Effects of Cold Rolling Deformation on Microstructure and Damping Capacity of a Fe-Mn-Cr-Co-Si Alloy

The microstructure evolution of Fe-19Mn-8Cr-1Co-0.2Si (wt.%) alloy and Fe-19Mn (wt.%) alloy during cold rolling and its effect on the damping capacity of the two alloys were investigated. It was shown that the damping capacity of the two alloys was enhanced significantly owing to the deformation-induced ε-martensite and stacking faults. The Fe-19Mn-8Cr-1Co-0.2Si alloy exhibited an accelerated phase transformation from γ-austenite to ε-martensite due to a higher content of retained γ-austenite and larger grain sizes compared with the Fe-19Mn alloy, resulting in a higher maximal increment of damping capacity in this alloy caused by deformation. It was observed that no twinned ε-martensite was generated in the Fe-19Mn-8Cr-1Co-0.2Si alloy during cold rolling, resulting in a remarkable increase in the volume fraction of α'-martensite owing to no impediment to ε → α' transformation, hence the deterioration of damping capacity was slow because the α'-martensite weakened the pinning effect of dislocations on damping sources. In addition, new damping sources were provided due to the occurance of γ-austenite twinning in the Fe-19Mn-8Cr-1Co-0.2Si alloy.

本研究针对Fe-19Mn-8Cr-1Co-0.2Si（质量分数，wt.%）合金与Fe-19Mn（质量分数，wt.%）合金在冷轧（cold rolling）过程中的微观组织演变（microstructure evolution），及其对两种合金阻尼性能（damping capacity）的影响开展了系统探究。研究结果显示，两种合金的阻尼性能均因形变诱发ε马氏体（deformation-induced ε-martensite）与堆垛层错（stacking faults）的形成而得到显著提升。相较于Fe-19Mn合金，Fe-19Mn-8Cr-1Co-0.2Si合金因残余γ奥氏体（retained γ-austenite）含量更高、晶粒尺寸更大，呈现出从γ奥氏体（γ-austenite）向ε马氏体（ε-martensite）更快的相变速率，进而在形变作用下获得了更高的阻尼性能最大增幅。观测表明，Fe-19Mn-8Cr-1Co-0.2Si合金在冷轧过程中未生成孪晶ε马氏体，由于ε→α'相变（ε→α' transformation）未受到阻碍，该合金中α'马氏体（α'-martensite）的体积分数显著升高；而α'马氏体削弱了位错对阻尼源（damping sources）的钉扎效应（pinning effect of dislocations），因此该合金的阻尼性能劣化速度较为缓慢。此外，Fe-19Mn-8Cr-1Co-0.2Si合金中发生的γ奥氏体孪晶（γ-austenite twinning）现象还为其提供了全新的阻尼源。