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The three-point bending fatigue method was used to determine the S-N fatigue curves of smooth specimens and straight-notched specimens to study the fatigue properties of Stellite12 cobalt-based alloy, and the fatigue fracture processes of the cobalt-based alloy were investigated by the observation of fracture morphology.The results show that the fatigue limit of the smooth specimen is 545 MPa, which is about 25.4% of the original bending strength of 1552 MPa. The fatigue limit of the straight-notched specimen is about 101 MPa, which is about 19.1% of static bending strength of 517.6 MPa. The fatigue sensitivity of smooth specimens and straight-notched specimens is 397 and 31, respectively. In addition, it is found that the fatigue cracks can initiate in the carbides aggregated regions in the near surface. Surface defects can also induce the initiation of fatigue cracks. The transgranular fracture of the carbides dominates in the crack propagation. The cobalt base metal presents a lot of tearing ridges under the condition of stress ratio R=0.1, but it also shows a certain degree brittle fracture mode, so the fatigue crack propagation mode is a mixed mode of true fatigue and static fatigue.

Colletotrin A (1), a new 1,4-benzoxazine derivative, and eight known compounds, including two alkaloids (2-3), one acylamide (4), one benzaldehyde (5), and four sterols (6-9) were obtained from endophytic fungus Colletotrichum gloeosporioides B-142, which was isolated from Dracaena cochinchinensis. Among them, 1,2,3,4-tetrahydroquinoline-4,8-diol (2) was reported for the first time as natural product. The structure of compound 1 was elucidated with help of spectroscopic data including IR, UV, electronic circular dichroism (ECD) calculation, HRESIMS, 1D and 2D NMR (COSY, HSQC and HMBC). The antimicrobial activities were evaluated by disc diffusion method. [ABSTRACT FROM AUTHOR]

The wetting of TA2 pure Ti by two industrial grade Al alloys (i.e.,6061 Al and 4043 Al alloys) was studied by using the modified sessile drop method at 600,650,700℃ under high vacuum. The results show Al/Ti system is a typical reactive wetting, the small amount of alloying element Si in the Al alloys can cause significant enrichment at liquid/solid interface and satisfy thermodynamic condition;the formation of the Si-rich phase (Ti7Al5Si12) strangling material exchange at triple line zone; Ti7Al5Si12 decomposition and Al3Ti formation can remove the oxide film and promote wetting;the spreading dynamics can be described by reaction product control model, further the whole wetting behavior can be divided into two stages:the first stage for the nonlinear spreading and the second stage forthe linear spreading;the activation energies which are 56kJ/mol, 47kJ/mol for nonlinear stages of 6061 Al and 4043 Al alloys, and 112kJ/mol for linear stage of 6061 Al alloys, respectively,Ti7Al5Si12 decomposition is corresponding to the nonlinear spreading.

The wetting behavior and interfacial microstructures of molten magnesium AZ61 alloy on the surface of two different Q235 and galvanized steel plates under the condition of cold metal transfer were investigated by using dynamic sessile drop method. The results show that the wetting behavior is closely related to the wire feed speed. Al-Fe intermetallic layer was observed whether the substrate is Q235 steel or galvanized steel, and the formation of Al-Fe intermetallic layer should satisfy the thermodynamic condition of such Mg-Al/Fe system. The wettability of molten AZ61 magnesium alloy is improved with the increase of wire feed speed whether on Q235 steel surface or on galvanized steel surface, good wettability on Q235 steel surface is due to severe interface reaction when wire feed speed increases, good wettability on galvanized steel surface is attributed to the aggravating zinc volatilization. When the wire feed speed is ≤10.5m·min-1, the wettability of Mg alloy on Q235 steel plate is better than on galvanized steel plate. However, Zn vapor will result in instability for metal transfer process.

Coarse grain heat affected zone (HAZ) of F460 steel was simulated by a Gleeble 3800 thermo-mechanical simulator. The microstructure, critical event of the HAZ formed at various heat inputs (E) were characterized and determined by optical microscopy (OM) and scanning electronic microscopy (SEM), and cleavage fracture stress σf was also calculated by ABAQUS software. Based on above systematic analysis, the intrinsic mechanism of ductile-brittle transition for F460 steel heat affected zones with different heat inputs were revealed. The results indicate that:with the improvement of heat input, the microstructures in sequence are a minority of lath martensite and massive fine lath bainite, more lath bainite with less granular bainite, more granular bainite with less lath bainite, bulky of granular bainite; and the maximum size of the original austenite grain and bainite packet becomes bigger with the improvement of heat input. The size of bainite packet is critical event of the cleavage fracture for coarse grain heat affected zone specimens with various heat inputs by comparing the relationships among residual crack length, original austenite grain size and bainite packet size. With the decreasing of the bainitic packet, the ductile to brittle transition temperature decreases. In addition, cleavage fracture stress σf is also calculated by ABAQUS software, σf gradually decreases with the increase of the heat input, which can explain the intrinsic mechanism of ductile to brittle transition temperature Tk with the change of the heat input.

In order to improve the cuttage propagation coefficient of fresh-eating peanut, the effect of different catting parts and ABT concentration on the cutting growth of fresh-eating peanut was studied by taking Jihuatian No. 1 plant as the test material. The results showed that the survival rate of cutting in different parts of peanut was in the order of the upper part > middle part > lower part. The upper cuttings of peanut plant were treated with five different concentrations of ABT rooting agents, among which the treatment with 150 mg ⋅ L-1 concentration had the best cutting effect and the most vigorous growth vigour. After 40 days of cutting, the survival rate was 83.3%, the average rooting was 12.7, the average root length was 2.85 cm, and the yield reached 3259.04 kg ⋅ hm², which was 148.48% higher than that of the control group with clear water, and the difference was very significant. The correlation detection analysis showed that the rooting number and root length of peanuts were positively correlated with the yield. [ABSTRACT FROM AUTHOR]