This paper reports on the dissolution of δ-ferrite in the weld fusion zone using post-weld normalizing and tempering (PWNT) and its effect on mechanical properties. The autogenous gas tungsten arc ...welding (GTAW) was used to prepare double-sided welded joints of P92 steel. After welding, post-weld heat treatment (PWHT) at 760 °C for 2 h and post-weld normalizing at 1050 °C for 1 h followed by tempering at 760 °C for 2 h were performed. The morphology, composition, structure, and hardness of δ-ferrite are verified. The effect of PWHT and PWNT on mechanical properties is also observed. In as-welded and PWHT conditions, the retention of δ-ferrite was observed while the dissolution of δ-ferrite was confirmed after PWNT. In the PWNT condition, uniform microhardness across the welded joint, increased ductility, and increased Charpy toughness of weld fusion zone (almost equal to as received material) were achieved. Dissolution kinetics of δ-ferrite is quantified using Thermo-Calc for Scheil's solidification calculation and DICTRA for calculating diffusion coefficients of Cr and W at 1050 °C in austenite.
In this work, NiAl bronze (NAB) alloys were subjected to friction stir processing (FSP) at a constant traverse speed of 100mm/min and rotation rates of 600rpm, 800rpm, 1000rpm and 1200rpm, ...respectively. Thereafter, heat treatment was performed at 675°C for 2h. The effects of rotation rates on strengthening mechanisms of friction stir processed and post heat treated NAB alloy were studied. The results showed that friction stir processed NAB alloy microhardness was increased as the rotation rate increased. During friction stir processing, martensite nanotwins could be formed due to high strain rates and peculiar martensitic structures of NAB alloys. A rotation rate increase, increased peak temperatures and strain rates in friction stir processed NAB alloys, leading to a significant amount of martensite nanotwins formation. As rotation rates increased from 600rpm to 1200rpm, in addition to grain refinement effects, the strengthening mechanism of friction stir processed NAB alloys gradually changed from secondary phase strengthening to solid solution, dislocations and nanotwin strengthening. During post heat treatment, discontinuous static recrystallization occurred and β′ phase decomposed into α and κ phases. Highest microhardness values were obtained at the rotation rate of 800rpm and the uniformly distributed second phases formed during friction stir processing contributed mainly to higher microhardness.
The influence of repeated and continuous dry heat treatments on structural, physicochemical, and digestive properties of sweet potato starch was investigated. The results showed that the original ...A-type crystallinity of sweet potato starch remained unchanged after dry heat treatments. The light transmittance, gelatinization temperature, and pasting temperature of sweet potato starch increased; while the pasting viscosities, swelling power, and solubility decreased after dry heat treatments. Relative crystallinity, solubility, swelling power, light transmittance, and thermal parameter values (To, Tp, Tc, ΔT) were found to be significantly higher for the continuous dry heat (CDH) treated starch than those of the repeated dry heat (RDH) treated starch after treatment for the same duration. However, CDH treated starch samples showed lower paste viscosity and digestibility than those of RDH treated samples after treatment for the same duration. In addition, the CDH treatment highly influenced the structure of starch granule surface compared with the RDH treatment. Generally, it can be concluded that RDH treatment highly influenced structural, physicochemical, and digestive properties of sweet potato starch compared with CDH treatment.
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•Sweet potato starch was subjected to repeated and continuous dry heat (RDH and CDH) treatments.•The dry heat treatment significantly influenced physicochemical and digestive properties of the sweet potato starch.•The original A-type crystallinity of the sweet potato starch remained unchanged after dry heat treatments.•The repeated dry heat treatment highly influenced properties of starch compared to continuous dry heat treatment.
Sodium trisilicate waterglass is an earth-abundant inorganic adhesive which binds to diverse materials and exhibits extreme chemical and temperature stability. Here we demonstrate the use of this ...material as an electrode binder in a lay-up based manufacturing system to produce structural batteries. While conventional binders for structural batteries exhibit a trade-off between mechanical and electrochemical performance, the waterglass binder is rigid, adhesive, and facilitates ion transport. The bulk binder maintains a Young's modulus of >50 GPa in the presence of electrolyte solvent while waterglass-based electrodes have high rate capability and stable discharge capacity over hundreds of electrochemical cycles. The temperature stability of the binder enables heat treatment of the full cell stack following lay-up shaping in order to produce a rigid, load-bearing part. The resulting structural batteries exhibit impressive multifunctional performance with a package free cell stack-level energy density of 93.9 Wh/kg greatly surpassing previously published structural battery materials, and a tensile modulus of 1.4 GPa.
The microstructures and tensile properties of a novel superalloy especially designed for additive manufacturing (AM) were investigated under four states: (1) AD (as-deposited), the state of part ...after LMD (laser metal deposition); (2) HT1, heat treated at 870 °C for 16 h + air cooling; (3) HT2, heat treated at 1080 °C for 4 h + air cooling; (4) HT3, heat treated at 1080 °C for 4 h + air cooling, then heat treated at 870 °C for 16 h + air cooling (HT2+HT1). Each of them were extracted from the vertical (V) and horizontal (H) section of the part, respectively. Methods such as OM, SEM, TEM, XRD and unidirectional tensile tests were used for the investigation. The AD sample displays cellular dendrite microstructures with crystal direction parallel to the building direction. The major phases are γ/γ'; while the minor phases are fine MC and Laves with no more than 1% in volume fraction. The size of primary γ′ ranges from 100 nm to 150 nm, the secondary γ′ particles are no more than 30 nm. With the aid of calculation, the processing HT1 and HT2 are confirmed as ageing and sub-solution treatment, respectively. The former raised the volume fraction of γ′ from 30.93% (AD) to 48.57% (HT1), and raised the size of γ′ at the expense of dissolving the secondary γ′ particles. The latter didn't change the volume fraction of γ′ strikingly, but refined the γ′ with the exception of a small amount of extraordinary large particles in the interdendritic region (IR). HT3 is a two-stage processing (HT2+HT1) which increased the volume fraction of γ′ slightly but raised the size apparently. The value of ultimate tensile strength (UTS) and yield strength (YS) of vertical samples are superior to that of the horizontal. The HT1-V shows the best UTS and poor Elongation (UTS, 1082 MPa; EL, 35.28%), while the AD-V has excellent strength and ductility match (UTS, 1054 MPa; YS, 744 MPa; EL, 50.45%); The best ductility is found among samples of HT3 (EL, 62.1% for HT3-H). The samples of HT2-H are inferior in both strength and ductility, and the obtained properties are scattered. These investigation results provide important fundamental support for optimizing the procedure, microstructure and properties of the new alloy in the future application research.
Similarities are established between well‐known reactivity descriptors of metal electrodes for their activity in the oxygen reduction reaction (ORR) and the reactivity of molecular catalysts, in ...particular macrocyclic MN4 metal complexes confined to electrode surfaces. We show that there is a correlation between the MIII/MII redox potential of MN4 chelates and the M‐O2 binding energies. Specifically, the binding energy of O2 (and other O species) follows the MIII‐OH/MII redox transition for MnN4 and FeN4 chelates. The ORR volcano plot for MN4 catalysts is similar to that for metal catalysts: catalysts on the weak binding side (mostly CoN4 chelates) yield mainly H2O2 as the product, with an ORR onset potential independent of the pH value on the NHE scale (and therefore pH‐dependent on the RHE scale); catalysts on the stronger binding side yield H2O as the product with the expected pH‐dependence on the NHE scale. The suggested descriptors also apply to heat‐treated pyrolyzed MN4 catalysts.
Descriptive knowledge: Reactivity descriptors for molecular MN4 catalysts of the oxygen reduction reaction are described, including donor–acceptor hardness, M‐O2 binding energies, and the M+n/M+(n−1) formal potentials of the catalysts. It is shown that the last two descriptors are directly correlated to each other. The mechanisms for oxygen reduction on MN4 resemble those on metal catalysts in terms of both pH dependence and product formation.
The Mn
Cl
mode of red emissive (C
NOH
)
Mn
Cl
·C
H
OH under thermal treatment will be cleaved into MnCl
in the green emissive (C
NOH
)
MnCl
with the departure of ethanol. The rapid conversion of ...luminescence from red to green provides new insight into the luminescence origin and thermal stability of organic-inorganic metal halide hybrids.
This study investigated the effect of local induction post-weld heat treatment (PWHT) on residual stress relief in thick submerged arc welded steel plates. A combination of numerical and neutron ...diffraction methods was used to examine the effect of various PWHT parameters, such as annealing temperature and holding time, on the relief of residual stress in welded plates with various thicknesses. A sequentially coupled thermal–mechanical finite element model was used to calculate the residual stress distribution in welded AH36 steel plates before and after PWHT. The model was validated by comparing its predictions with the experimental measurements, and the results showed good agreement. The residual stress of the thick welded plates was effectively reduced via PWHT with local induction. The primary mechanism for this stress release was identified as stress relaxation caused by creep strain. Furthermore, a process map was established considering the PWHT conditions and plate geometry. This map provides a means of determining the optimal PWHT conditions to achieve desired stress reduction levels.
Precipitation hardened CuCrZr alloy is the baseline option as heat sink material for the water cooled W divertor concept of DEMO owing to its combination of high thermal conductivity and strength. ...However, traditional processing of CuCrZr by casting and forging or hot rolling involves several challenges: coarsening of Cr precipitates, microstructures highly heterogeneous, or difficulties in obtaining complex geometries.
Additive Manufacturing (AM) enables creating innovative solutions with complex structures for heat exchangers and heat sinks. Compared to Laser Powder Bed Fusion (L-PBF), the EB-PBF (Electron Beam Powder Bed Fusion) AM technology offers advantages when processing copper alloys: it avoids difficulties associated to the high thermal conductivity and reflectivity of copper-based materials and prevents their oxidation by working under high vacuum.
In this work the study of AM of a CuCrZr alloy with nominal composition 0.6–0.9 Cr, 0.07–0.15 Zr (wt.%) has been performed by EB-PBF. A detailed process parameters study has been performed to identify the process window and obtain dense materials free of defects. The process parameters, including post-built heat treatments like age hardening, were correlated with the microstructural evolution, the thermal conductivity and the hardness.
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