Post-Processing Effects on Microstructure and Mechanical Properties of Additively Manufactured Ti-5Al-5V-5Mo-3Cr

Ti-5Al-5V-5Mo-3Cr (Ti-5553) is recognized as a promising material for structural parts due to the high hardenability and tailorable mechanical properties with heat treatment. Ti-5553 is a metastable beta titanium alloy available in both the wrought and powder form for additive manufacturing (AM). Beta titanium alloys offer an opportunity to increase hardenability, printability, strength, and damage tolerance versus the ubiquitous alpha-beta Ti-6Al-4V alloy. When printed with laser powder bed fusion, the Ti-5553 alloy solidifies as beta phase due to the quick cooling rate, which improves printability and results in a part that can be subsequently hardened with heat treatment.

Laser beam welding and heat treatment are post-processing options that can impact the final properties of the material. While it is ideal to integrate all features into a single AM part, limitations in build chamber size and design requirements can necessitate production of multiple parts with a secondary joining operation. Furthermore, an all beta as-printed microstructure may not be desirable for certain applications, and equivalent heat treatments on AM and conventionally manufactured material does not produce equivalent results.

In this study, various post-processing steps, including laser beam welding and heat treatment, will be performed on AM Ti-5553 and the resulting mechanical and microstructural properties assessed. Optical microscopy and scanning electron microscopy were used to characterize the microstructural constituents. Microhardness and tensile testing were used to assess mechanical properties. Impact of microstructure on stress distributions during tensile testing will be characterized with digital image correlation. Results from microstructural and mechanical characterization will be used to demonstrate the effect of post-processing on material behavior.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.