorphous Ni–W alloys are prone to form dense oxide films during ultrasonication. The Au film modification prevents oxide generation and increases the average shear strength of the soldering interface. The Ni–W alloy layer retards the interdiffusion between Cu–Sn, blocks the excessive growth of Cu–Sn IMCs, and reduces the reliability problems caused by interface failure.

Abstract Lead‐free polycrystalline manganese telluride holds great potential in the development of waste heat recovery due to its fascinating physical properties. However, the poor thermoelectric (TE) performance in the p‐type MnTe alloys always results from their inferior carrier concentration, leading to low power factor and high thermal conductivity which restrict the overall thermoelectric performance. In this work, the problem is solved by decoupling its electrical and thermal transports through the hole donor Ge‐deficiency in MnTe + x mol.% GeTe (0 ≤ x ≤ 4) compounds. Intrinsically, extra GeTe in MnTe + x mol.% GeTe compound offers free charge carriers due to a narrow bandgap comparatively, realizing not only a full assessment of stimulated electrical performance but also an enhanced power factor. Moreover, benefiting from the nano‐precipitates and tweed microstructures, the lattice thermal conductivity effectively reduces due to the intensive phonon scattering accordingly. Ultimately, a maximum ZT of ≈1.2 at 873 K in the 3 mol.% GeTe doped MnTe sample is realized.

Nickel-based superalloys have attracted significant attention due to their outstanding high-temperature strength, corrosion resistance, and oxidation resistance, and are widely used in aerospace and other fields. This article provides a comprehensive review of the preparation methods, common grades, and microstructure and properties of additive manufactured nickel-based superalloys, summarizes the current issues, and proposes future areas for exploration. Nickel-based superalloys prepared by metal additive manufacturing technology have excellent performance, can achieve precise forming of complex components, and have minimal material waste during the manufacturing process. They are expected to become an important production process for nickel-based superalloys components in fields such as aerospace. Common methods for additive manufacturing of nickel-based superalloys include laser powder bed melting, directed energy deposition, and arc additive manufacturing. Powder bed melting is widely used for manufacturing high-precision and complex parts, but it has a relatively slow manufacturing speed and higher equipment and material costs. Directed energy deposition has higher degrees of freedom and flexibility and can be used to prepare functional gradient materials, but it has lower accuracy. Arc additive manufacturing has lower equipment and material costs and is suitable for rapid manufacturing of large parts, but the surface roughness of the alloy produced by this method is poor and requires additional processing or post-treatment. Nickel-based superalloys widely studied in the additive manufacturing process include IN625, Hastelloy X, and other solid solution strengthened alloys, as well as IN718, CM247LC, IN738LC, and other precipitation strengthened superalloys. Compared with traditional casting and forging methods, the unique layer-by-layer forming and rapid cooling and heating process of additive manufacturing result in a coarse columnar grain structure and a unique microstructure with a large number of fine grains. It also forms unique melt pool structures and dislocation cell structures. However, the alloys obtained by additive manufacturing generally require heat treatment to control grain structure and precipitated phases, which affects the mechanical properties of the alloy. In addition, the mechanical properties of additive manufactured nickel-based superalloys are also related to specific preparation methods and alloy types. Although additive manufacturing has been widely used in the preparation of nickel-based superalloys, there are still issues such as anisotropy in microstructure and properties, high sensitivity to alloy cracking, and a lack of corresponding specifications and standards. In the future, further exploration is needed in areas such as heat treatment, customization and development of specialized alloys, investigation of the process-structure-function relationship, and computational modeling.

The continuous annealing treatment of 5052 aluminum alloy pipe fittings for alpine skiing sticks was carried out in the temperature range of 300-500 °C by means of metallographic observation and mechanical property test. The results show that with the increase of annealing temperature, the strength and hardness of the samples decrease continuously, and the impact value, section shrinkage and elongation change significantly. The experimental results provide a technical reference for preventing the fracture of alpine skiing sticks during use.

Abstract The use of cement-based composites (CBC) with high thermal conductivity for geothermal well cementing is extremely important for the efficient development and use of geothermal energy. Accurate prediction of thermal conductivity can save a lot of experimental costs and time. At present, there is no specific calculation model for the thermal conductivity of CBC. In this study, the microstructure, thermal conductivity model and influencing factors of CBC were investigated by experimental tests, theoretical analysis and numerical simulation. The results showed that the cement-based material could be simplified into a two-layer structure of hydrated and unhydrated layers. Mathematical and numerical models based on the coupled Series model and the Maxwell–Eucken model were established to calculate the thermal conductivity for CBC. The mathematical and numerical models were found to be more accurate by comparison with the conventional models and experimental test results. The cubic packing was more favorable than the spherical packing to improve the thermal conductivity of CBC. The plate material had significant anisotropy. The thermal conductivity of CBC showed a rapid decrease followed by a slow decrease, a decrease followed by a slow increase and finally a rapid decrease, a rapid increase followed by an up and down fluctuation and finally a plateau, respectively, with the increase of filler particle diameter, spacing and curing temperature. Based on these results, the effective methods and future research directions were proposed to maximize the thermal conductivity of geothermal well cementing materials in actual engineering applications. The research findings can provide some technical references for the efficient development of geothermal energy and research on CBC with high thermal conductivity.

The hot deformation behavior and microstructure of Fe-12.5Cr–4Al–2Mo-0.03Nb-0.08Y alloy were studied under conditions of 800 °C–1200 °C/0.01 s−1∼10 s−1 using a combination of hot compression experiments, EBSD and TEM characterization. The results indicate that the deformation temperature and strain rate have a significant impact on the flow stress and microstructure of the alloy, especially the deformation temperature. The constitutive equation constructed in this paper can reflect the hot deformation process and accurately calculate flow stress value of the FeCrAl alloy in corresponding states. The FeCrAl alloy undergoes DRV and DRX during hot deformation. DDRX grains distributed along the original grain boundaries mainly formed at low deformation temperatures and high strain rates, while CDRX grains mainly formed at high deformation temperatures and low strain rates and characterized by the internal distribution of the original grains. Moreover, the orientation of DDRX grains is mostly different from that of adjacent original grains, while the orientation of CDRX grains is relatively close to that of the original grains.