INFLUENCE OF PROCESSING PARAMETERS ON TEXTURE AND MICROSTRUCTURE IN ECAP'ED ALUMINUM

摘要

The influence of die relief angle, backpressure and number of passes on texture and microstructure during equal-channel angular pressing (ECAP) of commercially pure aluminum has been studied. Material was processed using a 90° die and examined by orientation imaging microscopy (OIM) after the initial pressing operation and after four passes by route A. Highly refined (sub)grain structures are achieved irrespective of die relief angle and backpressure but both microstructures and textures are inhomgeneous after the initial ECAP pass. The OIM data indicate that the distortion during ECAP generally corresponds to idealized ECAP especially when pressing with backpressure. ECAP textures comprise prominent shear texture components and high-angle boundaries are generally interfaces between particular shear texture components. A large (90°) die relief angle leads to spreading of shearing through a fan-shaped region at the die channel intersection and shear texture components that align with the fan. Backpressure suppresses this tendency and results in textures corresponding more nearly to idealized ECAP.