Date of Award

2026-05-01

Degree Name

Master of Science

Department

Engineering

Advisor(s)

Francisco Medina

Abstract

This study investigates the influence of build interruption on the microstructure, microhardness, tensile behavior, and fatigue performance of laser powder-bed fusion (LP-BF) specimens in both the as-built and heat-treated conditions using the GRX-810 alloy. The heat treated condition incorporated Hot Isostatic Pressing (HIP), and both interrupted and uninterrupted samples were evaluated to isolate the effects of processing variables. Results indicate that build interruption did not produce significant changes in yield strength, ultimate tensile strength, or ductility, suggesting that the LP-BF process is robust enough to tolerate controlled interruptions without compromising bulk mechanical integrity. Microhardness measurements and microstructural observations further supported this, showing consistent hardness values and no clear discontinuities at the interruption interface. In contrast, heat-treated specimens exhibited reduced strength and increased ductility compared to as-built samples, a behavior attributed to grain coarsening and reduced dislocation density during HIP. Additionally, HIP contributed to the closure of internal defects such as porosity, leading to a more homogeneous microstructure. Fatigue testing revealed a slight improvement in fatigue life for HIP-processed samples, likely due to the reduction of stress concentrators associated with additive manufacturing defects. However, build interruption did not have a measurable impact on fatigue performance, as crack initiation was primarily linked to pre-existing defects rather than the interruption interface. Fractographic analysis showed mixed-mode fracture behavior across all conditions, with features of both ductile and brittle mechanisms, as well as evidence of defect-driven crack initiation and propagation during cyclic loading

Language

en

Provenance

Received from ProQuest

File Size

102 p.

File Format

application/pdf

Rights Holder

Javier Eduardo Lares Monarrez

Download

Share

COinS