Studies On Preparation Of Corrosion-resistance High Strength FeCrMn/FeMnCr Composite Damping Alloys Based On High Saturation Vapor Pressure Of Mn Element

Damping alloys can convert mechanical vibration energy into heat energy and dissipate it.Therefore,making mechanical components with damping alloys can fundamentally reduce the generation of vibration and noise.Alloys used as mechanical components need to have high strength.Therefore,high strength FeMn based damping alloys have attracted special attention because their tensile strength can reach 700 MPa.In addition,FeMn based alloys have high damping capacity at large strain amplitude(>6 × 10-4).However,their damping capacity at low strain amplitude(~ 2 × 10-4)is extremely poor,while the strain amplitudes of damping alloys used as mechanical components are often below 2 ~ 3 × 10-4.Even after alloying,heat treatment and predeformation,the damping capacity at low strain amplitudes of FeMn based alloys is still low.In addition,because the microstructures of FeMn based damping alloys consist of dual phase,their corrosion resistance is very poor.The addition of Cr did not change the microstructures of duplex structure and therefore cannot substantially improve their corrosion resistance.In the early stage,our team fabricated a sandwich Fe17 Mn composite alloy with a Mn-depleted single-phase ferrite surface layer by vacuum annealing based on high saturated vapor pressure of Mn element.Its corrosion resistance was significantly improved,but the damping capacity at low strain amplitude was still poor.The ferromagnetic FeCr based damping alloys are essentially ferritic stainless steels with excellent corrosion resistance.They have excellent damping capacity at low strain amplitudes(~ 2 × 10-4),but their damping capacity quickly decays at large strain amplitudes(~ 5 × 10-4).It can be seen that the high strength FeMn based damping alloys and the ferromagnetic FeCr based damping alloys have complementary advantages.If the ferromagnetic FeCr based damping alloys can be formed on the surface of the FeMn based damping alloys,the composite alloys are expected to have the advantages of high corrosion resistance,high strength,and good damping capacity at low strain amplitudes.Studies showed that adding about 10% Cr to the binary Fe17 Mn alloy can improve the corrosion resistance to a certain extent without dramatically deteriorating the damping capacity.After vacuum annealing,a surface layer of Cr-rich single-phase ferrite can be formed on the Fe17Mn10 Cr alloy.The corrosion resistance must be markedly improved.However,the damping capacity of the composite alloy remains to be studied.On the other hand,the studies also showed that the damping capacity of Fe12Mn12 Cr alloy containing 52% ferromagnetic ?'-martensite was comparable to that of Fe22Mn12 Cr alloy containing 32% ?'-martensite.The damping capacity in both alloys were higher than that of Fe22Mn12 Cr alloy containing 5% ?'-martensite and 90%?-austenite.These results seem indicate that the ferromagnetic ?'-martensite should make a contribution to the damping capacity in FeMnCr based alloys.By adjusting the content of Cr and Mn,it can be expected that FeMnCr alloys develop into new damping alloys with dual damping sources,the damping source in ferromagnetic type alloys and the one in high strength FeMn based alloys.Based on the traditional Fe17 Mn alloy and Fe17Mn10 Cr alloy,a promising Fe14Mn13 Cr alloy with dual damping sources was designed by increasing Cr content and reducing Mn content.This paper systematically studied the damping capacity and corrosion resistance of composite alloys prepared by vaccum annealing at 1100?.Their properties were compared with the solution-treated alloys.Furthermore,the effect of stress relief annealing was studied on the damping capacity of the composite alloys.Based on the above researches,the following conclusions had been obtained:1.The Fe14Mn13 Cr alloy was an alloy containing dual damping sources in the ferromagnetic type alloys and high strength FeMn based alloys.The damping capacity at the strain amplitude of 2 × 10-4 in solution-treated Fe14Mn13 Cr alloy was comparable to that of traditional Fe17 Mn alloy containing more than 80% ?-martensite and less than 5% ?'-martensite.2.Compared with the Fe17 Mn based composite alloy prepared by vacuum annealing,the Fe14Mn13 Cr based composite alloy had higher corrosion resistance and higher damping capacity at low strain amplitudes.Its self-corrosion current density in3.5% Na Cl solution was one order of magnitude lower than that of Fe17 Mn based composite alloy.Its damping capacity at low strain amplitude of 2 × 10-4 was 28%higher than that of Fe17 Mn based composite alloy.3.Stress relief annealing could significantly improve the damping capacity in both the Fe17Mn10 Cr based and Fe14Mn13 Cr based composite damping alloys at low strain amplitudes.The damping capacity at the strain amplitude of 2 × 10-4 of Fe17Mn10 Cr based and Fe14Mn13 Cr based composite alloys were improved by 23%and 48% after 2 cycles of stress relief annealing between 25 ? and 300 ?,respectively.