In Situ TEM Study of Interaction between Dislocations and a Single Nanotwin under Nanoindentation

Abstract

Nanotwinned (nt) materials exhibit excellent mechanical properties, and have been attracting much more attention of late. Nevertheless, the fundamental mechanism of interaction between dislocations and a single nanotwin is not understood. In this study, in situ transmission electron microscopy (TEM) nanoindentation is performed, on a specimen of a nickel (Ni) alloy containing a single nanotwin of 89 nm in thickness. The specimen is prepared using focused ion beam (FIB) technique from an nt surface, which is formed by a novel approach under indentation using a developed diamond panel with tips array. The stiffness of the specimen is ten times that of the pristine counterparts during loading. The ultrahigh stiffness is attributed to the generation of nanotwins and the impediment of the single twin to the dislocations. Two peak loads are induced by the activation of a new slip system and the penetration of dislocations over the single nanotwin, respectively. One slip band is parallel to the single nanotwin, indicating the slip of dislocations along the nanotwin. In situ TEM observation of nanoindentation reveals a new insight for the interaction between dislocations and a single nanotwin. This paves the way for design and preparation of high-performance nt surfaces of Ni alloys used for aircraft engines, gas turbines, turbocharger components, ducts, and absorbers.

Deformation Twinning and Detwinning in Face‐Centered Cubic Metallic Materials

“…Strength and ductility are the two most important mechanical properties for structural materials . Deformation twinning has been considered to be an effective way to increase both strength and ductility . It is generally believed that TBs have a similar effect as GBs, which are strong barriers for dislocation motion due to the Hall–Petch effect.…”

“…[37,82,83] Deformation twinning has been considered to be an effective way to increase both strength and ductility. [37,38,[84][85][86] It is generally believed that TBs have a similar effect as GBs, which are strong barriers for dislocation motion due to the Hall-Petch effect. Twins in Cu, Ni, and steel with TB spacing of tens to hundred nanometers show an obvious Hall-Petch-type strengthening effect.…”

Interface-governed nanometric machining behaviour of Cu/Ag bilayers using molecular dynamics simulation

“…[7][8][9][10][11] However, nanoscale bilayer materials are routinely underutilized because of high machining cost and lower machining efficiency. Thus the deformation behaviors as property indicators are fully analyzed to further understand the machining of these materials in the nanoscale level, [12][13][14][15] thereby improving the machining properties and efficiency. Experimental observation oen has the features of uncertain measurements, high costs and long time durations.…”

“…Experimental observation oen has the features of uncertain measurements, high costs and long time durations. 14,15 Therefore, MD simulation is applied to track the deformation dynamics, identify the defect structure and reveal the deformation mechanism in nanoscale bilayer or polycrystal materials. 16,17 A number of MD simulation studies have provided valuable insights into the ultra-precision machining of bilayers.…”

Designing nanoindentation simulation studies by appropriate indenter choices: Case study on single crystal tungsten

“…Recently, the fundamental mechanism between dislocations and a single nanotwin was elucidated by in situ transmission electron microscopy (TEM) nanoindentation [12]. High speed scratching or grinding using a single diamond tip are proposed [13], to address the fundamental mechanisms for abrasive machining, such as grinding, polishing and lapping.…”