The effect of Mn content on the evolution of microstructure and the enhancement of mechanical properties in Fe-Nb-Mn hierarchical composites consisted of ultrafine eutectic and primary dendrite has been studied by using X-ray diffractometry, scanning electron microscopy, transmission electron microcopy and compression test. Fe-11Nb-5Mn hierarchical composite consisted of α′-Fe dendrite and urtrafine α′-Fe + Fe2Nb eutectic, and exhibited a reasonably good combination of mechanical properties, i.e. yield strength of 1283 ± 10 MPa and compressive plastic strain of 7.75 ± 5%, while Fe-11Nb-15Mn composite consisted of É-Fe dendrite and É-Fe + Fe2Nb eutectic structure with some retained γ phase, and exhibited a far better combination of mechanical properties, i.e. higher yield strength of 1462 ± 10 MPa and larger compressive plastic strain of 11.28 ± 2%. The origin for the simultaneous enhancement of high strength and large plastic strain is attributed to É-Fe martensite formation and strain-induced martensitic transformation from É to α′ during deformation.
Bibliographical noteFunding Information:
This work was supported by Defense Acquisition Program Administration (DAPA) and Agency for Defense Development (ADD), and also supported by the Global Research Laboratory Program of Korea Ministry of Science and Technology. T.E. Kim acknowledges the support from the Second Stage of Brain Korea 21 Project in 2011.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanics of Materials
- Metals and Alloys
- Materials Chemistry