Elevated temperature characterization of electron beam freeform fabricated Ti–6Al–4V and dispersion strengthened Ti–8Al–1Er

Authors

R W. Bush, U.S. Air Force Academy
C A. Brice, Lockheed Martin Aeronautics Co.

Document Type

Article

Date of this Version

2012

Citation

Materials Science and Engineering A 554, 2012

Comments

U.S. Government work

Abstract

Electron beam freeform fabrication is an additive manufacturing process that can be used to build fully dense, structural metallic parts directly from a three-dimensional computer model. This technique can replace conventional fabrication methods, such as forging or machining from plate, and enable significant cost, time, and tool savings. Additionally, this method enables the fabrication of alloys with novel compositions that are not well suited to production via ingot metallurgy processes. Ti–8Al–1Er is an experimental dispersion strengthened titanium alloy composition that requires rapid cooling to achieve optimal properties and thus is not amenable to ingot metallurgy production methods. Oxide dispersion strengthened alloys, such as Ti–8Al–1Er are known to have excellent thermal stability and improved high temperature properties.

In this work, the room temperature tensile, elevated temperature tensile, creep properties and oxidation resistance of electron beam additive manufactured Ti–6Al–4V and Ti–8Al–1Er were measured and compared to those of laser beam additive manufactured Ti–8Al–1Er and wrought Ti–6Al–4V. Elevated temperature tensile properties were measured between 93◦ and 538 ◦C. Creep tests were performed between 425◦ and 455 ◦C at stresses between 345 and 483 MPa. It was found that the elevated temperature properties of the electron beam additive manufactured products are comparable to those of wrought forms. The elevated temperature strengths of Ti–8Al–1Er are comparable to those of Ti–6Al–4V in percentage of room temperature strength retained at temperature. Based on a Larson–Miller analysis of the creep test data, the creep resistance of Ti–8Al–1Er is superior to that of Ti–6Al–4V, but inferior to that of laser beam additive manufactured Ti–8Al–1Er. The inter-alloy improvement in creep resistance increases with decreasing temperature and stress. The oxidation resistance of Ti–8Al–1Er is superior to that of Ti–6Al–4V.