Study On Damping Capacity Of Fe-Mn Alloys

Damping alloys are functional materials which can be applied on components thatrequire low levels of sound emission and vibration. Among the damping alloys,Fe-Mn alloys have better strength and lower price, and its damping capacityincreases with the strain amplitude, so this alloy can be used as the highly vibratingand shocking parts and has a better application prospect. So Fe-Mn damping alloyshave attracted more attention for these years. The work was conducted with threedamping alloys melt in vaccum induction melting furnace, including Fe-18Mn,Fe-17Mn-2Cr, Fe-16Mn-6Cr alloys.The JN-1 reversal torsion pendulum device was applied to investigate the dampingcapacity of the alloys. The Olympus microscope, transmission electron microscope(TEM) and H-700H electron microscope were used to analyze the microstructure ofthe alloys annealed at different temperatures. The phases of the alloy weredetermined using Philip X'Pert Pro MPD X-Ray diffraction instrument. Thecorrosive properties of 18-8,Fe-18Mn,Fe-17Mn-2Cr and Fe-16Mn-6Cr were testedusing loss-in-weight method in 3%NaCl solution. The following respects of thealloys were investigated in this paper.The logarithmic decrement of Fe-18Mn alloy increase linearly with increasing thestrain amplitude, and there is no peak value when the torsional strain amplitudeγ_maxis 6×10^-4. The damping capacity of Fe-18Mn alloy increase with raising of solutiontreatment temperature, reaching its maximum around 1000℃.Because Fe-18Mnalloy is solution treated after 1000℃,the quantity ofε-martensite is most and itsplates is thinnest, damping sources is most, damping capacity is highest. Cryogenictreatment after solution treated at 1000℃supply driving force of transformationγ→ε,so increasing the quantity ofε-martensite, and the damping capacity is furtherincreased. Fe-Mn alloys' Ms temperature is nearly identical with increasing Cr content,because of decreasing Mn content with increasing Cr content. The damping capacityof Fe-17Mn-2Cr and Fe-16Mn-6Cr alloys is lower than it of Fe-18Mn alloy a little,because crystal lattice of Fe-Mn alloys aberrant with increasing Cr content, crystallattice aberrance anchor damping sources and obstruct its anelastic movement.Proper deformation can raise the damping capacity of Fe-Mn-Cr alloys, reaching itsmaximum around 4%, because anisotropic martensite raising damping capacity, andthe dislocations introduced during deformation deteriorate the damping capacity, butthe anistropic mantensitic contribution to damping capacity bigger than deteriorationof dislocation. And Cr raising the erosion resistance of Fe-Mn alloys. The tensilestrength is raising with increasing Cr content because of solution strength, but theaffection for plasticity is small.Fe-18Mn alloy after ECAP lose the damping capacity because of deformation withtrue strain 0.67. The damping capacity increase with raising annealing temperature,reaching its maximum around annealing temperature at 900℃, this maximum is 82%more than Non-ECAP sample. By annealing at 900℃, the high density dislocationsof Fe-18 alloy have been recovered, the stacking faults can vanish completely,therefor the number ofε-martensite plates is more and the damping sources increase,and the damping capacity of the alloy is improved. It can be see that ECAP is anaffective method.