Core–shell nanoscale precipitates in Al–0.06 at.% Sc microalloyed with Tb, Ho, Tm or Lu

Krug, Matthew E.; Werber, Alexandra; Dunand, David C.; Seidman, David N.

doi:10.1016/j.actamat.2009.08.074

Cited by 67 publications

(13 citation statements)

References 48 publications

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“…The transition from nanoparticles to matrix appears to occur within less than 5 nm and is definitely not sharp. We did not observe any obvious core–shell structure although it was reported in the case of alloys …”

Section: Resultssupporting

confidence: 70%

Compositional Changes at the Early Stages of Nanoparticles Growth in Glasses

et al. 2019

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Doping material with nanoparticles is increasingly used as an effective method for improving their mechanical, optical, and sturdiness properties in many fields. More specifically, effective material development will depend on our ability to control nanoparticles’ shape, composition, and size. While crystalline nanophase can be examined easily, characterization of amorphous nanoparticles remains a challenge. Here, we investigate the chemical composition of sub-20-nm oxide nanoparticles grown in rare-earth doped silicate glass through the phase separation mechanism occurring under heat treatment. Using a combination of analytical techniques, we demonstrate that nanoparticle composition and, therefore, the chemical environment of encapsulated rare-earth ions, is nanoparticle size dependent. This new experimental evidence of composition change contributes unique insights on the phase separation mechanism that will lead to better comprehension and will guide development of future materials.

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Section: Resultssupporting

confidence: 70%

Compositional Changes at the Early Stages of Nanoparticles Growth in Glasses

et al. 2019

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“…2a and b for both alloys as a function of cooling rate. For Alloy 1, water quenching and fast oven cooling ($8°C/min) results in the same electrical conductivity ($31.2 MS m À1 ) and microhardness (200 MPa) values, which also matches the values for an a-Al matrix, 7,8 suggesting that this cooling rate range is sufficient to maintain Sc and Zr in a supersaturated solid solution. Slow oven cooling ($4°C/min) results in higher electrical conductivity ($32.0 MS m À1 ) and much higher microhardness (360 MPa), indicating that Al 3 (Sc,Zr) precipitation has occurred.…”

Section: Aging Treatment Optimization For the Aluminum Matrixsupporting

confidence: 59%

Development of a Precipitation-Strengthened Matrix for Non-quenchable Aluminum Metal Matrix Composites

Sorensen²,

Klier

et al. 2016

JOM

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Recent developments in metal matrix composite-encapsulated ceramic armor show promise in lightweight armor technology. The system contains ceramic tiles, such as alumina, sandwiched between unreinforced aluminum or aluminum metal matrix composite (Al-MMC), which has a better toughness compared to the ceramic tiles. The sandwich structures should not be quenched during the fabrication, as the large mismatch in the coefficients of thermal expansion between the ceramic tiles and the unreinforced aluminum or Al-MMC creates internal stresses high enough to fracture the ceramic tiles. However, slow cooling of most commercial alloys creates large precipitates making solute unavailable for the formation of fine precipitates during aging. Here, we develop a non-quenched, high-strength metal matrix utilizing dilute Al-Sc-Zr alloys. We demonstrate that the dilute Al-0.09 Sc-0.045 Zr at.% alloy and the same alloy containing 0-4 vol.% alumina short fibers do not result in precipitation upon slow cooling from a high temperature, and can thereafter be aged to increase their strength. They exhibit a moderate strength, but improved ductility and toughness as compared to common armor aluminum alloys, such as AA5083-H131, making them attractive as armor materials and hybrid armor systems.

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“…Moreover, we demonstrate that: (i) Li increases the number density of precipitates nucleated at 325°C by a factor of $2-5 as compared with Al-Sc or Al-Sc-Yb alloys [21], and more generally Al-Sc-RE alloys (RE = rare earth) [31] aged using similar aging conditions; (ii) Li substitutes for Sc and Yb in the L1 2 structure of the precipitates obtained after aging at 325°C, enabling high precipitate volume fractions as compared to an Al-ScMg alloy, which is the closest comparable Al-Sc alloy including an light alloying element [18]; and (iii) overaging of this alloy during an isothermal heat treatment is delayed as compared to similar alloys [18,21,22,31,34,70], suggesting that, due to the Li addition, the alloying elements have interactions that are absent in less complex alloys.…”

Section: Introductionmentioning

confidence: 97%

“…Dilute Al-Sc-X ternary alloys have been extensively studied, where the second alloying element X is chosen to partition either mainly to the a-Al matrix (Mg [14][15][16][17][18][19][20]) or to the precipitates (transition metals or lanthanoids [21][22][23][24][25][26][27][28][29][30][31]). Lithium is an unusual alloying element for Al-Sc alloys, since it has high solubility in the facecentered cubic (fcc) a-Al matrix [32][33][34][35][36][37][38] (similar to Mg) as well as in the L1 2 Al 3 Sc precipitates [39,40], which is similar to transition metals and lanthanoids, and additionally forming metastable L1 2 d 0 -Al 3 Li precipitates.…”

Section: Introductionmentioning

confidence: 99%