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Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, cement and dechlorinated Polyaluminum Chloride Residue (PACR) have been used to prepare a net slurry and mortar specimens. Two hydration activity indicators have been used to quantitatively analyze the dechlorinated PACR hydration activity. In particular, the effect of dechlorinated PACR content on the compressive strength of mortar has been assessed by means of compressive strength tests. Moreover, X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been employed to observe the microstructure of the considered hydration products. The following results have been obtained. The 28th day activity index of the dechlorinated PACR is 75%, and therefore it meets the criterion for the use of active admixture. The increase in the content of the dechlorinated PACR tends to reduce the compressive strength of mortar specimens, however, it is beneficial to its later strength growth. When the content is not greater than 10%, the strength remains unchanged, otherwise, it decreases. The PACR does not form a new crystalline phase in the cement slurry, and the dechlorinated PACR remains active until the age of the 28th day. The inclusion of the PACR mainly deteriorates the early strength of the cement slurry, but it promotes the production of hydration products in the cement slurry after the 7th day. [ABSTRACT FROM AUTHOR]

The microstructure evolution of TC18 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe) after β solid solution plus aging (β-STA) and β annealing slow cooling plus aging (BASCA) heat treatments were investigated in this paper. The effects of microstructure on tensile properties and plastic deformation behavior were studied. The results suggested that α lamellar structures are formed after both STA and BASCA heat treatment. A multi-scale lamellar structure consisting of micro- and nano-scaled α platelets is formed during BASCA treatment, whereas β-STA treatment mainly generated conventional lamellar structure. In addition, the alloy after β-STA treatment displayed high strength but limited elongation, while the alloy after BASCA treatment exhibited good strength-ductility combination. A model considering α/β phase boundary strengthening, solid solution strengthening and dislocation strengthening is applied to analyze the strength of the alloy. Finally, the plastic strain partition and deformation behavior of the lamellar structure are discussed. [ABSTRACT FROM AUTHOR]

AISI 4140 steel, known for its strength and wear resistance, is widely used in the oil industry, particularly for drilling equipment. However, its wear resistance varies based on the environment and drilling conditions, necessitating additional surface modifications for optimal performance. This paper investigates the microstructure and wear performance of AISI 4140 steel clad with WC-Ti composite powder using gas tungsten arc welding. Four different WC-Ti powders were used, with the Ti content ranging from 10 wt% to 40 wt%. The welding parameters were kept constant, except for the current intensity which was varied between 100 A and 120 A. The through-thickness micro-hardness profile and wear resistance were evaluated. Examinations revealed that, by increasing the current intensity from 100 A to 120 A, the size of the dendrites in the weld region grew. Simultaneously, mechanical properties such as hardness and wear resistance diminished. It was also found that, with the increase in the titanium content of the composite powder, the size of the dendrites decreased. The micro-hardness results indicated a rise in surface hardness from 250 HV (base metal) to a maximum of 850 HV (cladding). The higher the content of Ti in the composite powder, the greater the hardness and wear resistance of the cladding. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to deal with the problem that the marine concrete with large dosage of mineral admixture in the actual project faces the harsh marine environment prematurely and is easy to be eroded by chlorine salt, this paper proposed to use magnetized water instead of tap water to prepare marine concrete, studied the influence law of magnetized water on the mechanical properties and durability of marine concrete at different ages, and analyzed the microstructure of marine concrete using the mercury instrusion porosimetry and scanning electron microscope. The study shows that magnetized water improves the workability of marine concrete. Compared with tap water, magnetized water has obvious improvement on the early mechanical properties of marine concrete, in which the compressive strength and splitting tensile strength of C50 marine concrete with a curing age of 7 d increase by 17.9% and 16.5%, respectively. Regardless of different curing ages, the resistance to carbonation and chloride ion penetration of magnetized water marine concrete are better than tap water marine concrete. The degree of reaction of cementitious materials in magnetized water marine concrete is higher, with fewer cracks, and the microstructure between cementitious materials and aggregates is more compact. The overall porosity is lower, with more harmless pores and fewer harmful pores, leading to a denser microstructure. Thus the mechanical properties and durability of marine concrete are improved. [ABSTRACT FROM AUTHOR]

In this paper, the aluminum sulfate based alkali-free liquid accelerating agent was modified by fluorine silicon slag, and the performance index of alkali-free liquid accelerating agent modified by fluorine silicon slag was tested. XRD, TG-DTG and SEM were used to explore the action mechanism of aluminum sulfate base alkali-free liquid accelerating agent modified by fluorine silicon slag on cement hydration process. The results show that with the increase of fluorine silicon slag content, the rapid setting effect and strength of mortar increase first and then decrease. When the alkali-free liquid accelerating agent is modified by fluorine silicon slag, the appropriate content of fluorine silicon slag is 5.0% (mass fraction). At this time, the initial setting time is 1 min 20 s, the final setting time is 5 min 20 s, 1 d compressive strength is 13.8 MPa, and 28 d compressive strength is 52.4 MPa. Calcium silicate hydrate is formed by the reaction of silica in fluorine silicon slag and cement hydration product calcium hydroxide, which is beneficial to improve the early strength of cement. However, the process of cement hydration and hardening process is hindered by the reaction of fluorine and calcium hydroxide to produce a large amount of calcium fluoride precipitation. [ABSTRACT FROM AUTHOR]

In the manufacturing sector, welding has long been a popular method of combining materials. Hence, there has been a lot of research in this area, leading to evolution of conventional welding techniques. These developments widened its feasibility enabling the process to be functional in diverse crucial applications. A detailed review of various research efforts carried out in the field of welding provides an ideal repository which can effectively help identify various research gaps. This paper intends to throw light on the following aspects of welding: a detailed description of different fabrication methods involved in fusion and solid-state welding processes, weld performance evaluation on the basis of mechanical properties, microstructure, corrosion, wear and fatigue behaviour followed by a brief summary of various applications. The mechanical properties and microstructures of various commercially viable alloys like steel, DSS, Ti-6Al-4 V, Al- Mg alloy, AZ31, AA6061, Al-Zn-Mg-Cu and Ni-base super alloys have been discussed in detail. Various mechanisms which influenced the changes in microstructure and resulting mechanical behaviours have been discussed. The inferences obtained as a result of microstructural, mechanical, corrosion and wear property analysis have been correlated to understand major areas of application. The extensive data compiled in this study aims to give readers valuable insights and inferences on a vast topic, which promises great scope for development in the future. [ABSTRACT FROM AUTHOR]

Underwater welding offers a wide range of applications in a variety of disciplines. The notion of underwater welding appeals to many in the naval construction industry since it effectively repairs colliding and damaged ships. This paper mainly focuses on the characteristics of underwater weldings, such as arc bubble behaviour, rapid cooling and underwater welded joints. The properties of bubble behaviour, its effect on process stability and process parameters that influence bubble generation are discussed. Rapid cooling is a crucial problem faced by Underwater Wet Welding (UWW). Reducing welding speed and employing induction heating techniques can control the cooling rate while welding. The influence of water flow on weld metal shows that cold cracking is directly connected to the worse mechanical characteristics of wet weld joints under various flow conditions. The mechanisms of porosity generation are investigated using slag formation, CO production, hydrogen diffusion, and short-circuiting. Weld metal porosity is reduced when the hydrogen level and CO formation are reduced. Finally, the recent developments and challenges faced in UWW and industrial applications are addressed. [ABSTRACT FROM AUTHOR]

The phase changes of gypsum were considered to be sufficiently understood for a long time. However, due to the increasing importance of gypsum recalcination (connected with the planned closure of thermal power plants resulting in a lack of FGD gypsum) and new detailed research associated with it, gaps in the current knowledge have been discovered. This paper clarifies phenomena occurring during the production of gypsum binder, anhydrite, and potentially eco-friendly calcium sulfate-based ceramics at 22–1300 °C by in-situ XRD, thermal analysis, and SEM. It was found that undesirable insoluble anhydrite II arises even in the temperature range from 40 to 90 °C despite the current state-of-the-art. New knowledge about the existence of the individual phases, microstructure (cracking of crystals; fragmentation and sintering of anhydrite AII at temperatures above 700 °C when a ceramic-like material is formed), and their external consequences (changes in moisture and heat transport properties) has been gained. [ABSTRACT FROM AUTHOR]

Titanium alloys are considered lightweight alloys and are widely applied across various industries. However, titanium alloys are prone to wearing out or galvanic corrosion. In this paper, Ti6Al4V alloy was scanned by using a continuous laser in different atmospheres to prepare composite hardening coatings. The scanning speed was varied to adjust the heat input. When the alloy was irradiated in air, a whole coating composed of TiO2 and TiN was fabricated. With the increase in scanning speed from 10 mm/s to 20 mm/s, the melting area of the surface decreased from about 1.8 mm to 0 mm, but the thickness of the coatings underwent no significant change. When prepared under compressed oxygen with a speed of 10 mm/s, a coating with a thickness of about 60 μm was prepared. In addition, the layered phenomenon occurred, and an N-enriched layer was formed at the bottom of the coating. The coatings were composed of TiO2, TiN and Ti. With the increase in the scanning speed, the thickness of the coatings decreased obviously. The testing results show that the hardness of samples Ti-A10 and Ti-O10 increased by around 160% and 140% over that of untreated samples, respectively. The anti-corrosion performance of the samples treated via laser scanning was also improved. [ABSTRACT FROM AUTHOR]

Due to wear and improper operation, many machine parts become useless, which is why issues of friction and wear remain constantly relevant across all industrial sectors. This paper presents the results of research on the microstructure and properties of a nanostructural composite coating containing solid lubricant. The coating was deposited from a mixture of nanostructural WC-12Co powder and nanostructural Fe3O4 powder using HVOF spraying. Despite significant differences in grain size and density of both powders, the deposited coating consisted of WC-12Co matrix containing evenly distributed Fe3O4. The XRD analysis of the coating confirmed the presence of both components and the presence of W2C, which resulted from the decarburization of WC due to the high temperature during the spraying process. Furthermore, the microstructure analysis of the coatings confirmed that they contained both nanostructural WC and Fe3O4 grains that were present in the feedstock. The coefficients of friction, microhardness, and wear of the nanostructured composite coatings were determined using an experimental binomial program. Based on the ANOVA conducted, it was determined that the most significant impact on the friction coefficient is the Fe3O4 content in the sprayed mixture, while the oxygen to propane ratio affects the microhardness. For the wear of nanostructural composite coatings, the most important parameter is the spraying distance. [ABSTRACT FROM AUTHOR]

304 stainless steel demonstrates a low thermal conductivity and work hardening characteristics, resulting in its processing, and will adhere to the tip of the tool; as well as the phenomenon of chipping, shortening the life of the tool. AlTiN coatings are representative of coatings applied to carbide tools. In this paper, AlTiN coatings with different arc current processes were deposited on carbide milling inserts using arc ion plating. The microstructure, mechanical properties, and milling properties of the coatings were investigated by using the SEM, EDS, XRD, scratch meter, friction and wear meter, and vertical machining center. The findings revealed that all coatings displayed columnar crystal growth, free from cracks and voids. With an increasing arc current, there was a notable increase in surface droplets, pits, and coating thickness. The coating deposited at a 140 A arc current showed a pronounced (200) orientation preference. The adhesion force peaked at 56.0 N with a subsequent decline, and the friction coefficient hit its lowest point of 0.429 at 140 A, contrasting with its highest value of 0.55 at 160 A. After 39 min of dry milling, the tool with a 140 A AlTiN coating exhibited minimal wear of 0.196 mm, just below the 0.2 mm failure threshold, indicating superior performance at this arc current setting. [ABSTRACT FROM AUTHOR]

Laser cladding technology is an effective surface modification technique. In order to prepare coating with excellent properties on the surface of the cold heading die punch, stellite-6 cladding coating with different proportions of Y2O3 was prepared on the surface of W6Mo5Cr4V2 high-speed steel using laser cladding technology in this paper. The effects of different Y2O3 contents on the macroscopic morphology, microstructure, phase analysis, microhardness, and tribological properties of the stellite-6 coatings were investigated. It was determined that the optimal Y2O3 content for the stellite-6 powder was 2%. The results showed that the coating with 2%Y2O3 had the least number of pores and cracks and exhibited good surface flatness when joined. The microstructure became finer and denser, composed mainly of branch, cellular, equiaxed, and columnar grains. The coating consisted mainly of γ-Co, Fe-Cr, and Co3Fe7 strengthening phases, indicating good metallurgical bonding between the coating and the substrate. The average microhardness reached 539 HV when 2%Y2O3 was added, a 15.2% increase compared with the unmodified multilayer coating. The friction coefficient of the clad layer was 0.356, a 21.8% improvement over the unmodified stellite-6 coating. The average worn area of the cross-section was 3398.35 μm2, a reduction of approximately 27.8% compared with the unmodified stellite-6 clad layer. The wear surface primarily exhibited abrasive wear, with fewer cavities and a smoother surface. [ABSTRACT FROM AUTHOR]

Dried Athel leaves (DAL) are abundant agricultural waste that may have a detrimental effect on the environment due to improper disposal. The current paper is aimed at investigating the incorporation of DAL into lime treatment of heavy clays, presenting a novel sustainable waste management strategy. To the best of the authors' knowledge, this topic has not been investigated in the literature. The experimental programme is designed to thoroughly assess its effects on the hydro-mechanical properties of lime-treated clay in particular strength gain, swelling pressure and permeability. Tests were conducted on the specimens treated with different ratios of lime and DAL and cured under two different temperatures (i.e. 20 and 40 °C) for various periods. Moreover, microstructural analysis was undertaken to support the results. The results indicated that adding 2% DAL to lime-treated clay specimens cured at 20 °C for 3 months remarkably increased unconfined compressive strength by about 68% compared with those attained on lime-treated clay. Stress-strain relationships suggested that the specimens modified by DAL exhibited an enhanced ductile behaviour. Moreover, the incorporation of 2% DAL further reduced clay swelling pressure by 25% compared with those treated by lime only, resulting in a total swelling pressure reduction of 93.6% compared with that recorded on untreated specimens. Permeability enhancement in the specimens treated with lime and DAL was also observed and supported by the morphological analysis. The comprehensive experimental results confirmed the suitability of using DAL as an efficient enhancer to lime-treated clay. The research outcomes can provide valuable insights into the feasibility of DAL as an eco-friendly additive for improving geotechnical engineering practises. [ABSTRACT FROM AUTHOR]

A very common hazard in Rwanda is represented by the instability of steep road cut slopes in lateritic soil. In its natural state, this material appears as a fine-grained weak and altered rock, generally in unsaturated conditions. Steep cut slopes made by this material could remain stable for a long time unless weathering weakens its mechanical behavior and heavy rainfall provokes a rapid landslide. This paper presents the results of an experimental investigation on the microstructural, petrophysical, and geotechnical properties of lateritic soil from a road cut slope located in Kabaya (Ngororero District—Rwanda), which was recently subjected to a landslide. The mechanical properties of the material are strictly related to the geological origin and history of the deposits, their formation environment, and weathering processes. These characteristics were revealed by peculiar microstructural features (micro-texture, porosity, and degree of alteration of original mineral paragenesis). The experimental investigations included identification and classification tests, direct shear tests on saturated samples, and swelling tests. This multidisciplinary approach provided insights into the relationship between geotechnical properties and the microstructural, petrophysical, and chemical characteristics of the altered rocks. This study showed how different levels of chemical alteration operated by weathering processes, in conjunction with brittle deformation related to the tectonic history, formed in the same site two shallow rock layers with similar macro-scale features and mechanical behaviors but markedly different microstructural and chemical properties. The innovative aspect of this research suggests an integrated multidisciplinary approach to considering microstructural aspects in addition to mechanical behavior in the slope stability analyses in lateritic soil. In particular, this study demonstrates the importance of such an approach since the failure mechanism is better explained if it is based on microstructural observations instead of considering the soil shear strength parameters only. This research helped to explain the formation of the landslide failure mechanism in a specific road cut slope, which could be assumed as representative of many other similar slopes subjected to landslides in Rwanda. [ABSTRACT FROM AUTHOR]

In this paper, Al-Mg-Si alloys with a thickness of 4 mm are welded by using laser beam welding (LBW) and laser-MIG hybrid welding, respectively, and the microstructure and mechanical properties of the two joints are investigated. The results show that the fusion zone (FZ) of the two joints is composed of columnar crystal and equiaxed dendrite grain, and its main constituent phases are an α-Al matrix phase and a β(Mg2Si) strengthening phase. In the case of similar heat inputs, compared with those of the LBW joint, the grain size in the laser-MIG hybrid joint is smaller and there are more second phases such as the β phase in the FZ, which is related to the different action mechanisms on the base metal (BM) by the two welding processes. Under the three strengthening mechanisms of fine grain strengthening, precipitation strengthening, and solid solution strengthening, the laser-MIG hybrid welding joint shows better mechanical properties than that of the LBW joint. The maximum tensile strength of the LBW joint and the laser-MIG hybrid joint is 202 MPa and 253 MPa, respectively, and the elongation is 3.8% and 5.1%, respectively. [ABSTRACT FROM AUTHOR]

Desert areas contain abundant desert sand (DS) resources, and high-volume recycling of DS resources as components of cement-based materials can achieve high-value applications. In this paper, DS was processed into desert sand powder (DSP) and replaced with cement in high volumes (20 wt.%–60 wt.%) to produce cement pastes. The mechanical properties, heat evolution, nanomechanical characteristics, microstructure, and economic and environmental impact of cement pastes were studied. The results show that adding 20 wt.% DSP increases the compressive strength of pastes and accelerates cement hydration, compared with the control group (0 wt.% DSP). Meanwhile, incorporating an appropriate amount of DSP (20 wt.%) effectively reduces porosity, increases the proportion of harmless and less harmful pores, and reduces the proportion of more harmful pores. From the perspective of nanoscopic properties, the addition of 20 wt.% DSP increases the C-S-H volume fraction, especially enhancing the transformation of low-density C-S-H to high-density C-S-H. Notably, the sample incorporating 60 wt.% DSP exhibits the lowest values for CI coefficients (13.02 kg/MPa·m3) and Cp coefficients (2.29 USD/MPa·m3), thereby validating the application of high-volume DSP feasibility in cement-based materials. [ABSTRACT FROM AUTHOR]

Understanding the modification mechanism of C9 petroleum resin (C9PR) on styrene–butadiene–styrene (SBS) polymer modified asphalt properties is of significant importance. In this paper, dynamic shear rheometer (DSR), storage stability, fluorescence morphology (FM), scanning electron microscope (SEM), Fourier transform-infrared (FTIR) spectrometer, and molecular dynamic (MD) simulation were adopted to evaluate the rheological, chemical, and microstructure molecular motion state of C9PR and SBS composite modified asphalt at different aging states. The DSR storage results indicate that the addition of C9PR could improve the high-temperature property, storage stability, and temperature susceptibility. FM and SEM results indicate that the network microstructure was enhanced and the roughness between polymer resins and virgin asphalt was improved at the microscopic scale. The MD results indicate that the heterogeneity between C9PR and SBS modified asphalt was demonstrated, and the bonding energies were enhanced with the addition of C9PR. Moreover, the FTIR results indicate that new function groups were generated in addition to C9PR. In general, the addition of C9PR is a good approach to promote high-quality polymer modified asphalt (PMA) for pavement engineering. [ABSTRACT FROM AUTHOR]

In this paper, we report a phenomenon that equiaxed-to-columnar transition occurs during directionally solidified Ti46Al8Nb0.5B (at%) alloy. By analyzing microstructure and composition, it is found that this transition is induced by macro-segregation during directional solidification. Macro-segregation changes the solidified primary phase from ß phase to a phase, which governs the microstructural evolution. At the early stage of solidification, ß phase is the primary solidification phase, resulting in the formation of fine-equiaxed grains. As solidification proceeds, Al element enrichment and Nb weakened in liquid phase causes the primary phase transforms from ß phase to a phase. The continuous growth of primary a phase forms columnar grains in the later stage of solidification. Flexural strength test shows the average value of bending strength with 652 MPa at equiaxed-grain region is much higher that at columnar-grain region with 395 MPa. These results reveal that even a small change in the composition of TiAl intermetallics will have a great effect on the solidification structure and mechanical properties. [ABSTRACT FROM AUTHOR]

Additive manufacturing offers manufacturing flexibility for intricate components and also allows for precise control over the microstructure. This review paper explores the current state of the art in additive manufacturing techniques for Alnico permanent magnets, emphasizing the notable advantages and challenges associated with this innovative approach. Both the LPBF and L-DED processes have demonstrated promising results in fabricating Alnico with magnetic properties comparable with conventionally processed samples. The optimization of process parameters successfully reduced porosity and cracking in the LPBF processing of Alnico. The review further explored the significance of additive manufacturing process parameter optimization in managing the temperature gradient and solidification rate for a desired microstructure and enhanced magnetic properties. Other potential additive manufacturing methods suitable for the fabrication of Alnico were discussed, along with the challenges associated with the process. The insights provided also highlight how additive manufacturing holds the potential to replace post-processing techniques like solutionization, magnetic annealing, and tempering often necessary in Alnico production. [ABSTRACT FROM AUTHOR]

For many engineering applications, it is sufficient to use the concept of simple materials. However, higher gradients of the kinematic variables are taken into account to model materials with internal length scales as well as to describe localization effects using gradient theories in finite plasticity or fluid mechanics. In many approaches, length scale parameters have been introduced that are related to a specific micro structure. An alternative approach is possible, if a thermodynamically consistent framework is used for material modeling, as shown in the present contribution. However, even if sophisticated and thermodynamically consistent material models can be established, there are still not yet standard experiments to determine higher order material constants. In order to contribute to this ongoing discussion, system identification based on the method of self-adaptive filtering is proposed in this paper. To evaluate the effectiveness of this approach, it has been applied to second-order gradient materials considering longitudinal vibrations. Based on thermodynamically consistent models that have been solved numerically, it has been possible to prove that system identification based on self-adaptive filtering can be used effectively for both narrow-band and broadband signals in the field of second-order gradient materials. It has also been found that the differences identified for simple materials and gradient materials allow for condition monitoring and detection of gradient effects in the material behavior. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the microstructure, elemental and phase compositions of the eutectic alloy (wt %): Al–12.5 Si–0.8 Mg–0.4 Mn–0.7 Fe–0.9 Ni–1.8 Cu. A comparison of the microstructure of the alloy obtained at melt cooling rates of 102 and 105 K/s is made. It is shown that an increase in the melt cooling rate leads to the refinement of structural components, a decrease in the volume fraction of primary α-Al dendrites, an increase in the volume fraction of a mixture of eutectic silicon and aluminum, and a decrease in the silicon concentration in the interdendritic space from 23 to 13 wt %. Using energy-dispersive analysis and X-ray diffraction analysis, it was revealed that inclusions of intermetallic compounds Mg5Si6, Al17(FeMn)Si2, and Al3(CuNi)2 are formed at melt cooling rates of 102 and 105 K/s. A mechanism of the formation of a layered microstructure of an eutectic alloy is proposed. An explanation for the formation of X-ray amorphous nanosized particles in the foil layer adjacent to the mold is given. [ABSTRACT FROM AUTHOR]

Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete. In this paper, microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM, the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM, and the strengthening mechanism was analyzed. The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate. It is suggested that the replacement rate of recycled powder should not exceed 20%. The strength index and activity index of carbonated recycled powder mortar were improved, in which the flexural strength was increased by 27.85% and compressive strength was increased by 20% at the maximum. Recycled powder can be quickly and completely carbonated, and the improvement effect of CH pre-soaking carbonation was the best. The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder. Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect, alkaline polycondensation effect and carbonation enhancement effect. [ABSTRACT FROM AUTHOR]

Tribaloy™ T800, a Co-based alloy, exhibits remarkable tribological properties by virtue of its high-volume fraction of intermetallic Laves phase making it an attractive hard-facing material. Hard-facing by laser deposition results in dilution from the substrate, and thereby, the properties of the clad are altered. This paper reports the influence of processing parameters on the dilution, microstructure, and wear behaviour of Tribaloy™ T800 on AISI 316 stainless steel. A systematic set of 20 clads was deposited by varying laser power and cladding speed, keeping powder flow and spot diameter constant. While dilution decreased at lower laser powers (800 and 1000 W) with increasing cladding speed (5–20 mm s−1), at higher laser powers (1200 and 1400 W), the opposite trend was observed. The Fe intermixing from the substrate along with the cooling rate governs the volume fraction and size of the Laves phases which controls the properties of T800 clads. The clad with the least geometric dilution (5.7%) exhibits the lowest wear rate of 0.54 × 10−5 mm3 N−1 m−1, increasing to 2.88 × 10−5 mm3 N−1 m−1 as the dilution increased to 60%. [ABSTRACT FROM AUTHOR]

In this paper, high-density (60−x)Fe−Cr−Co−xCu (x: 0–6 wt.%) permanent magnet alloys were fabricated by laser powder bed fusion (LPBF) in-situ alloying technique, and the effects of Cu content on the microstructure, magnetic, and mechanical properties of the alloy were systematically investigated. The addition of 2 wt.% Cu enhanced the coercivity H c and the energy product (B H) max of the alloy in the isotropic state by 19.4 and 27.9%, respectively, compared to the alloy without Cu. The impacts of Cu content on the magnetic properties were investigated by combining experimental results and first-principles calculations. Furthermore, the addition of Cu improved the yield strength of the alloy, and the strengthening mechanism was analyzed in detail. The yield strength of the alloy with 2 wt.% Cu reached 908 MPa, representing a notable 7% increase relative to the Cu-free alloy. [ABSTRACT FROM AUTHOR]

Damage and fracture of archaeological potteries not only jeopardize the long-term preservation but also hinder their exhibition. To repair these pottery sherds effectively, this study introduces a novel inorganic phosphate-based adhesive and evaluates its effectiveness through a series of experiments. To determine the optimal base adhesive, the paper investigates the influence of varying weight ratios of the H2O–H3PO4 system and the Al(OH)3–H3PO4 system on properties including tensile lap-shear strength, microstructure, high-temperature resistance and phase composition. However, the original black color of the traditional CuO–phosphate adhesive limits its application. The innovation of this study lies in the addition of nano-TiO2 to the adhesive, which not only improves the bonding strength but also adjusts the color of the adhesive. This study has defined the optimal formulation (i.e., base adhesive = m[Al(OH)3]:m[H3PO4] = 7:100, filler = 10wt% nano-TiO2), and the final product shows no residual acid in adhesives. Additionally, the fracture surfaces are successfully bonded with a high strength of 3.56 MPa. Various ageing tests including dry-thermal ageing, hygrothermal ageing and UV irradiation ageing are conducted to assess the ageing resistance of the inorganic phosphate-based adhesive. The results indicate strong tolerance of adhesive to high temperature and high humidity environment. Preliminary applications in archaeological pottery restoration suggest that the inorganic phosphate-based adhesive offers considerable promise for repairing shattered pottery. [ABSTRACT FROM AUTHOR]

Gear shafts are commonly manufactured by machining of gear teeth and shaft separately. This kind of approach entails quite some problems, such as long processing time, large die, and low production efficiency. To tackle these problems, this paper innovatively proposes a new process of cross wedge rolling (CWR) that is specifically tailored to the manufacturing of gear shafts, with which the shaft and teeth are formed at one go. The finite element model of CWR forming of gear shaft is established to simulate and analyze the CWR forming process. A three-factor and three-level response surface test is designed to optimize the processing parameters, where the friction coefficient, rolling temperature, and die movement speed are chosen as three factors, and inhomogeneous deformation is set as the response. The optimal parameters are obtained as follows: the rolling temperature is 1240 ℃, the speed of the die movement is 336 mm/s, and the friction coefficient is 0.8. This result is subsequently verified by experiments. Further on, the microstructure evolution of the characteristic points of the CWR forming process of gear shaft is analyzed. It is found that the grains at the gear teeth section are continuously refined and grown from the boundary at the early section of deformation, and the final grains grown are much smaller than the original ones. In addition, the grains appear to grow in a short range of time in the process of deformation, but the overall trend is towards refinement. In the shaft section, the evolutions of the grains in the two stepped shaft segments are almost the same; the grain deformation shows cyclic changes; the degree of grain refinement in the shaft is higher than that in the teeth; and the degree of grain refinement in the shaft center is higher than that in the shaft edge. The results of the study provide a theoretical basis for short-process forming of high-performance gear shafts by cross wedge rolling. [ABSTRACT FROM AUTHOR]

Laser-based powder bed fusion (LPBF) is a widely utilized technique for additive manufacturing (AM) of metal components. The size of LPBF-produced parts is restricted by machine dimensions. Welding emerges as a feasible solution for connecting smaller parts generated via PBF. Nevertheless, the weldability of PBF parts differs from conventional ones due to the unique thermal history of PBF components. This paper investigated the weldability of stainless steel 316L and tensile behavior of welded samples, comparing samples produced through LPBF and the conventional wrought method. Tensile testing, grain size analysis, microhardness test, and assessment of secondary dendrite arm spacing were conducted on every welded combination of materials (AM-AM, wrought-wrought, and AM-wrought) using gas tungsten arc welding (GTAW). The findings indicate that the wrought material demonstrates a higher maximum strength (577.5 MPa) and a lower yield strength (231.7 MPa) compared to the AM material (with a maximum strength of 548.2 MPa and a yield strength of 399.9 MPa). This difference may be attributed to the annealing process applied to the wrought material, which has not been applied on the AM material. Additionally, welded wrought samples have a significantly lower tensile strength compared to non-welded samples. The wrought samples exhibit a larger average grain size (11.14 to 31.12 μ m ) in the heat affected zone (HAZ) compared to non-heat affected regions (8.13 μ m ). In contrast, it is found that grain coarsening does not occur in PBF samples, which exhibit a similar grain size in the HAZ (15.04 μ m ) vs 13.97 μ m outside of the HAZ. Larger grain sizes within the HAZ correspond to a larger reduction in tensile strength for the wrought samples, compared to PBF samples. Similar secondary dendrite arm spacing has been observed in the weld regions of both PBF and wrought materials. Microhardness test results indicated that the AM base material has the highest microhardness and gradually decreases as transitioning to the HAZ and weld region. In summary, the PBF samples exhibit less reduction of strength and ductility after welding than wrought samples. Therefore, it is determined that additively manufactured 316L stainless steel has a higher weldability than traditionally manufactured wrought 316 stainless steel. [ABSTRACT FROM AUTHOR]

As a typical form of damage, wear greatly affects the service properties of products, and non-destructive evaluation of the degree of wear is urgently needed. In this paper, the wear degree of AISI 1045 steel was evaluated by magnetic Barkhausen noise (MBN) testing. The root mean square (RMS) and full width at half maximum (FWHM) of MBN were extracted to establish the quantitative relationships between the tribological indicators and the stress state. The results indicate that the RMS decreases linearly and the FWHM increases quadratically with increasing tribological indicators, which can distinguish among different wear stages, including abrasive, adhesive and fatigue wear. However, the RMS shows a complicated nonlinear relation with the residual stress during the wear process. In addition, the MBNenergy parameter is also calculated to reveal the features of the hysteresis loop at the wear scar. Both the coercivity Hc and the maximum magnetic permeability μmax are linearly related to the tribological indicators and quadratically related to the stress, which reflects the effect of tribo-magnetisation on the MBN signals. The variation mechanism of MBN under different wear stages is attributed to the combined effect of plastic deformation and the stress state by microstructure observations. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the effect of calcium nitrite (CN) on improving the mechanical properties and microstructures of early-frozen cement paste. Cement pastes containing 1%, 1.5%, 2%, 2.5%, and 3% CN were prepared. One batch of samples was frozen at −6 °C for 7 days and then cured at 20 °C, and the other batch of samples was directly cured at 20 °C as a control. The compressive strength, ultrasonic pulse velocity, and resistivity of all specimens at different target ages were measured under these two curing conditions. The hydration products and microstructures of typical samples were observed using XRD and scanning SEM. The results showed that the addition of 1.5% CN could promote cement hydration and enhance slurry densification, thereby increasing the compressive strength, ultrasonic pulse velocity, and electrical resistivity of the slurry, and positively affecting the early freezing resistance of the slurry. However, when the CN dosage exceeded 1.5%, the internal structure of the slurry was loose and porous due to the generation of a large amount of nitrite–AFm, which negatively affects the properties of the cement paste. In addition, the effectiveness of CN is only limited to temperature environments above −6 °C. Concrete antifreeze suitable for lower temperatures still requires further research. [ABSTRACT FROM AUTHOR]

In recent years, asphalt pavement has been subjected to varied environmental conditions during its service life, conditions that predispose it to deformation and cracking. To enhance the performance of asphalt pavement, rock asphalt has been selected as a modifier due to its good compatibility with virgin asphalt binder and its ability to improve the fatigue cracking resistance of asphalt mixtures. Although scholars have conducted some studies on rock asphalt mixtures, research on the fatigue and self-healing performance of these mixtures under conditions such as ultraviolet (UV) aging and freeze–thaw remains limited. This paper presents findings from a study that employs a combined fatigue-healing test to assess the impact of such complex environmental factors on the fatigue and self-healing properties of fine aggregate matrix (FAM) mixtures containing three types of rock asphalts, i.e., Buton, Qingchuan (QC), and Uintaite Modifier (UM). The analysis of fatigue-healing test results, grounded in viscoelastic continuum damage (VECD) theory, indicates that rock asphalt can extend the fatigue life of FAM mixtures, albeit with a concomitant decrease in their self-healing capabilities. The study further reveals that UV aging, freeze–thaw, and UV aging–freeze–thaw conditions all led to a diminution in the fatigue and self-healing properties of FAM mixtures. However, FAM mixtures containing rock asphalt demonstrated greater resilience against these reductions. Atomic force microscope (AFM) results indicate that UV aging reduced the number of bee-structures and enlarged their area, whereas the incorporation of rock asphalt enhanced the uniformity of these structures' distribution, thereby improving the fatigue cracking resistance of FAM mixtures. Fourier transform infrared spectroscopy (FTIR) analysis reveals that while UV aging increased the carbonyl and sulfoxide indices within the asphalt binder, rock asphalt is effective in mitigating this effect to a certain degree, thereby enhancing the aging resistance of FAM mixtures. [ABSTRACT FROM AUTHOR]

In the finite element analysis of asphalt concrete (AC), it is nowadays common to incorporate the information from the underlying scales to study the overall response of this material. Heterogeneity observed at the asphalt mixture scale is analyzed in this paper. Reliable finite element analysis (FEA) of asphalt concrete comprises a set of complex issues. The two main aspects of the asphalt concrete FEA discussed in this study are: (1) digital reconstruction of the asphalt pavement microstructure using processing of the high-quality images; and (2) FEA of the asphalt concrete idealized samples accounting for the viscoelastic material model. Reconstruction of the asphalt concrete microstructure is performed using a sequence of image processing operations (binarization, removing holes, filtering, segmentation and boundaries detection). Geometry of the inclusions (aggregate) are additionally simplified in a controlled mode to reduce the numerical cost of the analysis. As is demonstrated in the study, the introduced geometry simplifications are justified. Computational cost reduction exceeds of several orders of magnitude additional modeling error occurring due to the applied simplification technique. Viscoelastic finite element analysis of the AC identified microstructure is performed using the Burgers material model. The analysis algorithm is briefly described with a particular focus on the computational efficiency aspects. In order to illustrate the proposed approach, a set of 2D problems is solved. Numerical results confirm both the effectiveness of the self-developed code and the applicability of the Burgers model to the analyzed class of AC analysis problems. Further research directions are also described to highlight the potential benefits of the developed approach to numerical modeling of asphalt concrete. [ABSTRACT FROM AUTHOR]

The paper presents the influence of the temperature of the sintering process on the microstructure and selected properties of boron carbide/TiB2/SiC composites obtained in situ by spark plasma sintering (SPS). The homogeneous mixture of boron carbide and 5% vol. Ti5Si3 micropowders were used as the initial material. Spark plasma sintering was conducted at 1700 °C, 1800 °C, and 1900 °C for 10 min after the initial pressing at 35 MPa. The heating and cooling rate was 200 °C/min. The obtained boron carbide composites were subjected to density measurement, an analysis of the chemical and phase composition, microstructure examination, and dry friction-wear tests in ball-on-disc geometry using WC as a counterpart material. The phase compositions of the produced composites differed from the composition of the initial powder mixture. Instead of titanium silicide, two new phases appeared: TiB2 and SiC. The complete disappearance of Ti5Si3 was accompanied by a decrease in the boron carbide content of the stoichiometry formula B13C2 and an increase in the content of TiB2, while the SiC content was almost constant. The relative density of the obtained boron carbide composites, as well as their hardness and resistance to wear, increased with the sintering temperature and TiB2 content. Unfortunately, the reactions occurring during sintering did not allow us to obtain composites with high density and hardness. The relative density was 76–85.2% of the theoretical one, while the Vickers hardness was in the range of 4–12 GPa. The mechanism wear of boron carbide composites tested in friction contact with WC was abrasive. The volumetric wear rate (Wv) of composites decreased with increasing sintering temperature and TiB2 content. The average value of coefficient of friction (CoF) was in the range of 0.54–0.61, i.e., it did not differ significantly from the value for B4C sinters. [ABSTRACT FROM AUTHOR]

In electronic packaging products in the service process, the solder joints experience thermal fatigue due to temperature cycles, which have a significant influence on the performance of electronic products and the reliability of solder joints. In this paper, the thermal fatigue failure mechanism of solder joints in microelectronic packages, the microstructure changes of the thermal fatigue process, the influence factors on the joint fatigue life, and the simulation analysis and forecasting of thermal fatigue life are reviewed. The results show that the solder joints are heterogeneously coarsened, and this leads to fatigue cracks occurring under the elevated high-temperature phase of alternating temperature cycles. However, the thickness of the solder and the hold time in the high-temperature phase do not significantly influence the thermal fatigue. The coarsened region and the IMC layer thicken with the number of cycles, and the cracks initiate and propagate along the interface between the intermetallic compound (IMC) layer and coarsened region, eventually leading to solder joint failure. For lead-containing and lead-free solders, the lead-containing solder shows a faster fatigue crack growth rate and propagates by transgranular mode. Temperature and frequency affect the thermal fatigue life of solder joints to different degrees, and the fatigue lifetime of solder joints can be predicted through a variety of methods and simulated crack trajectories, but also through the use of a unified constitutive model and finite element analysis for prediction. [ABSTRACT FROM AUTHOR]

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete. [ABSTRACT FROM AUTHOR]

The primary focus of the current paper centers on the microstructures and mechanical properties exhibited by a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt. %) (TNZTSF) alloy that has been produced through an intricate synthesis process comprising cold-crucible induction in levitation, carried out in an atmosphere controlled by argon, and cold-rolling deformation (CR), applying systematic adjustments in the total deformation degree (total applied thickness reduction), spanning from 10% to 60%. The microstructural characteristics of the processed specimens were investigated by SEM and XRD techniques, and the mechanical properties by tensile and microhardness testing. The collected data indicate that the TNZTSF alloy's microstructure, in the as-received condition, consists of a β-Ti phase, which shows polyhedral equiaxed grains with an average grain size close to 82.5 µm. During the cold-deformation processing, the microstructure accommodates the increased applied deformation degree by increasing crystal defects such as sub-grain boundaries, dislocation cells, dislocation lines, and other crystal defects, powerfully affecting the morphological characteristics. The as-received TNZTSF alloy showed both high strength (i.e., ultimate tensile strength close to σUTS = 705.6 MPa) and high ductility (i.e., elongation to fracture close to εf = 11.1%) properties, and the computed β-Ti phase had the lattice parameter a = 3.304(7) Å and the average lattice microstrain ε = 0.101(3)%, which are drastically influenced by the applied cold deformation, increasing the strength properties and decreasing the ductility properties due to the increased crystal defects density. Applying a deformation degree close to 60% leads to an ultimate tensile strength close to σUTS = 1192.1 MPa, an elongation to fracture close to εf = 7.9%, and an elastic modulus close to 54.9 GPa, while the computed β-Ti phase lattice parameter becomes a = 3.302(1) Å. [ABSTRACT FROM AUTHOR]

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 °C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks. [ABSTRACT FROM AUTHOR]

The early strength of geopolymers (GPs) and their composites is higher, and the hardening speed is faster than that of ordinary cementitious materials. Due to their wide source of raw materials, low energy consumption in the production process, and lower emissions of pollutants, they are considered to have the most potential to replace ordinary Portland cement. However, similar to other inorganic materials, the GPs themselves have weak flexural and tensile strength and are sensitive to micro-cracks. Improving the toughness of GP materials can be achieved by adding an appropriate amount of fiber materials into the matrix. The use of discrete staple fibers shows great potential in improving the toughness of GPs. Sisal is a natural fiber that is reproducible and easy to obtain. Due to its good mechanical properties, low cost, and low carbon energy usage, sisal fiber (SF) is a GP composite reinforcement with potential development. In this paper, the research progress on the effect of SF on the properties of GP composites in recent decades is reviewed. It mainly includes the chemical composition and physical properties of SFs, the preparation technology of sisal-reinforced geopolymers (SFRGs), the microstructure analysis of the interface of SFs and the GP matrix, and the macroscopic mechanical properties of SFRGs. The properties of SFs make them have good bonding properties with the GP matrix. The addition of SFs can improve the flexural strength and tensile strength of GP composites, and SFRGs have good engineering application prospects. [ABSTRACT FROM AUTHOR]

The direction in which wire and powder feedstock are fed influences deposit quality of as-built parts produced using laser-direct energy deposition (L-DED). While lateral wire feed has been explored in existing L-DED investigations, limitations like process instability persist, especially in achieving the required connection between the wire and the melt pool. Co-axial feedstock deposition offers a potential solution, enabling higher manufacturing flexibility and efficiency by co-axially feeding wire or powder. However, the full potential of L-DED using co-axial feeding for metal components remains underexplored due to equipment limitations. This study systematically evaluates the printability of stainless steel (SS) 316L and compares the microstructures and microhardness properties between co-axial powder-fed and wire-fed L-DED specimens. Utilizing the MELTIO M450 L-DED system in an argon environment, single-layer three-track specimens are produced with different combinations of process parameters. Comprehensive characterization, employing optical and scanning electron microscopy alongside microhardness testing, reveals powder-fed specimens exhibit greater melt pool depth and cooling rates, while wire-fed counterparts display fewer oxide inclusions and smoother surfaces. Microstructural differences include higher δ-ferrite content in wire-fed specimens. Microhardness values between powder-fed and wire-fed specimens are comparable. These findings hold implications for sequential powder and wire deposition, enabling the production of diverse mechanical structures with distinct characteristics. Overall, this paper provides an insight into feedstock selection for efficient metallic part production via co-axial feedstock deposition and recommends a range of process parameters suitable for fabricating SS316L parts using co-axial deposition in L-DED. [ABSTRACT FROM AUTHOR]

To efficiently isolate oxygen and block free radical reactions， sodium alginate (SA), sodium polyacrylate (PAAS), attapulgite (ATP), and melatonin (MLT) were selected to develop an oxygen-insulating physicochemical synergistic inhibitor. The water loss experiment, EPR experiment, and programmed temperature rise experiment were used to characterize the performance of the inhibitor. The results show that the optimal ratio of the oxygen barrier physicochemical synergistic inhibitor is 2.5 wt% SA, 1.5 wt‰ PAAS, 9 wt% ATP, 6 wt% MLT, and 3 wt% CaCl2. In the oxygen-insulating physicochemical synergistic inhibitor, the MLT can react with oxidizing radicals in the coal to slow down the process of the oxidation reaction of the coal, and the SA gel can fill the pore space to prevent oxygen adsorption on the coal surface, the inhibition rate of the inhibitor reaches 70% at 120°C. Compared with the original coal, the CO concentration of the treated coal samples is reduced by 253.9ppm compared with that of the original coal, the generation rate is reduced by 1. 13 × 10−11 mol·cm−3·s−1, and the rate of oxygen consumption is reduced by 90. 65 × 10−11 mol·cm−3·s−1 at 120°C. The above results show that the oxygen-insulating physicochemical synergistic inhibitor developed in this paper can effectively improve the fire extinguishing efficiency is environmentally friendly and pollution-free, and has good application prospects. [ABSTRACT FROM AUTHOR]

A potential anode material for lithium‐ion batteries (LIBs), Co3O4 has been widely considered by many scholars because of its excellent properties in terms of electrochemical characteristics and theoretical specific capacity. However, according to the existing research results, we found that the improvement of the electrochemical performance of Co3O4 has encountered a bottleneck because its intrinsic conductivity is not high enough, and more importantly, the volume expansion is too significant during the charge and discharge process, which leads to the material structure breaking. Therefore, this paper proposes a simple and scalable solvothermal and subsequent calcination method to prepare Co3O4 and reduced graphene oxide (RGO) composite nanoparticles with superior microstructures, and their morphological and electrochemical properties were investigated at different calcination temperatures. As a high‐performance anode material for lithium‐ion batteries, the Co3O4/RGO nanoparticles obtained at 550 °C exhibited terrific initial discharge capacity of 1714.2 mAh g−1, the reversible specific capacity of 1191.9 mAh g−1 with quality coulombic efficiency 98.17 % at 0.5 A g−1 after 100 cycles and extraordinary rate performance (907.6 mAh g−1 with a coulombic efficiency of 99.2 % at 2 A g−1). The facile synthesis method and excellent findings have led to better application prospects for Co3O4/RGO nanoparticles. [ABSTRACT FROM AUTHOR]

The poor mechanical and tribological properties limit the higher requirements of aluminum alloys in engineering and industrial applications, which leads to the rapid development of aluminum matrix composites (AMCs). Particulate reinforced AMCs have attracted extensive attention in automobile, electronics and military industries due to their low density, high strength, and excellent wear resistance. However, the interfacial reaction between reinforcements and the Al matrix tends to occur in conventional preparation processes owing to the higher reaction temperatures. The spark plasma sintering (SPS) technique is considered to be an efficient method for the fabrication of metal matrix composites, which can achieve rapid sintering, lower sintering temperatures, and higher densities than conventional fabrication processes. In addition, SPS can produce AMCs with excellent non-porous microstructure, fine grain size, and a strong bonding interface between reinforcement and Al matrix. Therefore, the interfacial reaction is effectively controlled and the structural integrity is maintained, resulting in enhanced strength and ductility. Based on the advantages of particulate reinforced AMCs and the SPS technique, the particulate reinforced AMCs fabricated by SPS have been extensively studied in recent decades, but have not been systematically evaluated. Therefore, this paper reviews the state-of-the-art particulate reinforced AMCs fabricated by SPS, focusing on the microstructure characterization, strengthening mechanisms, and mechanical and physical properties. Furthermore, the future research priorities and challenges of the high-performance particulate reinforced AMCs fabricated by SPS are also prospected. [ABSTRACT FROM AUTHOR]

In this paper, the contact heating technology was combined with the warm and hot stamping process of high-strength aluminum alloy, and the corresponding experimental device was developed. For the contact heating-warm stamping process, it's found that as the heating temperature increases, the mechanical properties of the parts first decrease and then increase, while the springback decreases. Meanwhile, for the contact heating-hot stamping process, it's found that the aluminum alloy sheets experience large plastic deformation during contact heating, resulting in the refinement of microstructure and the increase in dislocation density, and the performance of the formed parts is improved. [ABSTRACT FROM AUTHOR]

This paper presents the results of computer modeling of preliminary heat treatment and radial-shear rolling of L63 brass in the Deform program by cellular automata method. Quenching and annealing were simulated as pre-heat treatment modes. Radial-shear rolling consisted of three passes with a compression of 3 mm per pass. The variable parameters were the roll rotation speed (40 rpm, 70 rpm and 100 rpm) and the workpiece heating temperature before rolling (500°C and 700°C). It was found that the most effective mode of preliminary heat treatment of L63 brass is annealing at a temperature of 500°C. The most rational value of the heating temperature of the workpiece before rolling is 500°C, since in this case, at all selected speeds the recrystallization process does not start, which contributes to intensive grain grinding. An increase of roll rotation speed causes additional deformation heating, which contributes to recrystallization and a decrease of grain grinding intensity. [ABSTRACT FROM AUTHOR]

In this paper, the workability, mechanical, ion leaching, and drying shrinkage properties of alkali-activated concrete with recycled coarse and fine aggregates were studied, and the pore structure and micro-morphology of different alkali-activated recycled aggregate concretes (AARACs) were characterized by using the mercury intrusion method and scanning electron microscopy, respectively. The experimental results showed that with the increase in the replacement rate of the recycled fine aggregate (RFA), the flowability showed a decreasing trend. Adding a certain amount of RFA improves the mechanical properties of the AARAC. The compressive strength at a curing age of 28 days was 65.3 MPa with 70 wt% RFA replacement. When the replacement rate of the RFA was 100 wt%, the maximum splitting tensile strength (4.5 MPa) was obtained at a curing age of 7 days. However, the addition of the RFA had little effect on the flexural strength of the AARAC. As an extension of the curing age, the splitting tensile strength, flexural strength, tension-to-compression ratio, and flexure-to-compression ratio all showed an increasing trend at first and then a decreasing trend. At a curing age of 7 days, the tension-to-compression ratio and flexure-to-compression ratio were both high (except for those of R100), indicating that the ductility and toughness of the specimen were improved. The addition of the RFA increased the drying shrinkage of the AARAC. At a curing age of 120 days, compared to the specimen without the RFA, the drying shrinkage rate of the specimen with the addition of 70 wt% RFA increased by 34.15%. As the curing age increased, the microstructure of the reaction products became denser, but the proportion of large-diameter pores increased. This study evaluated the application of RFA in AARAC. The experimental results showed that the RFA-based AARAC had acceptable mechanical and durability properties. [ABSTRACT FROM AUTHOR]

The thermal conductivity of soil is an essential parameter for designing geothermal energy foundations and borehole heat exchange systems. To effectively improve the development efficiency of geothermal resources in the loess region of China, the plane heat source method was used to measure the thermal conductivity of loess samples with different water contents and temperatures, and scanning electron microscopy tests were conducted. Analyze the effects of water content, temperature, and soil microstructure on thermal conductivity. A weighted geometric mean model considering the soil temperature effect is proposed and compared with the traditional model. The experimental results reveal that soil thermal conductivity increases in stages as the temperature rises. After the temperature exceeds 30℃, the contribution of steam latent heat transfer to soil thermal conductivity gradually becomes significant. Within the temperature range of 1–60℃, the thermal conductivity increases with increasing saturation and tends to stabilize after saturation exceeds 60%; When the temperature is greater than 60℃, the thermal conductivity peaks near a saturation of 60%. As the water content increases, there is a significant difference in the thermal conductivity of undisturbed and remolded loess, which is related to the microstructure changes of the soil. The model calculation shows that the weighted geometric mean model proposed in this paper has the best prediction performance. The Leong model has good predictive performance for the thermal conductivity of loess, while the Gori and Lusen models have the lowest predictive accuracy. [ABSTRACT FROM AUTHOR]

Super sulphated cement (SSC) is a very promising substitute for traditional construction materials (i.e. Portland cement), due to its enhanced durability and particularly low environmental impact. This paper explores the microstructure and certain properties of SSC, focusing on the particular complexities of its microstructure and the difficulties of microanalysis of its hydrates. To do so, SSC paste samples were first cast to identify hydration products using X‐ray diffraction, then observed at early age using confocal laser scanning microscopy (CLSM) and at early and late age using scanning electron microscopy. In addition, concrete cores impregnated with fluorescein in order to highlight porosity, cracking and aggregates debonding were observed under UV light using optical microscopy (OM), showing a complete absence of cracking and aggregate debonding. Both microscopy techniques (CLSM and UV light OM) have been applied to this type of binder for the first time. The results show that SSC microstructure is characterised by a sophisticated intergrowth of various phases, including ettringite and amorphous calcium‐(alumina)‐silicate hydrate gels. Finally, Monte–Carlo simulation of electron‐matter has been provided for a better understanding of EDS analysis. LAY DESCRIPTION: This work focuses on the study of a particular construction material known as super sulphated cement (SSC). SSC appears to be a promising alternative to traditional building materials as it offers improved durability reduced and environmental impact attributed to its composition comprising at least 75% of a by‐product of the steel industry. This study investigates the microstructure and properties of this type of cement, focusing particularly on its complex microstructure and the challenges posed by the analysis of its hydration products. To do this, samples of SSC cement paste were first cast to identify hydration products using X‐ray diffraction. They were then examined at early stages using confocal laser scanning microscopy (CLSM) and at early and late stages using scanning electron microscopy (SEM). In addition, fluorescein‐impregnated SSC concrete cores were observed under ultraviolet (UV) light using optical microscopy (OM) to highlight porosity, cracking and delamination of aggregates, phenomena that may be present in such materials. These observations revealed the absence of these problems on this type of cement in this work. This research marks the first application of CLSM and OM under UV light to this type of cement. These microscopic techniques enabled us to understand the hydration phenomenon of this type of cement and its highly complex morphology. Finally, Monte–Carlo simulation was used in this study to model electron‐matter interaction, enabling us to understand the elemental analyses obtained and to gain a better understanding of the microstructure of SSC samples. [ABSTRACT FROM AUTHOR]

In this paper, by adding Co, Mo, and Ni metal binder and using spark plasma coupling high-frequency induction (SP–HF) sintering technology, high-entropy (W,Nb,Mo,Ta,Ti)C cermet with good performance was successfully prepared at 1350 °C. The sintering temperature was much lower than that of the solid-state sintering temperature adopted for high-entropy carbide ceramics (about 2000 °C) while maintaining high hardness and fracture toughness. The effects of sintering temperature, holding time and sintering pressure on the mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet were investigated. The experimental results show that the SP-HF sintering can promote the liquid phase flow inside the high-entropy (W,Nb,Mo,Ta,Ti)C cermet and improve the density. The high-frequency induction sintering effect of the high-intensity magnetic metal binder phase (Co, Ni) promotes the rapid diffusion of the constituent phases using the vacancy mechanism and the metal liquid phase, which helps to form a high-entropy cermet solid solution at a lower temperature. The different high-entropy effects of the inner and outer layers of high-entropy (W,Nb,Mo,Ta,Ti)C cermet materials play a role in strengthening and toughening the materials, and effective solid solution strengthening is the main reason for improving mechanical properties. The mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet are the optimized at 1350 °C, holding time of 8 min, and sintering pressure of 35 MPa. The Vickers hardness, fracture toughness, and flexural strength are 18.38 ± 0.19 GPa, 9.65 ± 0.25 MPa · m1/2 and 970 ± 30 MPa, Vickers hardness was measured at 49 N load. [ABSTRACT FROM AUTHOR]

Zirconolite (CaZrTi 2 O 7) glass-ceramic is considered as a potential stable matrix for the immobilization of Pu or minor actinides (Np, Am, Cm). In this work, the phase combination and evolution of glass (SiO 2 –Al 2 O 3 –Na 2 O–CaO–ZrO 2 –TiO 2 –B 2 O 3) with La as an actinide surrogate were investigated during the process of heating and cooling. By employing controlled cooling process, the zirconolite glass-ceramic with a controllable crystal size was successfully fabricated in borosilicate glass. The results demonstrate that heating and cooling exhibit distinct phase combinations. Both crystallization temperature and duration exert a significant influence on the composition of crystalline phases and microstructure. During the cooling of the melt, an increased degree of supercooling leads to an enhanced crystallization of zirconolite and a significant reduction in crystal size. The experimental results demonstrate that the optimal condition for preparing zirconolite glass-ceramic is held at 950 °C, for 4 h by one-step method, at which time the crystal exhibits a slender acicular morphology with a size of about 30 μm. Most of the simulated nuclides are enriched in crystals, and the rest are dissolved in glass. Zirconolite exhibits thermodynamic instability at elevated temperatures (1000 °C–1100 °C). Following the phase transformation, a proportion of Zr sequestered by titanite, while any excess Zr is either remain dissolved in the glass or gets precipitated as baddeleyite. For La, Al and other elements previously fixed in zirconolite, they are re-released to the glass and partially fixed by titanite, which may be detrimental to the long-term release behavior of the waste forms. In the aqueous durability test, both zirconolite glass-ceramic and phase transformation samples exhibited a low leaching rate, with LR Si , LR Zr , and LR La values of approximately 5 × 10−3, 4 × 10−6, and 6 × 10−6 g·m−2·d−1, respectively, after 28 days of leaching. By controlling the cooling process (one-step method), this paper provides useful information on the preparation of zirconolite glass-ceramic. [ABSTRACT FROM AUTHOR]