Effects of Precipitation Hardedning in Co-Ni-Cr Alloy on Dissipative Motion of Dislocations by Amplitude-Dependent Internal Friction Measurements / Wpływ Utwardzenia Wydzieleniowego Stopu Co-Ni-Cr Na Rozpraszający Ruch Dyslokacji Badany Przez Zależne Od Amplitudy Pomiary Tarcia Wewnętrznego

Abstract

The effects of precipitation hardening occurring in a Co-Ni-Cr alloy after annealing treatments have been studied by using mechanical spectroscopy. The amplitude-dependent internal friction (ADIF) due to the dissipative motion of dislocations reveals the presence of a threshold strain for weakly pinned dislocations. The change of ADIF curves and the increase of the elastic modulus after thermal cycles producing precipitates suggest that dislocations motion is hindered leading to increasing strength of the material. Precipitation is confirmed by the changes of thermoelectric power (TEP) and by hardness measurements showing a hardness increase at the same temperature as the maximum in TEP curve. The ADIF spectra as well as the interaction between dislocations and precipitates are interpreted by proposing a phenomenological model based on the Granato-Lücke theory.