Characterization of the hot-working behavior of a Cu-Ni-Si alloy

Cu-Ni-Si alloys and their variants constitute very important engineering materials, which have found a number of applications in different fields, as potential substitutes of the toxic Cu-Be alloys traditionally employed for the manufacture of different parts and components. However, the hot-working behavior of these materials has not been deeply investigated and only few studies have reported some limited information regarding the relationship between flow stress and deformation conditions. The present communication reports the main findings of an original investigation aimed at analyzing in detail the flow stress, work-hardening and work-softening behavior of a Cu-Ni-Si alloy deformed in the temperature range of 600 °C to 950 °C, at nominal strain rates in the range of 0.1-10 s−1. Particularly, for the first time, a general constitutive formulation able to describe the changes in flow stress, work-hardening and work-softening rates of this material as a function microstructure and deformation conditions, in the temperature range between 800 °C and 950 °C, is proposed. The nature of the constitutive description here advanced allows the computation of the flow stress either under constant and transient loading conditions, on the basis of physically-based and well established models. Such a constitutive formulation is able to reproduce the experimental values of the experimental flow stress with an accuracy of ±7 MPa and therefore, it represents a valuable tool for modeling hot-working operations conducted on this material. It has been concluded that, in order to take full advantage of the grain refining effects associated with dynamic recrystallization, hot-working of the alloy should be carried out at temperatures above 850 °C. Deformation at temperatures below 800 °C leads to a significant increase in the mechanical properties of the alloy and even fracture, as a consequence of the possible precipitation of fine secondary phases.