Vardanyan Vardan Hoviki, Urbassek Herbert M
Physics Department and Research Center OPTIMAS, University Kaiserslautern, Erwin-Schrödinger-Straße, D-67663 Kaiserslautern, Germany.
Materials (Basel). 2020 Apr 4;13(7):1683. doi: 10.3390/ma13071683.
Nanoindentation simulations are performed for a Ni(111) bi-crystal, in which the grain boundary is coated by a graphene layer. We study both a weak and a strong interface, realized by a 30 ∘ and a 60 ∘ twist boundary, respectively, and compare our results for the composite also with those of an elemental Ni bi-crystal. We find hardening of the elemental Ni when a strong, i.e., low-energy, grain boundary is introduced, and softening for a weak grain boundary. For the strong grain boundary, the interface barrier strength felt by dislocations upon passing the interface is responsible for the hardening; for the weak grain boundary, confinement of the dislocations results in the weakening. For the Ni-graphene composite, we find in all cases a weakening influence that is caused by the graphene blocking the passage of dislocations and absorbing them. In addition, interface failure occurs when the indenter reaches the graphene, again weakening the composite structure.
对镍（111）双晶体进行了纳米压痕模拟，其中晶界由石墨烯层包覆。我们分别研究了由30°和60°扭转边界实现的弱界面和强界面，并将复合材料的结果与元素镍双晶体的结果进行了比较。我们发现，当引入强（即低能量）晶界时，元素镍会硬化，而引入弱晶界时则会软化。对于强晶界，位错通过界面时感受到的界面势垒强度导致了硬化；对于弱晶界，位错的限制导致了弱化。对于镍-石墨烯复合材料，我们发现在所有情况下，由于石墨烯阻挡位错通过并吸收位错，都会产生弱化影响。此外，当压头到达石墨烯时会发生界面失效，这也会再次削弱复合材料结构。
