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To accurately predict the fatigue properties of additively manufactured (AM) titanium alloys, it is important to understand the fatigue damage origin behavior. However, this behavior is still ambiguous. Therefore, the effects of internal defects and microstructures on the fatigue damage origin behavior of laser direct energy deposited TC11 (LDED-TC11) alloy were investigated using a fatigue origin criterion. The criterion was proposed to analyze the competing and combining effects by coupling the plasticity-corrected crack driving force, the resistance of short cracks, and the modified Kitagawa-Takahashi diagram. Three scenarios corresponding to the criterion were clarified, representing the damage mechanisms dominated by the microstructure, the combined effect of internal defect and microstructure, and the internal defect. As a result, the fatigue fracture morphology of high-cycle fatigue tests demonstrates two fatigue origin modes, i.e. microstructure and gas pore origin modes. The two fatigue modes belong to Scenario Ⅰ and Scenario Ⅱ, respectively, which indicates that the fatigue damage origin process of this alloy is sensitive to microstructure. Besides, it was found that the width of the primary αphase of this alloy is strongly relevant to intrinsic defect size. Finally, the fatigue origin criterion was verified in three aspects.

Photovoltaic cooling is critical to ensure stable and safe operation of PV power station. Conventional cooling methods focus on heat dissipation from the surface of PV modules. Few studies have shown the in-plane thermal conductivity influence on the temperature of PV modules. In this paper, Al foil with high thermal conductivity was introduced in PV module and the in-plane temperature distribution of the monofacial double glass PV module was investigated. The results show that the temperature decreases gradually from the center to the edge of the PV module, and the maximum temperature and the in-plane temperature difference of Al incorporated PV modules are lower than that of the standard PV module. Al foil improves the heat dissipation along the in-plane direction and achieves a temperature difference reduction of 6.170 ℃ on the whole PV module. This demonstrates that the improvement of in-plane heat dissipation is of great significance to decrease the temperature of PV modules. Additionally, the temperature and in-plane temperature difference between PV modules with/without Al foil incorporation increases with the increase of ambient temperature and solar irradiation.