Study on Stress Relaxation Resistance and Microstructure Evolution of Cu-Ni-Si Alloy Strip

Abstract

The stress relaxation resistance of a Cu-Ni-Si alloy strip after 48 h of initial loading stress of 80% s0.2 at 125 °C was studied. The stress relaxation curve was fitted using the quadratic delay function exponential model. Utilizing EBSD, TEM and other methods, the study examined the microstructural changes in the Cu-Ni-Si alloy strip both before and after stress relaxation. The study obtained the stress relaxation mechanism of the alloy. The study reveals that the Cu-Ni-Si alloy strip exhibits a stress relaxation rate of 10.82% after 48 h at 125 °C. The stress relaxation process of the alloy strip is mainly divided into two stages. During the first stage, there is a significant rearrangement and movement of dislocations within the alloy strip, leading to a rapid decline in remaining stress. In the second stage, the interaction between Ni2Si phase, twins and dislocation leads to the slow decrease of remaining stress. After the stress relaxation of the alloy strip, the growth of the precipitated phase in the microstructure increases from 67 nm to 200 nm, the recrystallization microstructure increases from 57.91% to 62.42%, and the twin boundary content decreases from 22.1% to 18.5%. These observed alterations in the microstructure are expected to further diminish the stress relaxation resistance of the alloy strip.

Keywords: Cu-Ni-Si alloy；Stress relaxation；Microstructure；Effect mechanism