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• W90 and Mg alloy were firstly bonded by ultrasonic-assisted soldering at 250 °C. • A semi-coherent interface was formed between Sn and W. • The joint strength treated with the ultrasonication time of 2 s reached 10.4 MPa. W90 tungsten heavy alloy (W90) and AZ31B Mg alloy were firstly bonded by ultrasonic-assisted soldering using Sn in atmospheric environment. The wetting angle of Sn on W90 decreased to 130.7° under the action of ultrasound. The microstructure of W90/Sn/Mg joint treated with 2 s of ultrasounication time was W90/Mg 2 Sn + Sn/Mg 2 Sn layer/Mg. As the ultrasonication time increased to 4 s, the joint width reduced and the thickness of Mg 2 Sn layer increased. The joint strength decreased from 10.4 MPa to 5.1 MPa as the ultrasonication time increased from 2 s to 4 s. A semi-coherent interface formed at the Sn/W interface as the ultrasound was applied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabricated the extremely fine nanocrystalline HEA with phase thickness of 10 nm; • Identified the ultrastrong nanocrystalline HEA with yield strength of 2.49 GPa; • Analyzed the microstructure evolution of the dual-phase HEA during USP process; • Revealed the strengthening mechanisms of the gradient nanostructured HEA. The ultrastrong gradient nanostructured dual-phase high entropy alloy (DP-HEA) Fe 50 Mn 30 Co 10 Cr 10 has been fabricated by an efficient surface nanocrystallization method, e.g. ultrasonic shot peeing (USP) at room temperature. We investigated the effect of the USP duration on the microstructure of the DP-HEA Fe 50 Mn 30 Co 10 Cr 10 by the advanced materials characterization methods, e.g. Electron Backscatter Diffraction (EBSD), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). We found that the microstructure of the USPed DP-HEA Fe 50 Mn 30 Co 10 Cr 10 can be refined into several nanometers. Additionally, the FCC γ phase is transferred into the HCP ε phase during the USP process of the DP-HEA Fe 50 Mn 30 Co 10 Cr 10 and the portion of the HCP ε phase increases gradually with the increase of the USP duration. Nanoindentation tests indicate that the nanohardness of the nanostructured DP-HEA Fe 50 Mn 30 Co 10 Cr 10 can reach as high as 7.49 GPa, suggesting a yield strength of 2.49 GPa, which is 10 times higher than that of the coarse-grained materials. Additionally, nanocrystallization of the DP-HEA Fe 50 Mn 30 Co 10 Cr 10 can be triggered with a short peening duration and the transformation-induced plasticity (TRIP) effect can benefit the formation of a thick gradient nano-grained layer during USP. Micro-tensile tests revealed that the gradient nano-grained layer can significantly improve the yield strength of the DP-HEA Fe 50 Mn 30 Co 10 Cr 10 with sacrificing ductility. [ABSTRACT FROM AUTHOR]

Mg alloys were successfully bonded using Al interlayer via ultrasound-assisted transient liquid phase (U-TLP) bonding process. The effect of ultrasonic vibration (USV) time on the microstructure and mechanical property of joint was investigated. The microstructure of the joint treated with 3 s of USV consisted of diffusion zone, eutectic structure and Al Mg IMC. The number of Al Mg IMC gradually decreased and eventually disappeared as the USV time increased to 20 s. The joint width reduced and the joint strength improved with the extension of USV time. The maximum strength of the joint treated with 30 s of USV was 80.26 MPa, which was 93% of base metal strength. To understand to the effects of ultrasound, the traditional TLP bonding of Mg/Mg joints was conducted under the protection of argon and the bonding time was 30 min and 60 min. The interfacial microstructure and mechanical properties of the obtained joints were analyzed. It revealed that the introduction of ultrasound in TLP bonding process accelerated the atomic diffusion between Mg alloys and Al interlayer tremendously. • Mg alloys are bonded through ultrasonic-assisted TLP in air with Al interlayer to avoid Al-Mg IMCs. • IMCs of Al 3 Mg 2 and Al 30 Mg 23 are suppressed and eventually disappeared as the ultrasonic time increases to 20 s. • The maximum strength of joint treated with 30 s of ultrasonic vibration was 80.26 MPa. • The introduction of ultrasound accelerated the atomic diffusion and shortened the bonding time. [ABSTRACT FROM AUTHOR]

With the rapid increase of sludge production, large quantities of sludge with high water content (WC) are difficult to dispose of. It is necessary to evaluate sludge's physical-mechanical properties for waste sludge resource utilization and stability of landfills. In this study, freeze-thaw method is used to treat sludge. A series of tests, such as particle size analysis test, consolidation test, direct shear test, and SEM test, were carried out on the sludge treated by freeze-thaw. The influence of different refrigerating temperatures on the physical-mechanical properties is investigated. By analyzing the sludge morphology, particle distribution, pore change, consolidation and compression characteristics, shear characteristics, and microstructure, the influence mechanism of refrigerating temperature on sludge's physical-mechanical properties are revealed. The results show that after the freeze-thaw, the sludge particles gathered together, the water is easy to separate from solid particles. In addition, compressibility and void ratio of sludge decrease. At the same time, the permeability coefficient and consolidation coefficient increased by 1–2 orders of magnitude. When the freezing rate is slow, the sludge particles are pushed and squeezed by the ice layer, destroying the floc structure; when the freezing rate is high, the bound water can be better removed, which is conducive to forming a denser structure. Therefore, the cohesion of sludge decreases, and the internal friction angle increases after freeze-thaw treatment. Shear performance improved. The results of this study provide a reference for waste sludge resource utilization. • Freeze-thaw has marked effects on sludge's consolidation and shear properties. • Shear failure occurs at a horizontal displacement of approximately 2 mm. • The consolidation of sludge mainly occurs in the range of 0–50 kPa. • Fibers in sludge cake improve the shear properties after freeze-thaw. • The economic feasibility of freeze-thaw pretreatment is discussed. [ABSTRACT FROM AUTHOR]

• The heat-water-salt migration law is explored under evaporation. • The effect of surface crack growth on water-salt migration is analysed. • Heat-water-salt migration destroys the floc structure of shallow soil. • The EC profiles of soil after evaporation shows a V-shape. • Initial water content and temperature affect water-salt migration significantly. Evaporation in shallow soil has a great influence on the properties of surface soil. Therefore, under evaporation conditions, research on the rule and mechanism of heat-water-salt migration in surface soil has great significance for engineering geology and environmental science. In this study, with full consideration of the initial water content, salt content, atmospheric temperature, and groundwater supply, a series of indoor evaporation tests were performed on shallow saline soil to observe the heat-water-salt migration process. In addition, before and after the evaporation test, the soil microstructure at different depths was observed and analysed to explore the influence of heat-water-salt migration on the soil. The results show that during the evaporation process, salt carried by water migrates in the soil column, and the water-vapour phase transition causes salt accumulation, which also leads to the electrical conductivity (EC) profile showing a V-shape, and the salt content in the middle of the soil column is lower than that in the end. In addition, high atmospheric temperature significantly reduces the surface water content but alleviates salt accumulation. Under the condition of groundwater supplementation, the salt accumulation in the soil column surface is rapid. By observing the microstructure, it can be seen that a flocculent structure exists in the soil before evaporation. After evaporation, the surface microstructure changes significantly, and pores and salt crystals can be observed. The results provide a reference for understanding heat-water-salt transport in arid areas. [ABSTRACT FROM AUTHOR]

Abstract: Based on the biomineralization assembly concept, a simple and inexpensive biomimetic sol–gel method is found to synthesize high-performance mesoporous LiFePO4 (HPM-LFP). The key step of this approach is to apply Baker''s yeast cells as both a structural template and a biocarbon source. The formation mechanism of ordered hierarchical mesoporous network structure is revealed by characterizing its morphology and microstructure. The HPM-LFP exhibits outstanding electrochemical performances. The HPM-LFP has a high discharge capacity (about 153mAhg−1 at a 0.1 C rate), only 2% capacity loss from the initial value after 100 cycles at a current density of 0.1 C. This simple and potentially universal design strategy is currently being pursued in the synthesis of an ideal cathode-active material for high power applications. [Copyright &y& Elsevier]

The effect of B content on the structure, soft magnetic properties, and high frequency characteristics of as-deposited FeCoB-AlO nanogranular films fabricated by radio frequency magnetron co-sputtering was studied in this work. The introduction of B into the FeCo-AlO films leads to a refinement of granular microstructure. The FeCoB-AlO nanogranular films consist of the FeCoB nanoparticles uniformly embedded in the amorphous AlO matrix. An addition of a small amount of B into the FeCo-AlO films can markedly decrease the coercivity of the films. The excellent magnetic softness with a low coercivity of about 0.08 kA/m was achieved in the FeCoB-AlO films. The Henkel plots confirm the existence of intergranular exchange coupling in the FeCoB-AlO films. The FeCoB-AlO films with low B content exhibit a high permeability over 200 at low frequency and a high-resonance frequency of 3.2 GHz, implying a high cut-off frequency for high frequency applications. [ABSTRACT FROM AUTHOR]

Globally, landfill sludge (LS) has accumulated in large quantities, and its reduction and dewatering are urgently needed. To address pollution problems and clogging of drainage boards caused by chemical conditioning combined with traditional vacuum preloading (TVP), a freeze-thaw combined with step vacuum preloading (F/T-SVP) method is proposed. A comparative experimental study was carried out between TVP and SVP to explore the anti-clogging mechanism of F/T-SVP in treating LS. As a result, the water discharge for the original sludge (OS) is 1840 ml, the water discharge for TVP is 8830 ml and for SVP is 10,010 ml; The total settlement of SVP is 16% higher than that of TVP; TVP has a volume reduction ratio of 57.6%, while SVP has 66.8%; the OS's water content was 86%, which was reduced to 57.6% by F/T-SVP; The center of the drainage board of TVP is seriously clogged, while the particles of SVP are evenly distributed; The tendency for small particles to undergo transport is relatively low at the beginning of SVP, which can effectively reduce clogging; TVP mainly focuses on the compression of large pores into small pores, and SVP mainly focuses on the compression of large into small pores and micropores. In SVP, there is more consolidation and a more compact structure. When F/T-SVP is used to treat LS, the pores are gradually penetrated, effectively avoiding the generation of clogging and improving LS's drainage and consolidation. [Display omitted] • A combined freeze-thaw and step vacuum preloading method were proposed to treat landfill sludge. • The drainage and consolidation effects of TVP and SVP in treating LS were compared. • The microstructural properties of LS in using freeze-thaw and SVP were investigated. • The anti-clogging mechanism of SVP and TVP in treating LS were explored. [ABSTRACT FROM AUTHOR]

There is currently a considerable amount of landfill sludge (LS) accumulating worldwide, threatening the surrounding environment and land safety. It is urgent to dewater and reduce LS. Chemical conditioning is the most common treatment for LS, which can pollute the environment and limit resource exploitation. Therefore, a more environmentally friendly and efficient freeze-thaw combined vacuum preloading method is proposed. Experimental studies were conducted to investigate the influence of different freezing temperatures on the dewatering properties, compression and consolidation features, and the mechanism of microstructural change in LS. The results show that the freezing temperature has an important influence on the dewatering, compression, vacuum drainage, consolidation, and microstructure characteristics of LS. The compressibility of LS does not improve when the freezing rate is too high. Freeze-thaw cycles can improve sludge's permeability and consolidation properties by one to two orders of magnitude, and a suitable freezing temperature can significantly improve sludge's permeability and consolidation properties. After vacuum drainage and consolidation, the maximum volume reduction ratio of sludge can reach 55.3%, and the water content of LS can be reduced from 86% to 66%. The distribution of large pores and mesopores in LS increases as the freezing temperature decreases, reaching a maximum of −15 °C, which can substantially improve permeability, drainage, and consolidation efficiency. • The vacuum filtration characteristics of landfill sludge (LS) under different freezing temperatures were studied. • The LS's consolidation properties under different freezing temperatures were investigated. • The effect of freezing temperature on vacuum drainage characteristics of LS was studied. • The change of LS's particle size and pore size distribution under different freezing temperatures were investigated. [ABSTRACT FROM AUTHOR]

The materials of matrix-body polycrystalline diamond composite (PDC) bits were fabricated through pressureless melt infiltration method at 1200 °C for 1 h within vacuum furnace using molten CuNi metallic binder, Ni and WC powders (including cast WC, spherical WC, and fine WC). Various weight ratios of Ce 2 O 3 /(WC + Ni + CuNi) ranging from 0 to 0.01 were added to matrix-body materials. The influence of Ce 2 O 3 on the microstructure, phase formation, phase transformations, and related mechanical properties of matrix-body materials was thoroughly investigated. The results show that experimental temperature led to the decomposition of WC and partial dissolution of W and C in CuNi binder alloys. In matrix-body materials with no Ce 2 O 3 addition, only new W 2 C phase was formed. With further increase in Ce 2 O 3 /(WC + Ni + CuNi) ratios, spherical WC was dispersed into smaller WC particles. Meanwhile, new phases (namely Ni 2 W 4 C, C, and W 2 C) were found. The material exhibited an optimal hardness (HRA = 93.7) and transverse rupture strength (1846.8 MPa) when Ce 2 O 3 /(WC + Ni + CuNi) ratio was 0.006. However, impact toughness was slightly decreased, while the highest value of 6.45 J cm−2 was measured for the sample with Ce 2 O 3 /(WC + Ni + CuNi) ratio of 0.01. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Al2O3 content on the structure, electrical properties, magnetic properties, and interparticle exchange interactions of (Fe65Co35)1− x (Al2O3) x films with Al2O3 volume fractions x ranging from 0 to 0.50 was systematically investigated. Among the films with x between 0 and 0.25, the lowest coercivity of 0.56kA/m was achieved in the (Fe65Co35)0.82(Al2O3)0.18 film. This is ascribed to the strongest exchange interactions between the Fe65Co35 nanoparticles in this film. Combined with the microstructure analysis of the (Fe65Co35)1− x (Al2O3) x films, the modified Herzer''s model was extended to interpret the variation of the coercivity with x and analyze the effect of the exchange interactions between the Fe65Co35 nanoparticles on the magnetic softness. The remanence curves confirm the existence of the exchange interactions and reveal the evolution of the exchange interaction strength with Al2O3 content. [Copyright &y& Elsevier]

Microstructure and mechanical properties of WC-Cu-10Ni-5Mn-3Sn-1.5TiC cemented carbides fabricated by pressureless melt infiltration at 1200 °C for 90 min with different Ce 2 O 3 contents (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1.0 wt%) were investigated. Ce 2 O 3 accelerated the decomposition and dissolution of WC. The melt infiltration reaction products of high carbon solid solution, such as W, Ni 2 W 4 C, and (Ti,W)C 1-X are precipitated in binder alloys. High carbon solid solution gradually decreased or even disappeared, and W, Ni 2 W 4 C, and (Ti,W)C 1-X seemed to grow with the increase of Ce 2 O 3 contents. Considering the influence of decomposition and dissolution of WC and the formation of new phases, the size of WC particles decreased while the surface morphology of WC slowly changed from round and blunt to sharp-angle shaped, and the contiguity value of WC particles first decreased and then increased. The changes in microstructural properties of cemented carbides as a function of Ce 2 O 3 inevitably led to the change in mechanical properties. The sample with 0.4 wt% Ce 2 O 3 additions had the highest hardness (94.8 HRA). The highest values of impact toughness and TRS in 0.6 wt% Ce 2 O 3 cemented carbides were 7.15 J cm−2 and 1977.8 MPa, respectively. • The products of the infiltration reaction (high carbon solid solution, W, Ni 2 W 4 C and (Ti,W)C 1-X were precipitated in binder alloys. With the increase of Ce 2 O 3 additions, high carbon solid solution gradually decreased or even disappeared, and W, Ni 2 W 4 C, and (Ti,W)C 1-X seemed to grow. • Ce 2 O 3 promoted the decomposition or dissolution of cast WC and TiC particles. The decomposition of WC influenced the morphology, size and contiguity of WC. The size of WC particles decreased while the surface morphology of WC changed from round and blunt to sharp-angle shaped, and the contiguity value of WC particles first decreased and then increased. • The sample with 0.4 wt% Ce 2 O 3 additions had the highest hardness (94.8 HRA). The highest values of impact toughness and TRS in 0.6 wt% Ce 2 O 3 cemented carbides were 7.15 J.cm−2 and 1977.8 MPa, respectively. [ABSTRACT FROM AUTHOR]

Freeze-thaw (F-T) cycle is an important external factor affecting the mechanical properties of saline soils in cold regions. In this study, the effects of F-T cycles (0, 1, 5, 10, 30, 60 and 120) and salt contents (0, 0.5, 1.0, 2.0 and 3.0%) on the shear properties of saline soil in western Jilin Province of northeastern China, including stress-strain behavior, peak undrained shear strength ( τ u ), resilient modulus ( E R ), cohesion ( c u ) and internal friction angle ( φ u ), were investigated by conducting unconsolidated-undrained (UU) triaxial compression tests. The results demonstrated that, when the salt content was the same, the τ u , E R and c u basically showed a decreasing-steady-decreasing trend with increasing F-T cycles, and the dynamic evolutions of soil microstructure were mainly responsible for such variations. The Gouy-Chapman diffuse double layer together with matrix suction theories were employed to analyze the mechanism of the effects of salt content on the c u and φ u at different freeze-thaw cycles; the thicker diffuse double layer induced by higher sodium ion contents and the decreasing matrix suction were deemed as the main reasons that led the c u to continuous reduction; the φ u was believed to be successively affected by the enhanced lubrication effect and the salt crystallization process, and there was a threshold salt content (2.0%) which was influenced by the number of F-T cycles. Finally, by categorizing the different experimental combinations into relative undamaged, single-factor damaged and two-factor damaged states concerning the τ u , an empirical mathematical equation of high reliability ( R 2  > 0.985) was established to describe the combining effects of F-T and salinity on the changes in τ u . [ABSTRACT FROM AUTHOR]

Introduction: A one-dimensional ZnO nanostructure is a versatile and multifunctional n-type semiconductor. In this paper, ZnO nanorods were successfully prepared by the anodic arc plasma method in an oxidizing atmosphere. Methods: The composition, morphology, crystal microstructure, and optical properties of ZnO nanorods were characterized by using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and the corresponding selected-area electron diffraction (SAED), X-ray energy dispersive spectrometry (XEDS), ultraviolet-visible (UV-VIS) spectroscopy, Raman scattering spectrum (Raman), and photoluminescence spectrum (PL). Results: The experiment results show that ZnO nanorods synthesized by this method possess hexagonal wurtzite crystal structure with good crystallization, no other impurity phases are observed, the crystalline size is about 18 nm, and the lattice constant distortion occurs compared to that of bulk ZnO. The morphology of the sample is a rod-like shape, the length ranges from 100 nm to 300 nm, the average diameter is approximately 20 nm, and the aspect ratio is relatively high. The UV-VIS absorption spectrum occurs red shift, The Raman spectrum further demonstrates that the major peaks are assigned to ZnO optical vibrational modes, and the PL spectrum exhibits coexistence properties of ultraviolet (UV) and green emission. Conclusions: The results prove that ZnO nanorods with hexagonal wurtzite crystal structure were successfully prepared by the anodic arc plasma method in an oxidizing atmosphere. [ABSTRACT FROM AUTHOR]

• The relationships between laser parameters, shape of micro-dimples, residual stress and microstructure were explored in LPT process. • The influence of the geometric parameters of LPT on the surface friction characteristics of E690 high strength steel was analyzed. • The wear mechanism of LPT under starved lubrication was revealed. To investigate how laser peen texturing (LPT) parameters affect the patterns formed on the surface of E690 high-strength steel, and how these patterns subsequently influence tribological properties, the LPT process, including multiple shocks, was simulated by ABAQUS and verified by experiments. The residual stress and microstructure on the surface of micro-dimples after LPT were measured and observed by X-ray stress analyzer and transmission electron microscope. The tribological properties of specimens with different LPT density and depth were tested by reciprocating friction experiments, and the worn surfaces were observed using a scanning electron microscope. The experimentally obtained plastic deformation depths of the micro-dimples were − 8.82 μm, −18.31 μm, −28.72 μm and − 36.34 μm when the shock number was varied from 1 to 4. The simulation and experiment results were within 3.3 %, verifying the accuracy and reliability of the simulation. When the shock number was ≥ 2, the residual stress values in all directions at the test points within the micro-dimples tended to be consistent, and the full width at half maximum (FWHM) values gradually increased with increasing shock number. The TEM images and electron diffraction pattern of the specimen after three shocks showed that nanocrystals are formed on the bottom surface of the micro-dimple. In the friction experiments, the average friction coefficient first decreased and then increased with increasing LPT density. The average friction coefficient was the lowest when the LPT density was 20 %, for a constant micro-dimple depth. When the LPT density was 20 %, increasing the micro-dimple depth had little effect on the average friction coefficient, but the stability time of the specimens increased substantially. The wear surface of the untextured specimen showed deep and wide wear marks, and serious abrasive wear and adhesive wear occurred. Suggested LPT parameters for optimum wear resistance are an LPT density of 20% and shock number of 3. [ABSTRACT FROM AUTHOR]

The microstructure evolution in directionally solidified Ni-based superalloys DZ411 with different Tantalum (Ta) compositions (2.72, 3.10, and 4.00 wt%) was investigated to develop Ta-containing hot corrosion superalloys. It is found that the addition of Ta promote the element segregation in the interdendritic region, thus, leading to the increase in volume fraction of MC carbides and eutectics, while the morphology of them are not obviously changed. In addition, both the volume fraction of regions increases with increasing Ta composition, which is attributed to the reason that Ta is the main forming element of γ' phase. Besides, the previous controversy on the dependence of both the primary and secondary dendrite arm spacing on Ta composition was solved. The increase of dendrite arm spacing with increasing Ta composition can be attributed to increasing solidification range of these superalloys through both JMatPro and Different Scanning Calorimetry (DSC) analysis. Furthermore, the atomic arrangement of γ and γ' phases in alloys was characterized by spherical aberration corrected transmission electron microscopy. Both the saturation of refractory elements in γ matrix and the lattice constant of γ matrix was found to increase with increasing Ta composition, leading to the increase of lattice mismatch of γ/γ' phase and more regular shape of γ' phase which has also been confirmed by JMatPro analysis. [Display omitted] • DS of DZ411 containing Ta was performed by ProCAST simulation and experiment. • Increase in PDAS and SDAS with Ta was confirmed by JMatPro and DSC. • Ta was found to aggravate the segregation in the interdendritic region. • Lattice constant of γ increases with Ta, and lattice mismatch of γ/γ' increases. [ABSTRACT FROM AUTHOR]

The microstructure evolution in directionally solidified Ni-based superalloys DZ411 with different Tantalum (Ta) contents (2.72, 3.10, and 4.00 wt%) was investigated. After directional solidification, three alloys with different Ta contents were subjected to standard heat treatment: solution treatment (1230 °C/2 h/AC)+ primary aging (1120 °C/2 h/AC)+ secondary aging (870 °C/24 h/AC). Then, following isothermal long-term aging treatments were performed at 950 °C for 50, 100, 200, 500 and 1000 h. The addition of Ta can lead to the increase of the volume fractions of MC carbides, eutectics, and γ′ phases during directional solidification. In addition, with the increase of Ta content, the mismatch of γ/γ′ increases, thus, the shape of γ′ becomes more regular. After solution heat treatment, the MC carbides are decomposed, and more M 23 C 6 carbides are precipitated along the grain boundaries in alloys with increasing Ta contents. Besides, the eutectic cannot be completely eliminated. After secondary aging, more secondary γ′ phases are precipitated on the γ matrix channels in alloys with increasing Ta contents. Furthermore, the addition of Ta can delay the coalescence of the γ′ phase during long-term aging, which can be attributed to the reduction of the coarsening rate K according to the precipitation coarsening theory of Lifshitz and Slyozov and Wanger (LSW). • The content of Ta is increased on the basis of DZ411 alloy. • The effect of Ta on the cubicity of γ′ phase is studied. • The effect of Ta on coarsening behavior of γ′ phase during long-term aging is illustrated. [ABSTRACT FROM AUTHOR]

To further improve the mechanical properties of Mg–Li alloys, the microstructure evolution and mechanical properties of Mg–6.2Li–3.5Al–3Y alloy after different heat treatment processes (holding at 250 °C, 300 °C, 350 °C and 400 °C for 30 min, 60 min and 120 min, respectively) have been investigated in this study. It is found that the Mg 2 Y eutectic disappears after heat treatment, and the volume fraction of Al 2 Y precipitated phase decreases first and then increases with increasing heat treatment time. In addition, The tensile test results reveal that the tensile strength of the alloy increases first and then decreases with the increase of heat treatment time. The tensile strength and ductility of the alloy reach 182 MPa and 12.7%, respectively, after heat treatment at 400 °C for 30 min, which are 35.8% and 36.5% higher than those of as-cast alloy. The evolution of Mg 2 Y eutectic and Al 2 Y phase during heat treatment processes at different time and temperatures are analyzed in detail. It can be concluded that the tensile strength of the alloy is improved by the combined effects of precipitation hardening due to the formation of Al 2 Y phase, and the solid solution strengthening due to the decomposition of Mg 2 Y eutectic and Al 2 Y precipitated phase. [ABSTRACT FROM AUTHOR]

In order to study the effect of microstructure on mechanical properties of heat -treated Ti-47.5Al-3Nb-1.5Cr (at%.) samples, a heat treatment system was designed at 1573 K, 1623 K and 1673 K for 15 min, 30 min and 60 min. After the heat preservation, the samples were air-cooled. Among them, when the as-cast samples are keep at 1623 K for a period of time, the interlamellar spacing is refined. In addition, due to the heat treatment in the two-phase region, the elements are further diffused and more uniform in the sample. The room temperature tensile tests exhibits that the mechanical properties of the samples obtained by holding at 1623 K for 1 h and then air-cooling obtained the best improvement, the tensile strength and elongation at break from 372.54 MPa and 0.70% to 533.86 MPa and 1.04%. After analyzing the mechanical properties and structure of the alloy, it can be concluded that refining the interlamellar spacing and solid solution strengthening can effectively improve the elongation and tensile strength. ● Ti-47.5Al-3Nb-1.5Cr is designed by modifying elements based on the 4822 alloy. ● Heat treatment route is obtained to improve the mechanical properties of alloy. ● Relationship between heat treatment, microstructure and properties is clarified. [ABSTRACT FROM AUTHOR]

For backfill projects in seasonally frozen regions, freeze-thaw and compaction are two critical factors that affect engineering safety by changing the soil structure. This study investigated the effects of freeze-thaw cycles on the microstructure characteristics of saline soil with different compaction degrees using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and laser particle size analysis (LPSA). The compacted soil samples show a bimodal pore size distribution (PSD). With an increase in the freeze-thaw cycles, the volume of intra-aggregate pores (<4 μm) gradually decreases, while that of inter-aggregate pores (>4 μm) varies with the density of soil samples. Furthermore, compaction has a decisive effect on the volume of inter-aggregate pores. Under the effect of freeze-thaw cycles, the void ratio of the low-density soil sample decreases, and the soil structure gradually becomes denser, showing thaw settlement deformation. However, in the high-density soil sample, the void ratio increases and the soil structure becomes loose, showing frost heaving deformation. Moreover, the freeze-thaw cycle also leads to the breakage of coarse particles and the aggregation of fine particles. Correspondingly, the soil structure type changes from a flocculent structure to a granular stacked structure and then to a cemented-aggregated structure. After 60 freeze-thaw cycles, the cracks are penetrated and the water migration channels are formed, the soil structures all reach a new equilibrium state. Meanwhile, the void ratios of different compacted soil samples are close to the same residual value. Test results suggest that there may be an optimal compaction degree between 90% and 95%, where the soil microstructure is least affected by freeze-thaw cycles. This study may provide theoretical guidance for the construction of backfill engineering projects in seasonally frozen regions from a micro-perspective. [Display omitted] • The pore size distribution (PSD) of compacted soil samples is bimodal. • The freeze-thaw cycle is also a process of adjusting soil compactness. • After 60 cycles, the different compacted soil samples reach almost the same residual void ratio. • The coefficient of freeze–thaw (γ e) is proposed to describe the changes in soil microstructure. • During the freeze-thaw cycles, the breakage of coarse particles and the aggregation of fine particles occur simultaneously. [ABSTRACT FROM AUTHOR]

• Full lamellar eutectic is obtained in hypoeutectic directionally solidified HEAs. • Critical velocity for transition of leading phase is calculated by using IRF. • Relationship between the microstructure and mechanical properties is clarified. Recent studies report that eutectic high entropy alloys (EHEA) which possess both high strength and high ductility have potential industrial applications. In the present work, the solidification behaviors and mechanical properties of directionally solidified AlCoCrFeNi 2.1 EHEA obtained at different growth velocities are investigated. The microstructure of the as-cast AlCoCrFeNi 2.1 EHEA is composed of bulky dendrites (NiAl phase) and lamellar eutectic structures which consists of the CoCrFeNi (FCC) phase and the NiAl (BCC) phase. Although the actual composition of the alloy is shown to slightly deviate from the eutectic point, it is interesting to observe that the full lamellar structure of this alloy is obtained through directional solidification. In order to explain this contradiction, the maximum interface temperature criterion and the interface response function (IRF) theory are applied to calculate the velocity range of the transition from the primary phase to the eutectic, which is 1.2 µm/s-2 × 104 μm/s. Furthermore, the tensile test indicates that the directionally solidified AlCoCrFeNi 2.1 EHEA possesses a good combination of strength (1340 Mpa) and ductility (30.5%) at 100 µm/s, which can be attributed to the full lamellar eutectic structure after directional solidification. In addition, the compression tests demonstrated that the compressive strength of the axial specimen is greater than the radial specimen at the same growth velocity. Thus the directional solidification can effectively adjust the alignment of the eutectic structure and achieve better mechanical properties along the growth direction. [ABSTRACT FROM AUTHOR]

TiC-reinforced AZ91D magnesium alloy composites were synthesized through the in situ reaction between an AZ91D melt and Ti-C-Al preforms. The microstructural evolution characteristics and phase transformation were investigated at different melt reaction temperatures (1013, 1033, and 1053 K), with the aim of understanding the in situ formation mechanism of TiC particles from thermodynamic and kinetic perspectives. The results showed that the temperature played a critical role in determining the formation and morphology of TiC. Initially, only the Al3Ti phase was formed through the reaction between Ti and Al when the temperature was 1013 K. With the increase in the melt temperature, the A13Ti's thermodynamic stability decreased, and dissolution and precipitation reactions occurred at higher temperatures (1033 and 1053 K, respectively), contributing to the formation of TiC particles. The formation of the TiC phase was attributed to two factors: Firstly, A13Ti as an intermediate product reacted with carbon and formed TiC with increasing temperature. Secondly, the in situ TiC reaction was promoted due to the increased reaction-driving force provided by the increasing temperature. [ABSTRACT FROM AUTHOR]

Three heat treatment processing routes (heat treatment at 1300 °C, 1350 °C and 1400 °C for 15min, 30min and 60min respectively, and following air cooling) were developed to investigate the dependence of mechanical properties on microstructure evolution in a new Ti-47.5Al–3Nb-3.5Cr (at.%) alloy. When the heat treatment temperature approaching the solution precipitation temperature of γ phase (T γ-sol) (T γ-sol <1300 °C), the interlamellar spacing is found to increase obviously. Moreover, when the heat treatment temperature is between α phase transition temperature (T α) and T γ-sol (1400 °C < T α), the interlamellar spacing and average grain size decreases, the distribution of the B2 phase is more uniform. The Vickers hardness test shows that the Vickers hardness of the heat-treated samples are improved compared with the as-cast sample (352.6Hv). The best Vickers hardness of lamellar microstructure after heat treatment is 465.2Hv. The tensile test at room temperature shows that the good tensile strength and elongation at failure of the heat-treated sample can be obtained after air cooling at 1400 °C for 60min, which are 359.54 MPa and 2.04%, respectively. Compared with 405.06 MPa and 0.66% of the as-cast sample, heat treatment can significantly increase the elongation of the sample. Meanwhile, the observation of the microstructure also exhibits the dependence of microstructure on the mechanical properties. The results shows that the improvement of Vickers hardness is mainly attributed to solid solution strengthening. In addition, the distribution of B2 phase, the refinement of the interlamellar spacing and the average grain size play essential roles in the improvement of the tensile strength and elongation at failure. • The Ti-47.5Al–3Nb-3.5Cr (at.%) is designed based on the 4822 alloy. • Optimal heat treatment route is obtained to improve the mechanical properties. • Relationship between heat treatment, microstructure and properties is clarified. [ABSTRACT FROM AUTHOR]

Three heat treatment processing routes (heat treatment at 1300 °C, 1350 °C and 1400 °C for 15min, 30min and 60min respectively, and following air cooling) were developed to investigate the dependence of mechanical properties on microstructure evolution in a new Ti-47.5Al–3Nb-3.5Cr (at.%) alloy. When the heat treatment temperature approaching the solution precipitation temperature of γ phase (T γ-sol) (T γ-sol <1300 °C), the interlamellar spacing is found to increase obviously. Moreover, when the heat treatment temperature is between α phase transition temperature (T α) and T γ-sol (1400 °C < T α), the interlamellar spacing and average grain size decreases, the distribution of the B2 phase is more uniform. The Vickers hardness test shows that the Vickers hardness of the heat-treated samples are improved compared with the as-cast sample (352.6Hv). The best Vickers hardness of lamellar microstructure after heat treatment is 465.2Hv. The tensile test at room temperature shows that the good tensile strength and elongation at failure of the heat-treated sample can be obtained after air cooling at 1400 °C for 60min, which are 359.54 MPa and 2.04%, respectively. Compared with 405.06 MPa and 0.66% of the as-cast sample, heat treatment can significantly increase the elongation of the sample. Meanwhile, the observation of the microstructure also exhibits the dependence of microstructure on the mechanical properties. The results shows that the improvement of Vickers hardness is mainly attributed to solid solution strengthening. In addition, the distribution of B2 phase, the refinement of the interlamellar spacing and the average grain size play essential roles in the improvement of the tensile strength and elongation at failure. • The Ti-47.5Al–3Nb-3.5Cr (at.%) is designed based on the 4822 alloy. • Optimal heat treatment route is obtained to improve the mechanical properties. • Relationship between heat treatment, microstructure and properties is clarified. [ABSTRACT FROM AUTHOR]

Abstract: Hollow cuprous oxide (Cu2O) microspheres with a diameter of ca. 1.8μm are prepared by using yeast as template. The possible mechanism for the formation of the hollow Cu2O spheres is revealed. The biotemplated sample is investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) absorption spectra. The sample consists of the crystalline Cu2O microspheres with diameters of about 59.5 nm and lattice parameter of 4.264 Å. The observed optical band gap of the product indicates that the blue–shift effect occurs, which is attributed to the hollow Cu2O microspheres. [Copyright &y& Elsevier]

Cobalt thin films deposited by radio frequency sputtering were investigated. Microstructures of the Co films were analyzed by XRD and TEM. The results show that films microstructure varies with the variation of the sputter gas pressure PAr. Magnetic properties measured by VSM show that all the films possess relatively high saturation magnetization 4πMs, and strong in-plane uniaxial magnetic anisotropy field Hk. Co films deposited below 0.3 Pa show soft magnetic properties and its microwave permeability was measured by vector network analyzer in the 0.1–5 GHz range. [ABSTRACT FROM AUTHOR]

The influence of microstructure (bimodal and lamellar structure) on the fatigue crack growth (FCG) rate of Ti–6Al–3Nb–2Zr–1Mo alloy was investigated using compact-tension (CT) specimens. The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. The FCG paths in the early stage were observed by optical microscopy and scan electric microscopy. The results revealed that the FCG paths of lamellar structure were more tortuous than that of bimodal structure. The frequency of crack deflection and bifurcation of the lamellar structure is significantly higher than that of bimodal structure. The dominant mode of crack propagation for bimodal structure is crossing βtrans and αp, and for lamellar structure is crossing α colonies. Fatigue crack growth mechanisms at the early stage have been studied by observation of crystalline orientation near the crack propagation path at the crack tip, in combination with the slip trace analyzing. The results show that the fatigue crack growth directions in αp or βtrans for bimodal structure and α colony for lamellar structure are mostly consistent with that of prismatic or basal plane trace. This indicated that the cracks propagation modes of crossing αp or βtrans in bimodal structure and crossing α colonies in lamellar structure are resulting from the slip band cracking of the microstructure at crack tip, as the evidence of { 10 1 ‾ 0 } 11 2 ‾ 0 prismatic dislocation lines were observed in αp or βtrans for bimodal structure and α colony for lamellar structure by transmission electron microscope (TEM) near the fracture surface. • The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. • Cracks propagation modes were evaluated by EBSD-assisted slip trace analysis. [ABSTRACT FROM AUTHOR]