固溶温度对Fe-19Mn合金的γ→ε相变和阻尼性能的影响

Influence of Solution Temperature on γ→ε Transformation and Damping Capacity of Fe-19Mn Alloy

采用动态机械分析仪(DMA)对Fe-19Mn合金经950~1100℃固溶处理后的的阻尼性能进行了测试,利用OM和TEM观察了显微组织的演变,利用XRD进行了物相分析和不同类型层错几率的计算。结果表明:经固溶处理的Fe-19Mn合金的阻尼性能随振幅的增加呈近似线性增加,且振幅小于临界振幅A’(A’≈30μm)时的阻尼性能变化符合G-L位错模型,振幅高于A’时的阻尼性能变化与微塑性变形有关。随着固溶温度的升高,Fe-19Mn合金的阻尼性能降低,其中经950℃固溶处理后的阻尼性能最好。在不同的振幅范围内,其阻尼性能呈现不同的变化特征:当振幅小于等于170μm时,阻尼性能呈指数形式降低,并且与ε-马氏体中的形变层错几率的变化趋势相似,此时Fe-19Mn合金的阻尼性能主要受ε-马氏体中的形变层错边界的影响;当振幅大于170μm时,阻尼性能呈线性降低,并且与γ/ε相界面相对长度的变化趋势相似,此时Fe-19Mn合金的阻尼性能随固溶温度的变化主要受γ/ε相界面的影响。由γ-奥氏体中的层错观察可知,γ-奥氏体中的层错边界对Fe-19Mn合金的阻尼性能随振幅的变化无明显贡献。

Due to the high damping capacity and excellent mechanical properties, Fe-Mn alloy is considered to be a promising high damping alloy, and suitable for constructional and vehicle metal parts application, which can enhance the fatigue property of structures and metal parts, and also improve the working and living environment. It’s generally accepted at present that damping capacity of Fe-Mn alloy is influenced by the stacking fault boundaries in γ-austenite and ε-martensite, γ/ε phase boundaries and ε/εvariant boundaries;another view is that boundaries of the above damping sources are made up of partial dislocations, so the damping capacity of Fe-Mn alloy is caused by the motion of partial dislocations, and interpreted by G-L dislocation pinning model and stacking fault probabilities calculation. But there is no distinction between the probabilities of different type stacking faults. Both deformation stacking fault and growth stacking fault can be formed in γ-austenite and ε-martensite, and the change of process parameters has different influence on them, which will lead to different changes of deformation and growth stacking fault probabilities. So it’s necessary to analyze whether boundaries of different stacking fault types will have different effects on damping capacity of Fe-Mn alloy. Based on that, a hot-rolled Fe-19Mn alloy is prepared and then solution treated between 950~1100 ℃. Damping capacity is measured by dynamic mechanical analyzer(DMA). The microstructure evolution is observed by OM and TEM, and XRD is used to analyze phase constitution and to measure stacking fault probabilities. The results reveal that Fe-19Mn alloy shows amplitude-dependent damping capacity which almost linearly increases with amplitude, and frequency-independent damping capacity. From G-L plot, the variation of damping capacity below the critical amplitude A’(A’≈30 μm) is interpreted by G-L model, while it’s associated with micro-plastic deformation when above A’. As the increase of solution treatment temperature, the damping capacity of Fe-19Mn decreases, and possesses the best performance at 950 ℃;furthermore, it shows different characteristics in different amplitude ranges: when the amplitude is lower than 170 μm, damping capacity decreases in exponential form, which changes similarily with deformation stacking fault probability in ε-martensite, so it can be considered the boundaries of deformation stacking fault as the main damping source;when the amplitude is higher than 170 μm, damping capacity decreases linearly, which changes similarily with the relative length of γ/ε phase boundary, so it can be considered γ/ε phase boundary as the main damping source. Based on TEM observation of stacking faults in γ-austenite, it can be inferred that stacking fault boundaries in γ-austenite have no obvious contribution to the change of damping capacity of Fe-19Mn with amplitude.