The Effect Of Fe,Sn,Si Alloying Elements On The Damping Capacity Of Mn Cu-Al Based Alloys

The mechanism of damping degradation remains controversial in the previous investigations.The effect of Fe,Sn and Si alloying elements on the damping capacity of Mn-Cu-Al based alloys is not clear.Thus further investigations are needed.Mid-manganese?with 46.35-50.35 weight percentage manganese?Mn-Cu-Al based alloys were prepared by melting pure copper and manganese under an argon atmosphere in a vacuum induction furnace.During the melting process,the alloying elements,such as Fe,Sn and Si were also added.Differential scanning calorimeter?DSC?,X-ray diffraction?XRD?,transmission electron microscopy?TEM?,and torsional pendulum device were used to investigated the mechanism of damping degradation during the 120?aging process.The lattice distortion degree and the average inner stress were calculated from the XRD results to investigate the effect of Sn on the spinodal decomposition.The rate of stacking faults was obtained from the XRD results to demonstrate the effect of Si on the damping behavior and the damping mechanism.The damping degradation behaviors were fitted by using the decay function.The decay factors¹?are 1.94×10^-2 and 3.97×10^-22 for the Mn-Cu-Al alloy and the Mn-Cu-Al-1.5Fe alloy,respectively.The damping values tended to be stable at 0.034042 and 0.01875,respectively,after a long aging time.That 88.95%and 75.06%of the initial damping values,respectively for the Mn-Cu-Al alloy and the Mn-Cu-Al-1.5Fe alloy,were remained.The decline of FCT antiferromagnetic phase is contributed to the damping degradation.Otherwise,dislocations and precipitations also pin the boundaries of domains and twins.The added iron element retarded the spinodal decomposition.Thus the instability of FCT antiferromagnetic domains was enhanced.A faster decline of damping capacity was found in the Mn-Cu-Al-1.5Fe alloy.The Optimal damping values are 0.069 and 0.047 for the Mn-Cu-Zn-Al-1.0Sn alloy and the Mn-Cu-Zn-Al alloy,respectively.The damping improvement with the adding of Snare attributed to two main reasons.?1?Sn element enhances the instability of the supersaturated solid solution in the Mn-Cu-Zn-Al-Sn alloy,which expedites the spinodal decomposition.?2?The adding Sn element declines the coherent strain energy.Thus the spinodal decomposition was easier to process and more martensite twins were obtained.The optimal damping value are 0.084 and 0.037 for the Mn-Cu-Zn-Al-0.25Si alloy and the Mn-Cu-Zn-Al alloy,respectively.More stacking faults formed with the adding Si element.The stacking fault rates are 1.633 and 0.833 for the Mn-Cu-Zn-Al-0.25Si alloy and the Mn-Cu-Zn-Al alloy,respectively.The damping induced by the stacking faults were detected in the Mn-Cu-Zn-Al-0.25Si alloy.The synergistic effect of FCT martensitic twinning and the stacking faults contributed to a more superior damping behavior in the Mn-Cu-Zn-Al-0.25Si alloy.