The effect of creep on stress corrosion cracking (SCC) was studied by measuring crack growth rates (CGRs) of 30% cold worked (CW) Alloy 690 in supercritical water (SCW) and inert gas environments at temperatures ranging from 450 °C to 550 °C. The SCC crack growth rate under SCW environments can be regarded as the cracking induced by the combined effect of corrosion and creep, while the CGR in inert gas environment can be taken as the portion of creep induced cracking. Results showed that the CW Alloy 690 sustained high susceptibility to intergranular (IG) cracking, and creep played a dominant role in the SCC crack growth behavior, contributing more than 80% of the total crack growth rate at each testing temperature. The temperature dependence of creep induced CGRs follows an Arrhenius dependency, with an apparent activation energy (QE) of about 225 kJ/mol.

TiB whiskers and TiC particles reinforced Ti-6Al-4V composites (TMCs) were synthesized by in situ method and then extruded with different extrusion ratios (λ=7, 10 and 16) at 1258 K. The effects of extrusion ratio on the microstructural evolution and mechanical behavior have been systematically investigated. The room temperature tensile results indicate that the strength, elastic modulus and ductility of the TMCs are simultaneous to be improved after extrusion. With the increase of extrusion ratio, the yield strength of the TMCs increases and the fracture strain of the TMCs decreases, respectively. Meanwhile, the elastic modulus almost keeps as a constant during the extrusion process. The mechanical properties of the TMCs are found to be determined by the interplay of reinforcements and the metal matrix. With the increase of extrusion ratio, the aspect ratio of TiB whiskers decreases from ~4.3 to ~3.5. Nevertheless, the volume fraction of dynamic recrystallization of the matrix shows positive correlation with the extrusion ratio. It is up to about 72% of dynamic recrystallized grains at the extrusion ratio of 16. EBSD and TEM observations are used to study the texture evolution during extrusion process, which indicate that the type of the deformation texture is similar with the recrystallization texture, while its intensity is higher than the latter one.

The fracture toughness of two types 316LN welded joints in different orientations at 300 K and 623 K in air was investigated. The tests were conducted using single specimen method, where J-R curves and fracture toughness values (J0.2) were obtained. Microstructure of the specimens were characterized before and after the test. Results show that 2GT welded joint exhibits higher toughness as compared to 5GT welded joint, and orientation has slight effect on the fracture toughness. Moreover, the fracture toughness drops remarkably with the increase of temperature.

(TiB + TiC)/TC4 composites reinforced with different amounts of TiB whiskers and TiC particles are produced by common casting and hot forging technology. Then the fracture toughness of (TiB + TiC)/TC4 composites is analyzed by experiment and modeling. The experimental results indicate that not only reinforcement volume fraction but also the mole ratio between TiB whiskers and TiC particles can influence the fracture toughness of (TiB + TiC)/TC4 composites. Microstructure observations are carried out to examine the behavior of TiB whiskers and TiC particles in the fracture process. An analytical expression for predicting the fracture toughness of (TiB + TiC)/TC4 composites is built up. In particular, the coupling influences of TiB whiskers and TiC particles on the elastic modulus, yield strength, and fracture strain of TMCs are revealed in the modeling process. The results indicate that when TiB and TiC particles are coexisting in the TMCs, the fracture toughness of (TiB + TiC)/TC4 composites increases with the increase of the TiB whiskers aspect ratio, TiC particles volume fraction and size; however, with the increase of TiB whiskers volume fraction, the fracture toughness decreases. The breakage of TiB whiskers is the main reason for the fracture of TMCs. The acting mechanism of TiC particles on the fracture of TMCs transfers from blocking crack propagation and interfacial debonding to breakage with the increase of size, which can decrease the fracture toughness of (TiB + TiC)/TC4 composites. Considering the broken fraction of TiB whiskers, the fracture toughness of (TiB + TiC)/TC4 composites can be reasonably predicted.

•We evaluated the corrosion resistance of three different Cr content ODS steels at 650 °C in supercritical water.•Corrosion behavior of ODS steels is rarely reported and ODS steel may be promising material for generation IV reactors.•We found total opposite phenomenon compared to Lee's work before. Our result may be more reasonable.The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer.