Assessment of intra-build variations in tensile strength in electron beam powder-bed fusion Ti-6Al-4V part 1: Effects of build height

Published

June 2, 2022

Author(s)

Nicholas Derimow, Alejandro Romero, Aldo Rubio, Cesar Terrazas, Newell Moser, Orion Kafka, Jake Benzing, Francisco Medina, Ryan Wicker, Nik Hrabe

Abstract

In this work, rectangular blocks of electron beam powder-bed fusion (PBF-EB) additively manufactured (AM) Ti-6Al-4V were built, such that a total of 68 mini-tensile test coupons could be extracted for mechanical testing over a range of build height and build plate locations. These as-built tensile test coupons were uniaxially tested to fracture and subsequently studied via scanning electron microscopy, micro X-ray computed tomography, and inert gas fusion chemical analysis to systematically study the intra-build variations in tensile properties, microstructure, porosity, and chemistry. There were no significant contributions to this variation in yield strength (YS) from build location, porosity, grain size, or crystallographic texture. A strong correlation was observed between YS and build height, where YS was observed to decrease with increasing build height, up to 35 mm. Inert gas fusion oxygen measurements reveal the same trend, suggesting that oxygen content variation as a function of build height is causing the observed YS variation. The source of the oxygen content variation is thought to be a transient source of oxygen, such as moisture in the powder and build chamber. The establishment of this oxygen variation and its correlation to tensile properties motivates and facilitates improvements to PBF-EB Ti-6Al-4V processing, including powder mixing and handling.

Citation

Materials Science and Engineering A

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.msea.2022.143354

Local Download

Keywords

additive manufacturing, ti-6al-4v, oxidation, tensile properties, electron beam powder-bed fusion

Citation

Derimow, N. , Romero, A. , Rubio, A. , Terrazas, C. , Moser, N. , Kafka, O. , Benzing, J. , Medina, F. , Wicker, R. and Hrabe, N. (2022), Assessment of intra-build variations in tensile strength in electron beam powder-bed fusion Ti-6Al-4V part 1: Effects of build height, Materials Science and Engineering A, [online], https://doi.org/10.1016/j.msea.2022.143354, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934251 (Accessed September 13, 2024)