ABSTRACT
In this work, the as-cast directionally solidified (DS) Fe-B alloys with various Si contents and different boride orientation were designed and fabricated, and the as-cast microstructures and static oxidation behaviors of the DS Fe-B alloys were investigated extensively. The as-cast microstructure of the DS Fe-B alloys consists of the well-oriented Fe2B columnar grains and α-Fe, which are strongly refined by Si addition. The oxidation interface of the scales in the DS Fe-B alloy with 3.50 wt.% Si demonstrates an obvious saw-tooth shaped structure and is embedded into the alternating distributed columnar layer structures of the DS Fe-B alloy with oriented Fe2B and α-Fe matrix, which is beneficial to improve the anti-peeling performance of the oxide film compared with lower amounts of Si addition in DS Fe-B alloys with oriented Fe2B [002] orientation parallel to the oxidation direction (i.e., oxidation diffusion direction, labeled as Fe2B// sample). In the DS Fe-B alloys with oriented Fe2B [002] orientation vertical to the oxidation direction (i.e., labeled as Fe2B⟂ sample), due to the blocking and barrier effect of laminated-structure boride, Si is mainly enriched in the lower part of the oxide film to form a dense SiO2 thin layer adhered to layered boride. As a result, the internal SiO2 thin layer plays an obstructed and shielded role in oxidation of the substrate, which hinders the further internal diffusion of oxygen ions and improves the anti-oxidation performance of the Fe2B⟂ sample, making the average anti-oxidation performance better than that of the Fe2B// sample.
ABSTRACT
In order to investigate the effect of Si content on the microstructures and properties of directionally solidified (DS) Fe-B alloy, a scanning electron microscope (SEM) with an energy dispersive spectrum (EDS), and X-ray diffraction have been employed to investigate the as-cast microstructures of DS Fe-B alloy. The results show that Si can strongly refine the columnar microstructures of the DS Fe-B alloy, and the columnar grain thickness of the oriented Fe2B is reduced with the increase of Si addition. In addition, Si is mainly distributed in the ferrite matrix, almost does not dissolve in boride, and seems to segregate in the center of the columnar ferrite to cause a strong solid solution strengthening and refinement effect on the matrix, thus raising the microhardness of the matrix and bulk hardness of the DS Fe-B alloy.
ABSTRACT
OBJECTIVE: In order to provide help for preoperative assessment of cochlear implantation, related dissection of temporal bone was conducted guided by high resolution computerized tomography (HRCT) in accordance to the main steps of cochlear implantation, and was compared to HRCT measurements on a viewing workstation. METHOD: Six temporal bones were dissected according to the main steps of cochlear implantation and scanned in axial and semilongitudal planes by HRCT to observe the relationship between anatomy and HRCT. RESULT: The width of facial recess in dissection was (3.13 +/- 0.34) mm at the level of round window, and (4.12 +/- 0.44) mm at the level of oval window. The width of facial recess in HRCT was (3.20 +/- 0.38) mm at the level of round window, and (4.14 +/- 0.47) mm at the level of oval window. The whole course of facial nerve was visualized clearly in semilongitudal plane. No statistically significant differences were found between the results of dissection and HRCT. CONCLUSION: The distance in axial between facial nerve and posterior wall of external auditory canal and the distance from facial nerve to round window in semilongitudal plane are the most important parameters which reflect the position of facial nerve. The vertical portion of facial nerve, posterior wall of external auditory canal, round window are important measurement landmarks. Related preoperative measurements of cochlear implantation by HRCT can help to guide clinic surgery.
