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Stainless steels are used in a myriad of engineering applications, including construction, automotives, and nuclear reactors. Developing accurate, predictive mechanistic models for corrosion and electrochemical corrosion kinetics of stainless steels, specifically in chloride environments, has been a topic of research studies over many decades. Herein, we quantified the aqueous corrosion kinetics of a model austenitic Fe–18Cr–14Ni (wt.%) alloy in the presence and absence of applied potential using systematic in situ electrochemical atomic force microscopy (EC-AFM) studies and transmission electron microscopy (TEM). Without an applied bias, dissolution along the vertical direction of corrosion pits is controlled by surface kinetics/diffusion hybrid mechanism, whereas the dissolution along the lateral direction of pits is diffusion controlled. In the absence of an applied bias, both the “nucleation” and “lateral growth” of the pits contribute to total corrosion. When an electrical bias is applied, the increase in corrosion rate is dominated by nucleation of new pits rather than lateral growth of existing ones. This shift in the corrosion mechanism is attributed to the bias-induced redistribution of species with different charges. These insights gained by the in situ EC-AFM will allow applications of this method for quantitative understanding of corrosion of wider class of materials.

Colorectal cancer (CRC) has developed into the third leading cause of cancer-associated death worldwide. Studies have confirmed that circular RNAs (circRNAs) absorb microRNAs (miRNAs) to regulate the function of downstream genes., Colorectal cancer (CRC) has developed into the third leading cause of cancer-associated death worldwide. Studies have confirmed that circular RNAs (circRNAs) absorb microRNAs (miRNAs) to regulate the function of downstream genes. This study aimed to explore the underlying mechanism of circRNA 100146 in CRC. The expression of circRNA 100146, miRNA 149 (miR-149), and high mobility group AT-Hook 2 (HMGA2) was detected by quantitative real-time PCR (RT-qPCR). A series of biofunctional effects (cell viability, apoptosis, migration/invasion) were evaluated by the use of methyl thiazolyl tetrazolium (MTT), flow cytometry, and transwell assays. Protein levels were measured by Western blot assay. A xenograft model was established for in vivo experiments. The interactions among circRNA 100146, miR-149, and HMGA2 were evaluated by dual-luciferase reporter assay, RNA immunoprecipitation assays, or RNA pulldown assay. circRNA 100146 was upregulated in CRC tissues and cells. circRNA 100146 knockdown inhibited cell proliferation, promoted apoptosis, and suppressed migration and invasion in vitro and impeded tumor growth in vivo. Also, miR-149 was negatively regulated by circRNA 100146 and was targeted to HMGA2 and mediated its expression. Moreover, miR-149 interference abrogated the activities of silenced circRNA 100146 in proliferation, apoptosis, migration, and invasion. Furthermore, HMGA2 overexpression abated the effects described above caused by circRNA 100146 silencing, while the mutations on miR-149 binding sites in the 3′ untranslated region (3′-UTR) of HMGA2 led to its loss of this ability. circRNA 100146 knockdown repressed proliferation, enhanced apoptosis, and hindered migration and invasion in SW620 and SW480 cells through targeting the miR-149/HMGA2 axis.

A single phase, face-centered-cubic (FCC) Al0.3CoCrFeNi high entropy alloy usually has low yield strength. Here, a precipitate-strengthened Al0.3CoCrFeNi has been developed, exhibiting enhanced yield strength while retaining good ductility, which is attributed to a novel microstructure comprising a finely distributed, needle-like B2 phase within the grains of the FCC matrix and a granular σ phase along the grain boundaries. Such a microstructure was obtained by a two-step heat treatment of an as-cast Al0.3CoCrFeNi, whose parameters were determined by integrating CALPHAD-based thermodynamic calculations with microstructural characterization by atom probe tomography. In situ neutron diffraction, in conjunction with crystal-plasticity finite-element simulations, has revealed the strengthening effect owing to the load partitioning between the constituent phases. This work has important implications for understanding phase stability and deformation mechanisms in multi-principal component alloys, and paves the way for developing novel microstructures in complex alloys using correlative techniques.

A full picture of tensile deformation mechanism evolution in the FCC-to-HCP transformation-induced plasticity high entropy alloy (TRIP-HEA) was revealed by real-time in situ neutron diffraction. Three transition points, i.e. the triggering of TRIP in the FCC phase and the activation of single and multiple twinning in the HCP phase, were identified to result in significant stress redistribution. Accordingly, four deformation stages with distinct phase-specific work-hardening behaviors were recognized. It was concluded that the easily-triggered persisting TRIP and the work-hardening potential of the HCP contribute together to the persisting bulk work-hardening. The deformation mechanism evolution and phase-specific work-hardening behaviors of the FCC-to-HCP TRIP-HEA were unraveled, which provided a comprehensive understanding of the TRIP-assisted superior strength and ductility.

Carbon is doped into a CoCrFeMnNi high-entropy alloy as an interstitial atom, improving the single phase solid solution alloy with a good combination of strength and ductility at room temperature by introducing deformation twins. In situ neutron diffraction (ND) is applied to investigate the carbon-doped CoCrFeMnNi deformation mechanism and micromechanical behaviors during uniaxial tension at room and elevated temperatures. With in situ results accompanied with the microstructure and texture measurement, it is found that the plastic deformation is dominated by dislocation slip at an early stage at both temperatures. However, at high strain level, deformation is mediated simultaneously by deformation twins and microbands at room temperature, while it is governed solely by microbands at elevated temperature of 573 K. The evolution of lattice strain, peak intensity, and peak width from in situ ND elucidates the micromechanical behaviors regarding the role of slips and twins. The texture represented by orientation distribution function indicates that the initial specimen possesses a relatively strong {112}〈110〉 texture component, and the room-temperature tension deformed texture comprises of slip-induced fiber texture and twinning-induced {115}〈552〉 texture component.

The cryogenic plastic deformation of CrCoFeMnNi high entropy alloy is characterized by three distinct stages based on the change of the work hardening rate. Microstructure and bulk texture at different strain levels were studied by electron backscatter diffraction (EBSD) and neutron diffraction. Our findings indicate that the deformation twins led to the constant work hardening rate at Stage II and resulted in the appearance of 〈115〉//TA texture component, while the dislocation slip was involved all though the entire plastic deformation. The twinning-mediated tensile plastic deformation at cryogenic temperature finally induced the strong {111}-〈112〉 texture component and minor {001}〈110〉 texture component accompanied with twinning-induced {115}〈552〉 texture component. Keywords: HEA, twinning-mediated deformation, work hardening, texture, neutron diffraction

The TiZrNbHfTa alloy with a single body-centered cubic (bcc) phase is of particular interest among refractory high-entropy alloys (HEAs) because it exhibits significantly large ductility compared to other refractory HEAs. To have a convincing appraisal of its potential in structural applications, its fatigue behavior needs to be understood in depth as fatigue is one of the major failure modes in practice. The in-air, room-temperature high-cycle fatigue study of the alloy at a stress ratio of 0.1 and a frequency of 10 Hz gives a fatigue strength of 512 MPa and a fatigue ratio of 0.45 at 107 fatigue cycles. The comparison of fatigue resistance of many alloy systems at nearly equivalent conditions (stress ratio of -1) suggests that the TiZrNbHfTa alloy is superior to all other HEAs with reported high-cycle fatigue data, dilute bcc alloys, and many structural alloys in commercial applications such as steels, titanium alloys, and aluminum alloys. Through in-depth analyses of crack-propagation trajectories, fracture-surface morphologies and deformation plasticity by means of various micro-structural analysis techniques and theoretical frameworks, the remarkable fatigue resistance in the alloy is attributed to a synergy of intrinsic toughening (i.e., dislocation-mediated crack tip blunting) and extrinsic toughening (i.e., crack deflection and meandering, fracture-debris-induced crack closure, roughness-induced crack closure, and crack branching). Moreover, the stochastic nature of the fatigue data is neatly captured by the 2-parameter Weibull distribution model.

Non-hydrostatic compression of materials using a diamond anvil cell (DAC) can transform equilibrium microstructure of an alloy to novel, potentially metastable states. In this study, in situ synchrotron X-ray diffraction (XRD) during compression up to 24 GPa and subsequent ex situ, high resolution analytical electron microscopy (AEM) after decompression of an Al-Si alloy provided insight into the crystallographic changes during the compression as well as microstructural refinement, and defect structures caused by such a high pressure compression-decompression process. Pressure resolved in-situ synchrotron XRD was used to detail the phase transformation pathway of the eutectic Si phase in Al-Si alloy, from Si-I → Si-XI → Si-V during compression, and a final transformation predominantly to Si-III after decompression. Using scanning and transmission electron microscopy (S/TEM), site specific analysis of the alloy immediately underneath the anvil contact surface demonstrated a highly complex microstructure. A narrow region of thick amorphous Al oxide interspersed with nanocrystalline grains was found at the top surface. Underneath this Al oxide, while the majority the eutectic Si was transformed into highly-deformed, polycrystalline (PC) Si-III, a complex intermediate layer was discovered at the interface between Al and Si, comprised of a small fraction of Al nanocrystals and a majority of nanocrystalline Si-I. This combination of pressure resolved in-situ synchrotron XRD coupled with subsequent high resolution, electron microscopy resolved the phase transformation as well as non-equilibrium microstructures in a metallic alloy induced by a non-hydrostatic high pressure compression followed by decompression.

Non-hydrostatic compression of materials using a diamond anvil cell (DAC) can transform the equilibrium microstructure of an alloy to novel, potentially metastable states. In this study, in situ synchrotron X-ray diffraction (XRD) during compression up to 24 GPa and subsequent ex-situ, high resolution analytical electron microscopy (AEM) after decompression of an Al-Si alloy provided insight into the crystallographic changes during the compression as well as microstructural refinement, and defect structures caused by such a high pressure compression-decompression process. Pressure resolved in-situ synchrotron XRD was used to detail the phase transformation pathway of the eutectic Si phase in Al-Si alloy, from Si-I → Si-XI → Si-V during compression, and a final transformation predominantly to Si-III after decompression. Using scanning and transmission electron microscopy (S/TEM), site specific analysis of the alloy immediately underneath the anvil contact surface demonstrated a highly complex microstructure. A narrow region of thick amorphous Al oxide interspersed with nanocrystalline grains was found at the top surface. Underneath this Al oxide, while the majority of the eutectic Si was transformed into highly-deformed, polycrystalline (PC) Si-III, a complex intermediate layer was discovered at the interface between Al and Si, comprised of a small fraction of Al nanocrystals and a majority of nanocrystalline Si-I. This combination of pressure resolved in-situ synchrotron XRD coupled with subsequent high resolution, electron microscopy resolved the phase transformation as well as non-equilibrium microstructures in a metallic alloy induced by a non-hydrostatic high pressure compression followed by decompression.

Ion irradiation was applied to tailor the structural heterogeneities in Zr-based metallic glasses at room temperature. Experimental methods of X-ray diffraction, nanoindentation, and micropillar compression were conducted to examine the irradiation effects on their structural and mechanical property changes. It is found that the irradiated materials retained amorphous structure after room-temperature Ni ion irradiation. The reduction of elastic modulus and hardness measured by nanoindentation indicated the irradiation-induced mechanical degradation. A unified statistic model was employed to quantitatively predict the density and strength of irradiation defects, although their specific structural and physical nature is not explicitly included in this model. The transition of non-intersecting shear bands to multiple intersecting shear bands was observed on compression tests of irradiated micropillars with the increase of irradiation dose. The analysis of the displacement excursion of micropillar compression tests indicated a different deformation mode from the unirradiated state. These results from nanoindentation pop-in and micro-pillar compression tests suggested that irradiation eventually leads to a new state with different types and characteristics of structural heterogeneities from violent displacement cascades and non-equilibrium energy deposition/dissipation processes, which also proves ion irradiation as an effective method to tune the structure and mechanical properties of metallic glasses.

The in-situ neutron diffraction technique, in combination with both the full-field crystal elasto-viscoplastic finite element model and microstructural characterization, was used to study the deformation-induced damage anisotropy in a commercial Al alloy, subjected to uniaxial tensile and cyclic loading. The simulations capture well the crystallographic-orientation-dependent lattice strain behavior. The hard grains, e.g. those orientated with the and orientations parallel with the uniaxial loading direction (LD), feature large Taylor factors and seem more prone to form damage-related band structures. Their effective elastic moduli decrease with the accumulation of damage, which are different from the soft grains orientated with the orientation along the LD. Correlation between the distribution of voids and that of the residual lattice strain developed after failure may exist. The maximum tensile type residual lattice strain observed after failure may be resulted from the band structure formed in the hardest grains. It was revealed that the band structure triggered by the hard particles could be one of sources of damage. In addition, while the specimen was obviously damaged, a fast stress relief was evidenced after unloading from the tension, especially at the beginning of unloading. Our present investigations provide a novel method for exploring the damage mechanisms of polycrystalline materials during plastic deformation.

The micromechanical behavior under compression for a cube-oriented single crystal Ni-base superalloy was in-situ studied by synchrotron high energy X-ray diffraction at room temperature. Both elastic and plastic deformation altered the mismatch strain between γ and γ′ phases with different variances. The deformation-induced interface coherency strain relaxation was observed after yielding as evidenced by an increment of lattice mismatch and an abnormal decrease in full width at half maximum (FWHM), which is attributed to aggregating of dislocations toward phase boundaries. A dislocation-mismatch model is proposed to correlate the relative change in lattice mismatch and FWHM during deformation, which fits the experiment well.