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The current understanding of the formation mechanism and kinetics of the σ phase in DSS remains ambiguous. This study investigates the in-situ evolution of the σ phase in DSS through a multi-faceted approach. Distinct σ phase formation mechanisms were identified at 850 °C and 950 °C, with short-range diffusion of eutectoid decomposition at 850 °C and long-range diffusion of nucleation and growth at 950 °C. In-situ X-ray diffraction (XRD) revealed that the lattice parameter of the γ phase peaks at ∼ 600 °C. The thermal expansion coefficient (CTE) of the γ phase is 1.8 times higher than that of the α phase at low temperatures. Interestingly, the convergence of the CTEs of the α and γ phases above 600 °C triggers σ nucleation. The strain field diagram shows maximum impinging strain at the lattice parameter maxima just before the σ formation range. The adverse effects of the σ phase on DSS heat transport properties were also explored, showing an initial increase in thermal conductivity with an increasing γ volume fraction, followed by an 18 % decrease upon σ evolution. First-principle calculations highlight the correlation between Ni enrichment and lattice parameter maxima, supporting these findings.

This study aims to improve the quality and durability of materials used in turbocharger housing, particularly to limit the degradation of automobile engine parts. As a result, niobium (Nb)-bearing heat-resistant cast austenitic stainless-steel samples have been explored. Two distinct steel samples, denoted as Alloy-A (with 0 wt.% Nb) and Alloy-B (with 1.5 wt.% Nb), were fabricated by centrifugal casting for investigating the effects of Nb content on the corresponding microstructure and low-cycle fatigue properties of these samples. The phases formed within these alloys were predicted by thermodynamic calculations using the Thermo-Calc software, with the results aligning well with the experimental results. The addition of Nb promoted the formation of niobium carbide, resulting in increased hardness and greater area fraction of the carbides present in the steel samples. Alloy-B displayed enhanced high-temperature strength over Alloy-A, while the low-cycle fatigue resistances of the two alloys were similar. Fatigue cracks predominantly initiated at the outer surface of the specimens, mainly in the carbide regions, due to the mismatch between the matrix and carbide hardness. This paper is the first to report the effect of Nb addition on the microstructure and low-cycle fatigue properties of heat-resistant cast austenitic stainless steel.

The high-temperature phase stability of the NbCr2 Laves phase has not yet been established beyond disagreement. The well accepted C14 phase field has been eliminated from the Nb-Cr phase diagram in a recent study that claimed that the NbCr2 alloy shows the C15 structure up to melting. The present study was conducted to address these ambiguities. The experimental investigations show the presence of C14, C15, and C36 structures in the as-cast alloy. Differential scanning calorimetry studies of the as-cast alloy show the transformation of the eutectic mixture of bcc + NbCr2 to single-phase NbCr2 at 1338 K. An in-situ X-ray diffraction (XRD) study of as-cast alloy shows a phase transformation of C36 → C14 below 1273 K. Density functional theory (DFT) calculations confirm two phase transformations: (a) a metastable transformation of C36 → C14 at 783 K and (b) an equilibrium transformation of C15 → C14 at 1971 K, which was validated by high temperature DTA and TEM studies. Further, extended DFT calculations on supercells with four compositions of NbCr1.9, NbCr2, NbCr2.1, and NbCr2.2 also corroborated the presence of the C14 phase, and consequently, the Nb-Cr phase diagram is modified. This finding resolves the controversy regarding the existence of an equilibrium C14 phase field before melting.

Background/Aims: Adequate bowel preparation is important for successful colonoscopy. We aimed to evaluate the clinical feasibility and effectiveness of abdominal vibration stimulation in bowel preparation before therapeutic colonoscopy. Methods: A single center, prospective, randomized, investigator-blinded study was performed between January 2016 and December 2016. Patients for therapeutic colonoscopy were prospectively enrolled and assigned to either the vibrator group or walking group. Patients who refused to participate in this study as part of the experimental group consented to register in the control group instead. During the preparation period, patients assigned to the walking group walked ≥3,000 steps, whereas those assigned to the vibrator group received abdominal vibrator stimulation and restricted walking. All patients received the same colon cleansing regimen: 4-L split-dose polyethylene glycol (PEG) solution. Results: Three hundred patients who received PEG solution for therapeutic colonoscopy were finally enrolled in this study (n=100 per group). Bowel cleansing with abdominal vibration stimulation showed almost similar results to that with walking exercise (Boston Bowel Preparation Scale score for the entire colon: vibrator vs walking vs control, 7.38±1.55 vs 7.39±1.55 vs 6.17±1.15, p

Background/AimsLiver stiffness (LS) as assessed by transient elastography (TE) can change longitudinally in patients with chronic hepatitis B (CHB). The aim of this study was to identify the factors that improve LS.MethodsBetween April 2007 and December 2012, 151 patients with CHB who underwent two TE procedures with an interval of about 2 years were enrolled. Ninety-six of the 151 patients were treated with nucleos(t)ide analogues [the antiviral therapy (+) group], while the remaining 55 patients were not [the antiviral therapy (-) group]. The two groups of patients were stratified according to whether they exhibited an improvement or a deterioration in LS during the study period (defined as an LS change of ≤0 or >0 kPa, respectively, over a 1-year period), and their data were compared.ResultsNo differences were observed between the antiviral therapy (+) and (-) groups with respect to either their clinical characteristics or their initial LS. The observed LS improvement was significantly greater in the antiviral therapy (+) group than in the antiviral therapy (-) group (-3.0 vs. 0.98 kPa, P=0.011). In the antiviral therapy (+) group, the initial LS was higher in the LS improvement group (n=63) than in the LS deterioration group (n=33; 7.9 vs. 4.8 kPa, P