The ductile-brittle transition behavior of two austenitic Fe-18Cr-10Mn-N-C alloys with different grain sizes was investigated in this study. The alloys exhibited a ductile-brittle transition behavior because of an unusual brittle fracture at low temperatures unlike conventional austenitic alloys. The alloy specimens with a smaller grain size had a higher yield and tensile strengths than those with a larger grain size due to grain refinement strengthening. However, a decrease in the grain size deteriorated the low-temperature toughness by increasing the ductile-brittle transition temperature because nitrogen or carbon could enhance the effectiveness of the grain boundaries to overcome the thermal energy. It could be explained by the temperature dependence of the yield stress based on low-temperature tensile tests. In order to improve both the strength and toughness of austenitic Fe-Cr-Mn-N-C alloys with different chemical compositions and grain sizes, more systematic studies are required to understand the effect of the grain size on the mechanical properties in relation to the temperature sensitivity of yield and fracture stresses.

1. 서 론
 2. 실험 방법
 3. 결과 및 고찰
 4. 결 론
 Acknowledgements
 References

• 이상인(서울과학기술대학교 신소재공학과) | Sang-In Lee
• 이승용(서울과학기술대학교 신소재공학과) | Seung-Yong Lee
• 남승훈(한국표준과학연구원 산업측정표준본부) | Seung Hoon Nam
• 황병철(서울과학기술대학교 신소재공학과) | Byoungchul Hwang Corresponding author