Materials Science Forum Vol. 749

Abstract: Local electrochemical technique was used to measure the impedance of austenite in AISI 304 stainless steel under tensile strain of 0%, 10%, 20%, 30%, 40%. Scanning Kelvin probe (SKP) technique was used to measure the potential distribution of the surface. The results showed that the impedance of the austenite declined with the increase of the strain and declined sharply under the strain of 30%. Potential of austenite decreased non-monotonously with increase of the strain. The potential reached the minimum under strain of 30% and then increased. Through the transmission electron microscope (TEM) results, plane dislocation pile-ups were observed in the grain boundary under the strain of 30% and transformed to cellular substructure structure and cell wall under 40%. Combined with the results of local electrochemistry impedance spectroscopy (LEIS) and surface potential, it may be concluded that it was the dislocation density and dislocation structure influence the impedance spectroscopy significantly, while surface potential was sensitive to the dislocation structure.

Abstract: Nitrogen-doped TiO₂ nanotubes (N-TNTs) were fabricated on the titanium foil by anodic oxidation and followed by annealing at NH₃ environment. Highly ordered nanotubes, roughly 150 nm in the diameter and 20 μm in the length, were synthesized on the titanium foil. By controlling oxidation voltage, the thick TiO₂ nanotubes were peeled off from the titanium substrate. In one step annealing at NH₃ environment, nitrogen replaced oxygen and doped into TiO₂, but anatase phase was formed.

Abstract: The Phase Field model of solidification processes was carried out coupled with temperature field model. The influence of interface atomic time on dendrite growth morphology in undercooled melt was simulated with pure nickel. The experimental results show that when the interface atomic motion time parameter is minor, the liquid-solid interfaces were unstable, disturbance can be amplified easily so the complicated side branches will grow, and the disturbance speed up the dendrite growth. With the increase of , the liquid-solid interfaces become more stable and finally the smooth dendrite morphology can be obtained.