摘要:
利用扫描电镜、透射电镜、X射线衍射和电子探针等研究了0.2C-1.51Si-1.84Mn钢在配分阶段组织的演变情况.配分温度为400℃时,碳在10 s时就可以完成配分,得到残余奥氏体最大体积分数为13.4%.随着配分时间的增长,钢中马氏体发生回火现象,奥氏体发生分解,强度、延伸率降低.当配分时间达到1000 s时,屈服强度、延伸率突然升高.分析认为马氏体回火带来的塑性提高抵消了残余奥氏体量减少引起的塑性降低,并且由于渗碳体和碳化物的析出,变形时阻碍位错的运动,从而提高了屈服强度.通过电子探针分析说明配分阶段发生了碳的扩散,随着配分时间的增长,发生了渗碳体和碳化物的析出,降低了残余奥氏体中碳的含量.
Abstract:
Microstructural evolution in 0.2C-1.51Si-1.84Mn steel during partitioning process was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron microprobe analysis (EMPA). When partitioning at 400℃, carbon atoms have redistributed within 10 s, and the volume fraction of retained austenite is 13.4%. When the partitioning time increases, martensite is tempered and austenite decomposes, leading to the decrease of strength and elongation. However, when the partitioning time is 1 000 s, the tensile strength and elongation suddenly increase. The reason is that the elongation loss caused by decomposition of retained austenite is offset by tempered martensite, the precipitation of carbides and cementite impedes dislocation movement, and thus its tensile strength increases. EPMA results show that carbon atoms diffuse during partitioning process, and carbides and cementite precipitate when the partitioning time increases, which decreases the content of carbon in retained austenite.
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