Crystal-Glass Nano-Dual-Phase Alloys Achieve Ultrahigh Strength and Large Homogeneous Plastic Deformation

Higher strength and larger ductility are always the pursuit of goal in the research of structural materials. Grain refinement and amorphization can enhance the strength of alloys, yet have their own limitations. The ductility of nanocrystalline alloys is usually low (<5%), due to mechanical instability of the nanograin boundary. Shear band (SB) forms after yielding, inducing almost zero plasticity of metallic glasses (MGs). In this article, the recent development of the crystal-glass nano-dual-phase (CG-NDP) alloys, dramatically enhancing the strength and plasticity is reviewed. The grain boundary (GB) is replaced by a nanoscale amorphous phase. This structure configuration substantially increases the stress barrier against dislocation motion, enhancing the yield strength up to a near-theoretical value. Furthermore, global plastic flow behavior of the nano-sized amorphous phase can be activated, promoting emission of dislocations at the crystal-glass interface. Some of these dislocations pass through the crystalline phase and are absorbed by the amorphous phase on the opposite interface, depicting a continuous emission-motion-annihilation process. These deformation mechanisms promote the large homogeneous plastic deformation under both compression and tension. A new mechanism of crystalline-to-amorphous phase transformation is further reviewed. Finally, their functional applications as electrolytic catalysis and wear-resistant coatings is discussed.