Effect of Co/P micro-alloying on stress relaxation behaviour of Cu-15Ni-8Sn alloy

Abstract

To improve the stress relaxation resistance of the Cu-5Ni-S8n alloy, the effects of Co or P addition on its stress relaxation resistance were investigated by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction), X-ray diffraction, and high-temperature creep durability tester. The results revealed that the relaxation rate increased dramatically as the temperature rose. The thermal stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition; After 100 h of stress relaxation tests at 200°C or 250°C, the residual stress value of the Cu-15Ni-8Sn alloy increased by 23 MPa or 22 MPa with Co addition, which was associated with the consumption of vacancies by Co atoms and the pinning effect of Co atoms on dislocation. However, at 250°C, the stress relaxation resistance of the Cu-15Ni-8Sn-0.2P alloy was lower than that of the Cu-15Ni-8Sn alloy. This difference was due to the inclusion of P, which promoted the recrystallization reaction.

Article highlights

1. Recrystallization and the decrease of dislocation density are the major reasons for the stress relaxation of the samples.

2. The stress relaxation resistance of Cu-15Ni-8Sn alloy was significantly improved with Co addition.

3. The addition of the P element is not conducive to the improvement of thermal stress relaxation resistance.

KEYWORDS:

• Cu-15Ni-8Sn alloy
• cobalt or phosphorus addition
• thermal stress relaxation resistance
• discontinuous precipitation
• recrystallization

Author contributions statement

Yahui Gong: Conceptualisation, Methodology, and Writing – original draft. Chengjun Guo: Investigation, Writing – review and editing. Jian Huang: Methodology and Investigation. Yufan Shi: Investigation and Formal analysis. Xiangpeng Xiao: Conceptualisation and Writing – review and editing. Guihuan An: Data curation and Visualisation. Bin Yang: Formal analysis.

Data availability statement

The data presented in this study are available on request from the corresponding author.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Science and technology projects of Jiangxi Provincial Department of Education: [Grant Number GJJ210843]; Science and technology projects of Jiangxi Provincial Department of Education: [Grant Number GJJ200873]; The present work is financially supported by the National Natural Science Foundation of China: [Grant Number 51561008]; Scientific Research Starting Foundation for Advanced Talents of Jiangxi University of Science and Technology: [Grant Number 205200100570].