Microstructure and composition dependence of mechanical characteristics of nanoimprinted AlCoCrFeNi high-entropy alloys

Abstract

Molecular dynamics is applied to explore the deformation mechanism and crystal structure development of the AlCoCrFeNi high-entropy alloys under nanoimprinting. The influences of crystal structure, alloy composition, grain size, and twin boundary distance on the mechanical properties are carefully analyzed. The imprinting load indicates that the highest loading force is in ascending order with polycrystalline, nano-twinned (NT) polycrystalline, and monocrystalline. The change in alloy composition suggests that the imprinting force increases as the Al content in the alloy increases. The reverse Hall–Petch relation found for the polycrystalline structure, while the Hall–Petch and reverse Hall–Petch relations are discovered in the NT-polycrystalline, which is due to the interactions between the dislocations and grain/twin boundaries (GBs/TBs). The deformation behavior shows that shear strain and local stress are concentrated not only around the punch but also on GBs and adjacent to GBs. The slide and twist of the GBs play a major in controlling the deformation mechanism of polycrystalline structure. The twin boundary migrations are detected during the nanoimprinting of the NT-polycrystalline. Furthermore, the elastic recovery of material is insensitive to changes in alloy composition and grain size, and the formability of the pattern is higher with a decrease in TB distance.

Crack growth and fracture mechanics of CuCrFeNiCo high-entropy alloy during tension testing

“…The von Mises stress inside the GBs is significantly higher than other locations of the NC CuCrFeNiCo HEA and the TN CuCrFeNiCo HEA samples. A similar result has also been found by Nieto-Valeiras et al [57], Tran et al [58], and Doan et al [59] in previous studies. These phenomena are caused by the anisotropic elastic and of the incompatible plastic deformation between grains with different orientations.…”

Enhancing mechanical performance of Al0.3CoCrFeNi HEA films through graphene coating: insights from nanoindentation and dislocation mechanism analysis

“…The inter-atomic interactions of metallic alloying elements (Al-Co-Cr-Fe-Ni) in HEA are defined by utilizing an embedded-atom-method (EAM) potential function developed by Farkas and Caro [56]. This EAM potential is widely utilized to characterize the mechanical behaviour of AlCoCrFeNi HEAs in the MD environment [57][58][59]. The mathematical expression of the EAM potential function is presented in equation ( 2), wherein total energy E EAM is defined as…”

Study of nanoindentation behavior of NiCrCoAl medium entropy alloys under indentation process using molecular dynamics

“…In the study of NiCrCoAl MEA substrates, this study used the embedded atom method (EAM) potential designed specifically for the Fe-Ni-Cr-Co-Al system. This potential was originally proposed by Caro and Farkas [37] and has been previously used to examine five-element systems such as Al-Co-Cr-Fe-Ni [38], Al0.4-Co-Cr-Fe-Ni [39] and Al-Co-Cr-Cu-Fe-Ni six-element system [40]. The EAM potential E EAM is employed as follows:…”