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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys

This paper investigates the mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys as a function of Mg content. Cold spray (CS) is a solid-state deposition process that can be used as a repair technique for structural components. However, the limited ductility of cold sprayed materials is an unsettled issue in CS community. Herein, reproducible, and significantly increased elongation to failure (∼15%) in as-deposited conditions is reported in CS Al-Mg binary alloys with low Mg content (≤ 2.5 wt%). Furthermore, reducing Mg content down to 2.5 wt% in CS Al-Mg binary alloys demonstrated comparable mechanical strength to its wrought counterparts. Strengthening mechanisms were analyzed in wrought and CS Al-Mg alloys based upon microstructural characteristics, such as grain size, Mg solute concentration, and dislocation density. A quantitative evaluation of yield strength revealed that grain boundary strengthening is predominant in CS Al-Mg alloys as compared with their wrought counterparts. When comparing among CS Al-Mg binary alloys of different compositions, Mg solute concentration, and dislocation density governed mechanical strength. In conclusion, the underlying mechanism for the variation of mechanical properties and strengthening mechanisms is discussed in terms of these microstructural characteristics.

Additive manufacturing↗
NASA NTRS1991

Correlated study of initial Sr-87/Sr-86 and Al-Mg isotopic systematics and petrologic properties in a suite of refractory inclusions from the Allende meteorite

The abundance and the distribution of Al-26, and the initial Sr-87/Sr-86 ratios were determined in a suite of six coarse-grained Ca-Al-rich inclusions from the Allende meteorite, using, respectively, petrographic and chemical characterizations and ion-probe mass spectrometric analyses of the Al-Mg isotopic system, and thermal emission spectrometric analyses of the Rb-Sr system. Results establish a firm association between primitive Al-26/Al-27 and primitive Sr-87/Sr-86 found in each of these inclusions. None of the results required interpretation in terms of heterogeneously distributed Al-26.

Podosek, Frank A.↗
NASA NTRS1990

The roles of Zr and Mn in processing and superplasticity of Al-Mg alloys

Processing studies have been conducted on two alloys, of nominal compositions Al-10Mg-0.1Zr or Al-10Mg-0.5Mn, in order to clarify the role of the dispersoid forming Zr or Mn additions. Mechanical property data reveal that the Mn-containing alloy has a lower maximum elongation but exhibits superplastic response over a broader range of temperature. Microstructural investigations and texture analyses were utilized to assess the effect of the presence of Al8Mg5 precipitates in combination with either Al3Zr or Al6Mn dispersoid particles during isothermal rolling at 300 C and subsequent tensile deformation at temperatures from 200-425 C.

Mcnelley, Terry R.↗
DOE OSTI2024

Effect of Si impurities on microstructure and tensile properties of a cast Al-Mg-Fe alloy

Al-Mg alloys are attractive for structural castings owing to their superior strength and ductility in the as-cast state. However, given the tight tolerance for impurities, Al-Mg alloys produced from secondary sources still face multiple challenges. Here, we report the effect of increased Si impurity (0.05–1.6 wt%), which is commonly found in secondary Al sources, on microstructure and tensile properties of a cast Al-4.3Mg-1.6Fe (wt%) alloy, commercially referred to as Castaduct-42 alloy. Microstructural characterization revealed that Si addition increased the volume fraction, size, and aspect ratio of primary Al13Fe4 intermetallic particles as well as the volume fraction of other binary and ternary eutectic phases. Tensile testing results demonstrated that increasing Si impurities from 0.05 to 1.6 wt% reduced ductility from 14.3 ± 1.4 % to 2.2 ± 1.0 %. A particle cracking damage accumulation model coupled with failure analysis indicated primary Al13Fe4 intermetallic particles to be the major contributing factor to the deterioration in ductility with increasing Si content. Additionally, the stabilizing effect of Si on primary Al 13 Fe 4 was inconsistent with the CALPHAD calculation results based on existing CALPHAD databases which predict a slightly decreasing primary Al13Fe4 phase fraction with increasing Si concentration. This work provides new insights into the phase stability and mechanical behavior of the lesser studied Al-Mg-Fe-Si alloy system that will contribute to the development of sustainable cast Al-Mg based alloys.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Lack of Evidence of In-Situ Decay of Aluminum-26 in a FeO-Poor Ferromagnesian Crystalline Silicate Particle, Pyxie, from Comet Wild 2

One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.

Nakashima, D.↗
DOE OSTI2025

Mineralogical and isotopic constraints on early, high-temperature events and reservoirs recorded in the interior of a Type B Ca-Al-rich inclusion from the reduced CV3 chondrite Vigarano

A coordinated mineralogical and oxygen and Al-Mg isotopic study of a Type B Ca-Al-rich inclusion (CAI) from the reduced CV3 chondrite Vigarano was carried out using electron microprobe analysis, transmission electron microscopy, and secondary ion mass spectrometry. This CAI, a once molten igneous object, shows heterogeneous oxygen isotopic compositions among its constituent mineral phases. Spinel is uniformly 16 O-rich with Δ 17 O ≤ −23 ‰. The Δ 17 O values of Al,Ti-diopside in the CAI core range from −11 ‰ to −18 ‰, which are positively correlated with its TiO 2 contents, whereas diopside in the Wark–Lovering (WL) rim is 16 O-rich with Δ 17 O = −23 ‰. Melilite in the CAI mantle shows Δ 17 O values ≤ −10 ‰ only when Åk <15 but becomes more 16 O-poor (Δ 17 O = −3 ‰ to −9 ‰) when Åk >15 . These correlated chemical and oxygen isotopic variations were likely established during crystallization of melilite and Al,Ti-diopside from a partial melt, while spinel preserves the original 16 O-rich composition of the CAI precursor. We infer that a partial melt was isotopically evolving from 16 O-rich to 16 O-poor during melilite crystallization, then back to 16 O-rich during Al,Ti-diopside crystallization via exchange with different gas reservoirs of 16 O-poor and 16 O-rich compositions during heating event(s). Our Al-Mg isotopic measurements of the CAI core and mantle define a single isochron with an inferred initial 26 Al/ 27 Al ratio of (4.93 ± 0.18) × 10 −5 , indistinguishable from that of the WL rim. This indicates that multiple high-temperature events and oxygen isotope exchange with isotopically distinct gas reservoirs occurred rapidly during the CAI formation.

Al-Mg isotopic systematic↗
DOE OSTI2025

Initial Conditions of Planet Formation: Time Constraints from Small Bodies and the Lifetime of Reservoirs in the Solar Protoplanetary Disk

This review explores the timescales of the initial phase of planet formation, from nebular dust (CAIs and chondrules) to planetesimal accretion and differentiation, using evidence from meteorite research. Aluminium-Mg systematics of CAIs indicate either an extended period of CAI formation (∼0.3 Ma) or an initial 26 Al heterogeneity, with evidence supporting a homogeneous 26 Al abundance in the protoplanetary disk. Thermal and aqueous alteration on the parent body can disturb the U-Pb and Al-Mg chronometers in chondrules. Focusing on relatively robust isochron data from plagioclase of pristine (types ≤3.05) chondrites indicates a shift in chondrule formation locations, moving from the inner to the outer disk over time. Ages of basaltic achondrites show that silicate differentiation on small bodies was well underway within the first few million years (Ma) of our solar system. Their age record, however, reveals inconsistencies between different chronometers, partly caused by (i) secondary disturbances due to thermal metamorphism, aqueous alteration, or impacts, (ii) the presence of xenolithic minerals, and (iii) potentially variable initial 26 Al abundances due to disturbances at the mineral scale. Nucleosynthetic isotope data indicate that parent bodies of iron and stony meteorites formed in two distinct regions within the protoplanetary disk: the inner, non-carbonaceous (NC) and the outer, carbonaceous (CC) region. Based on Hf-W chronometry it has been demonstrated that NC and CC parent bodies of magmatic iron meteorites segregated their cores within ∼1–3 Ma after CAI formation, implying that parent body accretion occurred within <1 Ma in both reservoirs. Combining accretion ages with nucleosynthetic data further reveals that, at first order, NC and CC reservoirs in the solar protoplanetary disk were established within 1 Ma and existed over several Ma with limited exchange between them. In the CR chondrite accretion region of the disk, planetary bodies formed over at least 3 Ma, while in most other regions, formation spanned at least 1 Ma, with minimal changes in nucleosynthetic isotope compositions. Aerodynamical size sorting of dust likely introduced or amplified some of these variations.

26Al distribution↗
DOE OSTI2025

Secondary corundum‐bearing assemblages in Allende Ca,Al‐rich inclusions: Mineralogy, petrology, oxygen, and aluminum–magnesium isotope systematics

Here, we report on the mineralogy, petrology, oxygen, and aluminum–magnesium isotopic systematics of the secondary corundum-bearing assemblages in type B CAIs 3529Z and 3529G and fluffy type A (FTA) CAI ALH-2 from Allende (CV > 3.6). In 3529Z and 3529G, 2–5 μm-sized euhedral-to-subhedral corundum grains associate with secondary alumoåkermanite [(Ca,Na) 2 AlSi 2 O 7 ], grossular, spinel, grossite, celsian, kushiroite, and wadalite. In ALH-2, 2–5 μm-sized euhedral-to-subhedral corundum grains associate with secondary grossular, nepheline, spinel, and kushiroite. In 3529Z and 3529G, corundum and associated secondary grossite, spinel, alumoåkermanite, grossular, and kushiroite have similar 16 O-poor compositions (Δ 17 O = −2.2 ± 1.5‰); primary spinel is 16 O-rich (Δ 17 O ~ −23‰); Al,Ti-diopside shows a range of Δ 17 O (from ~ −24‰ to ~ −15‰); anorthite and melilite are 16 O-depleted to various degrees (−6.5‰ ≤ Δ 17 O ≤ −4.5‰ and Δ 17 O = −2.7 ± 0.8‰, respectively). In ALH-2, corundum shows a range of Δ 17 O, from ~ −9‰ to ~ −1‰; primary hibonite and spinel are 16 O-rich (Δ 17 O ~ −23‰); melilite and perovskite are 16 O-poor (Δ 17 O = −2.6 ± 1.5‰ and −3.1 ± 1.3‰, respectively). On the Al-Mg isotope diagram ( 26 Mg* versus 27 Al/ 24 Mg), primary Al,Ti-diopside, hibonite, melilite, and spinel in the Allende CAIs studied along the canonical isochron with inferred initial 26 Al/ 27 Al ratio [( 26 Al/ 27 Al) 0 ] of ~5 × 10 −5 . All secondary minerals have resolved excesses of 26 Mg*: alumoåkermanite, corundum, and grossite plot below the canonical isochron, whereas most spinel analyses plot above it. An internal isochron defined by the coexisting secondary corundum and alumoåkermanite in 3529Z has ( 26 Al/ 27 Al) 0 = (7.5 ± 2.6) × 10 −7 . We conclude that the corundum-bearing assemblages in Allende CAIs resulted from metasomatic alteration of primary melilite and anorthite, ~4–5 Ma after their crystallization. Metasomatic alteration of CAIs in the Allende parent asteroid by an aqueous fluid having Δ 17 O of ~ −3 ± 2‰ modified the O-isotope composition of their primary melilite, anorthite, and Ti-rich pyroxene; O-isotope compositions of primary hibonite, spinel, and low-Ti pyroxene escaped this modification.

Geosciences↗
NASA NTRS1971

The effect of solute additions on the steady-state creep behavior of dispersion-strengthened aluminum.

The effect of solute additions on the steady-state creep behavior of coarse-grained dispersion-strengthened aluminum alloys was studied. Recrystallized dispersion-strengthened solid solutions were found to have stress and temperature sensitivities quite unlike those observed in single-phase solid solutions having the same composition and grain size. The addition of magnesium or copper to the matrix of a recrystallized dispersion-strengthened aluminum causes a decrease in the steady-state creep rate which is much smaller than that caused by similar amounts of solute in single-phase solid solutions. All alloys exhibited essentially a 4.0 power stress exponent in agreement with the model of Ansell and Weertman. The activation energy for steady-state creep in dispersion-strengthened Al-Mg alloys, as well as the stress dependence, was in agreement with the physical model of dislocation climb over the dispersed particles.

Reynolds, G. H.↗
NASA NTRS1990

The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites

Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or silicon-carbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which consideres process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.

Stefanescu, Doru M.↗
NASA NTRS1992

Gelled liquid oxygen/metal powder monopropellants

Al, Al-80/Mg-20 wt pct, Si, and Fe powders were mixed with LOX and gelled with 2-3 wt pct Cab-o-Sil to viscosities of 100 to 900 cps, at shear rates of up to 300/sec. These monopropellants were burned in a cylinder that was submerged in a liquid nitrogen bath. Ambient pressure data have shown that the monopropellants were extinguished when the flame front reached regions that had been submerged under the liquid nitrogen. Burning occurred in a pulsed fashion, and was most nearly steady in the case of the Al-Mg mixture. No sparking or energetic burning occurred in any of the cases tested.

Wickman, John H.↗
NASA NTRS1994

Chronology of chrondrule and CAI formation: Mg-Al isotopic evidence

Details of the chondrule and Ca-Al-rich inclusion (CAI) formation during the earliest history of the solar system are imperfectly known. Because CAI's are more 'refractory' than ferromagnesian chondrules and have the lowest recorded initial Sr-87/Sr-86 ratios of any solar system materials, the expectation is that CAI's formed earlier than chondrules. But it is not known, for example, if CAI formation had stopped by the time chondrule formation began. Conventional (absolute) age-dating techniques cannot adequately resolve small age differences (less than 10(exp 6) years) between objects of such antiquity. One approach has been to look at systematic differences in the daughter products of short-lived radionuclides such as Al-26 and I-129. Unfortunately, neither system appears to be 'well-behaved.' One possible reason for this circumstance is that later secondary events have partially reset the isotopic systems, but a viable alternative continues to be large-scale (nebular) heterogeneity in initial isotopic abundances, which would of course render the systems nearly useless as chronometers. In the past two years the nature of this problem has been redefined somewhat. Examination of the Al-Mg isotopic database for all CAI's suggests that the vast majority of inclusions originally had the same initial Al-26/Al-27 abundance ratio, and that the ill-behaved isotopic systematics now observed are the results of later partial reequilibration due to thermal processing. Isotopic heterogeneities did exist in the nebula, as demonstrated by the existence of so-called FUN inclusions in CV3 chondrites and isotopically anomalous hibonite grains in CM2 chondrites, which had little or no live Al-26 at the time of their formation. But, among the population of CV3 inclusions at least, FUN inclusions appear to have been a relatively minor nebular component.

Macpherson, G. J.↗
NASA NTRS2001

Reaction Mechanisms and Particle Interaction in Burning Two-Phase Systems

The main objective of this research is to understand the mechanisms by which particle interactions affect ignition and combustion in the two-phase systems. Combustion of metal aerosols representing the two-phase systems is carried out in the microgravity environment enabling one to avoid the buoyant flows that mask the particle motion due to the particle-particle interaction effects. In addition, relatively large, e.g., 100 micron diameter particles can be used, that remain aerosolized (i.e., do not fall down as they would at normal gravity) so that their behavior ahead, behind, and within the propagating flame can be resolved optically. An experimental apparatus exploiting this approach has been designed for the 2.2-s drop tower microgravity experiments. A typical experiment includes fluidizing metal particles under microgravity in an acoustic field, turning off the acoustic exciter, and igniting the created aerosol at a constant pressure using a hot wire igniter. The flame propagation and details of the individual particle combustion and particle interactions are studied using high-speed movie and video cameras coupled with microscope lenses to resolve individual particles. Recorded flame images are digitized and various image processing techniques including flame position tracking, color separation, and pixel by pixel image comparisons are employed to understand the processes occurring in the burning aerosols. Condensed combustion products are collected after each experiment for the phase, composition, and morphology analyses. New experiments described in this paper address combustion of Ti and Al particle clouds in air and combustion of Mg particle clouds in CO2. In addition, microgravity combustion experiments have been conducted with the particles of the newly produced Al-Mg mechanical alloys aerosolized in air.

Dreizin, Edward L.↗
NASA NTRS2002

Circumstellar Oxide Grains in Ordinary Chondrites and Their Origin

Three new circumstellar hibonite and 14 circumstellar corundum grains have been found based on their highly anomalous oxygen. Al-Mg isotopes have been measured for these circumstellar oxides and for 14 oxides with a normal oxygen composition. Additional information is contained within the original extended abstract.

Krestina, Natalia↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Chondrules: The Never-Ending Story

The session "Chondrules: The Never-Ending Story" included the following reports:Dust Size Distribution in Solar Nebula Inferred from Shock-Wave Heating Model for Chondrule Formation; Collisional Destruction of Chondrules in Shock Waves and Inferred Dust to Gas Mass Ratio; Evaporation and Accompanying Isotopic Fractionation of Sulfur from Fe-S Melt During Shock Wave Heating ; Evaporation During Chondrule Formation, Recondensation as Fine Particles, and the Condensation of S and Other Volatile Elements; Fe Isotopes and the Formation of Chondrules; Pristine and Processed Metal in CR Chondrites: Condensation in the Solar Nebula and Partial Reequilibration During Chondrule Formation; Variation of the Condensation Path of Supercooled Silicate Melt; Volatile and Moderately Volatile Trace Element Composition of Chondrules and Matrix from CM Chondrites: Implications for Chondrule Formation; Opaque Mineral Assemblages at Chondrule Boundaries in the Vigarano CV Chondrite: Evidence for Gas-Solid Reactions Following Chondrule Formation; Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting; The Vaguries of Pyroxene Nucleation and the Resulting Chondrule Textures; Contemporaneous Formation of Chondrules in the Al-26-Mg-26 System for Ordinary and CO Chondrites; and Al-Mg Isotopic Systematics in Ferromagnesian Chondrules from the Unequilibrated Ordinary Chondrite.

Source record↗
NASA NTRS2004

Lunar and Planetary Science XXXV: From Ancient Mists: Presolar and Nebular Processes

The session "From Ancient Mists: Presolar and Nebular Processes" included the following reports: Interpretation of the Meteoritic Extinct Radioactivity - Mean Life Relation; On the Issue of Molybdenum Isotopic Anomalies in Meteorites: Is It Still "FUN"?; (26Al/27Al)o of the Solar Nebula Inferred from Al-Mg Systematic in Bulk CAIs from CV3 Chondrites; Magnesium Isotopic Compositions of Igneous CAIs in the CR Carbonaceous Chondrites: Evidence for an Early and Late-stage Melting of CAIs; The 26Al-26Mg Chronology of a Type C CAI and POIs in Ningqiang Carbonaceous Chondrite; Bulk Compositions of CAIs and Al-rich Chondrules: Implications of the Reversal of the Anorthite / Forsterite Condensation Sequence at Low Nebular Pressures; Synthesis of Refractory Minerals by High-Temperature Condensation of a Gas of Solar Composition; Elemental and Isotopic Fractionation by Diffusion-limited Evaporation; "Nonideal" Isotopic Fractionation Behavior of Magnesium in Evaporation Residues; Determination of Primordial Refractory Inclusion Compositions; Zoning Patterns in Spinel from Type B Ca-Al-rich Inclusions: Constraints on Sub-Solidus Thermal History; Radial Migration of Materials from Inner to Outer Solar Nebula: Evidence from Meteorite Matrix; and Refractory Forsterites in Chondritic Meteorites, a Link Between CAIs and Chondrules.

Source record↗