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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Microstructural evolution of nanotwinned Al-Zr alloy with significant 9R phase

Aluminum (Al) alloys have a multitude of applications, notably in the automotive, aerospace and coating industries, yet they exhibit significantly lower mechanical strength than conventional steels. Nanotwins drastically improve mechanical strength while retaining ductility. However, the high SFE of Al largely prevents twinning. Here, we synthesize Al-Zr alloy films containing an abundance of incoherent twin boundaries and 9R phases. These alloys exhibit an extended solid solubility of Zr, retaining a columnar nanotwinned structure across all compositions. These films reach a hardness up to 4.2 GPa with 10 at% Zr and demonstrate the capacity for producing strong Al alloys with nanotwins.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Diffusion, atomic transport, and ordering in Al-Zr alloys: FCC and liquid phases

Additive manufacturing of materials with controlled microstructure demands knowledge of atomic scale properties near the solid-liquid transition state. Many of these properties are not affordable by experimental techniques and computer modeling is the possible solution to the problem. In this paper, we present the results of an extended atomistic study of intrinsic atomic transport due to vacancy diffusion in FCC and L12 solid phases and diffusion in the liquid phase of Al-Zr alloys. A deceleration of the overall self-diffusion was observed when Zr was added to Al. The effect was stronger in the solid and weaker in the liquid. Additionally, the effect was strongly temperature dependent in the solid phases, but not in the liquid. Atomic transport was chemically biased: transport of Zr atoms was significantly slower than that of Al atoms, and this bias effect was stronger in the solid phases. The overall diffusion and chemical ordering processes in the liquid state were five to six orders in magnitude faster than in the solid. Chemical short-range order parameters in the liquid saturated at values close to those in the ordered L12 structure of Al3Zr. Chemical and structural ordering in the solid phases was negligible over the modeled microsecond time scale. Here, the results are discussed in view of optimizing additive manufacturing parameters for the controlled formation of metastable L1 2 precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis of precipitation-strengthened Al-Sc, Al-Zr and Al-Sc-Zr alloys via selective laser melting of elemental powder blends

Selective laser melting is used to create Al-1.5Sc, Al-1.5Zr and Al-0.75Sc-0.75Zr (at.%) alloys from blends of elemental Al, Sc, and Zr powders. This study investigates elemental alloying elements (Sc and Zr) which are high-melting and highly reactive, unlike previous work which focused on more concentrated elemental additions of lower-melting, lower-reactivity Cu and Si to aluminum. High-speed in situ synchrotron x-ray imaging and diffraction show that the 20–30 μm Al, Sc, and Zr powders fully melt and sufficiently mix in the molten state to create, on solidification, a homogeneous distribution of primary, micron-size L12 precipitates (Al 3 Sc, Al 3 Zr, and Al 3 (Sc,Zr), respectively) and nucleate micron-size Al matrix grains, as confirmed by SEM imaging of cross-sections. Here, a second laser pass, simulating a realistic additive-manufacturing build condition, fully remelts the initial volume which shows, after solidification, the same Al 3 (Sc,Zr) L1 2 primary micro-precipitates and very fine Al grains. After aging at 300–400°C, the alloys show large increases in hardness, consistent with an exceptionally high number density (1.4 × 10 24 m –3 ) and volume fraction (2.5%) of secondary Al 3 (Sc,Zr) nano-precipitates with a Sc-rich core and Zr-rich shell, as measured via atom-probe tomography.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Improving creep resistance of Al-0.27Zr-0.08Sn (wt%) via cold swaging while maintaining high electrical conductivity

This study investigates the effect of mechanical cold work (0, 50, and 90% cross-sectional area reduction via swaging) on the creep properties of cast aluminum alloys with high electrical conductivity including high-purity Al (HP-Al), Al-0.15Zr (Al-Zr), and Al-0.27Zr-0.08Sn (Al-Zr-Sn, wt%). The Al-Zr alloy is strengthened by Zr in solid solution while the Al-Zr-Sn alloy is additionally strengthened by Al3Zr nanoprecipitates (8 nm diameter). After 90% cold swaging, the alloys exhibit grains elongated along the swaging direction with their widths ranging between 8 and 152 μm perpendicular to the swaging direction. Creep testing at 200 °C shows that the minimum creep rate of all 90% swaged alloys shows high sensitivity to stress, which can be modeled via a threshold stress σth. Increasing swaging magnitude from 0 to 50 to 90% in Al-Zr-Sn improves the creep resistance without reducing electrical conductivity. The formation of subgrains, increased dislocation density, and columnar grain structure in swaged alloys all enhance creep resistance. HP-Al swaged to 90% exhibits much lower creep resistance (σth = 18 MPa) due to subgrain coarsening and the absence of precipitates compared to Al-Zr (σth = 40 MPa) and Al-Zr-Sn (σth = 40 MPa), which maintain stable subgrain structures and benefit from solid solution strengthening and Al3Zr nanoprecipitates, respectively. Although Al3Zr precipitates are known to stabilize the deformed microstructure by pinning grain-boundaries, this work demonstrates that Zr in solid solution alone can effectively stabilize the deformed microstructure resulting in enhanced creep resistance. This effect of Zr solute on stabilizing grain boundaries for creep performance was not previously well-defined in the literature. Despite similar creep performances of Al-Zr and Al-Zr-Sn, the latter shows 70% higher room-temperature microhardness and slightly improved electrical conductivity (56%IACS (International Annealed Copper Standard) vs. 57%IACS, respectively). This work provides new insights into creep mechanisms of cold-worked Al–Zr alloys that will guide the design of heat-resistant Al conductors for high-demand applications.

Coello ramirez, Ismael [Northwestern University,]↗
DOE OSTI2025

Relative phase stability of L1 2 and DO 22 /DO 23 structures in Al 3 Nb, Al 3 Zr and Al 3 V compounds

The relative stability of the different tri-aluminide (Al 3 M) phases in three binary systems (M = Zr, Nb and V) was assessed for their potential to form fine cubic L1 2 precipitates in additively manufactured alloys. Supersaturated thin films of Al-(8–30) at% M were sputtered and heat treated during in-situ x-ray diffraction (XRD) measurements to observe the temperature ranges of stability for each phase. As-sputtered films were then processed with laser tracks simulating additive manufacturing solidification conditions, and the formation of phases in the laser tracks was correlated with density functional theory (DFT) and nucleation rate calculations. We found that the metastable L1 2 structure is highly competitive with the stable DO 23 structure in the Al-Zr system, but much less stable than the DO 22 structure in the Al-Nb system, and both the DO 22 and Al 8 V 5 structure in the Al-V system. Furthermore, these experimental results were found to be in good agreement with the DFT and kinetic calculations, as we determined that the metastable L1 2 in Al-Zr only requires a small amount of undercooling to favor its nucleation over the stable DO 23 , suggesting additive manufacturing can be a viable pathway to develop Al-Zr alloys strengthened by a high volume fraction of L1 2 Al 3 Zr phase.

Perrin, Alice E. [Oak Ridge National Laboratory (O↗
DOE OSTI2025

Additively-manufactured Al-0.3Zr-0.2Ce-0.2Cu alloy with high creep resistance and electrical conductivity

Here, a new, solute-lean Al-0.3Zr-0.2Ce-0.2Cu (wt.%) alloy is developed for additive manufacturing that overcomes the classical tradeoff between conductivity and creep resistance. The rapid-cooling-enabled supersaturation of Zr, and its uniform distribution in α-Al matrix, along with formation of submicron (Ce,Cu)-rich intermetallic particles on solidification lead to unusually high creep resistance at 200 °C. Near-zero secondary creep rates are achieved up to the alloy yield stress (YS) of 65 MPa at 200 °C in as-fabricated state. The Zr-solute-induced dislocation-climb suppression mechanism underlying this improvement also restricts dynamic recovery above YS, as noted from appreciable primary creep and its transitioning to near-zero secondary creep rates. A combination of relatively coarse, epitaxially-grown α-Al grains, low Zr concentration in α-Al, and the impurity-scavenging effect of Ce to purify α-Al matrix produces high electrical conductivity of ∼48 %IACS. Aging precipitation of L1 2 -Al 3 Zr nanoprecipitates doubles the YS (to ∼150 MPa) at room temperature and increases alloy conductivity to ∼58 %IACS, but loss of solid-solution Zr out of α-Al matrix leads to activation of dislocation climb, degrading the creep properties as compared to the supersaturated Al-Zr solid solution in the as-fabricated state. Compared to L1 2 -Al 3 Zr nanoprecipitates, submicron (Ce,Cu)-rich particles formed on solidification are more effective at impeding dislocation climb, producing a threshold stress for dislocation creep of ∼ 50 MPa at 200 °C. The new alloy design concepts, especially solute-induced dislocation-climb suppression for creep resistance, explored here may pave way for the design of new metallic alloys for thermal/electrical conductors and other high-temperature applications.

Additive Manufacturing↗
DOE OSTI2025

Intermetallic phase formation in Al-Si-Zr alloys during hot isostatic pressing revealed by experiments and molecular dynamics

Understanding phase transformations at alloy interfaces is critical for the design of advanced structural materials. Here, in this study, we investigate the formation mechanisms of the Al 2 SiZr intermetallic phase in the Al-Si-Zr system under hot isostatic pressing (HIP) using molecular dynamics (MD) simulations and thermodynamic analysis. A unique aspect of our approach in MD involves the replacement of a disordered Al 2 SiZr stoichiometry with an ordered phase at the Al-Zr interface once HIP results in the desired Al 2 SiZr stoichiometry, allowing us to compute the total energetic cost of transformation by accounting for both formation energies and diffusion barriers. Diffusion coefficients and activation energies, extracted across a range of temperatures, reveal that HIP substantially enhances atomic mobility, creating favorable stoichiometry for phase evolution. Our results show that Al 2 SiZr phase formation is kinetically unfavorable at lower temperatures but becomes feasible when the thermodynamic driving energy surpass a critical energy threshold.

Roy, Ankit [Pacific Northwest National Laboratory ↗
NASA NTRS1985

Development of powder metallurgy 2XXX series Al alloy plate and sheet materials for high temperature aircraft structural applications, FY 1983/1984

The objective of this investigation is to fabricate and evaluate PM 2124 Al alloy plate and sheet materials according to NASA program goals for damage tolerance and fatigue resistance. Previous research has indicated the outstanding strength-toughness relationship available with PM 2124 Al-Zr modified alloy compositions in extruded product forms. The range of processing conditions was explored in the fabrication of plate and sheet gage materials, as well as the resultant mechanical and metallurgical properties. The PM composition based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.60 wt. pct. Zr was selected. Flat rolled material consisting of 0.250 in. thick plate was fabricated using selected thermal mechanical treatments (TMT). The schedule of TMT operations was designed to yield the extreme conditions of grain structure normally encountered in the fabrication of flat rolled products, specifically recrystallized and unrecrystallized. The PM Al alloy plate and sheet materials exhibited improved strength properties at thin gages compared to IM Al alloys, as a consequence of their enhanced ability to inhibit recrystallization and grain growth. In addition, the PM 2124 Al alloys offer much better combinations of strength and toughnessover equivalent IM Al. The alloy microstructures were examined by optical metallographic texture techniques in order to establish the metallurgical basis for these significant property improvements.

Chellman, D. J.↗
DOE OSTI2020

Materials Data on ZrAl by Materials Project

ZrAl crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Zr is bonded in a 7-coordinate geometry to seven equivalent Al atoms. There are a spread of Zr–Al bond distances ranging from 2.90–3.04 Å. Al is bonded in a 9-coordinate geometry to seven equivalent Zr and two equivalent Al atoms. Both Al–Al bond lengths are 2.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr4Al3 by Materials Project

Zr4Al3 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. there are two inequivalent Zr sites. In the first Zr site, Zr is bonded in a 8-coordinate geometry to eight Zr and six equivalent Al atoms. There are a spread of Zr–Zr bond distances ranging from 2.63–3.41 Å. All Zr–Al bond lengths are 3.06 Å. In the second Zr site, Zr is bonded in a 6-coordinate geometry to nine Zr and six equivalent Al atoms. All Zr–Zr bond lengths are 3.15 Å. All Zr–Al bond lengths are 3.13 Å. Al is bonded to eight Zr and four equivalent Al atoms to form a mixture of face, edge, and corner-sharing AlZr8Al4 cuboctahedra. All Al–Al bond lengths are 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr2Al by Materials Project

Zr2Al is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Zr is bonded in a 4-coordinate geometry to one Zr and four equivalent Al atoms. The Zr–Zr bond length is 2.95 Å. All Zr–Al bond lengths are 2.93 Å. Al is bonded in a 10-coordinate geometry to eight equivalent Zr and two equivalent Al atoms. Both Al–Al bond lengths are 2.69 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr3Al2 by Materials Project

Zr3Al2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are three inequivalent Zr sites. In the first Zr site, Zr is bonded in a distorted square co-planar geometry to four equivalent Al atoms. All Zr–Al bond lengths are 3.06 Å. In the second Zr site, Zr is bonded in a 6-coordinate geometry to six equivalent Al atoms. There are two shorter (2.80 Å) and four longer (2.94 Å) Zr–Al bond lengths. In the third Zr site, Zr is bonded in a 6-coordinate geometry to six equivalent Al atoms. There are two shorter (2.84 Å) and four longer (2.94 Å) Zr–Al bond lengths. Al is bonded in a 10-coordinate geometry to eight Zr and two equivalent Al atoms. There are one shorter (2.63 Å) and one longer (2.98 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr3Al by Materials Project

Zr3Al is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Zr is bonded to eight equivalent Zr and four equivalent Al atoms to form ZrZr8Al4 cuboctahedra that share corners with twelve equivalent ZrZr8Al4 cuboctahedra, edges with eight equivalent AlZr12 cuboctahedra, edges with sixteen equivalent ZrZr8Al4 cuboctahedra, faces with four equivalent AlZr12 cuboctahedra, and faces with fourteen equivalent ZrZr8Al4 cuboctahedra. All Zr–Zr bond lengths are 3.10 Å. All Zr–Al bond lengths are 3.10 Å. Al is bonded to twelve equivalent Zr atoms to form AlZr12 cuboctahedra that share corners with twelve equivalent AlZr12 cuboctahedra, edges with twenty-four equivalent ZrZr8Al4 cuboctahedra, faces with six equivalent AlZr12 cuboctahedra, and faces with twelve equivalent ZrZr8Al4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr2Al3 by Materials Project

Zr2Al3 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Zr is bonded in a 7-coordinate geometry to nine Al atoms. There are a spread of Zr–Al bond distances ranging from 2.88–3.21 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to six equivalent Zr and four equivalent Al atoms. There are two shorter (2.66 Å) and two longer (2.71 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 10-coordinate geometry to six equivalent Zr and four Al atoms. Both Al–Al bond lengths are 2.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr5Al3 by Materials Project

Zr5Al3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Zr sites. In the first Zr site, Zr is bonded in a 6-coordinate geometry to two equivalent Zr and four equivalent Al atoms. Both Zr–Zr bond lengths are 2.70 Å. All Zr–Al bond lengths are 2.90 Å. In the second Zr site, Zr is bonded in a 6-coordinate geometry to six Al atoms. There are a spread of Zr–Al bond distances ranging from 2.92–3.14 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to eight equivalent Zr and two equivalent Al atoms. Both Al–Al bond lengths are 2.70 Å. In the second Al site, Al is bonded in a distorted q6 geometry to ten Zr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr5Al3 by Materials Project

Zr5Al3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Zr sites. In the first Zr site, Zr is bonded in a 8-coordinate geometry to two equivalent Zr and six equivalent Al atoms. Both Zr–Zr bond lengths are 2.77 Å. All Zr–Al bond lengths are 2.92 Å. In the second Zr site, Zr is bonded in a 5-coordinate geometry to five equivalent Al atoms. There are a spread of Zr–Al bond distances ranging from 2.86–3.07 Å. Al is bonded in a 9-coordinate geometry to nine Zr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr2Al by Materials Project

Zr2Al crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Zr sites. In the first Zr site, Zr is bonded in a 8-coordinate geometry to eight Zr and six equivalent Al atoms. There are two shorter (2.98 Å) and six longer (3.20 Å) Zr–Zr bond lengths. All Zr–Al bond lengths are 3.20 Å. In the second Zr site, Zr is bonded to six equivalent Zr and five equivalent Al atoms to form a mixture of distorted face and corner-sharing ZrZr6Al5 trigonal bipyramids. There are three shorter (2.83 Å) and two longer (2.98 Å) Zr–Al bond lengths. Al is bonded in a 5-coordinate geometry to eleven Zr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZrAl2 by Materials Project

ZrAl2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Zr is bonded in a 12-coordinate geometry to four equivalent Zr and twelve Al atoms. There are three shorter (3.26 Å) and one longer (3.27 Å) Zr–Zr bond lengths. There are nine shorter (3.11 Å) and three longer (3.14 Å) Zr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to six equivalent Zr and six equivalent Al atoms to form a mixture of corner, edge, and face-sharing AlZr6Al6 cuboctahedra. All Al–Al bond lengths are 2.70 Å. In the second Al site, Al is bonded to six equivalent Zr and six Al atoms to form a mixture of corner, edge, and face-sharing AlZr6Al6 cuboctahedra. There are two shorter (2.58 Å) and two longer (2.71 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗