Abstract
Gas-atomized powders of two ternary alloys, Al-3.60Mg-1.18Zr and Al-3.66Mg-1.57Zr (wt.%), were densified via laser powder bed fusion. At energy densities ranging from 123 to 247 J/mm3, as-fabricated components are near-fully densified (relative density 99.2–99.9%) as verified by X-ray tomography. While Mg acts a solid-solution strengthener, Zr creates two types of metastable L12 Al3Zr precipitates, each playing dual roles: (a) sub-micrometer Al3Zr particles form in the melt upon solidification and act as grain refining agents, nucleating fine aluminum grains, which (i) prevent hot-tearing during the rapid solidification inherent to laser melting and (ii) enhance tensile strength (Hall-Petch strengthening) and ductility (influence a heterogenous grain structure) after fabrication; (b) Al3Zr nano-precipitates form in the solid alloy during subsequent aging, which (i) precipitation-strengthen the alloy leading to an increase of >40% in strength over the as-fabricated value, and (ii) promote thermal stability of the fine grain size (and the associated Hall-Petch strengthening) after exposure to high temperature due to the slow kinetics of Al3Zr coarsening (from the sluggish diffusivity of Zr in solid Al-Mg). While the Zr-richer alloy shows higher yield and ultimate tensile strength in the as-fabricated state, both alloys have identical mechanical properties after peak aging. Interconnected bands of fine (∼0.8 μm), equiaxed, isotropic grains and coarser (∼1 × 10 μm), columnar, textured grains – both containing oxide particles and Al3Zr precipitates - provide a combination of high yield strength and high ductility (e.g., ∼354 MPa, and ∼20%, respectively) with isotropic values in both as-fabricated and peak-aged samples, unlike Al-Si alloys processed via laser fusion of commercial Al-Si-based powders. The pre-alloyed, gas-atomized Al-Mg-Zr powders do not contain expensive alloying elements such as Sc, nor do they require blending with a second powder to nucleate fine grains, making them excellent candidates for economical, large-scale additive manufacturing applications.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 35-44 |
| Number of pages | 10 |
| Journal | Acta Materialia |
| Volume | 153 |
| DOIs | |
| State | Published - Jul 1 2018 |
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Keywords
- Additive manufacturing
- Aluminum alloys
- Heterogeneous grain structure
- Selective laser melting
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys
Cite this
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Microstructure and mechanical properties of Al-Mg-Zr alloys processed by selective laser melting. / Croteau, Joseph R.; Griffiths, Seth; Rossell, Marta D.; Leinenbach, Christian; Kenel, Christoph; Jansen, Vincent; Seidman, David N; Dunand, David C; Vo, Nhon Q.
In: Acta Materialia, Vol. 153, 01.07.2018, p. 35-44.Research output: Contribution to journal › Article
TY - JOUR
T1 - Microstructure and mechanical properties of Al-Mg-Zr alloys processed by selective laser melting
AU - Croteau, Joseph R.
AU - Griffiths, Seth
AU - Rossell, Marta D.
AU - Leinenbach, Christian
AU - Kenel, Christoph
AU - Jansen, Vincent
AU - Seidman, David N
AU - Dunand, David C
AU - Vo, Nhon Q.
PY - 2018/7/1
Y1 - 2018/7/1
N2 - Gas-atomized powders of two ternary alloys, Al-3.60Mg-1.18Zr and Al-3.66Mg-1.57Zr (wt.%), were densified via laser powder bed fusion. At energy densities ranging from 123 to 247 J/mm3, as-fabricated components are near-fully densified (relative density 99.2–99.9%) as verified by X-ray tomography. While Mg acts a solid-solution strengthener, Zr creates two types of metastable L12 Al3Zr precipitates, each playing dual roles: (a) sub-micrometer Al3Zr particles form in the melt upon solidification and act as grain refining agents, nucleating fine aluminum grains, which (i) prevent hot-tearing during the rapid solidification inherent to laser melting and (ii) enhance tensile strength (Hall-Petch strengthening) and ductility (influence a heterogenous grain structure) after fabrication; (b) Al3Zr nano-precipitates form in the solid alloy during subsequent aging, which (i) precipitation-strengthen the alloy leading to an increase of >40% in strength over the as-fabricated value, and (ii) promote thermal stability of the fine grain size (and the associated Hall-Petch strengthening) after exposure to high temperature due to the slow kinetics of Al3Zr coarsening (from the sluggish diffusivity of Zr in solid Al-Mg). While the Zr-richer alloy shows higher yield and ultimate tensile strength in the as-fabricated state, both alloys have identical mechanical properties after peak aging. Interconnected bands of fine (∼0.8 μm), equiaxed, isotropic grains and coarser (∼1 × 10 μm), columnar, textured grains – both containing oxide particles and Al3Zr precipitates - provide a combination of high yield strength and high ductility (e.g., ∼354 MPa, and ∼20%, respectively) with isotropic values in both as-fabricated and peak-aged samples, unlike Al-Si alloys processed via laser fusion of commercial Al-Si-based powders. The pre-alloyed, gas-atomized Al-Mg-Zr powders do not contain expensive alloying elements such as Sc, nor do they require blending with a second powder to nucleate fine grains, making them excellent candidates for economical, large-scale additive manufacturing applications.
AB - Gas-atomized powders of two ternary alloys, Al-3.60Mg-1.18Zr and Al-3.66Mg-1.57Zr (wt.%), were densified via laser powder bed fusion. At energy densities ranging from 123 to 247 J/mm3, as-fabricated components are near-fully densified (relative density 99.2–99.9%) as verified by X-ray tomography. While Mg acts a solid-solution strengthener, Zr creates two types of metastable L12 Al3Zr precipitates, each playing dual roles: (a) sub-micrometer Al3Zr particles form in the melt upon solidification and act as grain refining agents, nucleating fine aluminum grains, which (i) prevent hot-tearing during the rapid solidification inherent to laser melting and (ii) enhance tensile strength (Hall-Petch strengthening) and ductility (influence a heterogenous grain structure) after fabrication; (b) Al3Zr nano-precipitates form in the solid alloy during subsequent aging, which (i) precipitation-strengthen the alloy leading to an increase of >40% in strength over the as-fabricated value, and (ii) promote thermal stability of the fine grain size (and the associated Hall-Petch strengthening) after exposure to high temperature due to the slow kinetics of Al3Zr coarsening (from the sluggish diffusivity of Zr in solid Al-Mg). While the Zr-richer alloy shows higher yield and ultimate tensile strength in the as-fabricated state, both alloys have identical mechanical properties after peak aging. Interconnected bands of fine (∼0.8 μm), equiaxed, isotropic grains and coarser (∼1 × 10 μm), columnar, textured grains – both containing oxide particles and Al3Zr precipitates - provide a combination of high yield strength and high ductility (e.g., ∼354 MPa, and ∼20%, respectively) with isotropic values in both as-fabricated and peak-aged samples, unlike Al-Si alloys processed via laser fusion of commercial Al-Si-based powders. The pre-alloyed, gas-atomized Al-Mg-Zr powders do not contain expensive alloying elements such as Sc, nor do they require blending with a second powder to nucleate fine grains, making them excellent candidates for economical, large-scale additive manufacturing applications.
KW - Additive manufacturing
KW - Aluminum alloys
KW - Heterogeneous grain structure
KW - Selective laser melting
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UR - http://www.scopus.com/inward/citedby.url?scp=85046464655&partnerID=8YFLogxK
U2 - 10.1016/j.actamat.2018.04.053
DO - 10.1016/j.actamat.2018.04.053
M3 - Article
VL - 153
SP - 35
EP - 44
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -