Masing behavior in copper single crystals fatigued under load control

In a previous paper it was demonstrated that copper single crystals cycled under load control do not saturate in plastic strain once PSBs have nucleat ed. Thus, a powerful tool for describing and analyzing information from the stress-strain hysteresis loop is lost. This paper approaches the details o f the cyclic stress-strain response using Masing behavior as a tool for und erstanding the microstructural changes that prevent saturation from occurri ng. It is shown that under constant amplitude load control copper single cr ystals do not strictly exhibit Masing behavior. However, Masing behavior is observed in crystals that do saturate because the cycling conditions are n ot such as to lead to the nucleation of PSBs. This implies that the microst ructure is constantly evolving meaning, that the number of PSBs is increasi ng throughout life. The change in the microstructure is gradual and Masing behavior can be said to apply to the first degree. Under variable amplitude load control, however, copper single crystals exhibit Masing behavior if t he current load is lower than the previous load. This implies that the prev iously established microstructures are capable of supporting the deformatio n specified at the current load amplitude. (C) 2001 Elsevier Science B.V. A ll rights reserved.