Poster Session

Characterization of nano-sized precipitates in microalloyed steels

Junfang Lu, PhD student in Materials Engineering

Supervisor - Dr. Hani Henein, Dr. Douglas Ivey

Microalloyed steels are widely used in oil and gas pipelines. They have good strength, toughness and weldability, which are attributed in part to the presence of nano-sized Nb/Ti carbonitride precipitates. In order to understand the strengthening mechanisms and to optimize the strengthening effects, it is necessary to quantify the size distribution, volume fraction and chemical speciation of these precipitates. However, characterization techniques suitable for quantifying fine precipitates are limited. In this paper, chemical dissolution and electrolytic dissolution have been developed to extract the nano-sized precipitates from a Grade 100 (YS = 690 MPa) microalloyed steel. Scanning/transmission electron microscopy and x-ray diffraction are combined to analyze the chemical speciation of these precipitates. Laser scattering and filtration are used to quantify the precipitate volume fraction and size distribution.