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Lightweight strategy is essential for the development of transportation vehicles and aerospace industries. As a type of lightweight material, high-strength aluminum alloys are limited to service temperatures below 200 °C due to the rapid coarsening of strengthening nano-precipitates, which cannot satisfy the increasing demands of practical applications. High-temperature applications beyond 250 °C become the bottle-neck problem of Al alloys. In this paper, we review existing literature on the improvement of high-temperature performance of aluminum alloys by stabilizing nano-precipitates. On the basis of atomic-scale microstructure regulation, several design strategies, such as interface segregation, co-precipitation, core/shell structure, and interstitial ordering, have been proposed, resulting in the development of a number of heat-resistant Al alloys for use at 300–400 °C. Moreover, the fundamental theories of solid-state phase transformation, especially precipitation aging and coarsening, are correspondingly advanced on the frontiers of science. [ABSTRACT FROM AUTHOR]

The positive relationship between knowledge transfer and knowledge innovation is recognized by most scholars, while knowledge heterogeneity, as a knowledge situation of the enterprise organization, affects knowledge transfer within enterprise organizations. Therefore, as a state, knowledge transfer can be regarded as a result of knowledge heterogeneity, and it becomes the intermediary state between knowledge heterogeneity and knowledge innovation. The organizational structure of individuals within an enterprise organization may affect these three elements and their interrelationships. In this paper, data are collected by means of on-the-spot investigation and a network questionnaire for analysis. The results show that the microstructure state of the individual in the enterprise organization plays a moderating role for the first three elements. The lower that the micro-restriction of the individual is, the more favorable the knowledge heterogeneity is for the inverted U-shaped impact of knowledge transfer and knowledge innovation and the more favorable the occurrence of knowledge innovation. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure and mechanical properties of Al-6.5Si-5.5Cu-0.2Zr-0.01Sr-0.06Ti-0.2Ce cast aluminum alloys were investigated in multistage solid solution systems. The microstructure of the alloy was characterized using an optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), x-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The hardness and conductivity of the alloy were measured using a Vickers hardness and eddy current conductivity testers, respectively, and the tensile properties were described by a drawing machine. The results showed that the mechanical properties of the alloy are the worst under the four-stage solid solution system (G1). With the increase in multistage solution temperature and holding time, θ phase (Al2Cu) was gradually dissolved into α-Al matrix to enhance the effect of dislocation strengthening. When the solution temperature reached 510 °C, the mechanical properties of the alloy were the best, and the tensile strength and elongation were increased to 354.90 MPa and 9.02%, respectively. With the increase in temperature, eutectic Si agglomeration and large area of insoluble phase between metals were found, resulting in the decrease in mechanical properties. [ABSTRACT FROM AUTHOR]

The paper studies the influence of accelerated cooling after helical rolling on the structure and mechanical properties of X70 steel in different sections of the rod. Accelerated cooling is carried out in two modes: cooling and holding at a temperature of 530°C (mode I) and cooling to a temperature of 200°C without holding (mode II). It is found that conditions of cooling affect the fraction and morphology of the bainitic phase. This in turn determines different microhardness and strength in different sections of the rods. [ABSTRACT FROM AUTHOR]

The concentration of heavy metals in soil layers has increased due to the rapid development of the industry. Lead and zinc are two frequent heavy metal contaminants in soil. This paper aims to study the effect of these types of contaminants on different fines, including kaolinite, bentonite, and zeolite mixed with sand. First, mixtures of sand and kaolinite, bentonite, and zeolite were prepared, then they were contaminated by two contaminants of lead and zinc nitrates, separately. Consolidated undrained triaxial tests, Soil Conservation Service (SCS) double hydrometer tests, scanning electron microscope (SEM), Atterberg limits, and pH determination tests were conducted on the soil samples to investigate the changes in the strength and microstructure in the presence of heavy metals. In general, triaxial test results showed that various parameters influence the strength results of these heavy metal-contaminated sandy soil samples such as type, percentage, and structure of the fine portion, type, and concentration of contaminants, bonding mechanism of fine grains, and ion exchange capacity. For instance, in the presence of kaolinite (and kaolinite-zeolite mixtures), contamination with lead decreased the strength of soil samples, but in the soil mixtures containing bentonite (and bentonite-kaolinite mixtures), an opposite trend was seen. The plasticity index of mixtures containing kaolinite and zeolite increased in the presence of heavy metal contaminants, but it decreased when the fine portion of the soil was bentonite. Heavy metal contaminants decreased the pH of all soil mixtures and made them to be acidic. The results of the SCS double hydrometer test and SEM indicated that contaminated kaolinite and zeolite soil mixtures have a dispersed structure, while bentonite soil mixtures are not dispersive. [ABSTRACT FROM AUTHOR]

The mechanisms of microstructure transformation and mechanical anisotropy of laser-MIG hybrid additive manufacturing TC11 titanium alloy after solution aging treatment are investigated. In this paper, different solution temperatures and cooling modes are applied to tailor the microstructure and improve high-temperature properties and anisotropy. The result shows the microstructure of the samples in the as-deposited state is dominated by a widmanstatten structure composed of lamellar α clusters. Following solution aging treatment, a large area of basket-weave structure is obtained in the samples. A major influence of spheroidization of lamellar α clusters and dynamic recrystallization on mechanical anisotropy is revealed. The heat-treated samples exhibit more superior combined strength, elongation, impact toughness. The hardness difference between the layers and mechanical anisotropy decreases. During high-temperature tensile tests, the tensile strength increases with rising solution temperature; while, the elongation shows the opposite trend. The tensile fracture exhibits abundant uniform equiaxed dimples, and the fracture mode changes from intergranular fracture to transgranular fracture. Solution treatment at 990 °C for 2 h followed by air cooling is considered to be the optimal heat treatment process. Consequently, it results in a high tensile strength of 811 MPa and an excellent impact toughness of 50 J, representing improvements of 16.08% and 71.08%. [ABSTRACT FROM AUTHOR]

Plumology is being used in a variety of avian research fields such as from ecology and evolution to prey-predator relationship. However, very few systematic studies have been conducted in India using plumology. The paper compares macro- and micro-structural feathers' features from four species of family Columbidae viz. the Spotted dove (Spilopelia chinensis), Grey-fronted green pigeon (Treron affinis), Eurasian collared dove (Streptopelia decaocto) and Common pigeon (Columba livia) from different Indian localities. A morphometric analysis of the downy and contour feathers' structures of the listed species was carried out. Since the feathers were taken from significantly damaged carcasses, it was necessary to determine the pterylae of the flying feathers to which the latter belong. Morphometric features of feathers viz. calamus, rachis, vane and mounted barb length were measured. An atypical for Columbidae feature presence of villi has been observed but only for T. affinis species. The presence of typical pigmented quadrilobed nodes was noted in all Columbidae species. Pigmented and non-pigmented plain pronged nodes and plain swollen nodes were observed. The presence of three different nodes on barbules and nodes' pigmentation may be considered as key taxonomic characteristics for studied Columbidae species. The feather comparison method made it possible to identify pterylae of studied feathers. [ABSTRACT FROM AUTHOR]

Developing hollow components that integrate a large number of complex coolant channels for thermonuclear reactors remains a challenging task, owing to potential technical problems such as dissimilar metal connections, over-aging, and large welding areas (meter-scale). In this paper, CuCrZr/316L hollow components were manufactured using an improved explosive welding technique, where theoretical calculations and composite filling mold were used to achieve ideal welding conditions. Microstructure analysis showed that irregular waves of continuous and complete metallurgical bonding were detected at the bonding interface, and the defects at the corner of the flow channel were controlled at the hundred-micron level. The joint exhibited high shear strength (~ 292 MPa) under the given high-temperature conditions (200 ℃), whose peak strength, stress–distance curve, and failure mode were almost consistent with the experimental results at room temperature (25 ℃). Finally, under all conditions of the helium-leak test, the leak tightness of the CuCrZr/316L hollow component met the standard requirement. [ABSTRACT FROM AUTHOR]

This paper is a study of the mechanical properties and microstructures of the similar friction weld joints (TiAl6V4 and AA2024) using a servo-controlled Rotary Friction Welding (RFW) system. The friction welding operations were performed with seven different values of the friction pressure in the range of 2–14 MPa. The temperature is recorded during friction welding tests using k-type thermocouples. Tensile tests and microhardness measurements were carried out to obtain the mechanical properties of the friction weld joints. Microstructural changes of individual zone of the friction welds were investigated using an optical microscope (OM), and the fracture surfaces were observed using a scanning electron microscope (SEM). For AA2024, the fracture occurs most frequently in the central zone, resulting in lower tensile strength values, while for TiAl6V4, the fracture is occurs outside the friction weld interface, indicating that the friction weld joint is more resistant than the base metal. Microscopic analysis of the fracture surfaces of the AA2024 samples revealed diverse morphologies, with rough cupular surfaces predominating, indicating a dominant ductile fracture mode. Similarly, TiAl6V4's friction welded specimen also exhibited cupules of various sizes across its surface, primarily associated with a ductile fracture mode. Overall, the optimal friction pressure values (respectively 8 and 10 MPa for TiAl6V4 and AA2024) correspond to the highest values of the mechanical properties. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis and characterization of Al-0.35Cu-0.18Sc-0.06Zr alloys, possessing remarkable electrical and mechanical properties. Specifically, the electrical conductivity and tensile strength of this alloy are reported to reach 60.4%IACS and 169.46 MPa, respectively. The electrical conductivity combined with Wiedemann–Franz law was calculated for Al-0.35Cu-0.18Sc-0.06Zr alloys thermal conductivity as showing excellent thermal conductivity. Microscopic analysis shows that a large number of fine "bean-petal" shaped Al3(Sc, Zr) particles, i.e., the second phase, were diffusely distributed in the alloy. These particles are highly cohered with the matrix, resulting in small and shallow toughness dimples at the tensile fracture. Due to the low diffusion coefficient of Zr element, the growth rate of precipitated second phase particles can be effectively reduced, which leads to forming Al3(Sc, Zr) phase with Zr-rich shell and improving the intrinsic coarsening property of Al3Sc phase. The Al3(Sc, Zr) second phase exhibits a large surrounding strain of approximately 2.5%, resulting in a significant elastic strain field that inhibits dislocation movement, thereby increasing alloy strength. Furthermore, the heat resistance test results show that the alloy can operate steadily at 503 K for up to 350, 400 h. [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]

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]

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]

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]

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]

In this paper, the effect of ER2209 multi-stranded wire compared to single wire on the microstructure and pitting resistance of 2205 duplex stainless steel submerged arc welded joints was studied using electron backscatter diffraction, scanning electron microscopy, energy spectrum analysis, electrochemistry and other detection techniques. Compared with single-wire welding of duplex stainless steel, the multi-stranded wire deposited more metal and doubled the welding efficiency with the same heat input, while increasing the elemental concentration of Ni in the weld metal and the proportion of austenite in the heat-affected zone. Compared with single-wire welding, multi-stranded wire welding promotes the diffusion of the main alloying elements (Cr, Mo, Ni, N) in the welded joint and improves the mechanical properties and pitting resistance of the welded joint. [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]

This paper features a direct comparison of the response of AISI 316L and AISI 304 austenitic stainless steels to active screen plasma nitrocarburizing applied for a wide range of treatment temperatures from 380 °C to 480 °C (653 K to 753 K). Thereby, an active screen made of solid carbon was used without applying bias plasma to the treated steel samples. Since it is believed that the result of treatment strongly depends on the concentration of in-situ generated hydrogen cyanide, the conditions of the treatments were adapted to keep this concentration constant. Under such treatment conditions, it was shown that AISI 316L has a lower tendency to form CrN than AISI 304 at comparable treatment temperatures, where the threshold temperature was found below 480 °C (753 K) for the former and below 440 °C (713 K) for the latter. In addition, the decomposition of expanded austenite generated on the treated AISI 316L at high temperatures leads to CrN and (mainly) Cr-depleted austenite phase, which is possibly accompanied by minor amounts of α -ferrite. Instead, for the treated AISI 304, decomposition leads to CrN and transformed α -ferrite phase. The modified layer thicknesses achieved after a given treatment duration and the kinetics of the layer growth showed a characteristic temperature dependence for each steel, which is discussed in accordance with the results of microstructure analysis. [ABSTRACT FROM AUTHOR]

The mechanism of fluid and heat transmission within materials with complex porous structures has not yet been fully explored and understood using basic analytical techniques. Therefore, the lack of advanced equipment and techniques has left an important knowledge gap in explaining the complex mechanisms of fluid motion and heat transfer in complex porous structures. This review provides an overview of how image analysis and processing techniques allow insight into the complex and heterogeneous porous structure of materials and explains the mechanism of heat and mass transfer in these complex porous materials in 3D and 4D observation in different directions. Accordingly, it provides interesting results related to the evaluation of microporous properties of complex porous materials including porosity, distribution and size of pores, distribution and orientation of fibers, tortuosity and mechanism of cracking, and destruction of the porous materials under mechanical tests. It also explains the mechanism of liquid transport in porous materials through 3D/4D observation thanks to image processing techniques. Therefore, this review has completed some limited knowledge in microstructural analysis and helped to understand the physical phenomena of liquid transfer in complex porous materials that were not fully exploited by experimental or simulation work. The paper also provides useful data for physical model simulation of imbibition and drying porous materials. [ABSTRACT FROM AUTHOR]

In this paper, engine flywheel shell components of ZL104 aluminum alloy were formed by squeeze casting forming technology, and the effect of process parameters on mechanical properties and microstructure of the formed parts was investigated. Sixteen sets of orthogonal test schemes are designed according to four conditions of specific pressure, holding time, pouring temperature and mold temperature. After the mechanical properties of the castings under different sets of experimental conditions were analyzed, the optimum process parameters were derived from the comprehensive analysis according to tensile strength and elongation. The optimum process parameters involve a casting temperature of 655 °C, a scheme B mold temperature, a pressure holding time of 20 s and a specific pressure of 34 MPa. The average tensile strength and average elongation of the formed flywheel shell components under the optimum process conditions were 211.2 MPa and 7.7%, respectively. The microstructure of the formed parts is mainly composed of α-Al phase and eutectic silicon phase. When the process parameters are properly selected, high mechanical properties and microstructure with little cast defects were obtained in the parts formed by squeeze casting. Except for Al, Fe, Mn and Si elements are mainly enriched at the grain boundary. [ABSTRACT FROM AUTHOR]

To tackle the critical challenge concerning the disparate performance outcomes between the spoke and rim in extruded AZ80 magnesium alloy wheel hub, finite element simulation was used to optimize the shape parameters of the hollow billet and improved equivalent strain was achieved. The paper studied the microstructure evolution and mechanical property response of the alloy after the forming process. The experimental results showed that the grain sizes of the spoke and rim were 32.95 and 33.84 μm, respectively, when using the optimized shape parameters, and both of them were completely dynamically recrystallized. Although the fine grain strengthening and precipitation hardening effects were consistently obtained in both samples, a discernible distinction was revealed by the mechanical property analysis. Specifically, the yield strength (YS) and ultimate tensile strength (UTS) of the rim specimens evinced a notable 13.8 and 15.4% higher in comparison to the spoke specimens. This discrepancy was further elucidated by the texture analysis, which illuminated that the spoke was distinguished by an extrusion direction–transverse direction double-peak basal texture, while the rim was marked by a normal direction–transverse direction (ND–TD) double-peak basal component after extrusion. The distinct texture patterns gave rise to varying predominant deformation mechanisms during loaded at room temperature, where the textured TD-oriented grains within the spoke unfriendly promoted the initiation of {10-12} tensile twinning at low yield stress, while both the ND and TD component within the hub manifested a markedly high activation of prismatic slip with high yield stress. The cumulative effect of these contrasting deformation pathways ultimately led to a marked contrast in the YS between the two regions. [ABSTRACT FROM AUTHOR]

In this paper, the effect of deep cryogenic treatment (DCT) on the microstructure and properties of automotive 6063 aluminum alloy at different times was investigated with automotive 6063 aluminum alloy as the research object. The results show that under the conditions of deep cryogenic treatment, the lattice distortion occurs in the alloy matrix microstructure, and the resulting internal stress promotes the large proliferation of dislocations within the alloy and the increase of dislocation density; meanwhile, after the deep cryogenic treatment, the deformed grains are transformed into recrystallized and sub-crystals structural grains, the grains are refined, and the size of the grains is refined from the original 25.2 μm to 20.3 μm, with fine equiaxed crystals. Among them, the mechanical properties of the DCT36h specimen were the best, and its hardness, tensile strength, yield strength and elongation reached 142.44 HV, 328.32 MPa, 177.42 MPa, and 29.29%, which were 34.17%, 5.62%, 11.10%, and 32.77% higher than the original sample, respectively. We believe that the main mechanism for the increase in toughness is multiple reinforcement such as dislocation strengthening, grain refinement strengthening, precipitated phase strengthening and texture strengthening. [ABSTRACT FROM AUTHOR]

In this paper, preforms with three-dimensional structures and different thicknesses were constructed by 3D printing technology, and WC particle reinforced high-chromium cast iron (HCCI) composites was prepared by infiltration casting method. The microstructure of the WC/Fe matrix composites was investigated using scanning electron microscopy (SEM), energy spectroscopy (EDS), X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The effects of different preform wall thickness on the hardness and three-body abrasive wear properties of the composites were tested. The results showed that with the increase in the wall thickness of the three-dimensional preform from 2.5 to 10 mm, the volume of the composite zone formed by the dissolution diffusion reaction of WC and HCCI gradually increased from 31.8 to 41.2%. The microstructure was composed of composite zone, matrix and WC particles partially dissolved. The hardness of the composite zone increased at first and then decreased, while the wear weight loss of the composite showed an opposite trend. Compared with the wall thickness of 2.5 mm, the minimum wear weight loss of the composite was 0.2821 g for a wall thickness of 7.5 mm, and the wear resistance was improved by 12.8%. The hardness and wear resistance of WC/Fe matrix composites at different wall thicknesses were mainly related to the diffusion of the preform and the formation of the composite zone. [ABSTRACT FROM AUTHOR]

This research paper examines the effect of different solution heat treatments parameters (temperature and time) on Al–3.39%Cu–2.26%Mg (wt%) alloy's microstructure, thermal, mechanical and corrosion properties. 5754 alloy and Al–Cu alloy are used to make Al–3.39%Cu–2.26%Mg (wt%) by gravity die casting. Solution heat treatment at different temperature and time (500 °C-10 min, 500 °C-4h, 530 °C-10 min and 530 °C-2h). As-cast Al–Cu–Mg alloy have α-phase and eutectic phase. After solution heat treatment and aging, precipitates phases is observed in microstructure. X-ray diffraction analysis results have shown that a precipitate phase [S phase (Al2CuMg)] gets formed in as-cast conditions but undergoes dissolution during the solution heat treatment process. As-cast Al–Cu–Mg alloy has a Brinell hardness value of 77.2 HB. As-cast alloy has S (Al2CuMg) precipitate phase increases hardness by precipitation strengthening. After solution heat treatment and aging, Brinell hardness reduces. After solution heat treatment (500 °C for 4 h) and aging (200 °C for 5 h), Brinell hardness values becomes 63.6 HB (− 17.6% decrease). Corrosion resistance improves after the solution heat treatment due to the dissolution of the precipitate phase, forming an almost single-phase solid solution. The as-cast alloy exhibits a peak compressive stress of 494.2 MPa, which increases after solution heat treatment and water quenching to 572.7 MPa (without aging). After aging, peak compressive stress decreases to 508.4 MPa. Failure strain for the as-cast alloy is 39.6%, reducing to 31.1% after solution heat treatment and water quenching. It again increases to 43.1% after aging. [ABSTRACT FROM AUTHOR]

The paper investigates the influence of gas dynamic cold spraying followed by laser processing of stainless steel samples on their dynamic (spallation) strength under the impact load at a 105 s–1 strain rate. The impact velocity effect on the microstructure and dynamic strength is studied herein. It is shown that the dynamic strength of steel samples after laser processing remains unchanged compared to unprocessed samples. Amorphization and melting are observed in the spallation region of the processed samples. Intense mechanical twinning develops inside austenite grains after the load application, and a largest number of twins is observed in unprocessed samples. [ABSTRACT FROM AUTHOR]

AlCoCrFeNi2.1 eutectic high-entropy alloys (HEAs) are a new kind of alloy with high entropy and eutectic properties. Their advantages in terms of strength and shape matching can be fully exploited using extreme high-speed laser cladding (EHLA). In this paper, AlCoCrFeNi2.1 eutectic HEA coatings were prepared by conventional laser cladding (CLA) and EHLA. The microstructures and phase compositions of the two coatings were analyzed by scanning electron microscopy, x-ray diffraction, and electron backscatter diffraction. The microhardness and wear resistance values of the coatings were tested using a microhardness tester and a friction and wear tester, respectively. The results showed that the surface qualities of both the CLA and EHLA coatings were good and had no cracks or defects. Compared with those of the CLA coating, the EHLA coating had finer grains and a more uniform distribution. Both coatings contained face-centered cubic (FCC) and body-centered cubic (BCC) phases, but the BCC phase of the EHLA coating was less precipitated than the CLA coating. The higher microhardness and better wear resistance of the EHLA coatings occurred in the presence of Hall–Petch strengthening. [ABSTRACT FROM AUTHOR]

Improvement of the mechanical property of the near-β titanium alloy Ti-10V-2Fe-3Al (TB6) fabricated by laser additive manufacturing can be achieved through solution and aging treatment. In this paper, the changes in the microstructures and mechanical properties of the deposited TB6 specimens were tested by changing the solution temperature, aging temperature, and aging time and the effects of the primary α phase (αp) and secondary α phase (αs) on the mechanical properties were analyzed. The results show that the solution temperatures mainly determine the volume fraction of αp and grain boundary α phase (αGB). Aging temperature and time have large impacts on the morphology of αs. The strength of the solution- and age-treated specimens are controlled by the volume fraction and size of αs. The higher volume fraction, αs, obtained by the higher solution temperature could lead to a higher strength with balanced ductility. The coarser αs obtained by the higher aging temperature or longer aging time will contribute to higher ductility, but decrease the strength of the alloy. The fracture mode of tensile specimens is mainly intergranular fracture due to the strain incompatibility between the grains and the grain boundaries. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of Ti-6Al-4V alloy sintered by spark plasma was studied by multi-pass of hot compression experiment, and the influence of different thermal deformation parameters (hot compression temperature deformation: 950°C–20% for one pass, 850°C–20% for two passes and 900°C–10%/20%/30% for three passes) was studied. The results show that the dynamic recrystallization characteristic behavior appears in the three deformation passes. The microstructure after the first and second pass deformation is mainly composed of Widmanstätten structure. With the increase of strain rate, the thickness of lamellar α decreases gradually. In three pass, the grain boundary α phase and the layered α phase are twisted and bent when the deformation amount is 10% and 20%, and the deformation amount increases to 30%. The spheroidization of lamellar α phase occurs, and the size of β grain decreases obviously. The content of equiaxed α phase and grain size decrease with the increase of strain rate. [ABSTRACT FROM AUTHOR]

Herein, the effect of carbon content on the microstructures of Co–20Cr–15W–10Ni (mass pct, CCWN) alloys was systematically studied. For this, CCWN alloys with carbon contents of 0, 0.05, 0.10, and 0.20 mass pct, i.e., 0C, 0.05C, 0.10C, and 0.20C alloys, respectively, were prepared using an induction melting furnace. The as-cast alloys were solution treated at 1523 K for 7.2 ks, followed by cold swaging and heat treatment at 1173 K–1473 K for 0.15–7.2 ks. Consequently, η-phase (M6C-M12C type, M: metallic element) precipitates were detected in the as-cast 0.10C and 0.20C alloys, whereas no precipitates were observed in the 0C and 0.05C alloys. These precipitates were dissolved via a solution treatment. After cold swaging, the ε-phase formed through a strain-induced martensitic transformation in the 0C and 0.05C alloys. Following heat treatment, a single γ-phase matrix was observed in all the alloys, and μ-phase (Co7W6-type) and η-phase precipitates were observed in the 0C and carbon-added alloys, respectively. The precipitation temperature range of the η-phase increased with increasing carbon content. The stability of the precipitates qualitatively conformed with that of the calculated phase diagram. This is the first paper that reports the microstructural changes in CCWN alloys with varying carbon contents. [ABSTRACT FROM AUTHOR]

To reveal the influence mechanism of linear heat input (LHI) on the mechanical properties and corrosion behaviors of SUS304 weldments manufactured by local dry underwater pulsed metal inert-gas welding (LDU-PMIG), phase structure, grain structure, grain preferred orientation, and grain type of weld metal (WM) were investigated in this paper. With LHI increasing, ferrite phase morphology transformed from lath to skeleton, and grain size was enlarged. The content of equiaxed grains was increased, and that of columnar grains was reduced remarkably. The mechanical performance ascended first and then reduced with the increase of LHI. The increase of equiaxed grain content and the diversification of grain preferred orientation were beneficial to the improvement of mechanical performance, then, grain coarsening led to mechanical performance decreasing. Besides, the corrosion potential, corrosion current and pitting potential of WM were detected through electrochemical corrosion tests. The results illustrated that the corrosion resistance of WM was lower than that of base metal (BM), and the corrosion rate was enlarged with LHI enhancing, which meant the corrosion resistance declining. The corrosion resistance was mainly determined by Cr precipitates, ferrite phase and grain size. The microhardness, tensile strength, and elongation reached their maxima in the LHI of 336.7 J/mm. The greatest corrosion resistance of WM was obtained in the LHI of 256.2 J/mm and reached 69.9% of BM. This study is meaningful to promote the further development and application of LDU-PMIG in marine underwater welding field. [ABSTRACT FROM AUTHOR]

This paper adopted the new process of double-sided oscillation laser autogenous backing welding and double-sided oscillation laser–TIG hybrid filling welding to achieve 80 mm thick SA-738Gr.B steel narrow gap welding in the horizontal position. The microstructure, mechanical properties, and residual stress of the welded joints in the as-welded (AW) state and in the post-weld heat treatment (PWHT) state were analyzed comparatively. The results show that because of the high-temperature tempering effect of PWHT, the microstructure of the welded joint is transformed into a high-temperature tempered microstructure with the increase in alloy carbide precipitation. The grains growth of the backing weld and the base material is obvious. The relative frequency of the high-angle grain boundary of the weld increases. Under the PWHT, the tensile strength of the welded joint decreases, and the residual stresses of the welded joint are redistributed and reduced significantly. [ABSTRACT FROM AUTHOR]

Ni-based wrought superalloys are a type of superalloy produced through casting-forging processes, and usually their high-temperature performance is strongly influenced by microstructure and deformation mechanism. The typical microstructure of Ni-based wrought superalloys after heat treatments comprises equiaxed grains, numerous annealed twins, carbides within the grain interior and/or at grain boundaries, and spherical γ′ precipitates (typically comprises around 20% of their volume). The common deformation mechanisms in Ni-based wrought superalloys mainly include anti-phase boundary formed by paired dislocations shearing γ′ phase, stacking fault formed by single dislocation shearing γ′ phase, dislocation bypassing γ′ phase (precipitation-strengthened) and dislocation entanglement, dislocation networks (solid solution strengthened). In this paper, the microstructure and deformation mechanism of tensile and creep in Ni-based wrought superalloys for Advanced ultra-supercritical (A-USC) power plants are reviewed, for the two prominent areas of current research, Ni–Fe-based wrought superalloys exhibit superior processability and cost-effectiveness compared to Ni–Co-based wrought superalloys, thereby offering a more advantageous solution. [ABSTRACT FROM AUTHOR]

In this paper the influence introducing various plasticizers into an initial charge on the structure and properties of iron-based powder materials alloyed with copper is considered. It is shown that introduction of copper stearate into an initial powder mixture and warm mixing, pressing and subsequent sintering makes it possible to obtain low-porosity workpieces with relative porosity of 95%. Pores within the workpieces obtained have a small size of 10–15 microns and a rounded shape. Also, bending strength is determined for sintered samples of all the compositions of powder mixtures studied and the Rockwell hardness is determined on the C scale. Powder steels based upon mixtures have the best set of mechanical properties PZhRV 2.200.28 + 0.7 wt.% Br + 0.7 wt.% Cu + 1 wt. % StCu + warm mixing—hardness HRC 58. flexural strength 600 MPa PZhRV 2.200.28 + 1.4 wt.% Br + 1.4 wt.% Cu + 1.4 wt.% C + 1.0 wt.% StFe + warm mixing—hardness HRC 100, flexural strength 530 MPa [ABSTRACT FROM AUTHOR]

This paper is dedicated to studying the effect of replacing molybdenum with vanadium on the tendency to amorphisation, structure, and thermal properties of high-entropy alloys of the (Fe0.25Ni0.25Co0.25Cr0.125Mo0.125‑xVx)100‑yBy system, where x = 0; 0.0625; 0.125 and y = 17–25. The alloy structure was analyzed using X‑ray diffraction, scanning and transmission electron microscopy methods. Thermal properties were determined by differential scanning calorimetry. It was found that the replacement of molybdenum with vanadium leads to the formation of crystalline particles of complex nitrides (V, Cr, Mo)(N, B) in the ribbon structure. The dependences of the characteristic alloy temperatures have been established. Molybdenum replacement with vanadium was shown to stabilize the supercooled liquid in alloys with completely amorphous structure. [ABSTRACT FROM AUTHOR]

Steel matrix composites are widely used in automotive, aerospace, wear, and cutting applications due to their superior mechanical properties, ease of manufacture, and low cost. However, there are still some limitations in the strength, reinforcement dispersion, and interface control of steel matrix composites, which are mainly achieved through different preparation processes and the addition of reinforced particles with mixed metal powders. Previous studies have demonstrated the enhanced ability of various reinforcing particles such as titanium carbide, silicon carbide, and alumina to enhance the wear performance of steel substrates, but there are still some challenges, such as uneven particle distribution, interface cracks, and unsatisfactory wettability. In this paper, the preparation methods of ceramic-reinforced metal matrix, ceramic reinforcement, steel matrix composition, microstructure, mechanical properties, and wear properties, as well as the parameters affecting their properties, are reviewed. The preparation processes of different ceramic-reinforced steel matrix composites are introduced, which are very suitable for overcoming challenges such as insufficient strength, poor dispersion, uneven distribution, and poor interfacial wettability. The influence of the morphology distribution and volume fraction of reinforcement on the wear rate of steel matrix composites was discussed. The importance of the microstructure of ceramic reinforcement in steel matrix and the interface between ceramic and matrix to improve the mechanical properties of steel matrix composites were emphasized. This review identifies the development trends in the field of research to fully illustrate the importance of more in-depth scientific research in steel matrix composites. [ABSTRACT FROM AUTHOR]

Magnesium matrix composites (MMCs), prepared by adding reinforcements to magnesium alloys, are widely noticed for superior properties over the matrix. However, few studies on ZrO2p-reinforced AZ31 magnesium alloys were prepared by the powder metallurgy (PM) method. In this paper, AZ31 magnesium alloys with different ZrO2p contents were successfully prepared by powder metallurgy (PM), and the microstructure and mechanical properties of AZ31 and MMCs were investigated. The results show that ZrO2p hinders the migration of dislocations and forms a particle deformation zone (PDZ) around ZrO2p. The PDZ with higher energy storage can promote the nucleation process of dynamic recrystallization of MMCs. Meanwhile, ZrO2p pins the grain boundaries and hinders the growth of recrystallized grains, so the MMCs have higher recrystallization fractions and finer grains. In addition, the recrystallization process removes dislocation density and promotes the transition from low-angle grain boundaries to high-angle grain boundaries. As a result, the composites have superior properties due to the pinning of dislocations, grain refinement, and load transfer by ZrO2p. Compared with the AZ31 matrix, the UTS, YS, and hardness of the MMCs were increased by ~ 6.8%, ~ 5.0%, and ~ 16.5%, respectively. [ABSTRACT FROM AUTHOR]

Niobium alloy C-103 is a refractory alloy used in the manufacturing of spacecraft propulsion components for its mechanical properties at elevated temperatures. Fair weldability makes C-103 additively manufacturable (printable) utilizing laser powder-bed fusion (L-PBF). Printed C-103 parts are often subjected to hot isostatic pressing (HIP) to obtain a microstructure with fewer defects and more isotropic properties. Brief exposures to high-temperature environments are common for C-103 parts; experimentally, a high-vacuum annealing (HVA) process was employed to identify changes from temperature effects apart from the HIP process. This study compares the effects of HVA and HIP processes on the microstructure (i.e., grain size, morphology), formation of precipitates, microhardness, and anisotropy of C-103 fabricated by L-PBF. The results showed recrystallization and texture changes occurred during HIP but not HVA, contributing to retained, albeit altered, anisotropy in the HVA-ed material. The microhardness of HVA-ed C-103 was greater and more anisotropic than HIP-ed for annealing temperatures below 1200°C. Hafnium oxide precipitates were observed in all the samples and which coarsened with increasing HVA temperature. Oxide area% determined via image analysis showed a strong negative correlation with microhardness. Overall, this paper presents novel findings on the effects of HVA and HIP on C-103 printed via L-PBF and forms a basis for future post-processing of C-103 parts. [ABSTRACT FROM AUTHOR]

42CrMo steels are widely used for many general-purpose components served under thermal environment, owing to their relatively high strengths and low costs. The evolutions of microstructure and mechanical property of 42CrMo steel served at 425, 475, 500, 525, 550 and 575 for 500 h were reported in this paper, aiming to reveal the phase transformation and mechanical property evolution characteristics of the steel served at elevated temperatures. The microstructural investigation and phase composition measurement were performed using thermodynamic calculations, optical microscopy and scanning electron microscopy techniques. The extent of spheroidization for the microstructure was measured through the average aspect ratio of cementite phase. Mechanical properties were characterized through tensile strength, micro-hardness measurements and fracture morphology observation for the steel samples. Results showed that the microstructure consisting of ferrite and lamellar cementite was relatively stable below 500 °C. As the temperature increased from 500 to 575 °C, the spheroidization, dissolution of cementite and the softening of the ferrite matrix combined contributed to the degradation of the mechanical properties. The evolution rules of Cr and Si elements segregated in phases during these temperatures were revealed. A method of aspect ratio measurements (δ = 0.322–0.584) for cementite particles was proposed to assess the microstructure evolution and strength degradation (σb = 650–963 MPa) of the steel. Based on the above, the variation of property for the steel served at elevated temperatures can be naturally divided into three stages, including no change of cementite stage (T < 500 °C), spheroidization of cementite stage (500 °C ≤ T ≤ 550 °C) and dissolution of cementite stage (T > 500 °C). Additionally, the ultimate service temperature range of this type of steel was discussed. [ABSTRACT FROM AUTHOR]

The surface of the hot forging die is prone to failure due to severe high heat and cyclical load during service. The remanufacturing of a forging die by wire and arc additive manufacturing technology could greatly improve the performance of the die and prolong its service life. In this paper, the remanufactured zone of the die was divided into three additive deposition layers with gradient mechanical properties based on temperature and stress analysis, namely, the transition layer, intermediate layer and strengthen layer, according to the thermal and stress conditions. A wire and arc additive manufacturing experiment with gradient material was conducted on 5CrNiMo hot forging die steel. The microstructure and mechanical properties of the gradient additive layer were characterized and analyzed. The results indicated that the microstructure of the gradient additive layer presents a transformation process of bainite-to-martensite from bottom to top. The hardness and strength of the transition layer, intermediate layer and strengthen layer exhibit a rational gradient increasing trend, while the impact toughness shows a decreasing trend. The wear loss and cumulative friction dissipated energy of the strengthen layer are considerably lower than those of the other layers. The mechanical properties of the gradient additive layer are shown as a gradient increase in hardness, strength, and wear resistance at high temperature, which is conducive to enhancing the overall pressure bearing capacity and preventing the failure of plastic deformation on the surface of the remanufactured hot forging die. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure evolution of TC17 titanium alloy formed by laser solid forming were analyzed, and the influence of solution and two-stage aging heat treatment on the microstructure homogenization and room temperature tensile properties were investigated. The extension of heat treatment temperature and time will lead to the size and volume fraction of primary lath α phase increasing, but decreasing for secondary α phase. Aging has no effect on the change of grain morphology but leading to the primary α lath coarsening. The hardness is the lowest at the secondary solution temperature of 750 °C. The strength and plasticity of heat-treated samples suffering 920 °C/0.5 h/ water quenching + 750 °C/1 h/water quenching + 630 °C/4 h/air cooling match well. The anisotropy is basically eliminated at the secondary solution temperature of 830 °C. [ABSTRACT FROM AUTHOR]

In this paper, in-plane vibration characteristics of square metamaterial plates, which are made of three-dimensional periodic arrangement of the coated spherical particles embedded in a matrix, are investigated theoretically. First, the effective material properties of the plates, including elastic constants and mass density, are obtained by using a simple homogenization method. Then, the governing equations of in-plane vibration are derived and solved analytically for simply supported boundary conditions. In addition, to verify the proposed formulations, the resonance frequencies and corresponding mode shapes of the plates are calculated via commercial finite element method software. Then, a parametric study is performed to illustrate the effects of the geometrical and material properties of the unit cells on the frequencies of metamaterial plates. [ABSTRACT FROM AUTHOR]

Electric pulse treatment can regulate the microstructure and mechanical properties of metals under low temperature in a very short time and this affects their machinability. In the work presented in this paper, Ti-6Al-4V was treated by an electric pulse, the influences of the electric pulse treatment on the microstructure and the mechanical properties of the Ti-6Al-4V alloy were explored, and the machinability of the Ti-6Al-4V alloy with electric pulse treatment was studied. The metastable β phase of the sample having electric pulse treatment at 2.98 A/mm2 became less, resulting in a decrease in the hardness, the basket-like microstructure of the sample by electric pulse treatment at 3.98 A/mm2 enhanced the plasticity. The cutting force, cutting temperature and workpiece surface roughness values of the Ti-6Al-4V having electric pulse treatment were significantly reduced, but the electric pulse treatment enhanced the workpiece surface layer plastic deformation, deepening the depth of the processing metamorphic layer. [ABSTRACT FROM AUTHOR]

In this paper, a new fabrication technique for Mg-3Al-1Zn (AZ31) magnesium alloy tube, called tube extrusion expander shear (TEES), was proposed based on the existing extruded shear (ES) technique. The finite-element modeling (FEM) was used to simulate the forming process of TEES. The electron back-scattered diffraction (EBSD) was used to study the microstructures and textures evolution of AZ31 magnesium alloy during TEES process. The mechanical properties of the formed tube were tested. The results show that TEES process can effectively refine the grain size and weaken the basal texture. The hardness and plasticity of the tube processed by TEES process are significantly improved, the maximum elongation is 15%, and the hardness is 78 HV. Based on the analysis of intragranular misalignment axis (IGMA), the evolutions of twins in the TEES process were studied. It was found that twins and basal slip were the main deformation modes in the early deformation zone. With development of TEES process the twins disappear and multiple sliding systems were activated. The results show that the turning and shearing zones of TEES process are beneficial to the activation of multiple slip systems. [ABSTRACT FROM AUTHOR]

The stability of microstructure and performance after long-term service are crucial for the engineering application of ASME SA335-P92 steel. In this present work, a series of isothermal aging tests for P92 steel were performed at 680 °C as long as 21,000 h. Microstructure at different stages of evolution was characterized using scanning electron microscope and transmission electron microscopy. Strength and plasticity measurements under the static mechanical tensile condition were also carried out at room temperature. Results showed that Laves phases precipitated rapidly at the early aging stage and coarsened with a relatively high rate in the followed aging period, while M23C6 carbides were precipitated continuously during the aging process. The tensile strength and plasticity of P92 steel at room temperature declined rapidly at the early stage of aging. During the afterward aging process, strength overall presented a slowly falling tendency but plasticity remained a sustainable stability. Micro-mechanism of variation on mechanical tensile properties for P92 steel aged for a long-term time would be further revealed in this paper. [ABSTRACT FROM AUTHOR]

With the rapid development of industrial manufacturing, traditional WC–Co cemented carbides have exposed more and more problems. Therefore, the preparation of ultrafine/nanocrystalline-grained cemented carbides and the development of new binders have become a hot issue in the field of cemented carbides. Due to the unique design concept, the high-entropy alloys (HEA) binder not only has the unique properties of the HEA itself, but also can replace the traditional Co element as the binder of cemented carbide, which opens up the possibility for industrial manufacturing. The stable chemical properties of WC are coupled with the multi-principal element characteristics of HEA binder, which makes novel WC-HEA cemented carbides have the characteristics of grain refinement, compact structure, stable structure, and excellent capability. A multitude of studies have found that the new WC-HEA cemented carbide exhibits better service performance than WC–Co cemented carbide. In this paper, the main preparation processes of WC-HEA cemented carbide in recent years are summarized; the influence of the working principle, advantages, and defects of the two different preparation methods on the microstructure and properties of WC-HEA cemented carbide were described. The characteristics and influence mechanism of microstructure such as the composition of high-entropy alloy binder and the change behavior of phase structure of WC-HEA cemented carbide were discussed. The service performance characteristics of WC-HEA cemented carbides were discussed, including mechanical properties, wear resistance, oxidation resistance, and corrosion resistance. Finally, it summarizes the research challenges and prospects in the current research work, and provides an outlook on the research direction and application prospects of WC-HEA cemented carbide. [ABSTRACT FROM AUTHOR]

In this paper, the isothermal thermal compression simulation test of 2024 aluminum alloy was carried out. The deformation temperature is 573-723 K, the strain rate is 0.01-10 s−1, and the deformation amount is 50%. The experimental results show that the change of flow stress is inversely proportional to the deformation temperature, but directly proportional to the strain rate. OM and TEM were used to observe the microstructure after thermal deformation, the increase of temperature and the decrease of strain rate contribute to the formation of recrystallization and the decrease of dislocation density, which is the main reason for dynamic softening. The thermal deformation activation energy of 2024 aluminum alloy is 201.62 kJ/mol. The experimental peak stress constitutive model is in good agreement with the calculated value. Based on the Prasad instability model and the dynamic material model, the hot working diagram of 2024 aluminum alloy is established to construct the true strain of 50%. The ideal deformation conditions are the deformation temperature of 573-673 K and strain rate of 0.01-0.1 s−1. [ABSTRACT FROM AUTHOR]

The paper focuses on the investigation of the effect of heat input on the microstructure and mechanical properties of welded joints produced by electron beam welding of 4.0 mm-thick AW2099 aluminum-lithium alloy. This type of alloy is intended for application in an airplane fuselage. Information on electron beam welding of such type of materials is up to now is very limited. Non-dendritic equi-axed zone (EQZ) was observed at the heat-affected zone–weld metal interface. The higher heat input (HHI) led to the development of EQZ with a larger width. The thickness of EQZ was non-uniform across the base material thickness. EQZ was characterized by the presence of higher amounts of elements at the grain boundaries due to segregation. Eutectics based on α-aluminum + θ-Al2Cu were detected in those areas. Transmission electron microscopy detected the presence of AlLi and Al2Li3 intermetallic phases in the weld metal. Dissolution of the low-temperature δ'-Al3Li phase was observed by differential scanning calorimetry (DSC). Higher peak temperatures of a thermal cycle were measured during HHI welding. A peak temperature of 451 °C at a distance of 1.5 mm from the weld centerline was measured. The dissolution of precipitate particles caused by a thermal welding cycle resulted in the drop of microhardness in the fusion zone. Mean microhardness was slightly higher in the case of lower heat input (LHI) welding, i.e., 73% of that of the base material. The maximum weld tensile strength reached more than 83.8% of that of base materials. The fracture surface revealed the presence of dimples and bright brittle surfaces along with the microcracks and grain boundary eutectics. [ABSTRACT FROM AUTHOR]