Role of trace nanoparticles in manipulating the widmanstatten structure of low carbon steel

• Published in: Materials letters 2022-01, Vol.306, p.130853, Article 130853
• Main Authors: Wang, Bingxu, Zhang, Yu, Qiu, Feng, Cai, Gaoshen, Cui, Weiwei, Hu, Zirui, Zhang, He, Tyrer, Na, Barber, Gary C.
• Format: Article
• Language: English
• Subjects: Acicular structure; Carbon; Dispersion strengthening; Elongation; Grain size; Low carbon steels; Materials science; Microstructure; Nanoparticles; Nickel; Nucleation; Pearlite; Tensile properties; Tensile strength; Titanium carbide; Titanium diboride; Widmanstatten structure
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2021.130853

•The reinforced low carbon steels were prepared by using TiC-TiB2/Al master alloy.•The formation of widmanstatten structure was limited.•The grain size reduced and pearlite content increased.•The yield strength, tensile strength and ductility were improved simultaneously.•An E2EM model was utilized to discuss the heterogenous cores by nanoparticles.•The fine-grain, thermal-mismatch and dispersion strengthening mechanisms were discussed.•The toughening mechanisms including fine microstructure and scattering effect were discussed. The current research investigated the microstructure and tensile properties of as-cast low carbon steels manipulated by TiC-TiB2 nanoparticles. It was found that the microstructure mainly contained blocky ferrite and pearlite. Widmanstatten structure consisting of acicular ferrite was also obtained in the matrix of unmodified low carbon steels. After introducing 0.01 wt% and 0.02 wt% TiC-TiB2 nanoparticles, the formation of widmanstatten structure was inhibited. The pearlite content increased from 26.3% to 36% and 36.7% respectively. The grain size reduced from 58.3 μm to 43.3 μm and 42.8 μm. For tensile properties, the yield strength, tensile strength and elongation of low carbon steels increased by 9.8%, 7.6%, 20.4% and 14.0%, 11.0% and 8.2%. The as-cast microstructure was refined since the nanoparticles act as heterogenous cores to promote the nucleation rate and hinder the growth of grains. The improved strength could be associated with the fine-grain, thermal-mismatch and dispersion strengthening mechanisms, and the improved ductility could be associated with the fine microstructure and scattering effects of nanoparticles.