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Strain and Microstructural Evolution in Architected Lattices: A Comparison of Electron Beam and Laser Powder Bed Fusion
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Influence of Local Inhomogeneity of Thermomechanical Treatment Conditions on Microstructure Evolution in Aluminum Alloys
The influence of local inhomogeneity of the stress–strain condition on structure and texture evolution during thermomechanical treatment of aluminum alloys is studied in this work. For this purpose, laboratory rolling and plane strain tests that simulated roughing mill thermomechanical modes were performed. For all processes, the local inhomogeneity of structure evolution was estimated. For this purpose, x-ray texture analysis, EBSD and optical microscopy were used. Additionally, the calculations which allow to evaluate local inhomogeneity of stress–strain conditions for the each process were performed. The experimental results were compared with mathematical simulation output. They indicated structure and texture evolution inhomogeneities, especially during the plane strain and industrial rolling processes. In the plane strain test, typical local deformation zones occurred with different resulting grain size and texture effects than those observed in both rolling processes. This difference was mainly associated with different stress states, strain intensity and strain rate distribution throughout the deformation zone. This study demonstrated that the inhomogeneity of these parameters has a strong impact on structure and texture evolution in the first stage of thermomechanical treatment. In the center layer, laboratory rolling could adequately generate the structure and texture effects observed during rolling of ingots in a commercial mill. Plane strain tests can generate useful results only in the case of adequate choice of sample geometry.
Grain Refinement Mechanism and Microstructural Evolution of M50NiL Steel during Multi-directional Impact Forging
This study investigated the effect of varying temperatures and cumulative strains on M50NiL steel during multi-directional impact forging (MDIF). The grain size was found to increase gradually with increasing temperature, after being held at 1050, 1100, 1150 and 1180 °C for 30 min, with the minimum grain size observed at 1100 °C during the MDIF process. The M50NiL steel subjected to MDIF at 1100 °C and at varying cumulative strains of 0.6, 1.8, 3.6 and 7.2 exhibited grain sizes that decreased with increasing cumulative strain. The mean grain size gradually decreased to ~ 1 μm at a cumulative strain of 7.2. New small grains were nucleated at grain boundaries via dynamic recrystallization, and microbands were formed via the temperature drop during the continuous forging process. The grains were subdivided into subgrains by the microbands, and these subgrains were converted to new refined grains via transformation of their boundaries into high-angle boundaries. Further, martensite transformation was restrained owing to the grain refinement. Improved tensile strengths values are obtained after MDIF process.
Microstructure Evolution, Structural Integrity, and Hot Corrosion Performance of Nitrogen-Enhanced Stainless Steel Welds
This work articulated the multi-pass, gas tungsten arc welding by adopting pulsating current for joining nitrogen-enhanced, low-carbon austenitic stainless steel, AISI 316L(N). An austeno-ferrite stainless steel (ER2594) and an over-alloyed (ERNiCrMo-3) fillers were employed to join 6-mm-thick plates of AISI 316L(N). Acicular and lathy ferrite in the weld zone of ER2594 and the occurrence of secondary phases in the fusion zone of over-alloyed filler were observed. The notch tensile strength data attested that the joint strength was greater for the welds employing an over-alloyed filler. This study also affirms that the welds obtained with ER2594 filler resulted in better impact toughness (144 J) compared with ERNiCrMo-3 filler and base metal. Also the notch impact toughness of ER2594 weldment is increased to 60% in comparison with that of candidate metal. Corrosion studies were also performed by exposing the coupons in a eutectic salt mixture comprising of 40%K{sub 2}SO{sub 4}-60%NaCl for 50 cycles at 650 °C. It is observed that the weld zone employing over-alloyed filler experienced better high-temperature corrosion resistance compared to the base metal. The specific results of this investigation will be of greater demand to the nuclear and marine applications utilizing these joints.
In-situ TEM studies of 150 keV W+ ion irradiated W and W-alloys: Damage production and microstructural evolution
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Finite strain phase-field microelasticity theory for modeling microstructural evolution
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Effect of cyclic rapid thermal loadings on the microstructural evolution of a CrMnFeCoNi high-entropy alloy manufactured by selective laser melting
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Trade-offs in the latent representation of microstructure evolution
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In-situ ETEM study of plasma-facing tungsten nanofuzz oxidation at atmospheric pressure: Microstructure evolution and substrate-free oxidation kinetics
To enable sustainable carbon-free fusion energy, managing reactor structural material degradation during normal operation as well as accident scenarios is vital. Tungsten (W) plasma-facing materials (PFMs) are susceptible to aggressive high-temperature oxidation during air-ingress fusion reactor accidents, yet there's a lack of oxidation kinetic data for irradiated tungsten. Here, in this study, we utilize atmospheric environmental transmission electron microscopy (ETEM) to present the first kinetic data for substrate-free W nanofuzz oxidation at 400 ºC and 500 ºC in 1 bar dry air. Comparison with pristine bulk W during the early parabolic stage suggests an irradiationdecelerated oxidation for W nanofuzz. Our time-resolved in-situ characterization reveals a durable amorphous surface oxide, likely promoted by high-flux He + irradiation-induced surface defects, serving as an effective passivating layer that impedes nanofuzz oxidation onset. This surface oxide layer also interfaces well with newly formed orthorhombic WO 3 , facilitated by stress relief through He bubble shrinkage, providing lasting passivating protection throughout the nanofuzz parabolic oxidation. This new finding challenges conventional notions of irradiation's negative impact on metal oxidation, and calls for advanced characterization to enhance our understanding of fusion energy materials degradation, informed by further accident modeling.
In-Situ TEM study of microstructural evolution in proton irradiated single crystal UO2 under high-temperature annealing
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Microstructure evolution in ultra-high purity Fe-Cr alloys under low-PKA proton irradiation
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Electric conductivity and microstructure evolution of polymer-derived SiAlCO ceramics
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Helium ion irradiation effects on microstructure evolution and mechanical properties of silicon oxycarbide
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