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The grain boundary character distributions of TP347H stainless steel after different thermo-mechanical processes in terms of grain boundary engineering (GBE) were investigated by EBSD. DL-EPR and e...

The grain boundary (GB) network of a GB-engineered 304 stainless steel was investigated in three dimensions. The GB-engineered sample had a high proportion of twin-related boundaries (∼70%). Howeve...

Stress corrosion cracking (SCC) behaviours of Z3CN20-09M stainless steel in high temperature water containing Cl− were studied. The results indicated that SCC sensitivity was inconsistent with test temperature. The minimum and maximum of SCC sensitivity occurred at 320 and 290°C respectively, and SCC sensitivity at 250°C fell between them. SCC crack initiated preferentially at bottom of corrosion pit or along phase boundary between austenite and ferrite, and its propagation depended on relative orientation to the phase boundary. SCC crack parallel to the phase boundary propagated along the phase boundary, while that perpendicular to the phase boundary was hindered to propagate.

In order to study the effect of the phase boundary between austenite and ferrite phases on the nucleation and propagation behaviours of microcracks in nuclear grade Z3CN20-09M stainless steel, an in situ scanning electron microscopy (SEM) tensile technique was used to study the deformation, nucleation and propagation of microcracks during tension. The fractography was subsequently observed by SEM. The results indicated that, during tension, the deformation first occurred in the austenitic grains followed by in the ferrite, and the microcracks were subsequently preferential formed at the phase boundary between austenite and ferrite phases. In the case of the phase boundary perpendicular to the loading direction, microcracks nucleated and subsequently propagated along the phase boundary. In the case of the phase boundary parallel to the loading direction, microcacks nucleated at the intersection of slip bands and the phase boundary and propagated perpendicularly to the phase boundary, resulting in d...

TiBxNy thin films with different N contents were deposited using unbalanced magnetron sputtering at room temperature. Their structure, phase composition, hardness and dry sliding behaviour were investigated by X-ray diffraction, X-ray photoelectric microscopy, microindentation, pin on disc and scanning electron microscopy. The results indicated that the phase composition in TiBxNy thin films strongly depended on N content. Nanocrystalline (nc-) TiN was preferentially formed with incorporation of N into TiB0·65 till its mole fraction reached a maximum at ∼37 at.-%N. BN was promoted to be formed with further increasing N content. Both friction coefficient and wear rate strongly depended on phase composition rather than hardness. The friction coefficient was increased with increasing N content till its maximum, accompanying with the least amount of deformed wear debris, was achieved at the mole fraction maximum of nc-TiN. A decrease in friction coefficient was followed after formation of BN, accompan...

The stress induced martensitic transformation and the relationship between it and the nucleation and propagation of cracks in the Cu-Ni-Al shape memory alloy were investigated through in situ tensile tests by SEM and TEM. The results indicated that the stress concentration ahead of the crack tip could induce formation of stacking faults and different types of martensites. Transmission electron microscope observations showed that the martensites could transform from one type to another type and even reversely to parent during loading. The microcracks nucleated along the martensite/parent interface and intersections between two martensites. When the crack propagated a certain distance, the stress concentration ahead of the crack tip was large enough to result in formation of slip bands, in this condition the microcrack nucleated along slip bands more easily.

The deformation and fracture behaviours in fully lamellar TiAl alloys were investigated by unixial compression and an in situ TEM technique. The results indicated that the deformation and fracture behaviours in fully lamellar TiAl alloys were closely related to the relative orientation of the lamellae to the loading axis. When the lamellae were parallel to the loading axis, the slip in the α2 phase occurred along its prism plane, and microcracks nucleated preferentially along its prism plane. When the lamellae were perpendicular to the loading axis, slip became difficult, slip in the α2 phase occurred along its pyramidal plane, microcracks nucleated and propagated preferentially along its lamellar interface.