低合金高强度钢焊缝金属中针状铁素体的微观组织

利用光学显微镜,扫描电子显微镜及EBSD(electron backscattering diffraction)分析技术对800MPa级低碳微合金高强度钢的焊缝金属进行了分析.结果表明,焊缝金属组织主要为针状铁素体和贝氏体.针状铁素体以夹杂物为核心形核,该夹杂物主要是以Al2O3为核心形成的钛氧化物.针状铁素体以夹杂物为核心多维形核呈放射状生长,仅某些方向的针状铁素体晶核迅速长大,生长方向存在取向择优.EBSD分析同样表明针状铁素体晶粒存在取向择优.观察到由同一夹杂物生长,沿同一直线方向背向生长的针状铁素体取向相同,沿不同方向生长的针状铁素体取向不同,说明其沿原奥氏体惯习面生长,并非与夹杂物共格.

Microstructural analysis of weld metal microstructures in a low carbon high strength microalloyed steel

Microstructural observations and analysis of weld metal in a 800 MPa grade low carbon high strength microalloyed steel are studied by means of potical microscopy,SEM-EDS(Scanning Electron Microscopy-Electron Dispersed Spectrum) and EBBSD(Electron Backscattering Diffraction).The weld metal consists of bainite and acicular ferrite.Acicular ferrite laths or plates are nucleated on inclusions which consisted of an Al₂O₃ core and an outer layer of titanium oxide.Although multi-variant ferrite plates emanate radially from an inclusion,there are only some of them could enlengthen rapidly.It indicates growth direction of acicular ferrite preferred orientation.Results of EBSD analysis also indicate that the acicular ferrite grains in weld metal are not crystallographically oriented randomly,probably a certain orientation relationship being kept.Those acicular ferrite laths or plates nucleated on inclusions grown in opposite direction have the same orientation relationship,presumably because they have a Kurdjumov-Sachs(K-S) orientation relationship with the prior austenite grains.