Kazutomo Oyama1, Chosei Ueda2 and Osamu Izumi1
1The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai
Structures were investigated on the specimens of copper and copper-10∼40 wt% zinc alloys exttruded at various temperatures up to near solidus using the ``Dynapak'' machine.
Compared with the case of slow speed hot-extrusion, in which the working strain is simultaneously relaxed by recrystallization during deformation, the process of high speed hot-extrusion seemed rather similar to that in the case of cold-working. The material became to flow more uniformly with decreasing zinc content and with rising working temperature. The non-uniformly distributed ``Shear markings'' were observed in the extruded rods of the alloy specimen, and were sometimes developed to crack formation. In the region of the residual billet of the alloy specimen, the band-like ``Strain markings'' were observed. The markings developed differently with zinc content and working temperature: that is, they developed more remarkably in the specimen of higher zinc content and became widely spaced twin-like bands after deformation at elevated temperatures. An abnormal twin-structure, thought to relate to the formation of stacking-fault, was observed in the 70:30 brass billet deformed at 850°C. The extrusion at a high temperatures near solidus resulted in the failure of rods due to local melting by heat-generation. Two-phase alloy of 60:40 brass revealed a complex structure due to the phase change. Preferred orientations of the cold-extruded rods were also compared.
Please do not copy without permission.