| About this Abstract |
| Meeting |
2020 TMS Annual Meeting & Exhibition
|
| Symposium
|
Additive Manufacturing: Materials Design and Alloy Development II
|
| Presentation Title |
A-64: Investigating Solidification and Liquation Cracking in AA7075 Electron Beam Freeform Fabrication Deposits |
| Author(s) |
Mary Cecilia Mulvaney, James M. Fitz-Gerald, Marcia S. Domack, Karen M. Taminger |
| On-Site Speaker (Planned) |
Mary Cecilia Mulvaney |
| Abstract Scope |
Airframe manufacturers have long sought an aluminum alloy (AA) that is compatible with additive manufacturing (AM) methods such as electron beam freeform fabrication (EBF3) and that offers strength levels comparable to AA7050. Currently, composition-driven solidification and liquation cracking deem high-strength, wrought 7xxx-series AAs ‘unweldable’ in fusion-based AM processes. This research investigated cracks and alloying element losses that limit the compatibility of 7xxx-series aluminum with EBF3. AA7075 linear deposits were fabricated with EBF3 on 0.25” or 1” baseplates at an energy density of 24 kJ/cm3. Fractographic analysis revealed solidification cracking across most deposits, with periodic, surface-breaking cracks accentuated by increased baseplate thickness. X-ray computed tomography (XCT) showed internal liquation cracks initiating directly below the final layer of most deposits, a result of the contracting molten pool straining the partially-melted zone of a previous layer. Correlations were noted between the extent of vaporization of Zn and Mg and that of cracking. |
| Proceedings Inclusion? |
Planned: Supplemental Proceedings volume |