Strain hardening behavior of ARMCO iron processed by ECAP

6th International Conference on Nanomaterials by Severe Plastic Deformation

材料科学;化学

Bolaños, J. A. Muñoz^1 ; Cobos, O. F. Higuera^2 ; Marrero, J. M. Cabrera^1,3

Department of Materials Science and Metallurgical Engineering ETSEIB, Universidad Politecnica de Catalunya, Av Diagonal 647, Barcelona 08028, Spain^1

Faculty of Mechanical Engineering, Universidad Tecnológica de Pereira, Colombia^2

Fundación CTM, 2 Plaça de la Ciència, 08243, Manresa, Spain^3

关键词: Armco iron;    Crussard-Jaoul;    ECAP;    HAGB;    Hollomon;    LAGB;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/63/1/012143/pdf
DOI  :  10.1088/1757-899X/63/1/012143

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

The strain hardening behavior of an ARMCO iron processed by ECAP at room temperature up to sixteen passes following route Bc was investigated through Hollomon and differential Crussard-Jaoul models. Results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress-true strain curves while the differential Crussard-Jaoul analysis based on the Ludwik equation and the modified Crussard- Jaoul analysis based on the Swift equation fit better when two work hardening exponents are considered. As expected, the strength of the material increased with the number of ECAP passes. Indeed the ultimate tensile stress reached a maximum of ∼900MPa after 16 passes, which is more than three times higher than the UTS of the annealed material. Nevertheless, the strain hardening capacity of the material was reduced in comparison with the material without severe plastic deformation. For that reason the tensile ductility was also reduced at increasing ECAP passes. The increase in strength was attributed to the reduction of the grain size through refined sub-grains with high density of dislocations. After sixteenth passes the original grain size (namely 70 mm) was reduced down to 300 to 400 nm observing a good correspondence with the Hall-Petch relationship. The microstructural analysis, carried out by EBSD, showed an increasing amount in the fraction of high Angle Grain Boundaries (HAGB) after 1 pass due to the regeneration of the microstructure with a smaller grain size.