Phase evolution and mechanical properties of an intercritically-annealed Fe-10Ni-7Mn (wt. %) martensitic steel severely deformed by high-pressure torsion

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:804

Article

Kalahroudi, Faezeh Javadzadeh¹  Koohdar, Hamidreza²  Langdon, Terence G.³  Nili-Ahmadabadi, Mahmoud^1,4 

[1] Univ Tehran, Sch Met & Mat Engn, POB 14395-731, Tehran, Iran

[2] Iran Univ Sci & Technol, Sch Met & Mat Engn, Tehran, Iran

[3] Univ Southampton, Dept Mech Engn, Mat Res Grp, Southampton SO17 1BJ, Hants, England

[4] Univ Tehran, Sch Met & Mat Engn, Ctr Excellence High Performance Mat, Tehran, Iran

关键词: High-pressure torsion;    Intercritical annealing;    Phase transformation;    Microstructural evolution;    Mechanical properties;   

DOI  :  10.1016/j.msea.2020.140519

来源: Elsevier

【 摘 要 】

Experiments were conducted on an Fe-10Ni-7Mn (wt. %) martensitic steel processed by high-pressure torsion (HPT) after intercritical annealing in the dual phase (alpha+gamma) region at 600 degrees C for 2 h. Microstructural examination and phase analysis using electron backscatter diffraction (EBSD) confirmed that post-HPT processing led to a phase transformation of austenite to alpha'-martensite (gamma ->alpha' and gamma ->epsilon ->alpha') such that after 20 turns of HPT the microstructure included multi-phases of alpha'-martensite, austenite and epsilon-martensite. The HPT processing also produced a significant reduction in the alpha'-martensite and austenite grain sizes from initial values of similar to 3.8 and similar to 3.9 mu m to similar to 225 and similar to 60 nm after 20 HPT turns, respectively, while the epsilon-martensite final grain size was similar to 44 nm. Micro-hardness measurements and tensile testing showed a significant increase in hardness and in the ultimate tensile strength to about 680 Hv and 2235 MPa after 20 turns, respectively. Finally, the fracture surfaces of samples after HPT processing showed a combination of dimples, cracks and shear bands which confirmed a transition in fracture behavior from ductile to a mixture of a ductile and brittle mode.

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