磁畴结构对铁磁合金阻尼性能的影响机制

Ferromagnetic damping alloy, as a kind of high damping material, has been widely used to reduce vibration and noise for their elevated mechanical properties and good corrosion resistance. The influence of heat treatment and alloy elements on damping behavior has been systematically investigated. Recently, the author has found that the damping capacity of FeCrMo damping alloy can be affected significantly by magnetic domain structure. However, the influence mechanism is still not clear. In this project, FeCrMo based damping alloys will be used as the experimental alloys. Bitter technique will be used to investigate the magnetic domain structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) will be used to observe grain boundary morphology and precipitation. The domain strucuture morphology will be adjusted by heat treatment and the effect of heat treatment on magnetic domain structure will be studied. According to the damping curves of FeCrMo alloy, the influence of different domain structures on damping behavior will be investigated and the relationship between damping capacity and volume fraction of 90 domain structure will be revealed. While loading magnetic field, the mobility of different domain structures will be examined and its influence on damping capaclity will be researched. After addition of Cu in FeCrMo damping alloy,the morphology of grain boundary and carbide will be changed. The interaction between domain wall and grain boundary/carbide will be investigated and the mechanism of alloy element Cu on improving damping capacity for FeCrMo ferromagnetic damping alloy will be clarified.

铁磁型阻尼合金有优良的阻尼性能。目前，多数研究集中在热处理、合金成分等对阻尼性能的影响上。最近，申请者在研究铁磁型FeCrMo 阻尼合金时发现，磁畴结构对阻尼性能的影响较大，其具体的影响机制尚不清楚。本项目以FeCrMo 基阻尼合金为研究对象，利用比特技术观察磁畴结构，采用透射电镜、扫描电镜相结合研究合金晶界形态及析出相情况。通过热处理调整合金的磁畴结构，研究不同类型磁畴结构对阻尼性能的影响机制，并揭示90 畴结构所占比例与阻尼大小的关系；加载磁场后观察畴壁的移动特征，研究畴壁可动性与阻尼性能之间的关系。通过添加元素Cu改变晶界和析出相形态，加载磁场观察畴壁的移动与晶界、析出相作用，研究晶界、析出相对畴壁的阻碍作用机制，澄清合金元素Cu提高FeCrMo合金阻尼性能的原因。

FeCr系阻尼合金有优良的阻尼性能，但高温退火使合金晶粒粗化，严重影响了合金的强度，进而影响合金的工程应用。本项目采用金相（OM）、扫描透射电镜（STEM）、动态机械分析仪（DMA）和Bitter技术研究了Fe-16Cr-2.5Mo阻尼合金中Cu的析出行为和磁畴结构变化规律，及其对阻尼性能和力学性能的影响。Cu加入合金后主要固溶在铁素体基体中，而Cu是否沉淀析出主要受Cu含量、退火后的冷速及后期时效处理温度等的影响，Cu含量越高、冷速越慢和时效温度越高，则Cu的沉淀析出将越容易发生。Cu析出初期是与基体共格的富铜相，其尺寸小（<5nm）、含铜量低（约4%），后期析出是与基体非共格的富铜相，尺寸长大（>10nm），且Cu含量明显增加（>30%）。此外，Cu加入后不仅可阻碍晶界的扩散迁移，细化了晶粒，而且Cu加入后改善了合金的磁畴结构，树枝状畴结构的数量增加，其90°畴壁的数量增加，对阻尼性能有利。因此，利用Cu的固溶强化和细晶强化提高合金的强度，利用Cu改善畴结构提高阻尼性能，研制出一种高强度、高阻尼的FeCrMo系阻尼合金，其含Cu量0.5~1.0%，其最大阻尼值约0.05，抗拉强度约467MPa，延伸率和室温冲击功分别为35%和357J。