Effect of minor Zr element on microstructure and properties of Fe-16Cr-2.5Mo damping alloys

The Fe-16Cr-2.5Mo damping alloy was microalloyed with different amount of Zr element ranging from 0% to 0.5%. In this study, the effects of the different amount of Zr on the microstructure, mechanical properties and damping property of Fe-16Cr-2.5Mo alloys were investigated. The results suggested that the mean grain sizes of the Fe-16Cr-2.5Mo alloys with 0%, 0.1%, 0.3% and 0.5% Zr addition were 440 μm, 285 μm, 155 μm and 98 μm, respectively. The grain refinement strengthening was caused by Zener pinning and it leaded to improving the strength and elongation of the alloys. In addition, the Fe-16Cr-2.5Mo alloy with 0.1% Zr amount exhibited an impact toughness of 296J, which was much higher than those (<12J) of the alloys with more Zr element or without. On the other hand, Zr (Fe, Cr)₂ or Zr carbide precipitations (>0.5 μm) formed in the alloys notablely, based on the results of TEM and EDX. The large precipitations were apt to establish the cleavage initiation sites, thus damaging the impact toughness of the alloy. The maximum internal friction (Q⁻¹) of the alloys fluctuated within 0.016–0.014 with the increase of Zr content at a low strain amplitude (9 × 10⁻⁶∼3 × 10⁻⁴). However, their damping properties are still marvelous.