Date of Award

3-2025

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Ryan A. Kemnitz, PhD

Abstract

Tungsten (W), a Group VI transition metal, possesses a number of advantageous properties, most notably its impressive mechanical performance at extreme temperatures. While tungsten's nature render traditional manufacturing methods difficult, additive manufacturing through laser powder bed fusion (LPBF) presents a promising avenue for fabricating tungsten components. However, the material’s high ductile-to-brittle transition temperature combined with the embrittling effect of impurities mean that the residual stresses imparted by LPBF result in microcracking in tungsten, degrading its usefulness. This study sought to improve the characteristics of LPBF-W through the removal of embrittling oxygen content via alloying with low concentrations of reactive elements, including hafnium, silicon, titanium, and carbon. This strategy resulted in altered crack morphology in printed parts and significant improvements in strength and ductility in uniaxial compression, as well as in hardness, over pure tungsten. Fracture surface data indicates that the inclusion of these alloying constituents resulted in strengthened grain boundaries in the material, promoting transgranular fracture, which along with grain refinement and changes in crystallographic texture, contributed to the heightened mechanical characteristics.

AFIT Designator

AFIT-ENY-MS-25-M-150

Comments

An embargo was observed for this thesis.

This work is Distribution A: Approved for public release, Distribution Unlimited. PA case number 88ABW-2025-0493

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