Study on the creep properties of Cu-Se-(Te) alloys

Cu-Se-(Te) alloys have been melted in ZG-25 Vacuum Induction Furnace, and their creep properties are investigated by means of RDL Electronic Creep Relaxation Testing Machine at room temperature under a constant stress of 180 MPa. After that, the morphologies of samples before and after creep are observed via scanning electron microscope (SEM) respectively, meanwhile, EDS Mapping is employed to analyze the distribution of the element Se/Te and the composition of the second phases while Electron Back-Scattered Diffraction (EBSD) is used to confirm the existence of deformed twins after creep. Besides, the feature of tensile fracture surface is also characterized. Moreover, the hardness of copper matrix and the second phase is measured via CMM-20 Vickers tester separately. The results show deformation twins form in the process of creep of Cu-Se-(Te) alloys since the lower stacking fault energy of copper alloys exists and abundant dislocations incline to pile up on the twin boundaries and around the second phases. Therefore, both dislocation glide mechanism and twin mechanism are deduced to play a role. In addition, the content of Se and Te changes the characteristics including dimension, distribution, proportion and hardness of the second phases, which consequently affects the creep resistance and mechanical properties of the Cu-Se-(Te) alloys greatly. With the degree of dispersion, proportion and hardness of the second phases increasing, the interaction between the dislocations and the second phases is enhanced, resulting in an enhancement of the energy which the slip of dislocation needs to cut or bypass the second phase, and the resulting increase of the creep resistance of Cu-Se-(Te) alloys is extensive. Finally, the diversification of alloy elements also contributes to the improvement of creep resistance.