Study On Damping Capacity Of Fe-16Cr-2.5Mo Alloy

The paper is based in the background of engineering applications, it studies the effects of working temperature, heat-treating temperature and external magnetic field on damping capacity of Fe-16Cr-2.5Mo damping alloy. It analyses the effects of microstmctures and ferromagnetic on damping essence.The JN-1 reversal torsion pendulum device was applied to investigate the effect of working temperature, heat-treating temperature and external magnetic field on damping capacity of Fe-16Cr-2.5Mo alloy. The CK-40M types OLYMPUS optical microscope was used to observe metallurgical structure. The magnetic domain structure and the motion under the magnetic field were observed with the water-based magnetic fluid under the optical microscope. Major research results as follows:The effect of working temperature on damping capacity of Fe-16Cr-2.5Mo alloy is studied. When the working temperature changes from room temperature to 500℃, as the working temperature increase, the damping capacityδ_m and strain amplitudeγ_c of Fe- 16Cr-2.5Mo alloy decrease gradually. At 300℃C, the damping capacity still remains about 80 percent, the damping characters of the alloy is still higher. The reason for this change is that, as the working temperature increase, the atom-spacing enlargement, the atom exchange integral and magnetocrystalline anisotropic becomes lower, magnetostriction constantλ_s becomes lower, the energy densities of domain-wall becomes lower, the damping capacity decreases. The effect of heat-treating temperature on damping capacity of Fe-16Cr-2.5Mo alloy is studied. The results showed that heat-treating temperature affects greatly the damping capacity of Fe-16Cr-2.SMo alloy. When the heat-treating temperature changes from 800℃to 1100℃, the damping capacity of alloy increases gradually with the heat-treating temperature rising. At 900℃, the damping capacity reaches peaks (δ=0.28 ) . Over 900℃, it decreases with the heat-treating temperature increasing.The effect of direct-current magnetic field on damping capacity of Fe-16Cr-2.5Mo alloy is studied. The results showed that damping capacity of Fe-16Cr-2.5Mo alloy increases with magnetic field, damping capacity reach its maximum value at 0.08mT. Over 0.08roT, it decreases with the further increasing of magnetic field strength. Under condition of weak direct-current magnetic field, some fine magnetic domains of volume under unstablization have changed, the domain-boundary appeared movement of Barkhausen, the damping capacity of alloy increase. When the alloy is magnetic saturation, the damping capacity reaches at the minimum. Under condition of external magnetic field, magnetic domains become wide and homogeneous. Moreover it induces movement of the domain walls. The larger the domain size, the lower the ratio of the domain-boundary area in every cubic specimen and the lower the energy cost during the domain-boundary motion, the damping capacity decreases.The effect of alternate magnetic field on damping capacity of Fe-16Cr-2.SMo alloy is studied. The results showed that the damping capacity of Fe-16Cr-2.SMo alloy reaches its peak within the alternate field. But the damping capacity decreases more drastically than direct-current magnetic field. It is because that the domain-boundary vibrates within the alternate field. The domain-boundary vibration amplitude is larger than that of the direct field when the magnetic field intensity amplitude is the same. This may reduce the domain-boundary displacement resulting from the torsion strain, as a result, the damping capacity drops drastically.The effect of working temperature and external magnetic field at the same time on damping capacity of Fe-16Cr-2.5Mo alloy is studied. The results show that the damping capacity of Fe-16Cr-2.5Mo alloy reaches its peaks with magnetic field increasing under 350℃constant temperature. Compared of damping variation under direct-current magnetic field, the damping capacity each magnetic field phase of Fe-16Cr-2.5Mo alloy significantly decrease under 350℃constant temperature. On the other hand, the damping capacity of Fe-16Cr-2.5Mo alloy decrease gradually with working temperature increasing under 0.08mT constant magnetic field. Compared damping variation under working temperature, the damping capacity of each temperature phase of Fe-16Cr-2.5Mo alloy significantly increase under 0.08mT constant direct-current magnetic field. When the working temperature higher 200℃, the damping capacity of the alloy decreases slowly, the extent of decrease lower than condition of without magnetic field obviously.The reason is that a little of magnetic field enhanced the strength of magnetic pole and the cohesion of grain boundary, delay the happening of grain boundary relaxation.