About this Abstract |
| Meeting |
2025 AWS Professional Program
|
| Symposium
|
2025 AWS Professional Program
|
| Presentation Title |
Mechanical and Microstructural Considerations for Partial Penetration Ti-6Al-4V Laser Welds |
| Author(s) |
Jeffrey M. Rodelas, Erin Barrick, Mark Foster, Amanda Jones, Jack Herrmann, Austin Pisani, Austin Olivier, Donald Susan |
| On-Site Speaker (Planned) |
Jeffrey M. Rodelas |
| Abstract Scope |
The low process energy input, high melting efficiency, and ability to miniaturize make partial penetration laser welding a ubiquitous joining technique for high-reliability hermetic packaging. Considerable mechanical behavior data for laser-welded titanium alloys exist; however, most studies characterize full penetration welds. As a result, there is a need for representative partial penetration mechanical behavior for high-reliability designs. Partial penetration butt weld specimens of Ti-6Al-4V in the STA condition were produced using a continuous wave fiber laser, resulting in weld penetration approximately 55-57% of the specimen thickness (0.0625 in.). Specimens were loaded in tension until failure. Despite the expected 5-10% strain to failure for Ti-6Al-4V weld metal, the partial penetration laser weld specimens failed in a characteristically brittle manner. The behavior observed for Ti-6Al-4V partial penetration welds was distinct versus partial penetration laser welds for near-beta alloy, Ti-5Al-5Mo-5V-3Cr, and 304L stainless steel, which exhibit comparatively graceful failure when loaded beyond an apparent yield stress. Partial penetration Ti-6Al-4V laser welds made with varying levels of atmospheric contamination (up to 10% air) also exhibited similarly brittle tensile behavior. Fractographic examination showed limited evidence of macroscopic plasticity; however, microscopically ductile features were observed on crack surfaces. Increasing levels of air contamination in the coaxially delivered shielding gas resulted in higher levels of secondary cracking. Microstructural examination of the Ti-6Al-4V partial penetration welds revealed acicular martensitic weld metal microstructures with no apparent morphological changes due to air contamination up to 10%. Microhardness mapping, however, showed an increase of 50 HVN in weld metal versus uncontaminated welds. The overmatched weld metal, coupled with the stress triaxiality associated with the weld root during tensile loading, results in distinctly brittle mechanical behavior for partial penetration laser welds that must be considered in high-reliability engineering designs.
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| Proceedings Inclusion? |
Undecided |