The oxidation behavior of the single crystal Ni-based superalloy TMS-82+ was studied under cyclic condition at 900 and  1 000 ℃ for 200 h in air. The oxidation kinetics for the superalloy at both exposure temperatures was explained by the subparabolic relationship. The results show that increasing the exposure temperature from 900 to 1 000 ℃, the amounts of α-Al₂O₃, (Ni, Co)Al₂O₄ and NiCr₂O₄ increase, resulting in a higher mass gain. The oxides consist of (Ni, Co)O, CrTaO₄, AlTaO₄, Cr₂O₃, θ-, _­­­­α-Al₂O₃ and (Ni, Co)Al₂O₄ in the specimen at 900 ℃, but NiCr₂O₄ spinel forms for the specimen exposed at 1 000 ℃ except the above mentioned oxides. A continuous α-Al₂O₃ layer is responsible for a slow growth rate of the scale after an initial rapid oxidation of NiO.

The influences of pre-strain on the mechanical property and fatigue crack growth of 2E12 aluminum alloy were evaluated by SEM, TEM, mechanical property and fatigue tests. The axial fatigue tests were conducted under a constant amplitude sinusoidal wave loading at stress ratio of 0.1 in laboratory air and salt fog at room temperature. The results show that the yield stress of pre strain material is higher than that of the material without undergoing pre-strain, but pre-strain can not make the increase of the growth rate of fatigue crack. Fatigue crack growth rates of the alloy in salt fog are higher than those in air. The increased fatigue crack growth of the alloy in a given environment and more brittle striations can be observed in salt fog.

To improve the oxidation-resistance properties, SiC and TaC species were introduced in C/C composites by chemical vapor infiltration (CVI) methods. The oxidation-resistance properties of C-SiC-TaC-C composites were studied by X-Ray diffractometry (XRD), JEOL−6360LV scanning electronic microscopy (SEM) and Adventurer^TM electronic balance with precision of 0.1 mg. The results show that, 1) the oxidation rate of the composites increases continuously with time at all experimental temperatures; 2) The oxidation rate increases with temperature within 700−1 100 ℃, slowly in 700−800 ℃, acutely in 800−1 100 ℃; it reaches a maximum value at 1 100 ℃, then decreases within 1 100−1 400 ℃; 3) The relationship curve of oxidation rate with temperature can be divided into three regions. The oxidation rate is controlled by reactivity in region Ⅰ, the mixed effects of reactivity and gas diffusion in region Ⅱ, gas phase diffusion in region Ⅲ; 4) The composites exhibit a higher oxidation onset temperature in low temperature region and a lower oxidation rate at high temperature due to the oxidation of TaC to (Ta, O) and the formation of the dense SiO₂-Ta₂O₅ oxide layer respectively. With the addition of SiC/TaC species, the oxidation-resistant properties of C/C composites can be improved effectively.

The significant positive green environment influence of magnesium alloy usage in transport could be compromised by catastrophic fast fracture caused by stress corrosion cracking (SCC). Transgranular stress corrosion cracking (TGSCC) of AZ91 was evaluated using the linearly increasing stress test (LIST) and the constant extension rate test (CERT). The TGSCC threshold stress was 55−75 MPa in distilled water and in 5 g/L NaCl. The TGSCC velocity was 7×10⁻¹⁰−5×10⁻⁹ m/s. A delayed hydride-cracking (DHC) model for TGSCC was implemented using a finite element script in MATLAB and the model predictions were compared with experiment. A key outcome is that, during steady state TGSCC propagation, a high dynamic hydrogen concentration is expected to build up behind the crack tip. A number of recommendations are given for preventing SCC of Mg alloys in service. One of the most important recommendations might be that the total stress in service (i.e. the stress from the service loading + the fabrication stress + the residual stress) should be below a threshold level, which, in the absence of other data, could be (conservatively) estimated to be about 50% of the tensile yield strength.

The corrosion and high-temperature oxidation characteristics of AM60 Mg alloy in different environments were investigated by immersion test, electrochemical polarizing analysis and differential thermal analysis (DTA)/thermo gravimetric (TG) experiments. The influence of aging heat treatment on the corrosion resistance of AM60 Mg alloy was studied. AM60 Mg alloy shows better corrosion resistance in sea water than in 3.5%(mass fraction) NaCl solution. The corrosion resistance after aging for 24 h is better than that of both as-cast and aging for 48 h. Corrosion resistance of Mg alloy is controled by microstructure, composition of α-matrix. Precipitation of β phase along the grain boundaries acts as a barrier that decreases corrosion rate, whereas the decrease of aluminum content of α phase causes an increase in the corrosion rate. The DTA and TG curves of heating process in air are characterized with combustion after 590 ℃. When heated in helium, the curves show two endothermic peaks and a remarkable evaporation of magnesium. As for isothermal DTA and TG experiments, mass increment caused by oxidation does not happen till 520 ℃.

The corrosion behavior of B30 Cu-Ni alloy in a sterile seawater and a SRB solution was investigated. The results show that the corrosion potential of specimen in the SRB solution is much lower than that in the sterile seawater. The polarization resistance of specimen in the SRB solution decreases quickly after a period immersion and becomes much lower than that in the sterile seawater. It is concluded that the SRB accelerates the corrosion process of B30 Cu-Ni alloy greatly. An anti-corrosion electroless Ni-P coating was produced and applied to the alloy. The results show that specimens coated with Ni-P plating exhibit favorable corrosion resistance property in SRB solution. Severe pitting corrosion appears on the uncoated specimens in the SRB solution when the coated specimens are still in good condition. The anti-corrosion mechanism of Ni-P plating was analyzed. It is concluded that coating the B30 Cu-Ni alloy with electroless Ni-P plating is an effective technique against the attack of SRB in marine environment. 

Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids (SBFs). The influence of materials, solutions and their temperature on corrosion rate was mainly discussed. The results demonstrate that the free corrosion potential (E_corr) of AZ31 and AZ91 alloys rises rapidly at initial stage, and then stabilizes at some value. E_corr of WE43 alloy increases continuously. While E_corr of AZ91 alloy with macro-arc oxidation (MAO) coating decreases drastically in 3 min, and then fluctuates between −1 607 mV and −1 503 mV. The WE43 alloy has better corrosion resistance in Hank’s solution, compared with AZ31 and AZ91 alloys. Corrosion rates of the alloys are sensitive to the chemical composition and temperature of SBFs. A thin MgF₂ film slightly improves corrosion resistance. An MAO coating on AZ91 alloy significantly reduces corrosion rate and enhances E_corr. Pitting corrosion occurs on both AZ31 and WE43 alloys in Hank’s solution.

The oxidation of the Ni-10Cr-xAl(x=7%, 10%, molar fraction) alloys was studied at 1 100 ℃ under 0.1 MPa O₂ and compared with that of the binary Ni-7Al and Ni-10Al alloys. The results show that the binary alloys form NiO external scales associated with an internal oxidation of Al. On the contrary, the ternary Ni-10Cr-7Al and Ni-10Cr-10Al form external alumina scale in contact with the alloy substrate. An addition of 10%Cr(molar fraction) into Ni-7Al and Ni-10Al inhibits the internal oxidation of aluminum and considerably reduces the critical content of Al needed to form exclusive alumina scales with respect to binary Ni-Al alloy, providing an example of third-element effect.

The corrosion behavior of ternary Fe-15Cu-5Al (mole fraction, %) alloy was studied at 1 000 ℃ in 0.1 MPa pure oxygen. The Fe-rich alloy shows two parabolic oxidation stages, with a small increase of the parabolic rate constant from 1.9×10⁻⁹ to 4.1×10⁻⁹ g²/(cm⁴∙s). The scale grown on the alloy is very complicated, with formation of overgrown nodules interspersed among bulky stratified scales. The nodules and the bulky stratified scales are always composed of an outer layer of CuFe₂O₄ and of an inner layer containing Fe₂O₃ and Fe₃O₄. Beneath the external scale of the nodules, there is an internal oxidation zone where iron oxide is mixed with copper metal. Furthermore, the base of the internal oxidation zone is characterized by a discontinuous aluminum-enriched layer of either Al₂O₃ or FeAl₂O₄. For the stratified scales, no internal oxidation zone is present beneath the innermost Al₂O₃ or FeAl₂O₄ layer. Aluminum depletion is present in advance of the internal oxidation front, while iron depletion is not observed. The corrosion feature of the ternary Fe-15Cu-5Al alloy is partly associated with that of the corresponding binary Fe-Cu and Fe-Al alloys. The peculiar scale microstructure observed is considered mainly as a consequence of the limited solubility of the iron and copper components in one another and of the monovariant system of the ternary Fe-15Cu-5Al alloy.

The effect of temperature on oxidation behavior of ternary Fe-15Cu-5Al (mole fraction, %) alloy in pure oxygen was studied.  Fe-15Cu-5Al alloy presents an irregular high-temperature oxidation behavior between 700−1 000 ℃, though the kinetic curve at each temperature can be approximately considered as being composed of two quasi-parabolic stages. At 700 ℃ the alloy forms bulky stratified scales. On the contrary, at 800 ℃ the alloy forms an external protective Al₂O₃ layer. The trend of decrease of oxidation rate does not continue at elevated temperatures. Due to the high stress-growth effect at 900 ℃, the thin Al₂O₃ layer cannot completely prevent further oxidation of the alloy underneath. When the temperature rises to 1 000 ℃, the high stress-growth effect is more obvious and the alloy forms overgrown large nodules. Compared with the Fe-10Al binary alloy, the presence of 15 % Cu tends to greatly increase the flaw of the formed Al₂O₃ layer at elevated temperatures, resulting in a peculiar oxidation pattern of Fe-15Cu-5Al alloy.

Electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques were used to detect stress corrosion cracking (SCC) on 40Cr steel specimens exposed to the acidified chloride solution at ambient. To test these two techniques, slow strain rate tensile (SSRT) tests were performed with 40Cr specimen in the identical corrosive solution at room temperature. In impedance measurements, phase shifts in frequency range from 1 to 1 000 Hz show a clear difference between the stressed and non-stressed specimens, suggesting that stress corrosion cracks are detected by the impedance measurements. EN signals in the process of SCC were recorded and then analyzed by standard deviation (STD). On the other hand, the mechanical properties, such as maximum tensile strength (MTS) and fracture strain (FS) measured by the SSRT, decrease significantly when the specimens are exposed to the corrosive solution relative to that in an inert medium. The SSRT results are consistent with fractography of the tested specimens by scanning electron microscopy (SEM). Analysis of the fracture surface clearly shows intergranular attack, suggesting that stress corrosion cracks are formed.

The corrosion characteristics of copper in magnetic action system were investigated by mass loss method, electrochemical test, scanning electron microscopy (SEM) and energy analysis. It is found that the corrosion process of copper is influenced by magnetic field. The flow corrosion rate of copper decreases at the initial segment, then drives to gentle stage at the final segment. From electrochemical test, the corrosion rate of copper in the magnetized sea water is minimal compared with that in 3.5% NaCl solution and sea water. Electrochemical impedance spectroscopy (EIS) plots of copper in 3.5% NaCl, sea water and magnetized sea water are similar. However, EIS plot of copper in magnetized sea water shifts rightwards due to the effect of magnetic field on sea water. The corrosion process of copper in magnetized sea water is pitting corrosion. The surfaces of samples are finer in magnetized sea water relative to those in 3.5% NaCl solution and sea water. The corrosion products of copper include large amount of Cu element, O element and Cl element. Cu₂O and CuCl₂ are the primary products. This suggests that electromagnetic treatment has remarkable effect on the corrosion of copper.

Corrosion of magnesium alloys is an important issue for their applications in automobile and aerospace industry. pH values as a function of time in two types of simulated occluded corrosion cells (OCC) for magnesium alloys AZ80 and AM60 were measured. The influence of mass ratio of solution to material or liquid to solid ratio (L/S ratio), initial pH value and chemical compositions of solutions on pH value in OCC was discussed. The experimental results show that pH value for magnesium alloys increases gradually or rapidly in Occ, depending on L/S ratio, initial pH value of solution and chloride ions concentration etc, and then reaches up to 10.5−10.6 and finally stabilizes at the level. The onset in the pH value time curve corresponds to the precipitate of magnesium hydroxide according to the theoretical calculation.

The phosphated hot-dip galvanized (HDG) sheets were post-sealed with sodium molybdate solution to improve the corrosion resistance of phosphate coatings. The morphology, chemical composition and corrosion resistance of the coatings were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Tafel polarization measurements and neutral salt spray (NSS) tests, and were compared with those of the single coatings. The results show that post-sealing the phosphated HDG steel with molybdate solution, the pores among the zinc phosphate crystals are sealed with molybdate films containing Zn, P, O and Mo, and the continuous composite coatings are formed. The suppression of both the anodic and the cathodic processes of zinc corrosion on the samples are enhanced significantly. The synergistic corrosion protection effect of the single phosphate coatings and molybdate films for zinc is evident. The corrosion resistance of the composite coatings increases with phosphating time up to 300 s.

The effect of stress ratio on fatigue crack growth (FCG) behavior of Ti40 alloy was analyzed. A unified approach, developed by VASUDEVAN and SADANANDA was used. The approach is based on the realization that fatigue requires two load parameters for unambiguous description. They are two fracture mechanics parameters: the maximum stress intensity factor K_max and the stress intensity amplitude ΔK. The results show that there are two mechanisms controlling the FCG behavior of Ti40 alloy. The curves of the two mechanisms in trajectory map are similar. They deviate to K_max axial more strongly compared with other titanium alloy, which indicates that Ti40 alloy is more sensitive to environment.

The effect of minimum and the maximum stresses on the fatigue behaviour of a 30 mm thick plate of a 7B04-T7451 (Al-Zn-Mg-Cu) subjected to a tensile pre-strain level of 2％ was investigated, including the fatigue crack growth (FCG) rate, microstructure observation, fractographic examination and fatigue S-N curve, etc. The results show that the characteristics of fatigue facture can be observed obviously under high cycle fatigue condition, and the higher the stress amplitude, the wider the space between fatigue striations, the faster the rate of fatigue crack developing and going into the intermittent fracture and the greater the ratio of the intermittent fracture area to the whole fracture area.

The Ni microcantilevers were fabricated by femtosecond laser. The corrosion behavior of the micro-sized Ni cantilever beams was studied by electrochemical noise and a newly developed fatigue testing method. The results show that the micro-sized specimens exhibit general corrosion behavior under the studied corrosion condition, whereas the ordinary-sized plates exhibit the localized corrosion behavior. The critical load amplitude of the micro-sized Ni specimens under corrosion fatigue status was determined to be 15 mN. The maximum bending loads, which were measured by fatigue tests, decrease gradually prior to final fracture. Corrosion fracture first occurs in the range of notch with a higher tensile bending stress, and exhibits clear evidence of trans-columnar fracture. The variation of maximum bending loads with time agrees with that creep deformation of the micro-sized Ni specimens can easily occur at room temperature, which implies that the micro-sized Ni specimens appear to have an improved resistance towards total crack as compared with the ordinary-sized Ni specimens.

The influence of pack ply-rolling process and heat-treatment on the texture characteristics of Ti-6Al-4V alloy sheets was investigated applying the EBSD technique. The tensile properties and fatigue properties of the sheets possessing different type textures were measured. The results show that the alloy sheets possessing single type texture (B or T) exhibit lower fatigue strength compared with the mixed texture (B/T). The sheet possessing basal texture exhibits isotropy and its elastic modulus and yield strength are lower than those under other conditions.

Viscous pressure forming (VPF) of aluminum alloy AA3003 sheet metal at warm temperature was investigated by using coupled thermo-elastoplastic-viscoplastic finite element method. The influence of viscous medium temperature distribution on sheet fracture location was studied and the distributions of fracture factor at different temperatures were obtained by using ductile fracture criterion. The results show that the failure of sheet metal varies with increasing initial temperature of viscous medium. When the initial temperature of viscous medium is near that of sheet metal, the failure location occurs at dome center, and when the initial temperature of viscous medium is too low, however, the failure location occurs at die corner. The occurrence of fracture can be postponed and even prevented through controlling the temperature distribution in viscous medium.

The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallographs of the tested material were also observed and analyzed. It is found that the increase of either pre-loaded stress or heating-rate decreases the failure temperature. Metallographic analysis shows that high heating-rate may cause stronger local thermal inconsistency (LTI) and remarkably increase the microdefects in the material, which may markedly degrade the macroscopic mechanical properties of the material.

Under impact load, using energy estimation and updated finite element method, the crack propagation of Mg-Li alloys was studied, and the relations between high speed impact, time interval and crack propagation velocity were deduced. The effects of impact pattern characteristic parameters such as impact range and time interval on impact fatigue crack growth and propagation rates were discussed. The results show that with the development of crack length, the crack propagation rate along the central sample alloy swiftly increases to the maximum. Then, the crack of other parts has different rate variations. The calculation and simulation results fit well with the experimental ones, which verifies the validity of energy estimation and updated finite element analysis. Impact loading usually induces materials and accelerates the fatigue crack growth.