The precipitating behavior of Cu-riched particles during isothermally aging and its effect on hardness and damping capacity of Fe-16Cr-2.5Mo-1.0Cu damping alloy have been investigated by atom probe tomography (APT) and scanning transmission electron microscopy (STEM). The results show that aging at temperature range from 400 °C to 700 °C has minor influence on grain size. During aging at temperature below 400 °C, the supersaturated Cu dose not precipitate out. While aging temperature is 450 °C, a relatively small number of Cu-riched particles can be observed and the particle radius is small (1.5 ± 0.56 nm). With a further increasing aging temperature, the Cu-riched particles increase to 3.21 ± 0.52 nm at 550 °C and further grow to 12.88 ± 2.02 nm at 700 °C. As compared with 450 °C, the particle number increases significantly at 550 °C, and then decreases at 700 °C. Due to the stable grain size and no precipitate, the hardness keeps constant below 400 °C. With a further increasing aging temperature, the hardness increases gradually and reaches peak value aging at 600 °C due to the increase of Cu-riched particle number. The damping capacity significantly depends on particle. Once there appear Cu-riched particles, the damping capacity decreases obviously. During aging, both hardness and damping capacity of the alloy can keep stable when temperature is below 400 °C.
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