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Predicting the failure time of unstable slopes is one of the most pivotal issues. In this paper, the inverse square root acceleration (INSRA) method was proposed to estimate the time-of-failure (TOF) of landslides. Four collapsed slopes were presented in the three open-pit mines, two of them were probed by ground-based radar, and two of them were obtained from previous scientific papers. The inverse velocity (INV) method and INSRA method were adopted to analyze these four landslides and one slope which had great deformation but did not reach failure. Compared with the traditional INV method, the INSRA method can promote the forecasting effectiveness and has the advantage of higher accuracy.

This study systematically investigated the low cycle fatigue deformation of a high Nb-containing TiAl alloy with a nominal chemical composition of Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y at 850 °C by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and synchrotron-based high-energy X-ray diffraction (HE-XRD) techniques. Cyclic stress-strain (CSS) behavior, lattice strain, and peak broadening of {100}α2, {201}γ, and {202}ωo planes, phase transformations, and crack propagation behavior were obtained for samples with three total strain amplitudes: Δet/2 = ±0.25%, Δet/2 = ±0.28%, and Δet/2 = ±0.30%. At early deformation stages, α2lamellae transformed into ωo phase with a distinct orientation relationship, and a certain orientation relationship (OR) between them was observed after the following cyclic deformation. Furthermore, γ particles precipitated within the single ωo area. In addition, according to the peak intensity and peak broadening results, the ωo → B2 phase transformation occurred, leading to the appearance of single B2-phase areas. The lattice strains in the ωo phase were always in tension during the cyclic deformation and large differences of the lattice strains were found in the γ phase and α2 phase, not only the values but also the directions, which resulted in crack nucleated at and propagated along the α2/γ lamellar interface. This study provides a better understanding of the low cycle fatigue deformation of TiAl alloys.

Creep rupture tests of the as-forged Ti-45Al-8.5Nb-(W,B,Y) alloy with a duplex microstructure were carried out at 750–850 °C and 130–300 MPa. An investigation was performed to study the effects of temperature and stress on the microstructure and texture evolution, as well as on the creep properties of the forged high Nb-containing TiAl alloy with a duplex microstructure. The results show that the stress exponent n = 2.8–3.3, and the creep activation energy values are in the range of 300–400 kJ/mol. After creep, a regular arrangement of ωo precipitations was observed in the βo region. The un-transformed βo phase, which remained in the ωo interval, was examined using high resolution transmission electron microscope (HRTEM). It is shown that the growth of ωo precipitations and the morphology of residual βo phases are related to the creep temperature and stress. Certain βo stabilizer elements, such as Nb, segregate into α2 plates and cause ωo precipitation during dissolution of α2 plates at high temperature. The interfacial structure between the ωo and α2 phases was studied in detail using HRTEM. Meanwhile, texture evolution and dynamic recrystallization of the γ phase were studied using electron backscatter diffraction (EBSD). Observations on the deformation structure also demonstrate that ωo precipitation acts as an obstacle inhibiting crack propagation and growth of the γ phase. The corresponding formation mechanism and possible effects on creep are discussed.

This paper mainly carries out researches on the small part samples of the spindles. Through the Weibull distribution and least squares,the mathematical analysis has made on the lifetime of ...

Phase equilibria in the Ti-Al-Nb ternary system at 1400 °C was established, using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and electron probe micro-analysis (EPMA). No ternary compound was observed in this work. Compared with the calculated results, the α + β + γ three-phase region moves to higher Nb and Al contents and the σ + β + γ three-phase region moves to a lower Ti content in our experimental results. The tie-triangle of σ + δ + β moves to lower Ti and higher Nb contents. As a result, the homogeneity range of single α phase hugely expands to higher Nb and Al contents and the homogeneity range of single β phase region hugely expands to a higher Al content. The phase regions are also different with the previous reported experimental results.

Ordered omega (ω o ) phases are considered to be equilibrium phases in high Nb-TiAl alloys at intermediate temperatures. However, most studies have focused on the evolution behaviors of these phases during annealing, while the precipitation behavior has not been systematically studied. In the present work, the precipitation behavior of the ω o phase (B8 2 structure) in the Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y (at.%) alloy during annealing at 850 °C was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After annealing at 1150 °C for 2 h followed by water quenching, the ω o phase in the as-cast alloy transformed to the β o phase. At the initial stage of annealing processing at 850 °C, the ω o phase re-precipitated at the γ/β o boundaries and the size of the ω o phase increased with the annealing time. Moreover, the γ plates precipitated within the β o phase at this temperature became coarser and tended to globalize during annealing. In addition, the α 2 and D8 8 -ω phases were also observed at the γ/β o boundaries. Energy dispersive X-ray spectroscopy (EDS) and Scanning transmission electron microscopy (STEM) analysis showed that the D8 8 -ω phase is rich in W and Nb elements. The corresponding mechanisms of the transformation mentioned above were discussed.

The large scale ingot of Ti-45Al-8.5 Nb-(W, B, Y) alloy, which was manufactured by plasma arc cold hearth melting process, was successfully forged by a two-step canned forging process with a total deformation of 85%. The pancake is crack-free with smooth surface and presents recrystallized duplex microstructure. Additionally, the fraction of β/B2 phase in the as-forged microstructure has dropped. The high angle grain boundaries are dominant among recrystallized grains. After the heat treatments at different temperatures, the fine duplex, nearly lamellar and fully lamellar microstructures can be obtained respectively. Compared with the as-cast condition at room temperature, the ultimate tensile strength increases from 633 MPa to 897 MPa and the elongation improves from 0.23% to 2.2%. The strengths of as-forged TiAl alloy are relatively high at high temperatures. Moreover, superplastic behavior appears above 900 °C.

The microstructure and orientation relationship (OR) of the α2 and ωo phases in the Ti–34Al–13Nb (at. %) alloy were investigated. The α2 segments nucleated at the ωo boundaries after aging at 900 °C for 2 h. The ORs between the two phases were studied by selected area diffraction patterns using a transmission electron microscope and interpreted by the superimposed stereographic projections. Two ORs were defined as follows: $$ \left[ {1\bar{2}10} \right]\upalpha_{2} //\left[ {000\bar{1}} \right]\upomega_{o} $$ ; $$ (0002)\upalpha_{2} //\left[ {\bar{1}2\bar{1}0} \right]\upomega_{o} $$ and $$ \left[ {\bar{1}010} \right]\upalpha_{2} //\left[ {2\bar{4}2\bar{3}} \right]\upomega_{o} $$ ; $$ \left( {0002} \right)\upalpha_{2} //\left( {01\overline{12} } \right)\upomega_{o} $$ . Two α2 laths with parallel $$ \left\langle {\bar{1}102} \right\rangle $$ directions were observed in this alloy, which were explained by the different α2 variants nucleated at the ωo boundaries according to ORI and ORII.

The interaction between extracellular matrices and cancer cells plays an important role in regulating cancer cell behaviors. In this article, we use matrigel to mimic extracellular matrices and investigate experimentally how matrigel influences the shape and dynamics of breast cancer cells (MDA-MB-231-GFP cells). We find that matrigel facilitates cancer cells’ migration and shape deformation. The influences of the matrigel concentration are also reported.

GaN nucleation layers were grown on sapphire substrate by metal organic chemical vapor deposition (MOCVD) with different carrier gas. The morphology of nucleation layer which is crucial to GaN crystal quality was systematically studied using nitrogen and hydrogen as carrier gas. The GaN nucleation layer tends to form larger islands under H2 ambient, and forms higher density nucleation islands and thicker nucleation layer under N2 ambient.

Mutual transformation between α2 and ωo phases has been an interesting topic in recent years. In this study, martensitic α2 was obtained by air-cooling from 1250 °C in Ti-37.5Al-12.5Nb (at%) alloy while four ωo variants formed in the βo phase matrix during the cooling process. Nonetheless, only one ωo variant was observed at the periphery of the α2 plates in the βo phase and the orientation relationship between these two phases was [0001] α2//[\({1\overline{2}10}\)] ωo; (\({11\overline{2}0}\)) α2//(0002) ωo. Thin γ plates precipitated within the α2 phase and were thought to be related to the appearance of ωo phase. The redistribution of the compositions during the phase transformations was studied by energy dispersive X-ray spectroscopy analysis. The corresponding mechanisms of the phase transformations mentioned above are discussed.