Tuning mechanical properties of high entropy alloys by electro-pulsing method

Abstract

The single-phase face-centered cubic (FCC) high entropy alloys (HEAs) possess remarkable ductility but lower strength, limiting the engineering application in a wide range. The ductility-strength trade-off can be addressed by tuning the constituent and chemical composition to lower stacking fault energy (SFE) and introduce additional strain-hardening strategies. In this work, a series of non-equiatomic (Co40Fe25Cr20Ni15)95Al5 HEAs annealed by flash electro-pulsing treatments at different voltages, was prepared with the incorporation of deformation twining during plastic deformation. The 130 V-annealed sample demonstrates a good combination of tensile strength of 0.96 GPa and ductility of 16.5%, while the 150 V-annealed alloy showed dramatically increased ductility of 49.2%. The higher Hall-Petch coefficient kH (Kσy) value of 189.7 HV·μm0.5 (410.5 MPa·μm0.5) and the smaller recrystallization grain size is responsible for the improved tensile strength for 130 V-samples. Moreover, more stacking faults and deformation twins in 150 V-sample accommodate more plastic deformation and delay the fracture, resulting in increased ductility. Similar achievement using the flash electro-pulsing annealing treatment to another Fe50Mn27Ni10Cr13 alloy is also obtained, suggesting the universality for pulse electro-annealing method. This work provides a fast-effective method to tune the mechanical properties of HEAs by adjusting the annealing voltage and achieve in a minute, which might open the avenue for future industrial application.