| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 87 === This research is to investigate the effect of improvement of the extrusion die, changes of process parameters and lubricant on the surface microstructure and mechanical properties of 2014 aluminum alloy. To reduce the surface recrystallized layer which was produced during extrusion is a critical requirement for the production of qualified aluminum alloy. Zero degree bearing angle of extrusion die and silicide lubricant are usually applied in traditional aluminum extrusion. The experimented results indicate that a 5* bearing angle for the die may significantly reduce the surface coarse-grain layer, and using BN for lubrication can obtain a good surface condition ofr the product. An improved surface layer after extrusion is due to the mechanism of recrystallization and grain growth. This study also shows that the recrystallization depends on the strain rate, and the grain size decresases as the strain rate increases. The coarse grain near the surface occurs when the finish temperature of extrusion is too high. The optimized process parameters, such as temperature and strain rate, are also suggested in this study to obtain an extruded aluminum alloy product with improved microstructure and mechanical properties.
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