Abstract: X100 and X80 high grade pipeline steel dynamic plastic deformation behavior was investigated, by means of insitu SEM and insitu EEBSD analysis. The results show that, the microstructure of the two pipelines is mainly composed of acicular ferrite, granular bainite and M/A island. During the tensile process, acicular ferrite deforms firstly of the X100 microstructure. With the strain increase, the variable accumulation of the acicular ferrite leads to granular bainite deformation. Subsequently, inclusion nucleates micro crack nucleation core and extends with the externally applied stress increase. Micro-cracks connection leads to crack through the matrix until failure. Correspondingly, during insitu tensile process, the slide bands of the microstructure of the X80 pipeline run through the grains and deform cooperatively till fracture. By in-situ EBSD orientation of the X100 pipe, crystals after deformation rotate along the rolling surface for the {111} plane direction along the direction of tensile deformation.  

Key words: pipeline steel, plastic deformation, insitu stretching, orientation