Mechanical Property and Microstructural Characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel
JIANG Hai-tao1,DING Wei1,2,TANG Di1,HUANG Wei1
1. National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083, China 2. School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, Inner Mongolia, China
Mechanical Property and Microstructural Characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel
JIANG Hai-tao1,DING Wei1,2,TANG Di1,HUANG Wei1
1. National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083, China 2. School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, Inner Mongolia, China
ժҪ Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.31% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties.
Abstract��Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.31% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties.
JIANG Hai-tao,DING Wei,,TANG Di,HUANG Wei. Mechanical Property and Microstructural Characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel[J]. �й������ڿ���, 2012, 19(8): 29-36.
JIANG Hai-tao,DING Wei,,TANG Di,HUANG Wei. Mechanical Property and Microstructural Characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel. Chinese Journal of Iron and Steel, 2012, 19(8): 29-36.
2012, Vol. 19 
