An examination of microstructural evolution in a Cu-Ni-Si alloy processed by HPT and ECAP

Experiments were conducted to evaluate the evolution of hardness and microstructure in a commercial Cu-2.5Ni-0.6Si alloy (in wt%) after processing using High-Pressure Torsion (HPT) at room temperature with an imposed pressure of 6.0 GPa and Equal-Channel Angular Pressing (ECAP) at 423 K using a channel angle of 135°. Hardness measurements, X-ray diffraction and transmission electron microscopy (TEM) were used for microstructural evaluation and the results show a general consistency between these various techniques. The changes in the crystallite size and the dislocation structure as a function of the number of HPT revolutions and ECAP passes are discussed and compared with the results of the TEM observations. The detailed microstructural observations show a gradual evolution with increasing numbers of revolutions and passes with a saturation after 3 turns of HPT but with no saturation attained in ECAP even after 12 passes because of the lower imposed strain.