A simple and novel self-assembly based process is presented in this paper for the fabrication of gold triangular nanocavity arrays. This process combines nanosphere lithography (NSL) with some standard MEMS technologies. A carboxylated polystyrene (PS) nanosphere bilayer with a relatively large area is fabricated on silicon wafer as the starting template by spin-coating. Oxygen plasma etching, metal deposition and lifting-off of the PS upper layer are then orderly carried out for the formation of triangular space, which is made up of Cr film and the remaining PS nanoparticles. Then silicon etching is used to transfer the triangle pattern onto the silicon wafer. Finally, a 50 nm thick gold layer is deposited on the pattern to fabricate gold triangular nanocavity arrays. With this strategy, both the period and the cavity size can be adjusted independently. This will allow the tuning of the optical properties for desired application.
In metastable beta Ti alloys, microstructural features can be varied over a wide range of length scales by changing different heat treatment parameters. Effect of cooling methods on microstructure and mechanical properties of Ti-3537 alloy after solution treatment was investigated. The result shows that with the decrease of cooling rate, the Vickers hardness of the alloy gradually increases. Among the three cooling methods of OQ, AC and FC, Ti-3573 alloy has the best shape and moderate yield strength, but tensile strength. The fractography of the β-substrate specimens showed that the fracture mode was ductile fracture. In the FC state, the α phase precipitates in a large amount in the Ti-3573 alloy, the yield strength and the tensile strength are greatly increased and the elongation is remarkably lowered. The tensile fracture shows a shallow fracture dip with low toughness.
A microstructure consisted of granular bainite, upper bainite, acicular ferrite, polygonal ferrite, and a little of pearlite was obtained by controlling rolling and cooling in marine steel. The grain size of the two steels was refined to 5-9 μm. The size of the MA island was about 3-6 μm. Both steels had higher tensile strength, yield strength, elongation and hardness, and the performance of steel B was better than that of steel A. Both steels exhibited large and deep dimples at -80 °C impact fracture. The longitudinal impact energy of the specimens was above 250J, and the steel B even exceeded 300J. Its longitudinal impact performance was better than lateral impact performance. Both steels had achieved good performance due to fine grain strengthening, MA island strengthening, precipitation strengthening and dislocation strengthening caused by controlled rolling and cooling. The alloying element nickel effectively improved the low temperature impact toughness of the experimental steel. Excellent impact energy of both steels was attributed to higher texture strength for RD specimens.
In this regard, two beta titanium alloys in the Ti-Al-Mo-V-Cr system, Ti-3Al-5Mo-7V-3Cr (Ti-3573) and Ti-3Al-8Mo-7V-3Cr (Ti-3873), have been designed. Comparison of the microstructure and mechanical properties of both alloys after solution treatment was conducted. The result shows that the β grains in Ti-3873 alloy are abnormally grown at WQ. The elongation of Ti-3573 alloy is higher than that of Ti-3873 alloy, it is related to the the smaller grain size. The Ti-3873 alloy has moderate plasticity but higher yield strength and tensile strength. Fine and deep dimples associated with ductile fracture were obtained for the Ti-3573 alloy. The fractography of the β-substrate specimens showed that the fracture mode was ductile fracture. The Ti-3873 alloy has a combination of slip and twinning during deformation. It is possible for the Ti-3573 alloy to undergo both twinning and TRIP effect upon deformation. Therefore, Ti-3573 alloy exhibited good plasticity and strength matching.
Atmospheric corrosion test of TRIP steels was conducted in laboratory. The surface morphologies of the specimens were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and electro-probe microanalysis (EPMA). Corrosion performance of TRIP steels under atmospheric environment was investigated by discussing the protective mechanism. The corrosion rates of steel A are significantly greater than steel B in atmospheric environment tests. The enhancement of corrosion performance of TRIP steel is attributed to the additions of alloying elements, such as P, Cr, Cu, and Ni etc.. The alloying elements increase the compactness and densification of rust layers. Electrochemical characteristic of TRIP steel is improved by means of the enhancement of the thermodynamic stability.
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