Year

2026

Season

Spring

Paper Type

Master's Thesis

College

College of Computing, Engineering & Construction

Degree Name

Master of Science in Material Science & Engineering (MS)

Department

Engineering

NACO controlled Corporate Body

University of North Florida. School of Engineering

Committee Chairperson

Dr. Jutima Simsiriwong

Second Advisor

Dr. Nelson Delfino de Campos Neto

Rights Statement

http://rightsstatements.org/vocab/InC/1.0/

Third Advisor

Dr. Alexandra Schonning

Fourth Advisor

Dr. Albina Mikhaylova

Department Chair

Dr. Daniel Santavicca

College Dean

Dr. William Klostermeyer

Abstract

Additive manufacturing (AM) of TI-6AL‑4V Extra‑Low Interstitial (ELI) enables complex geometries for fatigue‑critical medical device applications, yet fatigue performance remains sensitive to process‑induced defects. This work investigates the effect of laser process parameter selection on the microstructure, mechanical properties, and fatigue behavior of TI- 6AL‑4V ELI fabricated via laser powder bed fusion (L‑PBF) using a Renishaw RenAM system. The influence of laser parameters was isolated by holding powder chemistry, build orientation, scan strategy, sub‑transus annealing, and post‑processing constant between a non‑optimized baseline and an optimized parameter set selected based on tensile performance.

Optical microscopy showed the optimized condition exhibited improved microstructural quality, reflected by reduced porosity and less pronounced raster track features, consistent with improved melt pool stability. Tensile testing demonstrated increased ultimate tensile strength and elongation to failure for the optimized condition. Four‑point bending fatigue tests conducted in accordance with ASTM F382 revealed higher mean fatigue life and the occurrence of runout specimens at lower applied stress levels relative to the baseline condition, while higher stress levels produced increased scatter. Fractographic analysis confirmed surface‑initiated fatigue cracking associated with surface‑connected lack‑of‑fusion defects in both conditions, with reduced defect severity observed for optimized specimens. The experimentally observed crack initiation locations were consistent with stress concentration regions identified using finite element analysis of the ASTM F382 test configuration.

These results suggest that tensile‑based laser parameter selection may be an effective approach for improving fatigue performance in AM TI-6AL‑4V ELI, while highlighting the importance of surface defect mitigation for fatigue‑critical medical device applications.

Download

Share

COinS
 

Accessibility Statement

This item was created or digitized before April 24, 2027, or is a reproduction of legacy material created before that date. It is preserved in its original, unmodified state specifically for research, reference, or historical recordkeeping. In accordance with the ADA Title II Final Rule, the Library provides accessible versions of archival materials by request. If you are experiencing difficulty accessing the information on the site due to a disability, please submit a request through the following form for assistance.