Profilometry-based indentation plastometry to obtain stress-strain curves from anistropic superalloy components

Dr Yuanbo Tang and Professor Roger Reed FREng from Oxford Materials and a team from Cambridge and Plastometrex Limited investigated superalloy samples produced by an additive manufacturing procedure. 

A microstructural examination confirmed that the samples exhibited a columnar grain structure, with the grains elongated in the growth ('build') direction, and showed a strong texture involving alignment of <100> parallel to this axis.

The samples were tensile tested along teh build and the transverse directions, and it was they were both stiffer and harder in the transverse direction.  This was well characterised anisotropy, which made the sample suitable for studying it affected the outcomes from an indentation-based procedure for obtaining stress-strain curves (known as Profilometry-based Inverse FEM for Plasticity Parameters from Indentation (PIP)).  

True stress-strain curves obtained using this methodology were found to be entirely consistent with the directly-measured curves.

The samples showed that full 3-D characterisation of the indent profiles can be used to obtain at least a semi-quantitative indicating of the nature and strength of the plastic anisotropy.  

This finding constitutes a significant advance in the context of a technique that could have a tranformative effect on mechanical testing procedures.

Read the full paper as published in Materialia.