Nanoindentation Creep Behavior of an Al0.3CoCrFeNi High-Entropy Alloy

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

“…At smaller depth, dislocations are closer to the free surface and therefore have higher mobility and diffusion leading to lower n. also be related to the mobility and diffusion of dislocations and how far they are from the free surface [41]. At smaller depth, dislocations are closer to the free surface and therefore have higher mobility and diffusion leading to lower n. The high values of stress exponent obtained from nano-indentation of the three alloys may be attributed to the complex stress state underneath the indenter [16,21,38]. The stress exponent is a complex function of microstructure, mobile dislocation density and/or the activation area underneath the indenter [42].…”

“…From Figure 4, it was concluded that the stress exponent determined from dynamic tests was slightly lower than that in static test. This may be because of oscillatory load which resulted in better propagation of dislocations and reduction of n. The high values of stress exponent obtained from nano-indentation of the three alloys may be attributed to the complex stress state underneath the indenter [16,21,38]. The stress exponent is a complex function of microstructure, mobile dislocation density and/or the activation area underneath the indenter [42].…”

“…Nano-indentation technique has been widely used to characterize the small-scale deformation behavior of materials [9][10][11][12][13][14][15]. However, there are limited reports on the creep behavior of MPEAs using nano-indentation, and majority of the studies are at room temperature with a maximum load of 100 mN [16][17][18][19][20][21][22]. There are no reports on the deformation behavior of MPEAs as a function of temperature comparing static and dynamic loads.…”

Creep, fatigue, and fracture behavior of high-entropy alloys

“…33 temperature. 31 The creep deformation of this alloy is sensitive to both applied loads and loading rates, as given in Figs. 3(a) and 3(c), 31 that is, the nanoindentation creep depth increases with increasing both the creep load and loading rate.…”

“…The creep behavior of a number of HEA systems has been studied in a range of temperatures, including the Al 0.15 CoCrFeNi HEA with a face-centered cubic (fcc) structure at 580-700°C, 29 the Al 0.6 CoCrFeNi HEA with fcc and body-centered cubic (bcc) phases at 580-700°C, 29 the Ni 47.9 Al 10.2 Co 16.9 Cr 7.4 Fe 8.9 Ti 5.8 Mo 0.9 Nb 1.2 W 0.4 C 0.4 HEA with fcc 1 L1 2 phases at 750-982°C, 30 the Al 0.3 CoCrFeNi HEA with an fcc structure at room temperature, 31,32 the AlCoCrFeNi HEA with a bcc structure at room temperature, 32 the CoCrFeMnNi HEA with an fcc structure at room temperature, 33 the as-deposited CoCrFeCuNi HEA film with an fcc structure at room temperature, 34,35 the annealed CoCrFeCuNi HEA film with an fcc 1 bcc structure at room temperature, 34 the as-deposited CoCrFeCuNiAl 2.5 HEA film with a bcc structure at room temperature. 35 The creep response of these alloys at room temperature was mostly characterized by spherical nanoindentation tests 33,34 or Berkovich nanoindentation tests 31,32,35 by virtue of the highly localized stress field generated in these circumstances, whereas uniaxial creep tests 30 and stress-relaxation tests 29 were utilized for elevated-temperature probing. Focus was placed on determining the value of such critical material parameters as the stress exponent (n) and activation volume (V*), from which creep mechanisms are likely to be deduced.…”