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

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

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

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

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

AlCoCrFeNi2.1 eutectic high-entropy alloy is characterized by a fine, homogeneous, and regular lamellar structure, as well as good organizational structure and mechanical properties with both strength and plasticity over a wide range of temperature (70-1000 K) and compositional deviation, thus making it the most widely studied eutectic high-entropy alloy at present. In this paper, regarding the additive manufacturing of AlCoCrFeNi2.1 eutectic high-entropy alloy, the influence of different processes and process parameters on the microstructure and mechanical properties of the alloy was reviewed, and the phase distribution, microstructure, and strengthening mechanism of AlCoCrFeNi2.1 eutectic high-entropy alloy prepared by the selective laser melting technology were highlighted. Finally, it points out the differences and deficiencies in phase formation mechanism and organization evolution process of the current additive manufacturing AlCoCrFeNi2.1 eutectic high-entropy alloy and puts forward the development direction of material modification of AlCoCrFeNi2.1 eutectic high-entropy alloy as the substrate of the material modification and the new technology of additive manufacturing high-entropy alloy, which will provide ideas for the promotion of the industrialized application of the alloy.

In view of the excellent corrosion resistance and high temperature strength of TiVNbTa refractory high entropy alloy, and the potential application prospect of the TiVNbTa RHEA/Inconel 600 joining component, the diffusion bonding properties were studied. Diffusion joining of the two materials under conditions ranging from 850 ℃ to 1150 ℃ were carried out, the joints achieved at 850~1000 ℃ were submitted for microstructure examining, and the joints joined at all temperatures were used for shearing test. The results indicate that except for the joints obtained at 850 ℃, which only contain a lot of Ni-rich interface layers, all other joints have a multi-layer interface structure of "Inconel 600/Ni-based diffusion layer/Cr-rich layer/Ti-rich layer/Ni-rich layer/TiVNbTaNi (Fe, Cr) diffusion layer/TiVNbTa RHEA". The Ni-rich layer is a Ni2Ti type intermetallic compound with rhombohedral crystal structure, and the Cr-rich layer is a Cr2X type intermetallic compound with hexagonal crystal structure. The joint achieved at 950 ℃ has the highest shear strength, which is 357 MPa. The fracture mainly occurs in the weak interfacial area of Ni2Ti in the joint, and the crack propagates through the multi-layer interface. The analysis of the joints formation mechanism shows that during the diffusion joining process, Ti, V, Nb, and Ta atoms diffuse from the RHEA side to the Inconel 600 side, while Ni, Fe, and Cr atoms diffuse from the Inconel 600 side to the RHEA side. The diffusion of Ti and Ni atoms is intense. The segregation of Cr and Ni elements occurs under the driving source of interfacial chemical reactions. The diffusion of Nb and Ta atoms is hindered by the formation of Ni2Ti type interfacial layers, resulting in delamination.

To study the energy dynamic change law of moisture-contained coal in the process of liquid nitrogen freezing, a self-developed acoustic emission (AE) experimental system for the whole process of liquid nitrogen frozen coal was utilized to analyze the characteristics and the change laws of AE energy dissipation in the whole process of liquid nitrogen freezing in coal with different moisture contents. The results shown that AE energy during liquid nitrogen freezing of coal was divided into steep, fluctuating and calm periods in the time domain. The primary and secondary peaks of energy were both positively linearly related to moisture content, and the primary and secondary energy peak of 5.96% moisture content were 1.66 and 2.26 times higher than those of dry coal. The cumulative energy of liquid nitrogen frozen coal, divided into three stages of steep increase, slow growth and stabilization versus time, was positively linearly related to moisture content, which of 5.96% moisture contained coal was 2.88 times higher than that of dry coal. The energy amplitude of different moisture content coals was mostly concentrated in the range of 40-50 dB, accounting for 94.39%-99.11% of the total, and decreased linearly with the increasing moisture content of coal. The time series of acoustic emission ringing counts in liquid nitrogen frozen coals had chaotic fractal characteristics, and the correlation dimensions of the steep increase, slow growth and stable stages were positively exponentially, linearly and linearly correlated with the moisture content, respectively. Furthermore, the correlation dimension in the steep increase stage of 5.96% moisture contained coal was 2.00 and 5.78 times higher than that of the slow growth and stable stage, respectively. The type of coal cracks produced by the liquid nitrogen freezing was mainly tensile, its proportion with the increasing moisture content was a negative exponential decrease, and the proportion of shear cracks positively linearly increased with the increasing moisture content. The increase of moisture in coal strengthened the freezing and expansion force generated by the water-ice phase transition during the liquid nitrogen freezing process, and the increase of energy dissipation contributed to the rapid development of pore-crack and the structural damage and plastic deformation of coal. However, the structural damage was difficult to detect in real time and can be inverted by AE energy.

In order to reveal the effect of changes in coal microstructure on gas desorption, this study selected coal samples from the Eighth Mine in Pingdingshan, Henan Province as the research object, and used two surfactants, 1-Butyl-3-methylimidazolium tetrafluoroborate and Sodium dodecyl sulfate, to soak the coal samples. The coal samples were investigated by low temperature liquid nitrogen adsorption, infrared spectroscopy, X-ray diffraction, the measurement experiment of adsorption constant a, contact angle measurement, and gas displacement and desorption experiment. The findings indicate that surfactants can dramatically alter the pore properties, molecular groups, and microcrystalline structure of coal. The specific surface area of the coal sample micropores decreases and the average pore diameter increases, so that the pore and fracture network is more smooth. The chemical functional groups of the coal samples change, the average chain length and the fat ratio decrease, and the oxygen enrichment degree increases. The aromatic ring layer spacing and aromaticity of the coal sample increase, while the aromatic layer stacking height and the number of aromatic stacking layers decrease, indicating that the structure arrangement of aromatic layer is more disordered and loose, the degree of condensation of aromatic ring is reduced, the arrangement of coal molecules is disrupted, and the range of ordered structure is narrowed. These changes in pore characteristics, molecular groups and microcrystalline structure greatly improve the wettability of coal and reduce the difficulty of solution intruding into coal samples, which helps to strengthen gas displacement and enhance the efficiency of gas extraction. At the same time, the solution in the pores of coal body increases, so after pressure relief, the coal sample gas desorption and discharge are blocked, the gas desorption rate decreases, and the water lock effect is enhanced. The results of this study provide a theoretical guidance for the exploitation of coal seam gas resources. By adding surfactants and other methods, the microstructure of coal is artificially changed, and then the gas desorption characteristics are directionally changed to improve the gas extraction efficiency. During coal seam mining, the sudden outflow of a large amount of gas can be avoided, so as to achieve an efficient and safe extraction of coal seam methane.

As there are some problems with the traditional noodle processing technology, a vibrating plate-type ultrasonic device designed in our laboratory was applied to dough processing, and the effects of ultrasonic time and power as well as dough pressure and thickness on the quality of fresh noodles were investigated by texture analyzer, scanning electron microscopy (SEM) and comprehensive weighted score method. The improving effect of ultrasonic-assisted dough processing on the texture of fresh noodles was evaluated. The results indicated that ultrasonic treatment had a significant effect on improving the quality of fresh noodles. The highest comprehensive weighted score was observed at ultrasonic time of 30 s, ultrasonic power of 330 W, dough pressure of 94.0 Pa and dough thickness of 3 mm. Compared with the control group, the elasticity and hardness of fresh noodles were increased by 19.5% and decreased by 18.1%, respectively. SEM showed that the cross section of fresh wet noodles treated by ultrasound exhibited a more complete and denser network structure, with smaller pore size and porosity. In addition, the starch granules were more uniformly and tightly wrapped in the gluten network structure, suggesting that ultrasonic treatment can contribute to a more stable and denser gluten network. Overall, ultrasonic-assisted dough processing technology can significantly improve the quality of fresh noodles. This study may provide a new idea for the production of flour products.

For improving the comprehensive performance of the cadmium coating, titanium ions were added into the pure cadmium plating solution, and the electrodeposition method was adopted to prepare the coating to improve the compactness and corrosion resistance of the non - cyanide electroplated cadmium coating. Field emission electron scanning microscope (FESEM) was utilized to observe the surface and cross - sectional microstructure of the coating and analyze the internal stress of the coating. X - ray diffractometer (XRD) was employed to investigate the phase composition and grain size of the coating. Moreover, an electrochemical workstation was used to study the corrosion resistance of the coating. Results showed that after adding titanium ions into the non - cyanide cadmium plating solution, the grain size of the coating decreased from 44.6 nm to 16.5 nm; the self - corrosion potential increased from -0.232 V to 0.089 V; the self - corrosion current density decreased from 3.56 mA/dm2 to 2.58 mA/dm2; within 5 000 s, the hydrogen permeation current density decreased to 8.6 μA/cm2 in case of a pure cadmium coating, while such value was only 3.2 μA/cm2 in case of a cadmium coating containing titanium ions, which indicated a much larger reduction rate. In general, the addition of titanium ions made the crystallization of the coating more detailed, enhanced the corrosion resistance of the coating, and improved the hydrogen - blocking ability of the coating.

Waste incinerators are faced with a problem of sever high temperature erosion in service, and applying a protective coating is an effective method to protect them from erosion damage. To research the service performance of Cr3C2-NiCr coatings in the high temperature erosion environment in waste incinerator, Cr3C2-NiCr coatings were prepared using high velocity oxy-fuel spraying, the influence of spraying distance on coatings' microstructure was studied, and the high temperature erosion resistance of coatings was examined. Results indicated that with the increase of spraying distance, both the amount of unmelted particles on the coating surface and the porosity of coating increased. The coating had the highest proportion of melted particles when the spraying distance was 225 mm. In the high temperature erosion test, the erosion rate of coating increased and the high temperature erosion resistance decreased while the spraying distance increased. Besides, the high temperature erosion resistance of coating decreased when the temperature of erosion test increased from 450 ℃ to 550 ℃.

Continuous drive friction welding technology was used to weld pure aluminum 1060/Q235 low carbon steel dissimilar material joints, and two cycles (30 d/60 d) thermoelectric coupling test (static load 392 N +high temperature 300 ℃+DC 60 A) was carried out. The effect of thermoelectric coupling on the microstructure, mechanical properties and interface growth of the welded joints of aluminum/steel dissimilar materials was studied. The results show that the thickness of the intermetallic compounds (IMCs) layer in the radial direction of the original joint interface is uneven, and there is no obvious IMCs formation in the central area. After 30 days of thermoelectric coupling, an IMCs layer with a width of 0.3-0.5 μm at the center of the interface is formed and dispersed from the steel side to the aluminum side in granular form, the overall tensile fracture is in the thermally affected zone of the aluminum base metal. After 60 days of thermoelectric coupling, a corrosion groove appears between the IMCs layer and the steel side, and the IMCs are broken, there are no cracks on the steel side, a large number of cracks and voids from the IMCs layer to the aluminum base metal are formed on the aluminum side, segregation of components occurs at the weld and crack tip, the overall tensile fracture is at the weld. The speed of interfacial corrosion and failure rate is proportional to the thickness of the interface IMCs layer, namely vcenter < v1/2R < v2/3R. Due to the uneven structure of the original joint interface and the difference in the growth rate of the structure at different positions of the interface during the thermoelectric coupling test, the boundary line of different fracture morphologies appears at the 2/3R position of the joint interface after thermoelectric coupling. The inner side of 2/3R is dominated by quasi-cleavage fracture, and the outer side of 2/3R is the combined result of dimple fracture and quasi-cleavage fracture.

To improve the thermal insulation performance of thermal insulation concrete for mining and save energy, we developed an environmentally friendly thermal insulation concrete with better thermal insulation and performance using a recyclable green organic matter wheat straw fiber. Scanning electron microscopy of the wheat straw fiber revealed that it had a large number of closed microporous structures, which are good heat insulation materials. Different percentages of wheat straw fibers(0%, 2%, 4%, 6%, 8%, 10%) and cement quality were mixed into the thermal insulation mortar, and the thermal conductivity of the thermal insulation concrete gradually decreased. When maintained at 0.201 0-0.200 2 W/(m·K), the compressive strength first increased and then decreased, and the maximum compressive strength was 7.14 MPa. Adding 2% of wheat straw fiber can improve the thermal insulation performance and compressive strength. Compared with the heat-insulation concrete without straw fiber, the heat-insulation property and compressive strength are improved, and the heat-insulation property and compressive strength are increased 7.5% and 5.9% respectively.

The effects of hypereutectic Al-17Si-4Cu-0.5Mg alloy were prepared by semisolid extrusion. The effect of solution time on microstructure and properties of hypereutectic Al-17Si-4Cu-0.5Mg alloy was studied. Results show that spheroidization occurs in the Si phase with the increase of solution time. When the solution time reaches 10 h, the circularity of eutectic Si is 0.72. High concentration of Cu element is enriched around Si phase in as cast state. After solution for 1 h, Cu element is rapidly dissolved into the matrix. As solution time is increased from 1 h to 16 h, the diffraction peak intensity of θ(Al2Cu) and Q(Al5Si6Cu2Mg8) phases on the XRD curve is decreased, and the dislocation density in the alloy matrix is greatly reduced. After aging treatment at 180℃ is performed on the solution treated samples, the θ' and Q' phases precipitate. As the solution time increases, the alloy strength value shows a "double peak" phenomenon. After solution treatment for 1 h, the tensile strength of the alloy reaches 269 MPa and the yield strength is 233 MPa. Compared with the unheated alloy, they are increased by 43.3% and 42.7%, respectively. This is mainly because there is still larger dislocation density in the matrix at the initial stage of solution, and the precipitation has stronger pinning hindrance to the dislocation after aging treatment. When the solution time is 10 h, the tensile strength and yield strength of the alloy reach 311 MPa and 263 MPa, respectively. The roundness of Si phase and the strengthening effect of fine precipitates are the main reasons for the formation of the second strength peak.

The effects of trace element Ag on the mechanical properties and microstructure of ZL114A aluminum alloy were investigated by the universal electron tensile testing machine, optical microscopy, scanning electron microscopy and spherical aberration correction field emission transmission electron microscopy. The results show that the tensile strength and yield strength of the alloy are enhanced with the increase of Ag content. However, no significant impact on the elongation is observed with the addition of Ag. When the Ag content reaches 0.55%(mass fraction), the peak aging tensile strength, yield strength, and elongation of ZL114A aluminum alloy increase from 351 MPa to 369 MPa, 309 MPa to 328 MPa, and 2.36% to 2.93%, respectively. There is no evidence of properties of α-Al dendrite and eutectic Si changing under the same condition. The increase of the Ag content promotes the amount of nucleation particles in GP zones, leading to the denser density of β". Ag atoms are observed in the β" phase under high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) mode, indicating that Ag atoms inhibit the diffusion of Mg atoms as well as Si atoms in the β" phase and the size of β" phase is reduced as a result.

As one of the core hot components of aeroengines, the safe service of turbine blades is crucial to the operation of aeroengines.When the aeroengines encounter some emergency conditions, the turbine blades may suffer overheating, the temperature of which is much higher than the highest normal operating temperature. Overheating can lead to serious microstructural degradation and even premature failure of turbine blades. In this paper,the methods of overheat inspection and failure analysis were introduced, as well asthe effects of overheating on the microstructural degradation and mechanical propertiesof aeroenginesturbine blades. In addition, the damage assessment, life prediction and microstructure rejuvenation of superalloys after overheating were prospected in this paper, which provide a guidance and theoretical basis for the degradation evaluation and failure analysis of turbine blades as well as the development of new superalloys.

The effect of different Ti contents on the microstructures and tensile mechanical properties of the hot-extruded Cu-15Ni-8Sn alloys was investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile test. The results show that both ultimate tensile strength and yield strength increase significantly with the increase of Ti content, while elongation decreases. The addition of 0.02% (mass fraction, the same below) Ti facilitates the precipitation of γ-(Cu, Ni)3Sn phase, and thereby leads to a significant refinement of recrystallization grain. When the content of Ti increases to 0.3%, a small quantity of needle-like Ni3Ti phase is formed, which abates the effect of γ precipitates on inhibition of recrystallized grains growth. With the addition of up to 0.5% Ti, a larger amount of Ni3Ti precipitates are formed, which enhance the effect of recrystallized grain refinement; however, a few Ni3Ti precipitates become large and deteriorate the elongation of the alloy. In this study when 0.3% Ti is added, the mechanical properties of the alloy are preferable, where the tensile strength, yield strength and elongation are 875, 713MPa and 24.1% respectively.

The apparent viscosity, rheology, resistance and residual resistance coefficients, microstructure and hydrodynamic radius of polymer solution after shearing by well transition zone shear simulation experiment device were investigated with hydrophobic polymer AP-P4 under different water absorption strength conditions. The results showed that the polymer AP-P4 solution lost up to 61.4% of viscosity and reduced more than 40.0% of its ability to build up the drag and residual drag coefficients with the increase of water absorption strength after shearing by the well ground transition zone, but the reduction of its ability to build up the residual drag coefficient was smaller than the reduction of its ability to build up the drag coefficient. The lower the energy storage modulus and loss modulus of the polymer solution, the more severely the microstructure is disrupted, and the smaller the hydrodynamic radius. [ABSTRACT FROM AUTHOR]

In order to clarify the microstructure of Al-Mg-Sc high-strength aluminum alloy prepared by ultra-high speed laser melting deposition, and study the relationship between structure and properties, Al-Mg-Sc high-strength aluminum alloy was prepared by using 7075 aluminum alloy as matrix and self-developed equipment(LDF3000-40 laser melting deposition machine). The effect of laser scanning rate on the microstructure and tensile properties of the materials was investigated. The results show that there are no obvious defects such as pores and cracks in the samples deposited by ultra-high speed laser melting, but contain a few small keyholes. The samples are composed of fine a-Al equiaxial crystals and dispersed Al3(Sc, Zr)particles. The effect of scanning rate on mechanical properties is further studied by numerical simulation. It is found that the faster scanning rate of laser in the range of 0.1-1 m/s can reduce the accumulation of powder materials and porosity of the surface of the deposition layer, thus the mechanical properties can be improved. The maximum tensile strength is 303 MPa and elongation at break is 22.5%. [ABSTRACT FROM AUTHOR]

The additive friction stir deposition(AFSD) experiment of 2219 aluminum alloy was conducted under the process parameters of the spindle rotational speed of 250-350 r/min and transverse speed of 50-150 mm/min, the effects of varying process parameters and multilayer thermal cycling on the macroscopic forming of deposited materials, microstructures and mechanical properties were investigated. The results show that well-formed single-pass 16-layer additive specimens can be successfully obtained under the process parameters of the spindle rotational speed of 250 r/min and the traverse speed of 100 mm/min. The grain size in the additive zone undergoes significant refinement, ranging from 4 to 6 m, and the fine equiaxial crystal organization replaces the coarse irregular grain organization characteristic of the feed rod. The additive specimen undergoes intense dynamic recrystallization, with overall recrystallized grains above 80%, and the bottom of the specimen(the 1st Layer)is subjected to multiple thermal cycles, with recrystallized grains reaching 91.8%. The texture of the additive zone basically consists of four recrystallized textures(Cube, Copper, P and RtB), as well as S, Brass and T textures. Significant softening of the hardness and tensile strength of the additive specimens occurs. The maximum hardness of the 16th layer is 80HV, which is about 55.6% of the base material of the feed rod, the hardness of the 1st-8th layers is uniformly 60HV. The average tensile strength of Layer 9-16 and 1-8 in the LD( longitudinal direction) direction of the additive zone is 243.0 MPa and 219.3 MPa respectively, which is about 60.0% and 52.9% of the base about 181.1% and 229.0% of the base material respectively. The fracture modes in the LD direction of the additive specimens are all ductile fracture. [ABSTRACT FROM AUTHOR]

Two bicrystal specimens containing high angle grain boundary (about 20 degrees) were prepared by seed crystal method. The effect of Hf on the as-cast, heat-treated grain boundary microstructure, composition and stress rupture properties under 1100℃/100MPa was investigated in Ni-based single crystal superalloy contained Re with different contents of Hf (mass fraction:0%, 0.4%). The results show that Hf addition results in the increase of the volume fraction of (γ+γ') eutectic and MC along the grain boundary. The volume fraction of cellular recrystallization microstructure is significantly decreased after heat treatment with Hf addition. The transverse stress rupture life is observed to increase significantly under 1100℃/100MPa in the Hf-containing alloy. The stress rupture properties are closely related to the type, morphology, content and composition of the precipitation phase along grain boundary, but the obvious segregation of Hf is not observed. This study can be helpful for the understanding of Hf's role of strengthening mechanism in grain boundary in advanced Ni-based single crystal superalloy.

An analytical approach was developed to investigate nucleation and growth of Ti-48Al (atom fraction/%) alloy droplets during their flight in an argon atomization process. Evolution of microstructure of the solidified powders was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scatter diffraction (EBSD). Newton cooling model based on the initial number of nuclei, liquid/solid interface velocity, cooling rate and size of droplets was established. The results show that statistical nucleation events increase exponentially with the increase of powders size, and the growth of nuclei is transformed from a twinned spherical segment into a concentric liquid/solid interface geometry. Temperature of atomized droplets decreases rapidly with the cooling rate of 105-106K·s-1.Then temperature increases sharply to near the liquidus temperature during recalescence. When the recalescence is completed, the droplet solidifies at a relatively slower rate. Afterwards the cooling rate of the fully solid phase decreases to about 105K·s-1.

Cu-P-Sn-Ag quaternary alloy brazing material is prone to brittle fracture of wire during industrial production, which seriously affects product quality. To improve its mechanical properties, Cu-P-Sn-Ag quaternary alloy ingots and brazing materials with different P contents were prepared. The effects of P content on the microstructure, hardness, tensile strength, and elongation of the brazing material were systematically studied. The results show that when the P content is between 5.0% and 5.2%, the brittle phase Cu3 P structure in the alloy is small and short rod-shaped, with grain size less than 5 µm. When the P content is between 5.4% and 6.0%, some Cu3 P structures in the alloy gradually transform into coarse fishbone like structures, with grain sizes greater than 30 µm. When the P content ranges from 5.2% to 5.4%, the hardness of the solder increases significantly with the increase of P content, from 247.7 HV to 260.4 HV; Its tensile strength and elongation significantly decreased from 844.38 MPa and 3.60% to 815.08 MPa and 3.07% respectively. The evolution relationship between P content and microstructure is the main factor affecting the mechanical properties of brazing materials. [ABSTRACT FROM AUTHOR]

This subject was raised by an automotive company.Based on the welding design on the curved surface,the effect of prior deformation on the weld structure was studied.Metal active-gas welding was used on the T-joint and pre-deformed plates of austenitic stainless steel 304L to find the proper welding parameters and observe the effect of prior deformation on the microstructure.The proper parameters acquired are:the speed of the torch is 4mm/s,the speed of delivery of welding wire is 2.5m/min and the voltage is 17V.In the T-joint and pre-deformed joint,the weld toes are in the zone with strain of 0% and 30%.In the pre-deformed welding specimen,it was observed that the fusion zone and partially melted zone are narrowed,carbide precipitation and ferrites are found less.In all,the microstructure in the pre-deformed weld joints on 304L is more uniform.

Alkali-activated cementitious material is a new type of low-carbon material. The pore solution of alkali-activated cementitious materials generally has more alkalinity than cement-based materials, inevitably leading to the different volume deformation caused by alkali-aggregate reaction. Granite was selected as a representative aggregate to prepare alkaliactivated metakaolin-slag mortar for exploring the relationship between the alkalinity of pore solution and alkali-aggregate reaction. The deformation behaviors of mortar immersed in the NaOH solution with different concentrations were studied. According to the microstructure analysis, it is shown that the volume shrinkage of alkali-activated cementitious materials can effectively suppress the expansion caused by alkali-aggregate reaction. Under different soaking conditions, the alkaliactivated metakaolin-slag mortar exhibits different deformation behaviors. The expansion behavior of alkali-activated metakaolin-slag mortar is caused by the alkali-aggregate reaction products and the transformation from a zeolite-like structure sodium silicaluminate hydrate gel to a zeolite structure gel. Alkali-aggregate reaction would occur when the hydroxyl ion concentration in the pore solution of alkali-activated cementitious materials is greater than 0. 209 mol/L. [ABSTRACT FROM AUTHOR]

(Fe0.52Co0.30Ni0.18)73Cr17Zr10 amorphous ribbons were prepared by melt-spun method and annealed at different temperatures. X-ray diffraction, atomic force microscopy and vibrating sample magnetometer were adopted to study the effect of annealing temperature on the microstructure and magnetic properties of this alloy.The results show that the crystallization process of this alloy is amorphous→α-Fe(Co)+amorphous'→α-Fe(Co)+Cr2Ni3+Fe3Ni2+Cr2Zr+ unidentified phase. When annealing temperature Ti is lower than Tg, the Ms increases slightly as a result of relaxation of the internal stress of the as-quenched amorphous alloy. When Ti is in between Tx and Tp1, the Ms significantly increases due to the partial crystallization of amorphous precursors to create a homogeneous distribution of α-Fe(Co) nanocrystals within a residual amorphous matrix. When Ti is higher than Tp1, the Ms drops rapidly, which may be caused by the grain growth and the formation of paramagnetic phase. This alloy after annealed at 565℃ has the best magnetic property(Ms=106.8A·m2·kg-1). The results of AFM observation show that in the annealed amorphous ribbons the grain size measured from AFM graphs is much larger than that of the α-Fe(Co) nanocrystal size caculated by Scherrer method, which is a typical phenomenon of coated grain.

In order to meet the welding requirements of offshore structures with high load capacity, the microstructure and mechanical properties of CO2 GMAW + SAW joint of high strength marine engineering steel DH36-Z35 with 60mm thickness were investigated. The results showed that no softening occurred in the joints with CHW50C6SM welding wire used for CO2GMAW, and CHW-S3 welding wire and CHF101 flux used for SAW. The mechanical properties of the joints met the requirements of relevant standards. Post-weld heat treatment at 350 °C and below for 1h could refine the microstructure of HAZ, but had little influence on the microstructure of weld, and reduced the strength and low temperature impact toughness of the joint to a certain extent. The bottom layer of CO2GMAW without preheating was a weak layer for the mechanical properties of the joints. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research 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.)

Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology 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.)

The rapid development of space technology has put forward higher requirements for electrical connector reliability. The reliability issues of electrical connectors under thermal cycling conditions are presented. A thermal cycling test scheme combined with the accelerated life test theory is proposed for electrical connectors. The accelerated thermal cycling test is carried out. It is found that the value of contact resistance increases slowly with the number of thermal cycles. The extrapolated value of thermal cycling life is calculated by gray model. Finally, the failure analysis on the jack of typical samples is illustrated. It is indicated that the crystal size rises, the fragmentation degree of the sub structure and the dislocation density increase, and there is more β'phase appearing in the jack of samples after test. The result shows that the change of microstructure is the fundamental reason for the stress relaxation phenomenon of jacks and the contact reliability degradation of electrical connectors. [ABSTRACT FROM AUTHOR]

Studying biofilms in long-distance raw water diversion pipe is beneficial to the analysis of water quality and the security of raw water quality. Therefore, the characters of morphology, microstructure, spatial and temporal distribution of biomass and microbiota community of bio-films in long-distance raw water diversion pipes were investigated using the simulated process of 8 bio-film annulus reactors (BAR) in series with different raw water. The results showed that the bio-film structure was significant different in water quality, and the particle color attached in pipe bio-film was an important influencing factor in the characters of morphology. Secondly, the structure of the rough bio-film changing with water flow increased the specific surface area of the bio-film which led to the growth and development of bio-film and pollutant removal. Thirdly, the biomass of A raw water reached the peak( 1.11 nmol ・ cm-2) in BAR3 running 75 d, and then became lower due to the less nutrient. However, the biomass along simulated pipes of B water changed subtly because of the limited DO (0.3 - 3.0 mg ・ L-1 ). Finally, the microbiota composition is highly correlated with the water quality, reacting water quality and purification effect. [ABSTRACT FROM AUTHOR]

For synthesizing the textile coating agent with high waterproof and moisture permeable performance, water-borne polyurethanes modified by silicone (WSPU) were prepared by polyaddition reaction using poly (tetramethylene oxide)glycol, polyethylene glycol, and α, ω aminopropyl polysiloxane as mixing soft segments, dimethylolpropionic acid as hydrophilic chain extender, 1,4-butanediol as hard segment regulator and isophorone diisocyanate. The chemical composition of WSPU was characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The microstructure of WSPU films were investigated by differential scanning calorimetry, transmission electron microscopy and positron annihilation lifetime spectroscopy. Mechanical properties of WSPU films were investigated by static tensile test. Results show that modified polyurethane(WSPU) membranes have significant micro-phase separation structure and large hole free volume that result in the increase of moisture permeability, maximum of which could reach 2 130.1 g ⋅ (m² ⋅ d)-1 This research has the value of industrial promotion. [ABSTRACT FROM AUTHOR]

In order to decrease the forging temperature and improve the microstructure and properties of titanium alloy blade, basted on the theory of hydrogen-induced plasticity enhancement at elevated temperature, thermohydrogen treatment technology was used in the forging process of titanium alloy blade in this paper. Microstructures of hydrogenated TC4 titanium alloy blade and TC4 titanium alloy blade without hydrogen forged at different conditions were investigated. The microstructures of hydrogenated TC4 alloy and TC4′ alloy without hydrogen after dehydrogenation treatment in vacuum and common heat treatment processes were compared. Results show that hydrogenation can decrease the forging load of TC4 titanium alloy blade. The microstructure is improved after heat treatment and the bimodal microstrueture with fine equiaxed ct phase is obtained. The reasonable heat treatment parameters of TC4 titanium alloy blade with 0.25wt. % hydrogen are dehydrogenation treatment in vacuum at 750 °C for 5 h after forging, then 900 °C anneal treatment for 1 h and 450 °C aging treatment for 4 h in conventional furnace. [ABSTRACT FROM AUTHOR]