ABSTRACT
Nanostructured metals have high strength while they usually exhibit limited uniform elongation. The HDI hardening due to the high internal stresses have in fact been reported in TWIP steels, TRIP steels, and dual-phase alloys to account for the strong strain hardening and the large ductility. The transformation behaviors should be different for various microstructures with different flow stresses, then the quantitative analysis for the martensite transformation of various microstructures has been conducted by a series of X-ray diffraction (XRD) measurements before and after tensile tests. The detailed microstructure evolutions have also been obtained by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) before and after tensile tests to further clarify the plastic deformation mechanisms. The present results could provide better understanding for the deformation mechanisms of the Fe-Ni-Al-C alloy and could provide strategies to achieve both ultrahigh strength and excellent ductility in metals and alloys.
