Strong yet ductile steels via a heterogeneous phase transformation strategy
Ran Ding (Tsinghua University, Tianjin University)
Yingjie Yao (Tsinghua University)
Binhan Sun (Max-Planck-Institut für Eisenforschung)
Hui Guo (Guangdong University of Science and Technology)
Yang Shao (Tsinghua University)
Wei Liu (Tsinghua University)
Andy Godfrey (Tsinghua University)
Zhigang Yang (Tsinghua University)
Xiaoxu Huang (Chongqing University)
Yongchang Liu (Tianjin University)
S Van Der Zwaag (TU Delft - Group Garcia Espallargas, Tsinghua University)
Hao Chen (Tsinghua University)
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Abstract
A new route towards strong yet ductile metals via architecting heterogeneities in both structure and metastability is presented. Such heterogeneities are generated and manipulated in a standard stainless steel using a heterogeneous phase transformation (het-PT) strategy, in which focused laser patterning is applied to stimulate site-specific phase transformations. The het-PT processed steel contains periodically arranged stripes of strong martensite and ductile austenite with different grain sizes and metastability. The resulting structural heterogeneity leads to a desirable strain gradient and heterogeneous deformation-induced martensitic transformation during deformation, which effectively accommodate strain localization and enhance work hardening capability in the het-PT-processed steel. These unique features result in an enhanced balance between strength and ductility, outperforming both homogeneously ultrafine-grained and coarse-grained counterparts. The het-PT strategy is expected to be applicable to tailoring structural heterogeneity and metastability in other steels and metals.