About

Tim Horn is an Associate Professor in the Department of Mechanical and Aerospace Engineering at NC State University. His research focuses on additive manufacturing, including electron beam powder bed fusion and laser powder bed fusion, with an emphasis on surface height reconstructions, microstructural analysis, processability, residual strain, and defect imaging of various materials such as niobium C-103 alloys, ODS steel, and tungsten components. He has contributed to understanding the atomistic mechanisms governing additive manufacturing processability and mechanical behavior of refractory complex concentrated alloys. His work also encompasses the development and evaluation of new materials and processes for advanced manufacturing applications, including RF products and microstructure engineering. Tim Horn has authored numerous publications in reputable journals and conferences, advancing the field of additive manufacturing and materials characterization. He is actively involved in research that integrates experimental and computational analysis to improve manufacturing techniques and material performance.

Research topics

• Materials science
• Metallurgy
• Composite material
• Chemical engineering
• Computer Science
• Nuclear physics
• Environmental health
• Virology
• Medicine
• Internal medicine
• Nuclear engineering
• Engineering
• Chemistry
• Physics
• Mechanical engineering

Selected publications

• A Methodology for Manufacturing 3D Disordered Metamaterials Using Laser Powder Bed Fusion from Granular Packings and Hyperuniform Point Clouds

  2026-03-09

  articleOpen access

  Three-dimensional open geometries originating from nontraditional manufacturing designs such as point clouds, sphere packings, and mathematical file generation can be challenging to manufacture when the structures have disorder and overhanging geometric features. This study algorithmically created rigid 3D geometries representing granular packings and hyperuniform point clouds suitable for fabricating metallic disordered metamaterial (MDM) geometries using additive manufacturing. This approach produced nonrepeating connecting beam angles ranging from 0° to 90° relative to the build plate. Prototyping using laser powder bed fusion (LPBF) was challenging for the low-angle connecting beams, due to heat transfer differences when printing on powder compared with a solid substrate. An initial set of unsupported MDM geometries revealed failed connecting beams and geometric inaccuracy. We performed a systematic study to emulate the complex beam angles by printing cylinders ranging from 1.0 mm to 3.0 mm in diameter and angles ranging from 10°, to 90°, relative to the build plate. Unsupported connecting beams tended to lose geometric integrity at angles below 30°, and failed at 10°, resulting in geometric deviation on the downfacing surfaces. However, varying LPBF input energies and support strategies mitigated the geometric deviati

  PublisherDOI

• Development and Validation of a Modular Actively Cooled High-Heat-Flux Test Stand Utilizing an Electron-Beam Powder Bed Fusion Platform

  SSRN Electronic Journal · 2026-01-01

  preprintOpen access
  PublisherDOI

• Unveiling Atomistic Mechanisms Governing Additive Manufacturing Processability and Mechanical Behavior of a Refractory Complex Concentrated Alloy

  Advanced Functional Materials · 2025-11-10 · 1 citations

  article

  Abstract Extending the concept of complex concentrated alloys (CCAs) to the refractory alloys (solidus temperature over 2000 °C) space potentially facilitates the design of lightweight structural alloys with service temperatures that exceed those of Ni and Co‐based alloys. However, the room and elevated temperature tensile properties of the current refractory‐CCAs (R‐CCAs) are inferior to those of the Ni/Co‐based alloys. Furthermore, the manufacturing scalability of R‐CCAs remains challenging, in that cracks are prevalent in all R‐CCAs when processed using near‐net shape manufacturing processes, such as fusion‐based additive manufacturing (F‐BAM). Still, mechanisms governing the poor F‐BAM processability of R‐CCAs remain unexplored. To this end, this work unveils the atomistic mechanisms underlying F‐BAM process‐induced cracking in a NbTiTaMoHfZrC R‐CCA. The implications of light elements’ presence for intrinsic ductility and grain boundary cohesion, and subsequently for F‐BAM processability and mechanical behavior, are revealed. Leveraging the insights, we accomplish what is, to the best of the knowledge, the first instance of crack‐free F‐BAM processing of any R‐CCA. Additionally, the R‐CCA exhibits over 20% tensile ductility and ≈160 MPa tensile yield strength at 1200 °C. In addition to facilitating the design of lightweight R‐CCAs, findings enable scalable manufacturing of these ultra‐high temperature alloys for structural applications.

  PublisherDOI

• Variations in GARS powder microstructure as a function of powder chemistry and particle size

  Powder Technology · 2025-02-01 · 6 citations

  articleOpen access
  PublisherOA PDFDOI

• State AIDS Drug Assistance Programs’ Contribution to the United States’ Viral Suppression, 2015-2022

  medRxiv · 2025-04-06 · 2 citations

  preprintOpen access

  Background: State AIDS Drug Assistance Programs (ADAPs) provide HIV medication access for people with HIV (PWH) with low incomes in the United States (US). We quantified the proportion of viral suppression (VS) that is from ADAP clients for 2015-2022. Methods: For 2015-2022, we obtained viral load (VL) test results and VS data from publicly available, jurisdiction-level data on ADAP clients and PWH. We report descriptive statistics including the proportion of PWH with a VL who had VS and were supported by ADAPs. Results: After excluding jurisdictions with missing data, PWH who were included in the analysis for each year was 63.7-96.4%. VS for PWH each year was 60-66.3%. VS for ADAP clients was 81.2%-91.4%. In all years, compared to all PWH, a lower proportion of ADAP clients had a reported VL and a higher proportion had VS. Over 2015-2022, the average proportion of PWH who were ADAP clients was 23.1%, the proportion of PWH with VLs who were ADAP clients was 22.2%, and the proportion of PWH with VS who were ADAP clients was 30.8%. Conclusions: Almost a third of the entire VS rate was from ADAP clients, despite ADAP serving less than 25% of PWH. A much higher proportion of ADAP clients achieved VS, compared to PWH. ADAPs' impact is not due to ADAP clients being over represented among PWH with reported VLs. ADAP does not directly receive any federal Ending the HIV Epidemic (EHE) Initiative funding. Policymakers should examine how ADAPs can support the EHE Initiative.

  PublisherOA PDFDOI

• A Review of the Influence of Processing Parameters on ODS Steels Produced via Additive Manufacturing Techniques

  JOM · 2025-10-20

  articleOpen access

  Abstract This paper reviews current observations regarding processing conditions for oxide dispersion-strengthened steels consolidated through additive manufacturing techniques. Variations in ODS steels observed across process parameters include changes in grain size, grain texture, oxide size, density of oxides, porosity, melt pool characteristics, and mechanical properties. These properties were then compared across techniques to understand which techniques and processing conditions lead to the highest strength, ductility, and oxide density. Current literature suggests that a mix of grain types, in the form of either morphology or phase, can significantly increase the strength of printed ODS steels. Meanwhile, the most ductile samples, regardless of consolidation technique or matrix material, were made from feedstock with oxide additions located on the powder surface. Reported grain and oxide sizes were plotted against the ratio of laser power to scan speed, volumetric energy density, and normalized enthalpy. No strong correlation between these values and microstructural features was observed. The plots that were made suggest that a larger data set, more in-depth representative equations, and more defined material properties as a function of specific feedstock used are necessary to determine a value that can be correlated to the printed ODS steel microstructure.

  PublisherOA PDFDOI

• An integrated microstructural high strain-rate experimental and computational analysis of the spall behavior of additively manufactured niobium C-103 alloys

  Additive manufacturing · 2025-08-01 · 1 citations

  articleOpen access

  Niobium alloys, such as C-103, have been used for high-temperature applications due to their oxidation resistance, high-temperature behavior, and ductility. These characteristics also render C-103 as an attractive material for additive manufacturing (AM) processing. However, there is a lack of fundamental understanding of how defects, such as dislocation density and dislocation density interactions, and texture affect high strain-rate and spall behavior in body-centered cubic (b.c.c.) AM processed C-103 alloys. To address these challenges, electron beam powder bed fusion (EB-PBF) was used to process and fabricate C-103 samples with highly textured columnar grains. Disc-shaped plate-impact test specimens were extracted from the AM-fabricated samples, with the grains oriented either parallel or perpendicular to the build direction, for experiments with loading velocities of up to 600 m/s. The tests were instrumented with a photonic Doppler velocimetry (PDV) system to obtain time-resolved free surface velocity data of the sample and compute the spall strength of C-103 across a wide range of loading rates. These experimental measurements were then integrated with computational predictions based on a dislocation-based crystalline plasticity (DCP) approach coupled with a fracture formulation to understand how defects, such as dislocation densities, affect the spall strength and the defect behavior of C-103. The predictive framework provided insights into how spall cracks nucleate due to a combination of tensile wave reflection and dislocation-density accumulation, and how immobile dislocation accumulation ahead of multiple crack fronts can blunt spall propagation. This interrelated approach provides an understanding of high strain-rate and dynamic fracture of textured AM b.c.c. microstructures that can be tailored to mitigate high-impact velocity and spall in niobium alloys.

  PublisherDOI

• Trends in AIDS Drug Assistance Program Support for People With HIV, by Age, Sex, Race, and US Region, 2008‒2021

  American Journal of Public Health · 2025-06-05 · 2 citations

  articleOpen access

  Objectives. To evaluate trends in AIDS Drug Assistance Program (ADAP) utilization among demographic subpopulations. Methods. For 2008 to 2021, we collected US state-level data regarding ADAP client utilization and estimated HIV prevalence data. We used descriptive statistics to describe state ADAP utilization by geography, demographics (age, sex, race), and programmatic characteristics. Results. ADAP utilization proportion increased from 14.0% of all people with HIV (PWH) in 2008 to 22.3% in 2021. The proportion of female PWH supported by ADAP was lower in both 2008 (12.2%) and 2021 (18.3%) compared with the proportion of male PWH supported (2008: 14.5%; 2021: 22.9%). In 2008, the utilization proportion was lower for Black PWH at 11.7% compared with 16.0% for White PWH. In 2021, the utilization proportion for Black PWH was 25.2% compared with 28.4% for White PWH. Conclusions. ADAP enrollment and utilization have increased substantially. Despite equity gains, Black PWH and women were served at lower proportions by ADAP. Public Health Implications. National and state partners of ADAPs should examine ways to ensure that ADAP utilization is equitable in terms of age, sex, race/ethnicity, and other sociodemographic factors. ( Am J Public Health. 2025;115(8):1288–1298. https://doi.org/10.2105/AJPH.2025.308101 )

  PublisherOA PDFDOI

• Multimodal Defect Imaging of Pure Tungsten Components Fabricated via Electron Beam Powder Bed Fusion

  Journal of Materials Engineering and Performance · 2025-03-07 · 3 citations

  articleOpen accessSenior author

  Abstract The utilization of additive manufacturing (AM) techniques for refractory materials in high-temperature environments has significantly expanded because of the ability to fabricate geometrically complex components. Electron beam powder bed fusion (EB-PBF), which provides lower residual stress, a cleaner vacuum environment, and better efficiency for high melting point, is one of the best-suited AM methods to produce advanced refractory components. However, the property variation attributed to the heterogeneous microstructure and process-induced defects has hindered the widespread adoption of EB-PBF-produced material like tungsten. While numerous in-situ monitoring and defect detection methods have been demonstrated for EB-PBF, a workflow that compares and evaluates process-induced abnormalities from different imaging perspectives is still limited. This study examines a feature-embedded tungsten component manufactured via the EB-PBF process to demonstrate the defect detection capabilities of a multimodal defect imaging workflow. The predefined and process-induced defects are evaluated by harnessing various imaging techniques, including in-situ electron imaging, layerwise near-infrared (NIR) imaging, post-build high-energy x-ray computed tomography (CT), and conventional destructive metallography. The results highlight the strengths and limitations of distinctive defect imaging techniques concerning specific defect types, sizes, and conditions. It was found that electron imaging can provide more abnormal detection capabilities while maintaining a higher measuring accuracy, against the conventional metallography in this case study, compared with NIR and CT imaging techniques.

  PublisherOA PDFDOI

• An Integrated Microstructural High Strain-Rate Experimental and Computational Analysis of the Spall Behavior of Additively Manufactured Niobium C-103 Alloys

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

Frequent coauthors

• Christopher Rock

  17 shared

• Christopher Ledford

  Government of the United States of America

  16 shared

• Harvey West

  North Carolina State University

  13 shared

• Iver E. Anderson

  Iowa State University

  13 shared

• Diana Gamzina

  11 shared

• Emma White

  Government of the United States of America

  9 shared

• P. Frigola

  RadiaBeam Technologies (United States)

  8 shared

• Matthew Auton

  8 shared

Labs

• Mechanical and Aerospace EngineeringPI