Mechanism of heat-induced damping attenuation for Fe-added Mn-Cu-Al alloys

The thermotolerance is of great importance for Mn-Cu damping alloys. However, the excessive relaxation behavior of spinodal face- centered cubic (FCC) phases in some thermal environments weakens the kinetics of phase transition from face-centered cubic phase to face- centered tetragonal (FCT) phase, and consequently lower the damping capacity of the alloys. The composition of Fe is regarded as a stabilizing element for FCC phases, but little is known about the role of Fe on the relaxation performance of FCC phases at higher temperatures. The phase structure of the Mn-Cu-Al and Mn-Cu-Al-Fe alloys was analyzed using X-ray diffraction. And their precipitates were observed by using a scanning electron microscopy (SEM) and transmission electron microscope (TEM). Our results show that the excessive relaxation performance happens after holding from 128 to 256 h at 120 degrees C. As a result, the amount of FCT phases are decreased and the internal friction has a distinct drop in the meantime. On the other hand, to some extent, the addition of Fe restrains the excessive relaxation performance of the FCC phases. The findings may be helpful for elucidating the mechanism of the heat-induced damping attenuation and promoting the industrial applications of the Mn-Cu alloys.