The microstructure and fatigue properties of Al-Cu-Li alloy sheets were investigated respectively under the conditions of without pre-deformation, 3% pre-stretching deformation and 8% pre-rolling ...deformation utilizing scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) in present work. Results show that the intensive Goss texture and relatively weaker Brass, Cube texture were formed in without pre-deformed alloy after aging treatment. The pole density level of Goss texture was decreased remarkably and the intensity of Brass, Cube texture was increased lightly after 3% pre-stretching deformation and 8% pre-rolling deformation. The magnitude order of fatigue crack propagation (FCP) rate of the alloy under different pre-deformation conditions was dadNpre−rolling > dadNpre−stretching > dadNnon−predeformation in stage II (Paris regime). The combined contribution of T1 phase with different size, amount and the intensity of Goss texture is the main factors affecting the FCP rate of Al-Cu-Li alloy.
•The formula of average grain size is established by the volume fraction of different texture.•The empirical relationship between fatigue crack propagation rate, damage tolerance and the volume fraction of Goss texture is established respectively.•The empirical relationship between the Goss texture pole density level and T1 phase size is investigated.•The intensity of texture is influenced by the size and number of T1 phase.•The fatigue properties of Al-Li alloy is improved by the intensive Goss texture.
High-throughput sequencing has ushered in a paradigm shift in gastric microbiota, breaking the stereotype that the stomach is hostile to microorganisms beyond H. pylori. Recent attention directed ...toward the composition and functionality of this 'community' has shed light on its potential relevance in cancer. The microbial composition in the stomach of health displays host specificity which changes throughout a person's lifespan and is subject to both external and internal factors. Distinctive alterations in gastric microbiome signature are discernible at different stages of gastric precancerous lesions and malignancy. The robust microbes that dominate in gastric malignant tissue are intricately implicated in gastric cancer susceptibility, carcinogenesis, and the modulation of immunosurveillance and immune escape. These revelations offer fresh avenues for utilizing gastric microbiota as predictive biomarkers in clinical settings. Furthermore, inter-individual microbiota variations partially account for differential responses to cancer immunotherapy. In this review, we summarize current literature on the influence of the gastric microbiota on gastric carcinogenesis, anti-tumor immunity and immunotherapy, providing insights into potential clinical applications.
Thermal stability plays an important role in practical application of Al-Zn-Mg-Cu alloy for oil drilling. In this work, a new four-stage aging treatment by employing a natural aging prior to re-aging ...is designed to improve thermal stability of Al-Zn-Mg-Cu alloy. The effect of T6, four-stage aging, three-stage aging and T74 on thermal stability was investigated by tensile testing, transmission electron microscopy (TEM) and atom probe tomography (APT). The results showed that after thermal exposure at 120 °C for 500 h, the tensile strength of the four-stage aged sample decreased only by 5.05%. APT analysis indicated that natural aging accelerates the diffusion of Mg atoms, and promotes the precipitation of GP zones during re-aging stage, and TEM observations also supports this result. Natural aging for 24 h prior to re-aging enhance the formation of GP zones, leading to an effective improvement of the strength properties and thermal stability of the studied alloy. In addition, precipitates in all aging samples gradually coarsen with the thermal exposure time increase. The influence of precipitates on mechanical properties of the investigative alloy after thermal exposure is also discussed.
Display omitted
•Deformation behavior during fatigue stage II conforms to the mixed law of elastic and plastic mechanics.•The simulation combines crystal plasticity, extended finite element method ...and cohesive zone model.•Grain orientation plays a predominated role in affecting fatigue crack propagation of Al-Cu-Mg alloy.•Goss orientation has the strongest ability in improving the fatigue resistance of Al-Cu-Mg single crystal.
A method combining crystal plasticity (CP), the eXtended Finite Element Method (XFEM), and cohesive zone model (CZM) with traction separation law is developed for an Al-Cu-Mg alloy to predict the effect of grain orientation on fatigue crack propagation (FCP) during stage ΙΙ within a single crystal. The simulation results show that of all the orientations, Goss grain possesses the largest fatigue crack deflection, then followed by Cube orientation. Comparatively, Brass, Copper, S and Random grains have relatively small crack deflection angles. Besides, it is found that Goss grain with the largest fatigue crack deflection possesses the lowest FCP rate as compared with other orientations. The results of simulations are consistent with previous experimental observations. This indicates that this coupled CP XFEM CZM simulation method is capable of well predicting the effect of grain orientation on FCP during fatigue stage ΙΙ of Al-Cu-Mg single crystal.
Texture and microstructure development of Al-4Cu-1.6Mg alloy during hot rolling was examined by using XRD, EBSD and TEM. The results showed that starting with a random texture during the early stages ...of rolling with reduction lower than 58.9% at blooming temperature of 430 °C, the materials developed a typical α-fiber texture in the center layer as deformation reduction reached 75.7%. And then the α-fiber textures in the center layer rotated into Brass component mainly through the activity of {111} slip system as the reduction reached 96.3%. Different from the center textures, the main texture in the surface layer was r-Cube with 96.3% reduction. The increase in rolling temperature was beneficial for the enhanced texture intensity of Brass component in the center layer. The analysis of substructure energy density indicated that Brass subgrain had a lower substructural energy density than other oriented subgrains, which together with increased slip rate at elevated temperature, contributed to the development of center Brass texture.
•The relationship among slip systems, substructural energy density and evolution of Brass texture was established.•The α-fiber textures in the center layer rotated into Brass mainly through the activity of {111} slip system.•The main texture in the surface layer was r-Cube with 96.3% reduction.•The high rolling temperature benefited the enhanced texture intensity of Brass component.•The low substructural energy density of Brass subgrain contributed to the development of Brass texture.
Display omitted
•Grain orientation effect on stress formation essentially attributes to the difference in Schmid Factors of slip systems.•No certain relationship exists between monocrystal stress ...formation and GB stress at bicrystal model.•Goss and Cube are the best two ones for relieving GB stress concentration.•The contribution from 5-independent slip system criterion needs to be considered at GB interaction.
Stress formation of monocrystals and bicrystals is investigated in specific oriented grains and grain boundaries of AA2024 alloy by using Crystal Plasticity Finite Element Method (CPFEM). The simulations show that the maximum Schmid factor (SF) value and the number of equivalent initial slip system (EISS) play a principal role in controlling the magnitude of internal stress within monocrystals. For bicrystal model, Goss and Cube grains are not the best ones for relieving stress concentration caused by their orientations, but they are the best ones for relieving grain boundary (GB) stress concentration. To this end, the dependence relations are discussed between GB stress and an advanced comprehensive factor combining SF, and geometry compatibility factor for 5 independent slip systems. It is found that this proposed comprehensive factor considering the contribution from 5 to independent slip systems effectively improves its dependence on GB stress.
Natural rock is considered a solution for thermal energy storage (TES). comprehensive understanding of the effect of high temperature on the physical and mechanical properties of rock has an ...important effect on the carbon footprint. The novelties of this paper are as follows. First, the influence of high temperature on the distribution characteristics of sandstone pores is studied by defining four kinds of pores. Next, the spatial evolution of cross-scale pores is revealed. Then the average pore radius that can quantitatively represent the overall pore distribution is proposed. Finally, the influence of thermal treatment on the characteristic stress of sandstone is analyzed. An abnormal change in compactness and mechanical parameters is observed at 450 °C, and a reasonable explanation is provided. The results show that the most of physical and mechanical parameters have significant critical temperatures. In the range of 150–450 °C, the trend in small-scale pores, porosity, and average pore radius initially increases and then decreases. The mechanical parameters reach a maximum at 300 °C, and the mineral composition changes dramatically from 600 to 900 °C. The large-scale pores, porosity, and average pore radius increase, and the mechanical properties are weakened. These results are of great importance for the stability of the surrounding rock under high-temperature environments (industrial waste heat, nuclear waste disposal, and tunnel fires).
Microstructures and mechanical properties of Al–Cu–Mg alloys containing various Ag additions were investigated by a combination of the tensile testing and quantitative transmission electron ...microscopy (TEM) analysis. Our results indicated that an increase of Ag from 0.46 to 0.88wt% promoted the precipitation of Ω phase, thereby leading to the noticeable improvement on the strength properties of the underaged Al–Cu–Mg alloys at various temperatures. This enhanced precipitation of Ω phase was also accompanied by the suppressed formation of θ′ phase. Despite further exposing at 300°C lead to a pronounced decrease in the number density of Ω phase, the higher plate number density was still revealed in 0.88Ag alloy rather than 0.46Ag alloy. Moreover, quantitative TEM results of the studied alloys highlighted the differences in the coarsening kinetics of Ω phase during further exposing at 300°C. Ω phase tended to experience a transition from the plate thickening to the plate lengthening by increasing Ag at 300°C. Our results also present the positive effect of pre-aging at 165°C for 2h on retarding the thickening kinetics of Ω phase at 300°C.
The fatigue behavior of three different AA2524 alloy sheets respectively with dominant Goss+Cube-grains, Cube-grains and Cube+Brass-grains was characterized in present work. Results showed ...Goss+Cube-grain sheet possessed a much lower fatigue crack propagation (FCP) rate than Cube-grain sheet and Cube+Brass sheet. The Cube+Brass sheet had the greatest fatigue crack propagation rate among the three kinds of commercial sheet in spite of the grain size smaller than Cube-grain sheet. EBSD detection results indicated Goss-grains had a twist component boundary or great tilt angle component boundary with the neighboring grains, thereby retarding fatigue crack propagation in fatigue Stage II more effectively. Apparently, the high intense Goss-grains were responsible for the enhanced fatigue crack propagation resistance of AA2524 alloy.
PDF
