Influence of constant magnetic field on fatigue life of diamagnetics: the role of the Zeeman effect in the fatigue strength of non-ferrous metals

Background. The relevance of the study is due to the need to study the effect of constant magnetic fields on the fatigue life of commercially pure copper and lead, widely used in industry and sensitive to magnetic effects, which will improve the reliability of products and control their mechanical properties. The purpose of the work is to study the effect of a constant magnetic field with an induction of 0.1-0.5 T on the fatigue life of commercially pure copper and lead. Materials and methods. Samples of commercially pure copper grade M1 and lead grade C2 measuring 4 × 12 × 130 mm were manufactured by electrical discharge cutting on a CNC machine. Fatigue tests were carried out on a setup with cyclic asymmetric cantilever bending at a temperature of (~ 300 K). The mode with a loading amplitude of 2.5 mm was selected. The fracture surface was studied by scanning electron microscopy (KYKY EM6900) with structure analysis in ImageJ, and the elemental composition was studied using Ultim Extreme. Results. The fatigue test results showed that the magnetic field increases the fatigue life of copper M1 by 9–28% and lead C2 by 7% at 0.3 T, but reduces it at 0.4–0.5 T; copper fracture occurs through three zones with the formation of a subgrain structure, while in lead the magnetic field changes the fracture morphology and the fracture mechanism. The Zeeman effect, causing splitting of the electron energy levels, changes the activation energies of dislocation motion in diamagnetic metals, which affects their sliding speed and mechanical properties. Conclusions. 1 The magnetic field (0.1–0.25 T) increases the fatigue life of copper by 9–28%, affecting the fracture mechanism through the formation of a subgrain structure. 2 A magnetic field of 0.3 T increases the fatigue life of lead by 7%, while at 0.4–0.5 T it significantly reduces it due to the effect on dislocation mobility and fracture morphology. 3 The Zeeman effect changes the electronic structure of diamagnetic metals, changing the activation energies of dislocation motion and their slip velocity, which affects mechanical properties.