냉간가공에 따른 Fe-20Mn-12Cr-3Ni-3Si 합금의 기계적 특성 및 조직학적 특성에 미치는 영향

Abstract

There are two types of damping materials which are organic or metallic material. Shortage of organic materials that they are easily polluted by environment and their applications are limited by temperature and wavelength. Thus, metallic materials that have lower dependence on temperature and wavelength have highly been attentioned. Also, the metallic materials are classified with the type of composite, ferromagnetism, dislocation or etc. However, they still had the problem that low strength, complication of manufacturing process. From these reason, their application on industrial field have been inhibited. Moreover, in the most case, damping materials are need to endure the noise and vibration and have the high damping capacity and strength in sametime. Almost every metallic damping materials are hard to be satisfied that condition. Thus, the new materials that have high damping capacity, high strength, mechanical properties and corrosion resistance in sametime. Thus, as the fundamental research for the development of high strength and damping capacity material, the newly composed alloy were used in this study. Fe-20Mn-12Cr alloy was used and 3Ni and 3Si was adopted as an alloying element. Alloying elements were choosed for increasing corrosion resistance and stacking fault energy. Alloy were melted in vacumm furnace and manufactured to ingot. And then, they were hot rolled at 1200 to process for appropriate size of plate shape. Every plates was leansed in acid after annealing at 1050 1H and quenched for solid solution. Finally, they were cold rolled with different rolling reduciton but plate shape to 2mm thickness on the room temperature. They were used to investigate the relationship between microstructure and mechanical properties or damping capacity. The damping capacity was measured by electric discharge machining from a cold-rolled sample to a test piece having a size of 2 mm × 120 mm × 10 mm, and then, using a horizontal internal friction measurement device to obtain the logarithmic damping rate under vacuum. The microstructure of each specimens was obeserved using optical microscopy and scanning electron microscopy. Also, transmission electron microscopy was used for phase identification. After cold rolling, After performing the cold working, martensite was generated by working from the previously formed austenite phase, which showed a larger amount as the working amount increased. In addition, martensite had two different phases, α′ and ε, and it was confirmed that they intersect or have directionality for a specific orientation. Of the two phases, α′ was initially formed, and as the stacking fault energy increased as processing proceeded, the fraction of the ε phase became higher. In this alloy, the damping properties were highly influenced by the ε phase. In particular, as the fraction of the ε phase increased, the interaction between austenite and the interface occurring in the ε phase, such as interfacial migration and the increase of stacking fault energy, increased, and the damping capacity characteristics increased. Changes in tensile properties such as strength in this alloy were also affected by the fraction of the ε phase, and as the fraction of the corresponding phase increased, its strength and elongation increased further.