e corrosion behavior of Alloy C-276 in high-temperature and high-pressure water at 500°C and 25 MPa, respectively, was investigated by means of mass gain, scanning electron microscopic observation, and X-ray diffraction. e results indicated that the mass gain rate of Alloy C-276 in supercritical water obeys the parabolic law. e oxide scale was formed on Alloy C-276 with a dual-layer structure, mainly consisting of an outer Ni-rich layer and an inner Cr 2 O 3 /NiCr 2 O 4 mixed layer. Tiny microcracks can also be found in the oxide scale if exposed for longer time. Meanwhile, higher temperature promotes oxide rate and results in thermal stress in the oxide film.

Aircraft are subjected to extreme weather conditions in coastal areas. This study reports long-term atmospheric exposure tests carried out on an epoxy primer-coated aluminum alloy in a coastal environment for 7, 12, and 20 years. The micromorphology and characteristics of the section and surface, the products of corrosion, electrochemical impedance, and molecular structure of the coated specimens were examined through a spectrophotometer, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectrometer (XPS). The results showed that the angles of contact of the specimens with different numbers of years of atmospheric exposure satisfied the normal distribution. Their fractal dimensions increased with an increase in the duration of exposure. Intergranular corrosion and exfoliation corrosion appeared in the specimens after 20 years, where the product of corrosion was Al(OH)3. The impedances and thermal properties of the epoxy coatings were influenced by the synergistic effects of aging and post-curing. The impedances of the coatings decreased greatly after long-term atmospheric exposure. After 20 years of corrosion, the specimen showed the characteristics of the substrate being corroded. The mechanism of corrosion and the electrochemical equivalent circuit were also analyzed.

Microstructure, age hardening response and mechanical properties of Mg-4.0Sm-xCa (x=0.5, 1.0, 1.5, wt%) alloys extruded followed by isothermal aging at 200 o C were investigated. The results indicate that with the addition of Ca, the bulk and particle-like Mg41Sm5 phase containing Ca and the needle/rod-like Mg2Ca phase are formed in the Mg matrix, grains of the alloy are refined and tensile mechanical properties are improved remarkably. Under T5 (peak-aging) condition, the Mg-4.0Sm-1.0Ca alloy shows the smallest grain size of 5.1 μm. With the increase of Ca content the amount of Mg2Ca phase increases gradually, but that of the bulk Ca-containing Mg41Sm5 phase, which is mainly distributed at the grain boundaries, decreases obviously when Ca content reaches 1.5 wt%. The peak-aged Mg-4.0Sm-1.0Ca alloy exhibits the highest hardness HV (820 MPa) and the optimal ultimate tensile strength, yield tensile strength and elongation of 267 MPa, 189 MPa and 24%, respectively. The improved mechanical properties of the alloy are attributed to the grain refinement, the solution strengthening and the precipitation strengthening of Mg2Ca phase and Mg41Sm5 phase.

The microstructure and age hardening response of deformed Mg-1.5Mn-xSn (x = 1 and 5, wt.%) alloys under three different aging temperatures (100°C, 150°C, 200°C) have been investigated. The aging behavior and the mechanical properties are improved by increasing Sn content. On ther other hand, the pre-rolling process is an effective method to improve the age hardening response, and therefore the mechanical properties of ERA (extruded + rolled + aging treatment) state alloys are improved compared with those of EA (extrusion + aging treatment) state samples. The improved mechanical properties of ERA alloys are mainly related to the extensive twins and dislocations formed during the extrusion/rolling processes and Mg2Sn precipitates formed in the aging treatment.

Based on the real annual average value of atmospheric environmental data in the Wanning area of Hainan Province in China by selecting 7075 ultra-high-strength aluminum alloy specimens for aviation, a new corrosion solution was designed and the traditional alternate immersion corrosion method of using the alternate immersion corrosion test box was improved to simulate the environment of the internal structure of the aircraft. On this basis, two kinds of corrosion damage parameters, the depth of corrosion pits and corrosion rate, were quickly and accurately obtained by the three-dimensional profile of the specimen and binarization images’ method. The optimal linear regression equation combination of pitting depth and corrosion rate was established, and the dynamic evolution equation of the depth of corrosion pits and corrosion rate was obtained. The results showed that: The depth of corrosion pits in the early stage of corrosion (8 h and 24 h) obeyed the Gumbel distribution and Weibull distribution, respectively, and the later stage (48 h, 72 h, 96 h, and 120 h) conformed to the normal distribution; the depth of corrosion pits’ evolution law was in the form of double straight lines and the corrosion rate evolution law was in the power function form (y = a × xb); and the depth of corrosion pits changed rapidly in the early stage and gradually slowed down in the later stage, while the corrosion rate was just the opposite.