Abstract
The equimolar Cr, Mn, Fe, Co and Ni alloy, first produced in 2004, was unexpectedly found to be single-phase. Consequently, a new concept of materials was developed: high entropy alloys (HEA) forming a single solid-solution with a near equiatomic composition of the constituting elements. In this study, an equimolar CoCrFeMnNi HEA was modified by the addition of 5 at% of either Al, Cu or Zr. The cold-rolled alloys were annealed for 30 minutes at high temperature to investigate the recrystallization kinetics. The evolution of the grain boundary and the grain size were investigated, from the as-cast to the recrystallized state. Results show that the recrystallized single phase FCC structures exhibits different twin grains density, grain size and recrystallization temperatures as a function of the at.% of modifier alloying elements added. In comparison to the equimolar CoCrFeMnNi, the addition of modifier elements increases significantly the recrystallization temperature after cold deformation. The sluggish diffusion (typical of HEA alloys), the presence of a solute in solid solution as well as the low twin boundary energy are responsible for the lower driving force for recrystallization.
Highlights
High entropy alloys (HEAs) are characterized by the concentration of each element in the range of 5-35 at.% and high mixing entropy in their liquid state
The sluggish diffusion, the presence of a solute in solid solution as well as the low twin boundary energy are responsible for the lower driving force for recrystallization
The alloys demonstrated the capability to form a single-phase solid solution (FCC), which is suitable to be used at cryogenic temperatures
Summary
High entropy alloys (HEAs) are characterized by the concentration of each element in the range of 5-35 at.% and high mixing entropy in their liquid state. The unique properties of HEAs are attributed to the inherent properties of multicomponent solid solution formation [7], such as distorted lattice structures [8], the cocktail effect [9], sluggish diffusion [4] and formation of nanoscale deformation twins [6][10] It is well-known that HEAs can exhibit sluggish diffusion and severe lattice distortion effects [11] which might hide the grain boundary migration in the re-crystallization process [12] and dislocation movements [13], respectively. Zr by means of a new production route which include vacuum induction melting followed by thermos-mechanical recrystallization[15] This novel processing scheme, considered as a valid alternative to traditional arc melting, could be exploited thanks to the low temperature involved. Preliminary results on chemical resistance in industrial and urban atmospheres were exhibited
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