Understanding and controlling low angle grain boundaries in additively manufactured metals

NON-TECHANICAL ABSTRACT

Additive manufacturing (AM), or 3D printing, with its ability to integrate materials synthesis and manufacturing into a single print, is attractive for a broad range of technological applications and may help usher industry 4.0 revolution. However, a fundamental understanding of the processing-structure-property relationship in most AM materials remains lacking.

Nearly all AM materials are made of numerous crystals called grains. Grains form interfaces when attached to each other. These interfaces can often control materials properties.

It has been particularly challenging to understand and control grain interfaces in AM materials, which may help us to achieve stronger and more bendable materials. This project advances understanding of the relationship between processing, interfaces between these grains, and resultant mechanical properties in a model 3D-printed material through an integrated experimental and computational effort.

The ability to control these interfaces via 3D printing could allow the creation for high-performance structural materials for various engineering applications. The involvement of under-represented undergraduate research through Samueli Diversity Program and collaborations with national laboratories provide educational and career advancement opportunities for young scientists in advanced manufacturing and materials science fields.

TECHANICAL ABSTRACT

The objective of this project is to understand and control low angle grain boundaries (LAGBs) in AM metals and alloys. The research focuses on pure metals fabricated by laser powder-bed-fusion (L-PBF), which often contain a substantial fraction of LAGBs that can lead to high strength, high ductility, and high thermal stability. The project aims at establishing mechanistic understanding of interconnections between laser processing parameters, interfacial microstructures (e.g., LAGBs), and resultant mechanical properties.

The research comprises of two major thrusts: Thrust 1 involves controlled fabrication of model materials with various fractions of LAGBs. An inverse pole figure orientation mapping using transmission electron microscopy (TEM) is used to characterize interfacial structures and correlate their characteristics to the deformation kinetics parameters and in situ synchrotron x-ray diffraction experiments.

Thrust 2 strives to develop processing sensitive models to correlate complex processing parameters and its thermal history with the observed microstructures. The processing model is tightly coupled with microstructure characterizations to reveal the fundamental relationship between the laser scan strategies and processing parameters and resultant microstructures.

The mechanistic insights obtained by these studies could guide the optimization of laser processing conditions to create high performance structural materials for diverse applications. Collaborations with national laboratories enhance the graduate student’s research experience. Partnership with the Samueli Diversity Program to engage undergraduate students from under-represented groups into these research activities increases the diversity of the future STEM workforce.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.