Effect of Cu content on microstructure and properties of Fe-16Cr-2.5Mo damping alloy

Five Fe-16Cr-2.5Mo damping alloys with different Cu contents (0%, 0.25%, 0.5%, 1.0% and 2.0%) were prepared. The microstructure was observed by scanning transmission electron microscopy (STEM) and the damping behavior was measured by using a dynamic mechanical analyzer (DMA). The results show that the grain size of experimental alloy with (0.25-1.0%) Cu was refined compared with the 0Cu alloy. The Cu element is fully dissolved in the matrix and there are no Cu precipitates and carbides observed. Although the internal stress increases because of Cu addition, the damping capacity of the 0.5Cu and 1.0Cu alloys has been significantly improved. The reason of damping improvement is that the magnetic domain structure is strongly modified. Meanwhile, the strength was improved gradually due to the Cu solid solution strengthening and grain refining. In the 2.0Cu alloy, lots of Cu-riched particles appeared in the matrix. These Cu precipitates with 10-15 nm in size are spherical and homogeneously distributed, which strongly induce strength improvement through precipitation strengthening. On the contrary, the elongation and impact energy of the 2.0Cu alloy decrease sharply. In addition, lots of Cu precipitates will significantly decrease the damping capacity by hindering the mobility of domain walls.