High-temperature internal friction in a Fe–38 at.% Al intermetallic

A new sub-resonant inverted torsion pendulum has been used to measure the internal friction and dynamic modulus of an Fe–38 at.% Al alloy as a function of temperature from 600 to 1350 K and constant oscillating frequency ranging from 0.01 to 3 Hz. Two internal friction peaks and a background increasing exponentially with temperature were observed. Both peaks overlap and have different shifts to lower temperatures with decreasing frequency indicating different involved relaxation mechanisms. We measured the activation parameters of the main peak. Finally we applied a recently proposed model to remove the high-temperature internal friction background and perform a spectra de-convolution to find the parameters characterizing both relaxations. The mechanisms responsible for both relaxations are discussed.