Role of solidification texture on hot deformation behavior of a Cu-Ni-Si alloy with columnar grains

Hot deformation behavior of an as-cast Cu-Ni-Si alloy with columnar grains in terms of flow stress, constitutive equation, processing map, microstructure evolution, and dynamic precipitation was investigated at deformation temperatures of 500 degrees C-800 degrees C and strain rates of 0.01 s(-1)similar to 1 s(-1). The results revealed that the true stress-strain curves of the as-cast Cu-Ni-Si rods exhibit continuously increased flow stresses. The relationships between the material parameters and strains were then modified by fourth power polynomial functions. Good fitness between the material parameters and strains was obtained. The constitutive equation derived using these relations predicts quite accurate values. Microstructure observed by confocal laser scanning microscopy, electron backscattered diffraction, and transmission electron microscopy indicated that the main hardening mechanisms of the continuously increased flow stress are attributed to the progressively occurred dynamic recrystallization and dynamic precipitation. The dynamic precipitates, unlike in the aged alloys, are very fine and have multiple orientation relationships with the Cu matrix, which is likely linked with the change of edge-on habit planes due to the plastic deformation and temperature imposed. It has also been found that the processing map developed is also dependent on the strain selected. The processing maps developed at low strains contain larger instability regions than those developed at high strains, which agree with the results of microstructure observations.