Indentation Strain Rate Sensitivity of CoCrFeNiAl_0.3 High‐Entropy Alloy

Abstract

In this paper, the mechanical properties of CoCrFeNiAl0.3 high‐entropy alloy (HEA) under different strain rates are investigated using nanoindentation at room temperature. Experimental results show that the contact stiffness increases almost linearly with indentation depth and the elastic modulus is invariable under different indentation strain rates, while the indentation hardness under higher strain rate is relatively larger, and the hardness under large indentation depth is relatively smaller for each indentation strain rate. The indentation size effect of hardness and strain rate sensitivity exponent m under different indentation strain rates are analyzed, then the hardness and m free from the effect of indentation depth are obtained. Finally, this investigation reveals the size effects of the hardness of HEA in light of the strain rate sensitivity and activation volume of the dislocation nucleation.

Strain-rate sensitivity of high-entropy alloys and its significance in deformation

“…The SRS of alloys is expected to increase with increase of the slope of the σ * y -temperature curves in Figure 2(b) as indicated in Equation 3. In FCC-HEAs with the strong temperature dependence of flow stress, high SRS has been reported in the previous studies [17,[27][28][29][30][31]. The variation of SRS with increasing the number of alloying elements in FCC metals and alloys is shown in Figure 3.…”

“…Their statement however suggests that the temperature dependence of flow stress in CrMnFeCoNi is greater than their theoretical estimate up to room temperature, suggesting that the SRS is larger and the V * is smaller than their values obtained by RSR tests in CrMnFeCoNi [7]. Extensive data and reports [1,8,9,17,[18][19][20][21][22][27][28][29][30][31] revealing the strong temperature dependence of flow stress in CrMnFeCoNi than conventional FCC alloys strongly suggest that the SRS is larger and the V * is smaller in CrMnFeCoNi compared to those of conventional FCC alloys [1,15,17]. The strong temperature and strain-rate dependencies of flow stress observed by the previous results [1,8,9,17,[18][19][20][21][22][27][28][29][30][31] do not support the suggestion of low SRS by RSR test [7].…”

“…The variation of SRS with increasing the number of alloying elements in FCC metals and alloys is shown in Figure 3. It is clearly shown that the reported SRS of FCC-HEAs [17,[27][28][29][30][31] is greater than that of pure metals and binary alloys [27,32,33]. The Peierls-barrier-dominated lattice friction [30], Labusch-type solution strengthening mechanism [27], and cutting through forest dislocations [7] have been suggested to be responsible for the temperature and strain-rate dependencies of flow stress in FCC-HEAs.…”

“…The failure [17,27,30,31], while two samples were tested at different strain-rates to measure SRS in Refs. [28,29].…”

Magnesium nanocomposites reinforced with rare earth element nanoparticles: nanoindentation-driven response

“…Nanoindentation is considered an approach of desire to investigate the mechanical behavior of small volumes, especially to measure the strain rate sensitivity exponent [11][12][13][14][15]. This paper objective at assessing small-scale properties and strain rate sensitivity of pure Mg, Mg-0.5 vol% Sm 2 O 3 , Mg-1.0 vol% Sm 2 O 3 , and Mg-1.5 vol% Sm 2 O 3 nanocomposites at ambient temperature using a depth-sensing nanoindentation approach.…”