low-temperature solution method, which makes it a promising candidate for flexible devices. [19][20][21][22][23] Novel devices based on perovskite have proven great potential for further application. [24][25][26] However, perovskites are very sensitive to air moisture which invades cracks of flexible films and accelerates the damage to devices. In the base of environmental protection, the toxicity of lead also demands for long working life for perovskite devices to avoid the disposal of lead waste. [27][28][29] These problems indicate that mechanical stability remains as a significant concern for flexible perovskite devices. Solutions including interface treatment and mixture of polymer have been employed, but they can only withstand limited bending cycles and strength. [30][31][32][33][34] To resolve these critical issues, the concept of self-healing has also been applied to flexible perovskite devices. [35,36] Selfhealing polymers can act as encapsulation layers or flexible substrates, which only prevent external air moisture while cracks inside perovskite films still exist and block carrier transport. In addition, it is difficult to endow the ABX 3 crystal structure of perovskite with special chemical bonds (such as H-bonds) to trigger the capability of self-healing. To address this challenge, Chen et al. creatively utilized polyurethanes (PU) to provide a micro-self-healing framework for perovskite crystals without damaging its power conversion efficiency and cracks caused by stretching were healed by heating films at 100 °C. [36] The heating treatment may damage organic carrier transport layers or accelerate ion diffusion of metal electrodes; moreover, perovskite devices usually operate at the room temperature. Thus, it is necessary to design a perovskite material with self-healing capability which does not need any harsh external stimuli.Herein, we design a moisture-triggered self-healing flexible perovskite photodetector with poly(vinyl alcohol) (PVA) as an additive. Moisture, as a negative factor affecting the stability of perovskite, is also used to activate the self-healing process of perovskite films. PVA organic framework fills grain boundaries, which are weak points that generate cracks. The moisturesensitive framework absorbs water molecules from the air and recovers the conductivity lost from the cracks, which is proved to be the dominant reason for the decomposition of the flexible lateral perovskite photodetector. The device can recover over 90% of its initial performance under a relative humidity (RH) of 80%, maintaining remarkable mechanical stability. Furthermore, PVA stabilizes the formamidinium lead iodide (FAPbI 3 ) film in the black phase, and the photodetector shows a high responsivity Flexible devices are urgently required to meet the demands of next-generation optoelectronic devices and metal halide perovskites are proven to be suitable materials for realizing flexible photovoltaic devices. However, the tolerance to moisture corrosion and repeated mechanical bending remains a critical c...

The Al-Si piston alloys always bear different temperatures because of its peculiar component structure and service condition. Therefore, the tensile strength, elongation to fracture, and corresponding damage mechanisms of Al12SiCuNiMg piston alloys (ASPA) have been investigated with in situ technique at different temperatures. The tensile properties show two-stage tendencies: the former stage (25-280 C) is determined by easily broken phases with inherent brittleness (such as primary Si), and the fracture behavior presents rapid brittle fracture after reaching the critical stress (about 430 MPa, based on in situ technique and the elastic stress field model). The later one (280-425 C) is dominated by particles debonding and θphase coarsening. The plastic deformation behavior, dynamic recovery, and flow process become more significant on account of thermal activation. The Consid ere criterion h ¼ K indicates that the transition of damage behaviors from insufficient local strength to insufficient matrix strength and the corresponding failure model shifts from brittle to ductile fracture. Based on the damage mechanisms, the elastic field model and thermal activation relation model have been established to characterize the strength of the ASPA at different temperature ranges.

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