Study On Preparation And Properties Of High Manganese Damping Alloy

Mn-Cu based damping alloys were widely applied in manufacturing of damping elements for machine tools,engine basements and other equipment so as to reduce vibration and noise from the very beginning.The damping performance of Mn-Cu based damping alloy increases with higher Mn content.However,a high vapor pressure of Mn makes vacuum furnace cannot be in the preparation of highly manganese alloys.Therefore,it is of great practical significance to develop a novel preparation technique of high manganese Mn-Cu based damping alloy.In this work,a high-manganese Mn-Cu based damping alloy was prepared by a uniquely designed gas protection intermediate frequency furnace.Direct reading spectrometer,x-ray diffraction analysis(XRD),microstructure analysis(OM,SEM,TEM),energy diffraction spectrum analysis(EDS),differential scanning calorimetry(DSC),thermal expansion analysis,martensite phase analysis,damping performance testing as well as normal mechanical property test methods were applied for characterizing composition,microstructure,damping and mechanical properties of prepared alloy.The effects of solid solution aging and direct aging heat treatment on the microstructure evlution,damping and mechanical properties of the alloy were studied too.Based on above mentioned characterization,the anti-ferromagnetic transition,martensitic transformation,crystal structure and twins crystal of the alloy were deeply investigated for interpreting its damping mechanism.For industrial application practice,the influence of ambient temperature on the damping performance of the alloy was also investigated.Most important results are listed in following paragraphs:1,For the preparation of high-manganese damping alloy,gas protected intermediate frequency furnace is basically feasible.Mn content was more than70wt.%which means volatilization of manganese was effectively controlled.2,As-cast alloy have significant damping properties(tan?=0.0433).This is due to the occurrence of antiferromagnetic transition and martensitic transformation in the local Mn rich zone formed by dendrite segregation in the cooling process,and the transformed martensite twin crystal moves under external forces and consumes dissipation energy,dampens the vibration.3,Compared with direct aging,damping and mechanical properties were improved efficiently after solid solution and aging treatment.With increasing aging temperature and time,the damping performance,tensile strength and hardness of the alloy have similar tendency,increasing at beginning and decreasing later the best damping performance(tan?=0.0806)and mechanical properties(Rm=540MPa,205.6HV0.3)were achieved under condition of 900?1hour solid solution and 430?8hours aging.This is due to the formation of Mn-rich zone with higher Mn content due to spinodal decomposition during aging of the alloy,higher antiferromagnetic transition point T_N and martensite transformation point Ms,resulted in more martensite twin crystal.At the same time,because of spinodal strengthening and aging strengthening,the comprehensive properties of damping and mechanical of the alloy after aging heat treatment were clearly enhanced.4,The damping performance of the alloy gradually decreases with increasing ambient temperature.When the surroundings temperature is lower than 120°C,damping effect decreases linearly and slowly with increasing temperature.When the surroundings temperature is higher than 120°C,the alloy peak damping decreases dramatically.This is due to the reverse transformation of martensite with increasing surroundings temperature,resulting the number of martensite twin crystal decreases,and damping performance decreases or disappears.