Correlation of Microstructure and Nanomechanical Properties of Additively Manufactured Inconel 718

Abstract

Additive manufacturing (AM) has emerged as a crucial technology in recent decades, particularly within aerospace industry. However, the thermally cyclic nature of these processes introduce significant variations and defects in microstructure, which can adversely affect final part performance and hinder the widespread adoption of the technology. Traditionally, characterization of AM parts has relied on conventional bulk testing methods, which involve analyzing many samples to gather sufficient data for statistical analysis. Unfortunately, these methods are unable to account for local nanoscale variations in material properties caused by the microstructure, as they measure a single averaged property for each tested sample. In this work, we use AM Inconel 718 as a model system in developing a novel approach to correlate nanomechanical properties obtained through nanoindentation with microstructure obtained through electron backscatter diffraction (EBSD). By associating mechanical properties obtained from each indent with the corresponding crystallographic direction measured with EBSD, we calculate the weighted average hardness and modulus for each orientation. This enables us to generate inverse property figure maps depicting the relationship between mechanical properties and crystallographic direction. Our method yields results in good agreement with literature when calculating the part modulus and hardness. Furthermore, it effectively captures nanoscale variations in properties across the microstructure. The key advantage of this methodology is its capability to rapidly test a single AM part and generate a large dataset for statistical analysis. Complementing existing macroscale characterization techniques, this method can help improve AM part performance prediction and contribute to the wider adoption of AM technologies.