EXPERIMENTAL RESEARCH ON THE EFFECT OF ANNEALED TREATMENT ON MICROSTRUCTRUE AND MECHANICAL PROPERTIES OF PURE COPPER

The effects of annealed treatment on the microstructure and mechanical properties of pure copper were investigated by using X-ray diffraction (XRD), optical microscopy, hardness test, tension and fatigue tests, and scanning electron microscope (SEM) methods. The effect of surface topography for fatigue life was studied. Observation of fatigue crack propagation was operated using notched specimens. The quantified results of crack growth rate and the relationship between roughness and fatigue life were obtained. The results show that the microstructure and mechanical properties changed after the annealing. Firstly, the diffraction peaks became narrow and the grains became larger. Secondly, the tensile strength, elasticity modulus, Vickers hardness (HV) and fatigue strength of annealed pure copper were significantly decreased. Lastly, the sensitivity of fatigue life on roughness became lower, and the fatigue crack initiated earlier and propagated faster.