CAREER: A Novel Approach for Tungsten Alloy Additive Manufacturing Enabled by Rolling-Assisted Extrusion, Binder Removal, and Hybrid-Phase Sintering

About This Grant

This Faculty Early Career Development (CAREER) award supports fundamental research to understand the processing mechanisms of a novel additive manufacturing (AM) approach for high-performance tungsten alloy fabrications. Tungsten alloys hold significant promise for use in demanding applications, such as aerospace, defense, medical, and nuclear fields, due to their high density and excellent mechanical properties. High-temperature AM, such as powder bed fusion or direct energy deposition, has been used to fabricate tungsten alloy components with short lead time. Nevertheless, tungsten alloys are extremely refractory and have a remarkable ductile-to-brittle transition that makes the materials highly sensitive to temperature changes. The large temperature gradient and huge heating/cooling rates in high-temperature AM pose critical challenges to the fabrication because of the inherent brittleness of tungsten alloys to cracking, leading to the difficulty in creating highly dense components. To address the challenges, this CAREER project takes a unique manufacturing strategy to better tailor and control the formation and densification of as-built components through compression-enabled filament-extrusion AM, binder removal, and hybrid-phase sintering integrating both solid-phase densification and liquid-phase strengthening. If successful, this project will advance the innovation of next-generation, scalable AM processes for high-performance refractory alloy fabrications. The integrated educational and outreach activities will inspire and train students at all levels to acquire multidisciplinary knowledge and skills for future excellence in manufacturing. This CAREER project aims to establish a fundamental understanding of the mechanisms underlying the innovative extrusion-based, sintering-assisted AM of tungsten alloys. First, in-situ rolling-induced particle compaction behaviors during the extrusion of green parts will be discovered. A multi-physics simulation framework coupling discrete element method with computational fluid dynamics will be created to identify the distributions of metal particles and interlayer pores. Then, atomic-scale phase transformation and microstructure evolution during hybrid-phase sintering will be unveiled using molecular dynamics and phase field model, respectively. The established mechanistic understanding will be experimentally validated by measuring phase content, grain morphology/size, and relative density. Finally, time-dependent macroscopic shrinkage, ductile-to-brittle transition temperature, and thermomechanical properties of finished tungsten specimens will be quantified using an integrated approach of constitutive modeling, in-situ measurements within a customized furnace, and thermomechanical testing. The research outcomes can be readily generalized to other metal AM processes, such as ink writing, binder jetting, and aerosol jet printing, that are followed by subsequent debinding and sintering. 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.