Cyclic Nanoindentation and Nano-Impact Fatigue Mechanisms of Functionally Graded TiN/TiNi Film

Abstract

The mechanisms of nanoscale fatigue of functionally graded TiN/TiNi films have been studied using multiple-loading cycle nanoindentation and nano-impact tests. The functionally graded films were sputter deposited onto silicon substrates, in which the TiNi film provides pseudo-elasticity and shape memory behaviour, while a top TiN surface layer provides tribological and anti-corrosion properties. Nanomechanical tests were performed to investigate the localised film performance and failure modes of the functionally graded film using both Berkovich and conical indenters with loads between 100 lN and 500 mN. The loading history was critical to define film failure modes (i.e. backward depth deviation) and the pseudo-elastic/shape memory effect of the functionally graded layer. The results were sensitive to the applied load, loading mode (e.g. semi-static, dynamic) and probe geometry. Based on indentation force-depth profiles, depth-time data and post-test surface observations of films, it was concluded that the shape of the indenter is critical to induce localised indentation stress and film failure, and generation of pseudo-elasticity at a lower load range. Finite-element simulation of the elastic loading process indicated that the location of subsurface maximum stress near the interface influences the backward depth deviation type of film failure.

Inverse Method to Determine Fatigue Properties of Materials by Combining Cyclic Indentation and Numerical Simulation

“…In classical indentation experiments, only single loading and unloading on the specimen is performed for determining the desired mechanical properties. However, to study the fatigue life in materials, the cyclic indentation has attracted the attention of many authors [ 17 , 18 , 19 , 20 ]. For example, Lyamkin et al [ 17 ] have shown the potential of cyclic indentation for studying the fatigue properties.…”

“…As the cycles of indentations are repeated at the same location, the elastoplastic area of high cyclic indentation demonstrates fatigue under these conditions. For instance, a nanoimpact fatigue test has been studied by Faisal et al [ 18 ] by using cyclic indentation, and they have concluded that the indenter geometrical shape (Berkovich or conical) and the indentation loading history are crucial in inducing film failure. Moreover, Haghshenas et al [ 19 ] have employed cyclic nanoindentation in order to determine the indentation size effects and the strain rate sensitivity for tantalum.…”

Cyclic nanoindentation studies of HgCdTe epitaxial films

“…Nanoindentation has emerged as a suitable techniques to study the deformation behavior of the material in the near-surface region with varying loads and other related parameters [6][7][8][9][10][11][12]. It has been previously used for primarily studying the mechanical properties of HgCdTe alloys by several researchers [13][14][15][16][17].…”

“…These studies although explored several useful properties of the HgCdTe films, they were focussed mainly on single cycle nanoindenation and lacked in providing the desired parameters and deformation behaviour during actual lapping and polishing induced cyclic loading/unloading, which could better be studied using cyclic nanoindentation. The cyclic nanoindentation can provide crucial information on the evolution of mechanical properties with repeated loading-unloading of the near surface material [12,18,19].…”

Cyclic Indentation of Iron: A Comparison of Experimental and Atomistic Simulations

“…Mechanical characterization of materials by means of micro-and nanoindentation in the form of a hardness test or cyclic indentation with different indenter shapes and measurement parameters is a useful and well-established way to estimate important material parameters such as elastic modulus, or, in some cases, even fatigue limit [1][2][3][4]. Furthermore, numerical methods add more detailed information to the experiments concerning the stress-strain behavior [3,5,6]. Molecular dynamics (MD) simulations specifically provided a valuable understanding of the nanoplasticity and dislocation density generated underneath a nanoindenter [7,8].…”