Extremely high strength and work hardening ability in a metastable high entropy alloy

Design of multi-phase high entropy alloys uses metastability of phases to tune the strain accommodation by favoring transformation and/or twinning during deformation. Inspired by this, here we present Si containing dual phase Fe42Mn28Co10Cr15Si5 high entropy alloy (DP-5Si-HEA) exhibiting very high strength (1.15 GPa) and work hardening (WH) ability. The addition of Si in DP-5Si-HEA decreased the stability of f.c.c. (γ) matrix thereby promoting pronounced transformation induced plastic deformation in both as-cast and grain refined DP-5Si-HEAs. Higher yet sustained WH ability in fine grained DP-5Si-HEA is associated with the uniform strain partitioning among the metastable γ phase and resultant h.c.p. (ε) phase thereby resulting in total elongation of 12%. Hence, design of dual phase HEAs for improved strength and work hardenability can be attained by tuning the metastability of γ matrix through proper choice of alloy chemistry from the abundant compositional space of HEAs.

[1]  D. Raabe,et al.  Strong and Ductile Non-equiatomic High-Entropy Alloys: Design, Processing, Microstructure, and Mechanical Properties , 2017, JOM.

[2]  R. Mishra,et al.  A framework for shear driven dissolution of thermally stable particles during friction stir welding and processing , 2016 .

[3]  C. Tasan,et al.  Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off , 2016, Nature.

[4]  D. Raabe,et al.  The influence of stacking fault energy on the microstructural and strain-hardening evolution of Fe–Mn–Al–Si steels during tensile deformation , 2015 .

[5]  D. Ponge,et al.  Design of a novel Mn-based 1 GPa duplex stainless TRIP steel with 60% ductility by a reduction of austenite stability , 2011 .

[6]  P. Liaw,et al.  Friction Stir Processing of a High Entropy Alloy Al0.1CoCrFeNi , 2015 .

[7]  B. Hu,et al.  High dislocation density–induced large ductility in deformed and partitioned steels , 2017, Science.

[8]  S. S. Nene,et al.  Enhanced strength and ductility in a friction stir processing engineered dual phase high entropy alloy , 2017, Scientific Reports.

[9]  M. Calcagnotto,et al.  Orientation gradients and geometrically necessary dislocations in ultrafine grained dual-phase steels studied by 2D and 3D EBSD , 2010 .

[10]  H. Hänninen,et al.  Strain hardening of cold-rolled lean-alloyed metastable ferritic-austenitic stainless steels , 2016 .

[11]  P. Rivera-Díaz-del-Castillo,et al.  Understanding martensite and twin formation in austenitic steels: A model describing TRIP and TWIP effects , 2017 .

[12]  D. Ponge,et al.  Improvement of the work hardening rate of ultrafine grained steels through second phase particles , 2005 .

[13]  C. Tasan,et al.  A TRIP-assisted dual-phase high-entropy alloy: Grain size and phase fraction effects on deformation behavior , 2017 .

[14]  Y. Estrin,et al.  Twinning-induced plasticity (TWIP) steels , 2018 .

[15]  C. Schuh,et al.  Six decades of the Hall–Petch effect – a survey of grain-size strengthening studies on pure metals , 2016 .

[16]  T. Shun,et al.  Nanostructured High‐Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes , 2004 .

[17]  H. Bhadeshia.  Twinning-Induced Plasticity Steels , 2012 .

[18]  D. Rafaja,et al.  Deformation of Austenitic CrMnNi TRIP/TWIP Steels: Nature and Role of the ɛ−martensite , 2015 .

[19]  D. Raabe,et al.  Ab initio assisted design of quinary dual-phase high-entropy alloys with transformation-induced plasticity , 2017 .

[20]  S. Kaloshkin,et al.  Face-centered cubic phase stability and martensitic transformation under deformation in Fe-Ni and Fe-Mn alloys nanostructured by mechanical alloying and high-pressure torsion , 2008 .

[21]  C. Tasan,et al.  Interstitial atoms enable joint twinning and transformation induced plasticity in strong and ductile high-entropy alloys , 2017, Scientific Reports.

[22]  D. Raabe,et al.  The influence of manganese content on the stacking fault and austenite/ε-martensite interfacial energies in Fe–Mn–(Al–Si) steels investigated by experiment and theory , 2014 .

[23]  A. Rabinkin,et al.  A study of γ → ε phase transformation in FeMn alloys induced by high pressure and plastic deformation , 1978 .

[24]  D. C. Aken,et al.  Thermodynamic Driving Force of the γ → ε Transformation and Resulting MS Temperature in High-Mn Steels , 2016, Metallurgical and Materials Transactions A.

[25]  R. Xiong,et al.  Thermodynamic calculation of stacking fault energy of the Fe–Mn–Si–C high manganese steels , 2014 .