Influence of choked angle of bearing channel on profile grain structure during multi-hole extrusion of aluminum alloy

Direct extrusion of aluminum alloy EN AW-6060 was carried out applying a four-hole die with pair-wise parallel and choked long channels. Due to the dissimilar friction inside parallel and choked channels profiles with different length were extruded simultaneously. In order to investigate the grain structure evolution along the whole extrusion process, multiple sections from the beginning to the end of the products were analyzed. Macroetch tests revealed unrecrystallized fibrous, fully recrystallized as well as partially recrystallized grains. The results also showed an axial and radial grain structure variation. At the beginning of the extrudates unrecrystallized fibrous microstructure was observed, while a fully recrystallized structure characterized the end of the products. Additionally, finer grains were present at the surface, whereas coarser grains were found in the center of the extrudates. Finally, numerical simulations allowed estimating the temperature, strain and strain rate evolution along the whole product length. Thus, a correlation between the extrusion parameters, deformation conditions and the grain structure was obtained

Influence of temperature and sliding speed on the subsurface microstructure evolution of EN AW-6060 under sticking friction conditions

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1896, 140012 (2017) and may be found at https://doi.org/10.1063/1.5008168.The microstructure evolution of the friction boundary layer of the aluminum alloy EN AW-6060 was investigated. Sticking friction tests at different temperatures and sliding speeds were carried out. A severe deformation below the friction surface was observed by means of LOM and EBSD mapping. Thus, the thickness variation and the grain structure of the high deformation zone could be described. Fibrous structure was observed at 300 °C and 400 °C, while equiaxed grains with high misorientation angle (>15°) were generated at higher temperatures. Additionally, abnormal grain growth and coarse grains were detected at high sliding speeds (10 mm/s, 42 mm/s) at 450°C and 500 °C respectively

Nickel-hydrogen separator development

The separator technology is a critical element in the nickel-hydrogen (Ni-H2) systems. Previous research and development work carried out at NASA Lewis Research Center has determined that separators made from zirconium oxide (ZrO2) and potassium titanate (PKT) fibers will function satisfactorily in Ni-H2 cells without exhibiting the problems associated with the asbestos separators. These separators and their characteristics were previously discussed. A program was established to transfer the separator technology into a commercial production line. A detailed plan of this program will be presented and the preliminary results will be discussed