The present author has sometimes reported on the peculiar mechanical properties of extruded. Aluminium alloys. From these experiment reported here it is concluded that the pecurialities are mainly caused from the fibre structure of extruded materials. It will be inferred also that this fibre structure, which extruded materials possess, is produced in the stage of hot working among the extruding process, and can not of be distinguished by the solution heat-treatment. If another deformation process, such as forging or rolling, is applied, the recrystallization temperature is lowered, and then the cxcellent properties disappear by the solution heat-treatment.
This inference on the relation between the peculiar properties and the fibre structure is reinforced by the knowledge of the relation between the mechanical properties and the orientation of crystal observed by Karnop.and Sachs.
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