Recently, γ′ phase has been introduced into the solid-solution strengthening Haynes 230 alloy to improve alloy strength for better satisfying the rigorous service environment. However, previous ...research shows that γ′ phase was not precipitated under the as-fabricated condition and harmful Laves phases with high-W content, which have never been reported, appeared in the novel alloy. Therefore, in this study, Laves phase dissolution mechanisms during solution heat treatments (SHT) and γ′ strengthening mechanism after subsequent aging heat treatment (AHT) of a novel γ′-strengthening superalloy prepared by laser powder bed fusion (LPBF) were first investigated. The results show that Laves phases continue to dissolve with the increment of SHT temperature and finally disappear after SHT-ed at 1200 °C. The higher dissolution difficulty of Laves phases is closely related to the lower diffusion coefficient of W element. The long-range diffusion of solute atoms mainly controls the dissolution of Laves phases in the early homogenization stage. As the holding time increases, the γ/Laves interface widths for the solute atoms diffusion decrease and thus the dissolution process is gradually governed by the interface reaction in the later stage. After AHT, numerous nanosized γ′ particles are precipitated. With increasing SHT temperature, the ultimate tensile strength (UTS) and yield strength (YS) of the AHT-ed samples decrease while the elongation (EL) increases, which is mainly caused by the Laves phases dissolution and grain recrystallization. The 1200+AHT sample presents an excellent combination of strength and ductility with UTS of 1467.7 MPa, YS of 1244.6 MPa and EL of 6.3%. The dominant strengthening contributions in the AHT-ed samples are γ′ strengthening and solution strengthening.
•Laves phase dissolution is mainly controlled by the long-range diffusion of solute atoms in the early stage and gradually governed by the interface reaction in the later stage.•The 1200+AHT sample presents an excellent combination of strength and ductility with UTS of 1467.7 MPa, YS of 1244.6 MPa and EL of 6.3%.•The dominant strengthening mechanisms are γ′ strengthening and solution strengthening.
The engineering and tailoring of porous materials to realize the precise discrimination of CO2 and C2H2, with almost identical kinetic diameters, is a challenging task. We herein report the first ...example of the kinetic‐sieving of relatively larger molecule of C2H2 from CO2 by a novel sulfonic anion‐pillared hybrid ultramicroporous materials of ZU‐610a. Specifically, ZU‐610 constructed from copper(II), isonicotinic acid and 1,2‐ethanedisulfonic acid is synthesized and shows the preferential affinity for C2H2 over CO2. After the post‐synthetic heat treatment of ZU‐610, ZU‐610a with a contracted aperture is obtained. Interestingly, the C2H2‐selctive ZU‐610 was reversed to the CO2‐selective ZU‐610a. High purity C2H2 (>99.5 %) could be directly obtained from the dynamic breakthrough experiments on an equimolar C2H2/CO2 mixture at 298 K. This study provides guidance for the design of adsorbents aimed at separation systems with similar kinetic diameter.
The fine‐tuning of the pore structure without changing the topology is possible through post‐synthetic heat treatment and gives the novel sulfonic anion‐pillared hybrid ultramicroporous material ZU‐610a. It achieves the kinetic sieving of C2H2 and CO2 which have the same kinetic diameter. It produces C2H2 with purity higher than 99.5 % in only one adsorption process.
Zero‐dimensional (0D) metal halides have drawn increasing attention due to the attractive structure dependent photoluminescence (PL) properties. Here, we report two new 0D organic–inorganic hybrid ...Sb‐based halides, (MTP)6SbBr6Sb2Br9⋅H2O (MTP=Methyltriphenylphosphonium, crystal 1) and (MTP)2SbBr5 (crystal 2), featuring a reversible structural phase transformation and tunable orange and red emissions upon dehydration and rehydration of H2O molecules. Intriguingly, a subsequent heat treatment further enables the formation of glassy state (MTP)2SbBr5 (glass 3) with near‐infrared luminescence, moreover, a sequential reverse phase transformation from glass 3 to crystal 2 and 1 is triggered by acetonitrile and water vapor stepwise. The anti‐counterfeiting demo based on the tunable and reversible PL switching is finally achieved and thus the phase structure engineering in 0D metal halides expands their multiple applications in optical fields.
We report the sequential and reversible phase transformation and photoluminescence switching of orange (MTP)6SbBr6Sb2Br9⋅H2O crystals, red (MTP)2SbBr5 crystals and (MTP)2SbBr5 glass with near‐infrared emission. Utilizing their luminescence switching nature accompanied by reversible phase transformations, we achieved multiple and repeatable anti‐counterfeiting applications.
Additively manufactured (AM) metallic materials commonly possess substantial microscale internal stresses that manifest as intergranular and intragranular residual stresses. However, the impact of ...these residual stresses on the mechanical behaviour of AM materials remains unexplored. Here we combine in situ synchrotron X-ray diffraction experiments and computational modelling to quantify the lattice strains in different families of grains with specific orientations and associated intergranular residual stresses in an AM 316L stainless steel under uniaxial tension. We measure pronounced tension-compression asymmetries in yield strength and work hardening for as-printed stainless steel, and show they are associated with back stresses originating from heterogeneous dislocation distributions and resultant intragranular residual stresses. We further report that heat treatment relieves microscale residual stresses, thereby reducing the tension-compression asymmetries and altering work-hardening behaviour. This work establishes the mechanistic connections between the microscale residual stresses and mechanical behaviour of AM stainless steel.
Fabrication of nuclear reactor components using additive manufacturing (AM) methods is now a practical option since the AM technologies have advanced to allow for building of complex parts with high ...quality materials. To assess the mechanical performance of printed components in reactor-relevant conditions and to build a property database for the AM 316L stainless steel (SS), mechanical testing and characterization were performed before and after neutron irradiation. Miniature tensile specimens were irradiated at the High Flux Isotope Reactor (HFIR) to 0.2 and 2 displacements per atom (dpa) at 300 and 600°C. The AM 316L SS was tested in the as-built, stress-relieved, and solution-annealed conditions, and the wrought (WT) 316L SS in solution-annealed condition as a reference alloy. The baseline test result showed that the AM 316L SS, regardless of the post-build heat treatment, had higher strength than the WT 316L SS, but similar ductility. Post-irradiation tensile testing was conducted at RT, 300°C, and 500°C for selected irradiation conditions. Neutron irradiation induced significant changes in the mechanical behavior of the AM stainless steels, including both hardening and softening. Although the as-built 316L steel after 300°C irradiation showed necking just after yielding, the overall property changes of the as-printed alloy became less significant after 600°C irradiation. Irradiation-induced ductilization was also observed after the higher temperature irradiation. In general, the strength change was smaller in the relatively stronger as-built and stress-relieved AM SSs than in the solution-annealed AM and WT SSs. These relatively lower strength 316L SSs overall retained higher ductility in the irradiation conditions tested, but the stronger 316L SSs demonstrated a similar level of ductility after the higher temperature (600°C) irradiation. It is a positive assessment for the AM 316L materials that no embrittlement was observed within the test and irradiation conditions of the experiment.
The inherent acidity of fruit products acts as a hurdle to microbial growth; however, enzymatic stability is still a concern for its shelf-life. In the last two decades, the fruit processing industry ...has shifted to nonthermal treatments to fulfill the demand for microbial and enzymatic stability. Nevertheless, while deciding the nonthermal process intensity for a fruit product, microbial safety is targeted along with maximum retention of phytochemicals to fulfill the demands of both manufacturers and consumers. However, retailers demand a stable fresh-like product devoid of enzymatic spoilage.
This review briefs about enzymatic spoilage in fruit products and the mechanism of nonthermal inactivation of enzymes such as polyphenoloxidase and pectinmethylesterase. The extent of enzyme inactivation in fruit products by various nonthermal treatments with or without any added hurdle is discussed. The hurdles include coupling a nonthermal treatment with other nonthermal treatments, mild thermal treatment, antimicrobials, coatings, etc.
The intensity of a nonthermal treatment may not often be sufficient to achieve a complete inactivation of spoilage enzymes. The product matrix, viz., fruit pieces, purees, or juice, plays a vital role in the extent of enzyme inactivation. Hurdle technology of nonthermal treatment with mild heat treatment (40–70 °C) is better for achieving adequate inactivation. Nevertheless, there is enough evidence that the enzyme might regain its activity during storage. To satisfy the demands of all the stakeholders, the nonthermal process design for a fruit product should emphasize achieving enzyme inactivation while ensuring microbial safety and quality retention.
•The review briefs about the enzymatic spoilage in fruits products.•The nonthermal inactivation of spoilage enzymes in fruit products is discussed.•Limited studies exist on the stability of those spoilage enzymes during storage.•The enzyme might regain its activity during storage after the treatment.•The nonthermal treatment should achieve enzymatic stability and quality retention.
Crystallographic texture in metals influences material properties, e.g., r-value. In this work, a moderately strong texture is obtained in AA5182-O through continuous-bending-under-tension processing ...followed by a recovery heat treatment from the initial weak cube texture. EBSD scans confirm that the texture is retained after heat treating. The processed material exhibits increased strength and reduced planar anisotropy, providing benefits to subsequent forming operations, compared to the as-received material. Crystal plasticity simulations confirm the texture change during deformation and predict the flow stress response. Such simulations can be used for stress superposition process design to intentionally manipulate material properties.
Inconel 718 superalloy has been fabricated by selective laser melting technology (SLM). Its microstructure and mechanical properties were studied under solution+aging (SA) standard heat treatment, ...homogenization+solution+aging (HSA) standard heat treatment and as-fabricated conditions. Precipitated phases and microstructures were examined using OM, SEM, TEM and X-ray analysis methods. The fine dendrite structures with an average dendrite arm spacing of approximately 698nm accompanying some interdendritic Laves phases and carbide particles can be observed in the as-fabricated materials. After standard heat treatments, dendrite microstructures are substituted by recrystallization grains, and Laves phases also dissolve into the matrix to precipitate strengthening phases and δ particles. The test values of all specimens meet Aerospace Material Specification for cast Inconel 718 alloy, and the transgranular ductile fracture mode exists for the three conditions. The strength and hardness of heat-treated SLM materials increase and are comparable with wrought Inconel 718 alloy, whereas their ductility decreases significantly compared with the as-fabricated material. This is because of the precipitation of fine γˊ and γ〞strengthening phases and needle-like δ phases. For the as-fabricated alloy, the formation of finer dislocated cellular structures that develop into a ductile dimple fracture shows excellent ductility. Due to dislocation pinning from γˊ and γ〞strengthening phases and the impediment of dislocation motion caused by the needle-like δ phases, the ductility of the SA materials decreases and causes a transgranular fracture, compared with the as-fabricated samples.
In this study, an alternative heat-treatment route has been explored to optimize the mechanical as well as the fatigue properties of Ni-based 718 alloy fabricated using additive methods. The test ...coupons were prepared using the laser-based powder bed fusion technique and post-processed with a new heat-treatment condition (NHT): solution treatment at 1130°C for 2hr followed by water cooling (WC) and the artificial aging at 730°C for 13hr followed by furnace cooling (FC). It was found that the NHT parameters enhanced the mechanical properties as well as the fatigue properties as compared to the standard heat-treatment (SHT) conditions: solution treatment at 980°C-1hr-FC followed by two-step artificial aging 720°C-8hr-FC(55°C/hr up to 620°C) + 620°C-8hr-FC. The NHT condition resulted in a more homogenized and recrystallized microstructure with a higher volume fraction of γ′ and γ′′ precipitates, high-angle coincidence site lattice (CSL) as well as the twin boundaries and marginally reduced grain size. The microhardness, tensile strength, and fatigue strength after the NHT condition were improved by ∼15%, ∼16%, and ∼12.5%, respectively, and it was mainly accredited to the high volume fraction of fine strengthening precipitates and homogenized microstructure.
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•A new heat-treatment for the additively manufactured IN718 alloy was explored.•A homogenized and recrystallized microstructure with smaller grains was obtained.•A high volume fraction of coherent and finer γ′ and γ'' precipitates was observed.•Metal carbides and lave phases were nearly dissolved after the new heat-treatment.•Both mechanical as well as fatigue properties were significantly improved.
Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the ...microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉// building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ, TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.
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