Mechanisms of subgrain coarsening and its effect on the mechanical properties of carbon-supersaturated nanocrystalline hypereutectoid steel
Mechanisms of subgrain coarsening and its effect on the mechanical properties of carbon-supersaturated nanocrystalline hypereutectoid steel
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DOI：
10.1016/j.actamat.2014.10.027
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发表时间：
2015-02-01
期刊：
影响因子：
9.4
通讯作者：
Raabe, D.
中科院分区：
文献类型：
--
作者：
Li, Y. J.;Kostka, A.;Raabe, D.
采用大幅度冷拉珠光体组织制备了抗拉强度为6.35GPa的碳过饱和纳米晶过共析钢。纳米晶体材料在200至450摄氏度的温度下退火时经历软化。断裂伸长率方面的延展性表现出对温度的非单调依赖性。在这里，负责在机械性能的变化的微观结构机制进行了研究，使用透射电子显微镜（TEM），TEM为基础的自动扫描纳米束衍射和原子探针层析成像（APT）。纳米晶过共析钢的TEM和APT研究表明，退火后亚晶粗化，导致强度降低以下霍尔佩奇定律。APT分析亚晶界附近的Mn分布，并在方解石提供了强有力的证据，毛细驱动的亚晶粒粗化发生通过亚晶界迁移。在高于350 ℃的温度下退火后，延展性的显著劣化归因于亚晶界处的马氏体的形成。碳原子在铁素体亚晶界处的整体偏析在退火时给予纳米晶材料优异的热稳定性。(C)2014 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Carbon-supersaturated nanocrystalline hypereutectoid steels with a tensile strength of 6.35 GPa were produced from severely cold-drawn pearlite. The nanocrystalline material undergoes softening upon annealing at temperatures between 200 and 450 degrees C. The ductility in terms of elongation to failure exhibits a non-monotonic dependence on temperature. Here, the microstructural mechanisms responsible for changes in the mechanical properties were studied using transmission electron microscopy (TEM), TEM-based automated scanning nanobeam diffraction and atom probe tomography (APT). TEM and APT investigations of the nanocrystalline hypereutectoid steel show subgrain coarsening upon annealing, which leads to strength reduction following a Hall Petch law. APT analyzes of the Mn distribution near subgrain boundaries and in the cementite give strong evidence of capillary-driven subgrain coarsening occurring through subgrain boundary migration. The pronounced deterioration of ductility after annealing at temperatures above 350 degrees C is attributed to the formation of cementite at subgrain boundaries. The overall segregation of carbon atoms at ferrite subgrain boundaries gives the nanocrystalline material excellent thermal stability upon annealing. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.