论文标题
纳米级调查微裂纹和晶界润湿的压力固化镀锌20MNB8钢
Nanoscale Investigation of Microcracks and Grain Boundary Wetting in Press Hardened Galvanized 20MnB8 Steel
论文作者
论文摘要
通过电子反向散射衍射，螺旋散射衍射，能量分散X射线探针分析，原子探针探针和透射量显微镜在NANANOMOS尺度上，通过电子反向散射衍射，Energy Electron Electron Spartroction，Energy Electron Electrospopicy，Energy Electracsy Elective Elective Elective Electron Microscopy分析了锌诱导的晶粒边界削弱和覆盖的初步阶段。观察到了先前奥斯丁岩晶界处的微裂纹，并鉴定出在微裂纹形成后开发的结构。在裂纹表面和楔形的裂纹尖端处存在粒度大小小于100 nm的粒度的Zn/Fe金属间相。为了获得完整的图片，包括在破裂前的微观结构，一个未呈现的电解涂层的参考样品，该样品接受了与压制硬化材料相同的热处理。在这里，Zn按一个原子层或更小的顺序沿着涂层中实际的Zn/Fe相几个微米远离几微米。这种晶界通过在奥氏体化和/或热形成过程中先前的奥氏体晶界的Zn润湿是微裂纹形成的必要条件。
Grain boundary wetting as a preliminary stage for zinc induced grain boundary weakening and embrittlement in a Zn coated press hardened 20MnB8 steel was analyzed by means of electron backscatter diffraction, Auger electron spectroscopy, energy dispersive X-ray analysis, atom probe tomography and transmission electron microscopy on the nanometer scale. Microcracks at prior austenite grain boundaries were observed and structures that developed after microcrack formation were identified. Zn/Fe intermetallic phases with grain sizes smaller than 100 nm in diameter are present at the crack surfaces and at the wedge-shaped crack tips. In order to get a complete picture, including the microstructure before cracking, an undeformed, electrolytically coated reference sample which underwent the same heat treatment as the press hardened material was investigated. Here, Zn, in the order of one atomic layer or less, could be found along prior austenite grain boundaries several micrometers away from the actual Zn/Fe phases in the coating. Such a grain boundary weakening by Zn wetting of prior austenitic grain boundaries during austenitization and/or hot forming is a necessary condition for microcrack formation.
