The Effects of Co on the Microstructure and Mechanical Properties of Ni-Based Superalloys Prepared via Selective Laser Melting.

In this work, two Ni-based superalloys with 13 wt.% and 35 wt.% Co were prepared via selective laser melting (SLM), and the effects of Co on the microstructure and mechanical properties of the additively manufactured superalloys were investigated. As the Co fraction increased from 13 wt.% to 35 wt.%, the average grain size decreased from 25.69 µm to 17.57 µm, and the size of the nano-phases significantly increased from 80.54 nm to 230 nm. Moreover, the morphology of the γ' phase changed from that of a cuboid to a sphere, since Co decreased the γ/γ' lattice mismatch from 0.64% to 0.19%. At room temperature, the yield strength and ultimate tensile strength of the 13Co alloy reached 1379 MPa and 1487.34 MPa, and those of the 35Co alloy were reduced to 1231 MPa and 1350 MPa, while the elongation increased by 52%. The theoretical calculation indicated that the precipitation strengthening derived from the γ' precipitates made the greatest contribution to the strength.

Effect of Coating Pre-Treatment on Surface Recrystallization of DD6 Single Crystal.

Thermal barrier coatings (TBCs) are widely used to protect high-temperature components against harsh environments, such as extremely high temperatures. In this work, a second generation Ni-based single crystal superalloy (DD6) was treated in two ways: (1) via simple surface sandblasting under different pressures with no additional coating, and (2) through simple surface sandblasting under different pressures and then by applying NiCoCrAlYHf (HY5) coatings. The effects of pre-treatment (sandblasting) and the HY5 coating on the surface recrystallization of the alloy were thoroughly investigated. According to the results, both sandblasting pressure and the presence or absence of a coating significantly influence surface recrystallization. In particular, the critical sandblasting pressure for recrystallization increased the maximum recrystallization depth in both the coated and uncoated samples. Meanwhile, the recrystallization depth of the alloy with a coating was reduced compared to that without a coating. In addition, the number of recrystallized cells in the coated alloy was decreased, which indicated that the HY5 coating effectively reduced the degree of recrystallization.

Curcumin inhibits pancreatic cancer cell proliferation by regulating Beclin1 expression and inhibiting the hypoxia-inducible factor-1α-mediated glycolytic pathway.

Background: Pancreatic cancer has a high degree of malignancy and high mortality. Understanding its biological status can provide more therapeutic targets for the future. The present study was to investigate whether curcumin can inhibit pancreatic cancer cell proliferation by regulating Beclin1 expression and inhibiting the hypoxia-inducible factor-1α (HIF-1α)-mediated glycolytic pathway. Methods: Two pancreatic cancer cell lines, PANC-1 and SW1990, were treated with different concentrations of curcumin (0, 20, 40, and 60 µM). Cell viability was detected using the Cell Counting Kit-8 (CCK-8) assay and flow cytometry was performed to determine the apoptosis rate and cell cycle arrest of the pancreatic cancer cells. PANC-1 and SW1990 cells were treated with different concentrations of curcumin under hypoxic conditions for 48 hours to detect the relative expression of the Beclin1 protein. The co-immunoprecipitation (co-IP) method was used to determine whether curcumin could inhibit the interaction between Beclin1 and HIF-1α. Results: The proliferation inhibition rates of PANC-1 cells after exposure to 0, 20, 40, and 60 µM curcumin were 0%, 31.6%, 47.2%, and 63.9%, respectively, and that of SW1990 cells were 0%, 18.8%, 46.3%, and 63.5% respectively. Western blot analyses showed decreased expression of Beclin1 in cells treated with curcumin. The expression of Beclin1 in the nucleus and cytoplasm decreased with increasing concentrations of curcumin. Co-IP results demonstrated that curcumin inhibited the interaction between Beclin1 and HIF-1α. Treatment with the higher doses of curcumin (40 and 60 µM) significantly decreased the protein expression levels of HIF-1α. In addition, the expression levels of Kidney-Specific Cadherin (HSP70, HSP90, and von Hippel-Lindau protein (pVHL) were significantly decreased in pancreatic cancer cells while the expression of prolyl hydroxylase (PHD) and receptor of activated protein kinase C (RACK1) increased significantly. Furthermore, curcumin reduced cellular adenosine triphosphate (ATP) production in a dose-dependent manner. Compared with control pancreatic cancer cells, the expression levels of GLUT1, HK2, LDHA, and PDK1 gradually decreased with increasing curcumin concentrations. Conclusions: Curcumin can inhibit the expression of Beclin1 and HIF-1α in pancreatic cancer cells under anoxic conditions, thereby affecting the glycolysis pathway and inhibiting cell proliferation.

Quasi-static and dynamic experimental studies on the tensile strength and failure pattern of concrete and mortar discs.

As concrete and mortar materials widely used in structural engineering may suffer dynamic loadings, studies on their mechanical properties under different strain rates are of great importance. In this paper, based on splitting tests of Brazilian discs, the tensile strength and failure pattern of concrete and mortar were investigated under quasi-static and dynamic loadings with a strain rate of 1-200 s-1. It is shown that the quasi-static tensile strength of mortar is higher than that of concrete since coarse aggregates weaken the interface bonding strength of the latter. Numerical results confirmed that the plane stress hypothesis lead to a lower value tensile strength for the cylindrical specimens. With the increase of strain rates, dynamic tensile strengths of concrete and mortar significantly increase, and their failure patterns change form a single crack to multiple cracks and even fragment. Furthermore, a relationship between the dynamic increase factor and strain rate was established by using a linear fitting algorithm, which can be conveniently used to calculate the dynamic increase factor of concrete-like materials in engineering applications.

Spherical and cylindrical cavity expansion models based prediction of penetration depths of concrete targets.

The cavity expansion theory is most widely used to predict the depth of penetration of concrete targets. The main purpose of this work is to clarify the differences between the spherical and cylindrical cavity expansion models and their scope of application in predicting the penetration depths of concrete targets. The factors that influence the dynamic cavity expansion process of concrete materials were first examined. Based on numerical results, the relationship between expansion pressure and velocity was established. Then the parameters in the Forrestal's formula were fitted to have a convenient and effective prediction of the penetration depth. Results showed that both the spherical and cylindrical cavity expansion models can accurately predict the depth of penetration when the initial velocity is lower than 800 m/s. However, the prediction accuracy decreases with the increasing of the initial velocity and diameters of the projectiles. Based on our results, it can be concluded that when the initial velocity is higher than the critical velocity, the cylindrical cavity expansion model performs better than the spherical cavity expansion model in predicting the penetration depth, while when the initial velocity is lower than the critical velocity the conclusion is quite the contrary. This work provides a basic principle for selecting the spherical or cylindrical cavity expansion model to predict the penetration depth of concrete targets.