Amorphous bands induced by low temperature tension in a non-equiatomic CrMnFeCoNi alloy

Abstract

Single-phase face-centered cubic multi-principal-element alloys (fcc MPEAs) comprising transition metal elements Cr, Mn, Fe, Co or Ni generally show strong temperature dependence of stacking fault energy (SFE) of {111} plane, the lower temperature the lower SFE. Through uniaxial tension of a non-equiatomic Cr26Mn20Fe20Co20Ni14 alloy at low temperature, we observed nanoscale microstructures including stacking faults bands, nano-twins, hexagonal-close packed (hcp) phase bands and amorphous bands. The formation and interactions of stacking faults, twins and amorphous bands are characterized at different strain levels, and thermal stability of these nanostructures are investigated by subsequent tempering. We highlight the formation of extensive nanoscale amorphous bands and their much higher thermal stability above 650 °C than nano-twins and hcp bands. Amorphous bands ensure the enhanced strength and good ductility of high temperature tempered Cr26Mn20Fe20Co20Ni14 alloy. Amorphous bands can plastically co-deform with matrix. The interfaces between amorphous band and fcc matrix provide not only strong barriers for dislocation motion, strengthening materials, but also natural sinks of dislocations, disrupting stress concentrations and delaying decohesion and fracture initiation. Our results demonstrate that engineering amorphous bands could be an efficient strategy in remaining enhanced mechanical properties of fcc MPEAs at high temperature.