Microstructure and Mechanical Properties of a Ni-Based Superalloy Thin Film Investigated by Micropillar Compression

Abstract

The microstructure and local micromechanical properties of a Ni-based superalloy thin film produced by magnetron sputtering using ERBO/1 sputter targets were investigated. The thin film consists of columnar nanograins (an average size of ~ 45 nm) with mostly < 111 > orientation. Inside the nanograins, very fine nanotwins with an average thickness of ~ 3 nm are present. In-situ micropillar compression tests, complemented by nanoindentation, were conducted to evaluate the mechanical characteristics. The microhardness and Young’s modulus of the thin film correspond to ~ 11 and 255 GPa, respectively, the critical strength to ~ 4 GPa. The plastic deformation of the micropillars occurs through the formation of a shear band initiating at the top of the pillar. Inside the shear band, globular grains with random orientation form during the deformation process, while the regions near to the shear band remained unaffected.

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“…The stress state, phase formation kinetics, and the nature of such a small volume affects the thermodynamic equilibrium state, so that the phases that can form or the location of the phase boundaries are not necessarily the same as found in bulk material of the same composition. [1,21] This issue can be seen in a recent publication by Kalchev et al [22] DOI: 10.1002/adem.202301316…”

“…The stress state, phase formation kinetics, and the nature of such a small volume affects the thermodynamic equilibrium state, so that the phases that can form or the location of the phase boundaries are not necessarily the same as found in bulk material of the same composition. [ 1,21 ] This issue can be seen in a recent publication by Kalchev et al [ 22 ] who investigated the Ni‐based superalloy ERBO/1 as a thin film created by magnetron sputtering and found a fcc single‐phase, nano‐grained, and nano‐twinned microstructure which was never observed in bulk specimens. [ 23–26 ] The investigation of microstructure related properties is also challenging.…”