Martensitic Transformation And Damping Characteristics Of Fe-mn Based Damping Alloys

Fe-Mn based alloys have attracted much attention for many years due to their high damping capacity,good mechanical properties,and commercial importance.In this paper,microstructure,martensitic transformation behavior,mechanical properties and damping properties of Fe-17Mn-xNb?x=0,0.1,0.5,1,2,4 wt%?alloys were tested by scanning electron microscopy,transmission electron microscopy,X-ray diffraction,differential scanning calorimetry,electronic universal material testing machine and dynamic thermal mechanical analyzer.The effects of Nb on the microstructure and properties of Fe-Mn based alloys were systematically investigated and analyzed.The result was shown that,at room temperature,the microstructures of solid solution and hot-rolled Fe-Mn based alloys were composed of?martensite and?austenite.The microstructure of Fe-Mn based alloy is obviously refined by the addition of Nb.Addition of proper amount of Nb element is beneficial to the increase of volume fraction of?martensite and can refine the martensite lath.Besides?and?phases,a large amout of fine precipitations present due to the addition of Nb.They are determined to be Fe₂Nb by means of XRD and TEM,the amount of which increases with increasing Nb content.The phase transition behavior analysis show that the???martensitic transformation and the???martensitic reverse transformation occur in the Fe-Mn-Nb alloys during the heating and cooling processes respectively.The addition of Nb element decreases the phase transition temperature slightly,and the hysteresis of phase transformation becomes larger as the Nb content increases.With the increase of the number of thermal cycles,the martensitic transformation temperature of the alloy decreases,but the reverse transformation temperature increases;the addition of appropriate amount of Nb element will improve the thermal cycling stability.With the increase of Nb content,the yield strength and the microhardness of Fe-Mn-Nb alloys all show an increasing trend.The tensile strength and elongation of the solid solution2Nb alloy are about 950MPa and 18.5%respectively,mainly because the distribution of Fe₂Nb phase in 2Nb alloy is more even and dispersed.Hot rolled 4Nb alloy possesses the highest yield and tensile strength of about 715 MPa and 1038 MPa,respectively,while the elongation is relatively low,which is due to the large content of Nb and the uneven distribution of Fe₂Nb hard precipitates.During the continuous heating,Fe-Mn-Nb alloy showed a damping peak.The damping peaks of solid-solution and hot-rolled alloys increase first and then decrease as the content of Nb increases,and The alloys in the two treatment states reach the maximum values of Tan?=0.095 and Tan?=0.094,respectively,in the 1Nb alloy.The damping peak is caused by the reverse phase transformation of???martensite.The results of this study show that the refinement of?martensite laths and the content of Fe2Nb precipitates in the alloy are the main factors that improve the damping performance of Fe-Mn-Nb alloys.The refinement of?martensite laths increases the number of damping-related interfaces and the proper amount of Fe2Nb hard precipitates increases the energy consumption when the interface moves,and thus the damping performance increases.