Metals by micro-scale additive manufacturing: comparison of microstructure and mechanical properties

TL;DR

This paper reviews the microstructural and mechanical properties of metals produced by state-of-the-art micro-scale additive manufacturing methods, highlighting their potential and variability for microfabrication applications.

Contribution

It provides a comprehensive comparison of microstructure and mechanical properties of metals fabricated by various high-resolution AM techniques, establishing a baseline for future optimization.

Findings

Metals exhibit a wide range of microstructures and properties depending on the AM method.

Some AM-fabricated metals have dense, crystalline microstructures with excellent mechanical properties.

Performance variability is linked to microstructure and the physico-chemical principles of each printing method.

Abstract

Many emerging applications in microscale engineering rely on the fabrication of three-dimensional architectures in inorganic materials. Small-scale additive manufacturing (AM) aspires to provide flexible and facile access to these geometries. Yet, the synthesis of device-grade inorganic materials is still a key challenge towards the implementation of AM in microfabrication. Here, we present a comprehensive overview of the microstructural and mechanical properties of metals fabricated by most state-of-the-art AM methods that offer a spatial resolution $\leq$10$\mu$m. Standardized sets of samples were studied by cross-sectional electron microscopy, nanoindentation and microcompression. We show that current microscale AM techniques synthesize metals with a wide range of microstructures and elastic and plastic properties, including materials of dense and crystalline microstructure with excellent mechanical properties that compare well to those of thin-film nanocrystalline materials. The large variation in materials performance can be related to the individual microstructure, which in turn is coupled to the various physico-chemical principles exploited by the different printing methods. The study provides practical guidelines for users of small-scale additive methods and establishes a baseline for the future optimization of the properties of printed metallic objects $-$ a significant step towards the potential establishment of AM techniques in microfabrication.