Abstract
A new additively manufactured (AM) Al-7.5Ce-4.5Ni-0.4Mn-0.7Zr (wt.%) near-eutectic alloy is reported, which shows unprecedented creep resistance up to 400 °C (a homologous temperature of 0.72). The eutectic solidification microstructure comprises ∼ 27 vol% of coarsening-resistant second phase network with an ultrafine (<100 nm) inter-phase spacing. Both Mn and Zr contribute to creep resistance of the alloy. Small amount of Mn addition promotes selection of coarsening resistant phases without compromising the alloy processability. Zr not only improves hot-tearing resistance, but further enhances the second phase coarsening resistance resulting in improved creep resistance. Neutron diffraction performed during creep deformation reveals that the underlying mechanism for creep resistance in this alloy is impedance to dislocation motion stemming from the ultrafine eutectic solidification microstructure, whereas load transfer strengthening becomes less effective as the creep temperature increases. The second phase forms a continuous network in the as-fabricated condition, which is maintained during long-term creep at 300 °C. However, this network is fragmented into fine dispersoids at higher temperatures. It is proposed that the rate-limiting deformation mechanism at 300–400 °C is (i) dislocation climb for the alloy with fragmented second phase dispersoids and (ii) Orowan looping for the alloy with a continuous second phase network. The present design of an AM-processable multicomponent eutectic alloy with high creep resistance can be applied to other metallic systems exhibiting eutectic reactions, with expected extreme creep resistance.
| Original language | English |
|---|---|
| Article number | 119787 |
| Journal | Acta Materialia |
| Volume | 268 |
| DOIs | |
| State | Published - Apr 15 2024 |
Funding
The research was co-sponsored by the Powertrain Materials Core Program (PMCP) under the Vehicle Technologies Office (VTO) and Advanced Materials & Manufacturing Technologies Office (AMMTO) under Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy (DOE). APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at ORNL. The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments. In situ creep experiments were performed at the Vulcan beamline of Spallation Neutron Source, a DOE Office of Science User Facility operated by ORNL. The authors would like to thank Kevin Sisco for help with neutron diffraction experiments, Yan Chen for training on GSAS software for Rietveld refinement, Kelsey Epps for ex situ creep testing, and Dana McClurg for heat treatments.
| Funders | Funder number |
|---|---|
| Center for Nanophase Materials Sciences | |
| U.S. Department of Energy | |
| Office of Science | |
| Office of Energy Efficiency and Renewable Energy | |
| Oak Ridge National Laboratory | |
| Advanced Materials and Manufacturing Technologies Office |
Keywords
- Additive manufacturing
- Aluminum alloys
- Creep
- Eutectic alloys
- Neutron diffraction
