The effect of aging process on the microstructure and mechanical properties of a Cu-Be-Co-Ni alloy

摘要

The paper investigated the effect of two aging processes (i.e. normal aging and interrupted aging) on the micro-structure and mechanical properties of a Cu-Be-Co-Ni alloy. The results of tensile and Kahn tear tests showed that the interrupted aging (IA) process could significantly improve the uniform elongation and plane stress fracture toughness with tiny decrease in ultimate tensile strength, when compared with the results from normal aging (NA) process. Under the scanning electron microscope, the fracture surface of samples treated by NA followed the intergranular fracture, while that of the samples treated by IA followed the transgranular fracture. The transmission electron microscope study revealed the differences between the microstructure of the alloy treated by NA and IA processes. After the NA process, the slender strip of γ' precipitates aggregated at grain boundaries with a length of approximately 10 to 45 nm; the disk-shaped γ" precipitates in the alloy treated by IA distributed homogenously throughout whole grains with a length of about 3 to 10 nm. The discussion of strengthening mechanisms demonstrated that the mechanism of precipitate shearing by dislocations made a contribution to the strengthening of the alloy treated by IA, while the Orowan mechanism was the dominant strengthening mechanism in the alloy treated by NA.