No abstract

TiC particles have been synthesized in common straight steels with three different carbon contents by in situ reaction during melting process. Experimental results show that the distribution of TiC particles in the steels containing 0.55 mass%C and 0.8 mass%C is uniform, however, slight segregation of TiC particles has been observed in the steel containing 1.4 mass%C. With the formation of TiC more ferrite precipitates from the steel with 0.55 mass%C, while the TiC formation inhibits the precipitation of secondary cementite in the steel containing 1.4 wt%C. In the present investigation a proper technique of heat treatment has been designed, after which good mechanical properties as well as high wear resistance have been obtained from the steel with TiC additions. However the effect of TiC addition on wear resistance is weakened with the increase of carbon concentration.

The microstructure and localized corrosion behavior of the 7050‐T6 Al alloys treated with different quench transfer time were investigated. Optical microscope observations show that the volume fraction of the recrystallized grains increases slightly with prolonging quench transfer time. Scanning electron microscope observations reveal that the stable η (MgZn2) phase nucleates and precipitates on grain boundaries in the process of transferring to quench. Further observations, using transmission electron microscope, found that the size, nearest neighbor distance, and copper content of the grain‐boundary precipitates increase with quench delay. As a result, the open‐circuit potentials and charge transfer resistance (Rt) of the alloys reduce with increasing transfer time, while the susceptibility to intergranular corrosion (IGC) and strength loss after exfoliation corrosion tests increase sharply. In addition, the IGC network appearance changes from large network to fine network structure, due to the different temperature range where very rapid η phase precipitation takes place between on grain boundaries and on sub‐grain boundaries.

No abstract

No abstract

No abstract

Mesoporous (MSU) Ce 0.5 Zr 0.5 O 2 mixed oxide with a high specific surface area has been synthesized under weak acidic condition in the presence of an anionic surfactant, sodium dodecylbenzenesulfonate. The effect of the pH value on the formation of mesostructure and the thermal stability of the material has been evaluated. The products were characterized by transmission electron microscopy, powder X-ray diffraction and nitrogen adsorption-desorption measurements. The results showed that the as-prepared Ce 0.5 Zr 0.5 O 2 mixed oxide possessed a specific surface area of 163.3 m 2 •g -1 , which had a cubic fluorite-type structure and possessed specific surface areas of 148.4 and 62.4 m 2 •g -1 after calcination at 500 and 800 ℃ for 2 h, respectively. The material showed excellent thermal stability.

No abstract