Use of Indentation Plastometry to Obtain Stress-Strain Curves from Small Superalloy Components Made by Additive Manufacturing

Abstract

This investigation concerns superalloy samples that were produced by an additive manufacturing procedure. Microstructural examination confirmed that they exhibited a columnar grain structure, with the grains elongated in the growth (“build”) direction and exhibiting a strong texture involving alignment of parallel to this axis. Samples were tensile tested along both build and transverse directions, being found to be both stiffer and harder in the latter. Corresponding plots obtained solely via the novel technique of Indentation Plastometry (involving measurement of the profiles of indents created using a spherical indenter and extraction from these of the stress-strain relationship) were found to be entirely consistent with these directly-measured curves. Furthermore, it is shown that full 3-D characterization of the indent profiles can be used to obtain at least a semi-quantitative indication of the nature and strength of the plastic anisotropy. This constitutes a significant advance in the context of a technique that could have a transformative effect on mechanical testing procedures.