Laser additive manufacturing is attractive for the production of complex, three-dimensional parts from metallic powder using a computer-aided design model
. The approach enables the digital control ...of the processing parameters and thus the resulting alloy's microstructure, for example, by using high cooling rates and cyclic re-heating
. We recently showed that this cyclic re-heating, the so-called intrinsic heat treatment, can trigger nickel-aluminium precipitation in an iron-nickel-aluminium alloy in situ during laser additive manufacturing
. Here we report a Fe19Ni5Ti (weight per cent) steel tailor-designed for laser additive manufacturing. This steel is hardened in situ by nickel-titanium nanoprecipitation, and martensite is also formed in situ, starting at a readily accessible temperature of 200 degrees Celsius. Local control of both the nanoprecipitation and the martensitic transformation during the fabrication leads to complex microstructure hierarchies across multiple length scales, from approximately 100-micrometre-thick layers down to nanoscale precipitates. Inspired by ancient Damascus steels
-which have hard and soft layers, originally introduced via the folding and forging techniques of skilled blacksmiths-we produced a material consisting of alternating soft and hard layers. Our material has a tensile strength of 1,300 megapascals and 10 per cent elongation, showing superior mechanical properties to those of ancient Damascus steel
. The principles of in situ precipitation strengthening and local microstructure control used here can be applied to a wide range of precipitation-hardened alloys and different additive manufacturing processes.
As the demand for “clean label emulsions” and natural emulsifiers is increasing, whey proteins have a big potency to be used as an emulsifier in food emulsions. However, in order to enable their ...application, whey proteins should withstand high temperature processing. Hence, the limited heat stability of whey proteins is a major drawback: they are highly heat labile and thus prone to heat induced protein denaturation and aggregation. As this phenomenon highly impacts their functionality, it is of utmost importance to increase the heat stability of whey proteins to broaden their application in the food industry, which requires a thorough knowledge of the heat stability properties of whey proteins.
To better understand the heat stabilizing activity of whey protein-polysaccharides conjugates, studies on the heat stability of whey proteins and whey protein stabilized emulsions, as well as approaches to improve their heat stability, especially using the dry heat treatment method are reviewed.
Chemical modification by combining whey proteins and polysaccharides has been reported to successfully improve the heat stability of the obtained conjugates. Hence, this new whey protein-polysaccharide material is promising to be used as a natural emulsifier.
•Whey proteins and whey protein stabilized emulsions are heat labile.•Heat stability is crucial for the broader industrial application of whey proteins.•Whey protein-polysaccharide conjugation largely increases the heat stability of whey proteins.•This is attributed to electrosteric stabilization provided by the attached polysaccharides.
Heat treatments tailored for additive manufactured Ti-6Al-4V can be used to attain desirable microstructures associated with superior mechanical properties. Rapid heat treatments, for example, can be ...used to recrystallise the microstructure of laser powder bed fusion (L-PBF) Ti-6Al-4V to obtain refined and quasi-equiaxed prior-β grains. In this study, we discuss the interplay between refined microstructures and the tensile properties of Ti-6Al-4V specimens. The influence of individual microstructural constituents on the tensile properties are examined in detail and directly compared to those found in specimens subject to conventional annealing treatments. It was found that rapid heat treatments into the β phase field can significantly refine the size of the prior-β grains found in as-built L-PBF Ti-6Al-4V, as well as alter the size and morphological arrangement of the resulting α laths. The proposed new heat treatments are clearly shown to have strengthened the alloy with no apparent detriment to the ductility of the material.
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Previous studies have already demonstrated a clear influence of the different subsurface microstructures resulting from variations in case-hardening on machinability during gear grinding. However, ...the impact of the alloy system has not yet been considered in detail. In order to fill this knowledge gap, case-hardening layers are analysed using six case-hardening steels with different alloy systems and their resulting machinability during discontinuous profile grinding of gears is compared. In particular, the results indicate that the outer subsurface area (up to approx. 30 µm in depth) formed as a function of the alloy system has a significant influence.
Atomically dispersed transition metal sites have been extensively studied for CO2 electroreduction reaction (CO2RR) to CO due to their robust CO2 activation ability. However, the strong hybridization ...between directionally localized d orbits and CO vastly limits CO desorption and thus the activities of atomically dispersed transition metal sites. In contrast, s‐block metal sites possess nondirectionally delocalized 3s orbits and hence weak CO adsorption ability, providing a promising way to solve the suffered CO desorption issue. Herein, we constructed atomically dispersed magnesium atoms embedded in graphitic carbon nitride (Mg‐C3N4) through a facile heat treatment for CO2RR. Theoretical calculations show that the CO desorption on Mg sites is easier than that on Fe and Co sites. This theoretical prediction is demonstrated by experimental CO temperature program desorption and in situ attenuated total reflection infrared spectroscopy. As a result, Mg‐C3N4 exhibits a high turnover frequency of ≈18 000 per hour in H‐cell and a large current density of −300 mA cm−2 in flow cell, under a high CO Faradaic efficiency ≥90 % in KHCO3 electrolyte. This work sheds a new light on s‐block metal sites for efficient CO2RR to CO.
Atomically dispersed magnesium atoms embedded in graphitized C3N4 (Mg‐C3N4) show weak CO adsorption because of nondirectionally delocalized Mg 3 s orbit. Mg‐C3N4 exhibits a high turnover frequency (TOF) of ≈18 000 hour−1 under a CO Faradaic efficiency ≥90 %. Furthermore, the flow cell fabricated with Mg‐C3N4 reaches a large current density of −300 mA cm−2 under a CO Faradaic efficiency ≥90 %.
Textured vegetable protein (TVP) is gaining popularity as the market for meat analogues grows, but research on processing to improve the texture of TVPs is needed. Heat treatments can change the ...textural properties during the processing of meat and meat analogues. Therefore, this study analyzed the textural characteristics of low‐moisture TVPs following heat treatments using steaming, oven‐cooking, microwaving, and vacuum‐autoclaving, which combines vacuum packaging and autoclaving. The moisture content of the meat analogues had different patterns depending on the treatment used, with the most significant decrease in moisture occurred with microwaving. The morphological analysis of the meat analogues showed that oven‐cooking and microwaving preserved a large air–cell structure and that steaming and vacuum‐autoclaving caused a small air–cell structure to form. The texturization index tended to increase only with microwaving. Disulfide bonds were increased with steaming and vacuum‐autoclaving; this was thought to be related to the increase in tiny air–cell structures. In conclusion, the most helpful cooking method was vacuum‐autoclaving since it allowed the treated meat analogues to trap moisture well, and this led to the formation of a dense structure and a lowering of the texturization index. Therefore, the proposed technique of vacuum‐autoclaving was shown to be significant for its potential as a way of processing meat analogues.
Practical Application
It is expected to improve the quality of plant‐based meat analogue products by controlling the physical properties of low‐moisture textured vegetable protein (TVP) through steaming, oven, microwave, and vacuum autoclave as post‐heat treatments.
As a crucial branch for titanium industry, high-strength titanium alloys (HS-TAs, with UTS ≥ 1100 MPa) are indispensable structural materials for advanced engineering applications such as aerospace ...and marine fields. Along with the expansion of HS-TAs’ market, achieving satisfying synergies of high strength, high ductility (elongation ≥ 6%) and high toughness (KIC≥ 50 MPa⋅m1/2) has been identified as the uppermost technical bottleneck for their research and development. To overcome the challenge, two primary strategies have been initiated by the titanium community, developing novel alloys and innovating processing technologies. For the former, a dozen of newly-developed alloys were reported to exhibit excellent strength-ductility-toughness combinations, including Ti-5553, BT22, TC21 and Ti-1300, for which the ideal mechanical performances were based on specific microstructures realized by low impurity rate (e.g. oxygen content ≤ 0.15 wt%), complicated processing and complex heat treatment. For the latter, several innovatory forging and heat treatment technologies were originated for the mature alloys to optimize their balanced property by extraordinary microstructural characteristics. In this review, we provide a comprehensive overview over the research status, processing and heat treatment technologies, phase transformation, processing-microstructure-property correlation and strengthening-toughening mechanism of HS-TAs for aerospace engineering applications manufactured via melting-forging process. Finally, the prospects and recommendations for further investigation and development are proposed based on this review.
This paper investigates the effect of dwell time and heat treatment on the modified friction stir clinched (MFSC) joint of AA2024-T3/AA6061-T6 Al alloys. The precipitation-hardening heat treatment ...method involves the combination of solution heat treatment (at 520 °C for 1 h) and aging (at 165 °C for 18 h) processes. The microstructure, failure load, hardness, and fracture behavior of the as-welded and heat-treated MFSC joints were investigated. TEM images show that re-precipitation of strengthening Al2CuMg and MgZn2 phases, dislocation density, and tangles are more pronounced in the heat-treated MFSC joint. A rise in dwell time increases the average grain sizes (1.39–6.65 μm), tensile-shear strength (101–133 MPa), and cross tension strength (59–88 MPa) of the MFSC welded 2024-T3/6061-T6 joints due to an upsurge in the in-process exposure time-induced heat input and inter-material flow. An increase in dwell time beyond 15 s is undesirable. It induces the formation of nugget cracks and micro-voids in the joints and an impaired joint failure load consequently ensues. Heat treatment processing further causes grain coarsening (2.48–9.15 μm) and improves the hardness (at the weld center), tensile-shear (146 MPa), and cross tension (102 MPa) failure strengths of the MFSC joints due to the re-precipitated strengthening phases.
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