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Materials Science in Additive Manufacturing Thixotropic metal 3D printing

Figure 14. Comparison of line width under different platform moving speed.

A C 5. Conclusion
This study demonstrated that metals and alloys may
be thixotropically processed and printed by a properly
designed extrusion-based 3D printing system, and the
thixotropic properties can improve the metal printability.
Direct thixotropic metal printing can help optimize
the metal printing procedure to reduce post-printing
B
treatments. Thixotropy as a time-dependent property for
SSM processing was investigated, and the major process
parameter on printability was also examined. Low-
melting-point alloys were chosen as materials for process
demonstration and feasibility study.
An integrated SSM extruder and system were designed
D and utilized to produce uniform and qualified semi-
solid alloy. The SSM extruder was designed to endure
the harsh environment in alloy processing convoluted
with thermomechanical competing effects. Meanwhile,
modulated studies were conducted to understand the
functional considerations of individual building blocks in
the SSM extruder, for example, a properly designed heating
mechanism. The SSM extruder may be used for direct
printing or, alternatively, to create thixotropic alloy filaments
that may be reheated for printing. In addition, computation
simulations were conducted to better understand the
dynamics of the process. Our simulation results showed that
the viscosity and velocity change during processing could
Figure 15. Printed line for (A) 1.5 mm diameter nozzle and (B) 1.0mm significantly affect the dynamics of extrusion. The simulation
diameter nozzle (C) Thixotropic bismuth alloy was extruded out from the also assisted in the determination of a temperature profile to
reservoir at an extrusion speed of 7.87 mm/s. (D) Printing test for 1.5 mm create the desired liquid fraction for thixotropic processing.
nozzle with zig-zag geometry. The first section of the line was considered
as the extruder preparation section, and the material became stable and Parametric studies were also conducted to understand
continuous after this section. the effects of the major process parameters on the

Volume 1 Issue 1 (2022) 11 http://doi.org/10.18063/msam.v1i1.5