Effect of Precrack Configuration and Texture Variation on the Elastic-Plastic Fracture Toughness of Additively Manufactured Ti-6Al-4V parts

Published

July 28, 2020

Author(s)

Enrico Lucon, Jake Benzing, Nik Hrabe

Abstract

A comparison between fatigue precracked and sharp-notched Charpy-type fracture toughness specimens will be presented for characterizing the elastic-plastic fracture toughness of Ti- 6Al-4V parts (produced by electron beam melting, a powder bed fusion method). The effect of processing and post-processing conditions on crystallographic texture, grain morphology, elastic-plastic fracture toughness of additively manufactured Ti-6Al-4V parts are currently under investigation at NIST in Boulder, Colorado. Industrially relevant processing variables include the use of support structures (supported and non-supported) and variations in scan lengths (20 – 90 mm). The specimens tested were also subjected to Hot Isostatic Pressing (HIP), which is a commercial post-processing step known to seal internal porosity in additively manufactured Ti-6Al-4V parts. More specifically, new sub- transus HIP cycles (800 °C, 200 MPa) were applied, which tend to seal the internal porosity, but are not expected to drastically change the crystallographic texture. In this work, the following variables and their effects on room temperature fracture toughness (measured by means of three-point-bending unloading compliance tests on Charpy-type specimens) are specifically addressed: notch configuration (fatigue precrack vs. sharp EDM notch), specimens directly attached to the build plate (non- supported) vs. connected to the build plate using standard thin wafer supports (supported), as well as the presence of macroscopically visible lack of fusion zones on the fracture surface of some of the specimens tested. The results of this preliminary investigation will guide the choices for the remaining fracture toughness characterization of Ti-6Al-4V under various processing and post-processing conditions.

Volume

9

Issue

5

Conference Dates

May 15-17, 2019

Conference Location

Denver, CO, US

Conference Title

19th International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics
(42nd National Symposium on Fatigue and Fracture Mechanics)

Pub Type

Conferences

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DOI Link

Keywords

Additive manufacturing, elastic-plastic fracture toughness, lack of fusion, tearing modulus, Ti-6Al-4V, unloading compliance

Citation

Lucon, E. , Benzing, J. and Hrabe, N. (2020), Effect of Precrack Configuration and Texture Variation on the Elastic-Plastic Fracture Toughness of Additively Manufactured Ti-6Al-4V parts, 19th International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics (42nd National Symposium on Fatigue and Fracture Mechanics), Denver, CO, US, [online], https://doi.org/10.1520/MPC20190155 (Accessed April 30, 2024)