The columnar-grained Cu–Al–Mn shape memory alloys (SMAs), which have good shape memory properties and are prepared by a unidirectional solidification technique, were subjected to a gradient heat treatment under temperatures ranging from 100 to 450 °C. After this treatment, the microstructure, hardness, transformation temperature and shape memory properties of these samples could exhibit gradient changing trends, all of which were investigated by optical microscope, scanning electron microscopy (SEM), a Vickers microhardness tester, and a compression machine. The microstructure observation result shows that the acicular bainite-precipitated phase produces from scratch and then grows continuously with the increasing of the heat treatment temperature, finally presenting a graded distribution from one end section to another of the sample. The hardness tests give the samples results also increasing with temperature. Specifically, the change relationship between hardness and the treatment temperature mathematically satisfies dynamic function. In addition, it can be concluded from mechanical tests the compressive elastic–superelastic strain and strength of the samples show gradient variation features. Overall, our experimental investigation indicates that a gradient heat treatment is an effective way to conduct microstructure control or design for the Cu–Al–Mn SMAs, and their graded properties are mainly caused by the different fractions of the bainite phase producing in different local areas after the gradient heat treatment.
Technology diffusion plays an important role in the improvement of technological innovation capabilities and can provide strong support for sustainable economic development. This paper aims to analyze the influence mechanism of technology diffusion on sustainable development, such as the initial investment willingness, technology spillover effects and absorptive capacity, technology transfer prices and intellectual property protection, government subsidy support and penalties. However, there is a lack of systemic game mechanism and numerical simulation methods for heterogeneous enterprises. Based on the government, OFDI companies, and domestic companies that are not involved in FDI, we have proposed the evolutionary game model for technology diffusion on sustainable development. The results show that: (1) The government, OFDI firms, and domestic firms are influenced by each other’s initial willingness to a different extent; (2) Different combinations of technology spillover and absorptive capacity lead to different sustainable evolution results of technology diffusion; (3) Reasonable technology transfer pricing and enhancing the protection of property rights can improve the efficiency of the technology diffusion sustainable development system; (4) Both financial support and penalties encourage technology diffusion sustainable development, but excessive financial support reduces the government’s willingness to participate ultimately. Therefore, this paper proposes that the government should increase its willingness to participate and increase punishment for unreasonable pricing behaviors. The stronger the stimulus effect of OFDI firm technology spillover and domestic firm absorptive capacity, the stronger the stimulus effect; however, there is a certain threshold effect, at the same time increasing the property rights protection of OFDI firms and the penalties for opportunistic behaviors of domestic firms, and establishing a diversified financial support policy, will increase the efficiency of the technology diffusion sustainable development system.
The SUS304 stainless steel is widely used in many industries, and the prediction and detection of fracture tendency in these stainless steel applications are very important for their safety and serviceability. The ductile fracture is caused by micro damage and its accumulation, whose mechanism can be described by the micro void nucleation, growth and final extension to failure. The nucleation, growth and extension of the micro voids are related with the movement of the dislocations. In this paper, the optic microscope, X-ray diffraction and scanning electron microscope were used to observe the changes of the sample during uniaxial tensile tests, and analyse the relationship between micro void and dislocation density, and finally establish a dislocation density-strain model. This model provides a new idea for non-destructive testing, which can be applied to the early identification of fracture tendency.
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