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Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys
Author(s) -
Lu Wenjun,
Liebscher Christian H.,
Dehm Gerhard,
Raabe Dierk,
Li Zhiming
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201804727
Subject(s) - materials science , stacking fault energy , microstructure , high entropy alloys , metastability , stacking , alloy , stacking fault , ductility (earth science) , kinetic energy , nanotechnology , composite material , dislocation , classical mechanics , physics , nuclear magnetic resonance , quantum mechanics , creep
Microstructural length‐scale refinement is among the most efficient approaches to strengthen metallic materials. Conventional methods for refining microstructures generally involve grain size reduction via heavy cold working, compromising the material's ductility. Here, a fundamentally new approach that allows load‐driven formation and permanent refinement of a hierarchical nanolaminate structure in a novel high‐entropy alloy containing multiple principal elements is reported. This is achieved by triggering both, dynamic forward transformation from a faced‐centered‐cubic γ matrix into a hexagonal‐close‐packed ε nanolaminate structure and the dynamic reverse transformation from ε into γ. This new mechanism is referred to as the “bidirectional transformation induced plasticity” (B‐TRIP) effect, which is enabled through a near‐zero yet positive stacking fault energy of γ. Modulation of directionality in the transformation is triggered by local dissipative heating and local micromechanical fields. The simple thermodynamic and kinetic foundations for the B‐TRIP effect render this approach generally suited for designing metastable strong and ductile bulk materials with hierarchical nanolaminate substructures.