The influences of Si and Fe upon the extrusion-characteristics of duralumin was examined by X-ray diffraction method and obtained following results : (1) The structure of extruded bars is fibrous one in general, but the details of the structure such as orientation,degree of fibrousness etc.,varies according to its locality of the bars ; tail or middle part,centre or outer layer and shows more or less different structure.(2) Though extruded bars containing 1%Fe or 1.5%Si as the impurity always show fibrous structure,and the structure becomes rather unstable when the impurity percentage exceeds the above figures.(3) Comparing the effect of Fe and Si to the degree of fibrousness,the former affects more vigorously than the latter,that is,the existance of Fe is more affection able to prohibit the development of the fibrous structure.(4)The fibrous structure of extruded bars disappears by heating.The larger the content of Fe,the higher its disappearing or annealing temperature becomes.On the contrary,the larger the content of Si,the lower the temperature becomes. (5) The fibre axis changes its direction by adequate hetatreament ;i.e.,the fibre axis .,which is the common axis when the specimen was in the state of asextruded and coincides to the direction of the axis of the bar,changes to  by moderate heating.This will be very interesting result though the experiments relating to this point are not yet sufficient.
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