In this paper, the surface of 7N01 aluminum alloy profile is sandblasted or electropolished. The influence of different surface conditions on its conditional fatigue strength and fatigue mechanism under the alternating load after prefabricated short crack are studied. Results show that the 7N01 aluminum alloy with sandblasting treatment has formed a work hardened layer and its fatigue strength is increased by 42.9% comparing with the original surface specimens. The fatigue strength of the 7N01 aluminum alloy after electropolishing is almost unchanged compared with the original specimen. The fatigue behavior of the 7N01 aluminum alloy after prefabricated side straight through the notch deviated from the theoretical smooth specimen law and long crack propagation law in which is a 'shortage effect'. When the notch size is smaller than the transition crack size a 0 , the fatigue limit of the notched specimen is lower than the fatigue limit of the smooth specimen. When the notch size is larger than the transition crack size, the fatigue limit of the long-notched specimen is still lower than that predicted by linear elastic fracture mechanics. Due to the 'short notch effect', the effective notch propagation threshold ΔK eff.th of the long crack is 0.39 Mpa m 1/2 based on the effective notch propagation size a 0 eff of the alloy.

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Perovskite structure chromite is an important functional material and has a wide range of applications in the fields of catalysis, magnetism, and dielectrics. [1][2] LaCrO 3 is a perovskite-type (ABO 3 ) composite oxide with a melting point of 2490°C and an orthogonal structure (P bmn space group) at room temperature. The lattice constants a, b, and c are 0.5520 nm, 0.5483 nm, and 0.7765 nm, respectively. Orthogonal structure transform to rhombohedral structure at 240°C-280°C, and rhombohedral structure transform to cubic structure at 1650°C. The electrical transport in LaCrO 3 is dominated by small-polaron hopping in which the charge carriers are considered to be localized at the Cr sites [3][4][5] , the conductivity of LaCrO 3 at room temperature is poor and the conductivity in air at 1000°C is 0.6-1.0 S/cm. 6 With proper A and B site doping, the sintering performance, electrical conductivity, mechanical properties, and chemical stability of lanthanum chromite-based ceramics will be greatly improved. Work in the literature found that the A-site doped lanthanum chromate with 20 at.% Ca has obtained good comprehensive mechanical properties with a fracture toughness of 3.52 MPa•m 1/2 and a bending strength of 131.3 MPa. 7 At the same time, the study of Homma 8 also found that the conductivity of lanthanum chromate doped with 20 at.% Ca at 800°C increased from 0.2 to 12 S/cm. Due to its high melting point (2490°C), oxidation and corrosion resistance, LaCrO 3 is used as interconnects or electrode materials 9-11 for solid oxide fuel

The hot-rolled alloy Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y was exposed to 700 °C air for up to 10,000 h. The changes in microstructure were observed using scanning and transmission electron microscopies. It was found that the α2 laths, α2 + γ lamellae, and B2(ω) structure of the alloy showed thermodynamic instability. There were three types of phase transformation in the alloy during long-term thermal exposure. The first was α2 → γ, which occurs in the interior and boundary of the α2 + γ lamellae. The second was α2 + γ → B2(ω), which occurs on the α2 + γ boundary. In addition, B2(ω) also precipitates on the γ/γ interfaces. The third was B2(ω) → γ, which describes the precipitation of micron-scale γ phases in the B2(ω) area after thermal exposure of 5000 h. The volume fraction and size of the B2(ω) area and equiaxed γ grains continued to increase throughout the exposure process. Large-sized γ grains and a B2 area of tens of microns appeared in the microstructure after long-term thermal exposure. The volume fractions of the B2 area and the equiaxed γ grains after thermal exposure of 10,000 h reached 16.8% and 63.2%, respectively.