•Cold-drawn 316 steels with deformation twins show higher SCC susceptibility.•Cl degrades SCC resistance of solution-treated and especially cold-drawn steels.•Oxides containing higher Cr concentration (FeCr2O4) nucleate on the crack tip.•Fe-rich oxides (Fe3O4) form on the crack flank during the crack propagation.•Deformation twins activated by cold-drawing accelerate oxygen diffusion during SCC.The stress corrosion cracking (SCC) behavior of solution-treated and cold-drawn 316 austenitic stainless steels was investigated in simulated pressurized water reactor environment by slow strain rate tensile test. Both cold drawing and Cl addition in simulated primary environment can observably increase SCC susceptibility of 316 austenitic stainless steels. The oxides containing higher Cr concentration initially nucleate on crack tip, and then react with dissolved oxygen and H2O to form the Fe-rich oxides on crack flank during the subsequent crack propagation in abnormal water containing Cl. The deformation twins activated by cold-drawing provide paths to accelerate the oxygen diffusion during SCC.

The Ti–20V wt.% alloy containing a low level of oxygen plastically deforms via stress-induced ω phase transformation, while the same alloy with a high level of oxygen deforms via {3 3 2}〈1 1 3〉 twinning. The high level of oxygen suppresses stress-induced ω phase transformation. The high-oxygen Ti–20V wt.% alloy has a much lower Young’s modulus and high yield strength compared with the low-oxygen alloy. Oxygen plays a significant role in stress-induced ω phase transformation and {3 3 2}〈1 1 3〉 mechanical twinning, which governs the mechanical properties of βTi–20V wt.% alloys.

The coarsening and hardening behaviors of Cu-rich precipitates in Super304H austenitic steel aged at 923 K, 973 K, and 1023 K (650 °C, 700 °C, and 750 °C), respectively, have been investigated through measuring the particle size by transmission electron microscopy and microhardness. The results showed the Cu-rich precipitates have a cubic-to-cubic crystallographic relationship and coherent interface with the austenitic matrix during long-time aging, and that the coarsening behavior of the Cu-rich particles can be predicted with the help of the Lifshitz–Slyozov–Wagner theory. The activation energy for coarsening of the Cu-rich precipitates was evaluated to be 212 ± 3 kJ/mol. The coarsening of Cu-rich precipitates is controlled mainly by the volume diffusion of copper atoms in the austenitic matrix. The contributions to the maximum microhardness occurring at different aging temperatures from precipitation strengthening range from about 17 to 25 pct. The strengthening of the Cu-rich precipitates arises mainly from the coherency strain and partially from stacking-fault strengthening.

The present investigation of transmission electron microscopy reports the precipitation of nanosized and cubical-shaped incoherent Nb-rich MX at the coherent Cu-rich phases in the austenitic matrix of the Super304H steel. In addition, the nanosized Nb-rich MX phases were often observed to precipitate on dislocations during creep. It is concluded that the dense incoherent Nb-rich MX and coherent Cu-rich precipitates with a nanosized diameter contribute excellent creep resistance in the steel.

Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923–973 K and at applied stress of 190–210 MPa. The results show that the apparent stress exponent and activation energy in the creep deformation range from 16.2 to 27.4 and from 602.1 to 769.3 kJ/mol at different temperatures, respectively. These high values imply the presence of a threshold stress due to an interaction between the dislocations and Cu-rich precipitates during creep deformation. The creep mechanism is associated with the dislocation climbing governed by the matrix lattice diffusion. The origin of the threshold stress is mainly attributed to the coherency strain induced in the matrix by Cu-rich precipitates. The theoretically estimated threshold stresses from Cu-rich precipitates agree reasonably with the experimental results.

•Elastic constants of bcc Cu increase with increasing pressure.•Tetragonal shear modulus of bcc Cu increase with increasing pressure.•Critical pressure for mechanical stable of bcc Cu is 7.5 GPa.•Stability of bcc Cu precipitates is due to coherent constraint in ferritic matrix.The ground state properties, elastic constants and moduli and electronic structure of the bcc structured Cu under pressure were calculated by ab initio method based on the projector augmented wave pseudopotential and generalized gradient approximation. The results show that the elastic constants of the bcc Cu increase with increasing pressure. The tetragonal shear modulus C' also increases from negative to positive with increasing pressure and the critical pressure is about 7.5 GPa. The increase of the mechanical stability of the bcc Cu under pressure can be interpreted by the change of the electronic structure. Based on the calculated results, it can be concluded that the bcc structured Cu precipitates can be stabilized by the strain imposed by the constraint of coherency with the matrix of ferritic steels.

The structure and elastic property of nanosized complex oxide particles in a ferritic/martensitic alloy containing titanium and silicon were studied by transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). The nanosized complex Y–Si–O particles were found in the matrix of the alloy in addition to Y–Ti–O, and the size of Y–Si–O is smaller than that of Y–Ti–O particles. The formation of Y2.16Si1.76O7 and Y2.15Ti1.95O7 were further confirmed by O K, Si L2,3 and Ti L2,3 edges, respectively. The bulk modulus of Y2.16Si1.76O7 was shown to be lower than that of Y2.15Ti1.95O7, which implies that the nanosized Y2.16Si1.76O7 particles would provide more effective dislocation pinning at elevated temperatures.Highlights► Nanosized complex Y–Si–O particles in the ODS alloy in addition to Y–Ti–O. ► The size of Y–Si–O is smaller than that of Y–Ti–O particles. ► Formation of Y2.16Si1.76O7 and Y2.15Ti1.95O7 confirmed by O K, Si L2,3 and Ti L2,3. ► The bulk modulus of Y2.16Si1.76O7 is lower than that of Y2.15Ti1.95O7. ► Y2.16Si1.76O7 provides more effective dislocation pinning at elevated temperatures.

Corrosion behavior of a newly developed multifunctional β-type Ti–23Nb–0.7Ta–2Zr–O (mol%, TNTZO) alloy in Ringer's physiological solution was evaluated by open circuit potential, potentiodynamic polarization and X-ray photoelectron spectroscopy (XPS) techniques. Corrosion property of Ti–6Al–4V was also measured for comparison. The results showed that the TNTZO alloy possesses much better corrosion property than the Ti–6Al–4V alloy, corroborated by a high corrosion potential and broad passive region, which is attributed to the stable and inert passive TiO2 film modified by the oxides of Nb, Ta and Zr on the surface of the TNTZO alloy.

Serrated flow behavior of the AL6XN austenitic stainless steel has been investigated at different temperatures and strain rates. The results show the serrated flow, peak/plateau in flow stress and negative strain rate sensitivity appearing in tensile deformation of the AL6XN steel at 773–973 K and 3.3 × 10−5–3.3 × 10−3 s−1 (excluding 873 K, 3.3 × 10−5 s−1), suggesting the occurrence of dynamic strain aging (DSA). The activation energy for type-A and -(A + B) serrations was calculated to be 304 kJ/mol and diffusion of substitutional solutes, such as chromium and molybdenum is considered as the mechanism of serrated flow. TEM observations further revealed a typical planar slip mode in the regime of DSA of the deformed AL6XN steel.

The deformed microstructure and evolution of microstructure and texture during recrystallization of the cold-swaged multifunctional Ti-23Nb-0.7Ta-2Zr-1.2O (TNTZO, at. pct) alloy were investigated by optical microscope, electron backscatter diffraction, and transmission electron microscope. This alloy has been reported, by Saito et al., to possess a specific dislocation-free plastic deformation mechanism. In this study, the results show a curly grain or swirled structure and a pronounced fibrous \( {\left\langle {110} \right\rangle } \) texture along the swaging axis in the cold-swaged TNTZO alloy. The normal to the swirled grain surface is near \( {\left\langle {001} \right\rangle } \) in the cross section of the rod. This characteristic microstructure can be considered to arise from the plane strain deformation of the grains under applied stress, which is similar to that in ordinary bcc metals after heavily drawing or swaging. It is also shown that recovery involves the redistribution and partial annihilation of dislocations within the deformation bands, and recrystallization proceeds by a typical new grain nucleation-growth mechanism during annealing of the TNTZO alloy. The fibrous \( {\left\langle {110} \right\rangle } \) deformation texture is gradually replaced by random orientations with increasing annealing time. Thus, it could be concluded that the TNTZO alloy deforms by the traditional dislocation glide on \( {\left\langle {111} \right\rangle }{\left\{ {110} \right\}} \), {112}, or {123} slip systems, rather than the dislocation-free mechanism.