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Materials Science in Additive Manufacturing

ORIGINAL RESEARCH ARTICLE
Design, simulation, and experiments for direct

thixotropic metal 3D printing

1
1
Yifan Fei , Jie Xu , Donggang Yao , Richard Chiou , Jack Zhou *
1
3
2
1 Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA
2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
3 Department of Engineering, Leadership, and Society, Drexel University, Philadelphia, PA, USA

Abstract
Compared with current powder-based 3D metal printing, thixotropic metal 3D
printing has great potentials and advantages in equipment cost, product quality, and
process efficiency. In this paper, detailed problem statement, technique challenge,
and development method regarding thixotropic metal 3D printing are discussed.
A shear mixing and extruding prototype machine for thixotropic alloy fabrication
was designed. We developed a direct thixotropic metal 3D printing machine and
conducted a modeling and simulation process for the system. The printability of this
direct metal 3D printing machine was studied. At the end, conclusions and future
directions are also presented.

Keywords: Thixotropic 3D printing; Thixotropy; Semi-solid metal; Semi-solid metal
processing; Direct metal printing

*Corresponding author:
Jack Zhou (Zhoug@drexel.edu) 1. Introduction
Citation: Fei Y, Xu J, Yao D, For traditional metals such as titanium and stainless steel, laser melting/sintering of
et al., 2022, Design, simulation, and
experiments for direct thixotropic powders is a typical additive manufacturing (AM) process. However, laser melting/
metal 3D printing. Mater Sci Add sintering, not mentioning its slow and expensive process, is technically not suitable for
Manuf. 1(1): 5. chemically reactive metal powers such as Al, Mg, and Zn powders because these powers
http://doi.org/10.18063/msam.v1i1.5
under normal conditions are covered naturally by a passivated oxidation layer. Al, Zn,
Received: February 5, 2022 and Mg are metals with low melting point (660°C, 519.5°C, and 650°C, respectively),
Accepted: March 7, 2022 but their oxides have melting temperature close to 2000°C or even higher. The high laser
energy needed to break the oxides leads to poor fusion quality caused by undesired
Published Online: March 28, 2022
metallurgical defects such as porosity, cracking, and evaporation of alloying elements .
[1]
Copyright: © 2022 Author(s). Likewise, other powder-based binding (e.g., using an organic binder) and sintering
This is an Open Access article processes are also not suitable for processing Al, Mg, and Zn alloys into precision parts
distributed under the terms of the
Creative Commons Attribution with high fusion quality.
License, permitting distribution,
and reproduction in any medium, Ideally, liquid-state deposition by jetting or by extrusion is highly desired in AM of
provided the original work is low-melting-point Al, Mg, and Zn alloys. At present, almost all commercially available
properly cited. jetting/extrusion machines rely on a binder material to formulate a printable compound
Publisher’s Note: Whioce for metallic materials. One major drawback of the existing method is additional post-
Publishing remains neutral with printing process such as debinding and sintering. In jetting, droplets of building material
regard to jurisdictional claims in
published maps and institutional are formed by capillary breakup and selectively deposited on substrate; by comparison,
affiliations. in extrusion, material is extruded as a liquid thread and deposited on substrate

Volume 1 Issue 1 (2022) 1 http://doi.org/10.18063/msam.v1i1.5