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Designing novel bulk metallic glass composites with a high aluminum content.

Chen ZP, Gao JE, Wu Y, Wang H, Liu XJ, Lu ZP - Sci Rep (2013)

Bottom Line: The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades.These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting.However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China.

ABSTRACT
The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades. In this paper, we reported formation of a series of BMG matrix composites which contain a high Al content up to 55 at.%. These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting. Our results indicate that proper additions of transition element Fe which have a positive heat of mixing with the main constituents La and Ce can appreciably improve the formability of the BMG matrix composites by suppressing the precipitation of Al(La,Ce) phase resulted from occurrence of the phase separation. However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys.

No MeSH data available.


Related in: MedlinePlus

SEM images for the as-cast, 10 mm rods with 50% Al; (a) Al50(CoCu)5(LaCe)45, (b) Al50(CoCu)5(LaCe)45Fe5, and (c) Al50(CoCu)5(LaCe)35Fe10. (d) shows the corresponding XRD patterns.
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f4: SEM images for the as-cast, 10 mm rods with 50% Al; (a) Al50(CoCu)5(LaCe)45, (b) Al50(CoCu)5(LaCe)45Fe5, and (c) Al50(CoCu)5(LaCe)35Fe10. (d) shows the corresponding XRD patterns.

Mentions: As mentioned earlier, BMG composites in Al-(Co,Cu)-(La,Ce) alloy system is difficult to form when the content of Al exceeds 50 at.%. In our study, it was found that additions of proper elements which have a positive heat of mixing with the rare earths (i.e., La and/or Ce) could effectively facilitate formation of BMG composites. Figure 4 shows the morphology and the corresponding XRD pattern of the as-cast 10 mm rod for the Al50(CoCu)5 (LaCe)45−xFex(x = 0, 5 and 10 at.%) alloys. As can be seen, the Al50(CoCu)5(LaCe)45 alloy with no Fe addition exhibits three different contrast regions, i.e., the dark Al2(La,Ce) phase, the grey Al(La,Ce) phase and the bright amorphous matrix (Fig. 4a), and their volume fraction is estimated to be 47, 33 and 20%, respectively. For the alloy in which the rare-earth elements were substituted by Fe, their morphology and phase formation changed appreciably, as demonstrated in Figs. 4b and c. For the alloy doped with 5 at.% Fe, i.e., Al50(CoCu)5(LaCe)40Fe5, formation of the grey Al(La,Ce) phase was suppressed and a small portion of the black AlFe phase and the grey needle-like Al2Fe phase appeared instead. In addition, the volume fraction of the dark Al2(La,Ce) phase and the bright amorphous matrix is determined to be approximately 60 and 35%, respectively (Fig. 4b). With the increase of Fe, the alloy is still comprised of the black AlFe phase, the dark phase Al2(La,Ce) and the bright matrix (Fig. 4c), however, the volume fraction of the glass matrix was drastically decreased because of strong formation of AlFe and Al2(La,Ce).


Designing novel bulk metallic glass composites with a high aluminum content.

Chen ZP, Gao JE, Wu Y, Wang H, Liu XJ, Lu ZP - Sci Rep (2013)

SEM images for the as-cast, 10 mm rods with 50% Al; (a) Al50(CoCu)5(LaCe)45, (b) Al50(CoCu)5(LaCe)45Fe5, and (c) Al50(CoCu)5(LaCe)35Fe10. (d) shows the corresponding XRD patterns.
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f4: SEM images for the as-cast, 10 mm rods with 50% Al; (a) Al50(CoCu)5(LaCe)45, (b) Al50(CoCu)5(LaCe)45Fe5, and (c) Al50(CoCu)5(LaCe)35Fe10. (d) shows the corresponding XRD patterns.
Mentions: As mentioned earlier, BMG composites in Al-(Co,Cu)-(La,Ce) alloy system is difficult to form when the content of Al exceeds 50 at.%. In our study, it was found that additions of proper elements which have a positive heat of mixing with the rare earths (i.e., La and/or Ce) could effectively facilitate formation of BMG composites. Figure 4 shows the morphology and the corresponding XRD pattern of the as-cast 10 mm rod for the Al50(CoCu)5 (LaCe)45−xFex(x = 0, 5 and 10 at.%) alloys. As can be seen, the Al50(CoCu)5(LaCe)45 alloy with no Fe addition exhibits three different contrast regions, i.e., the dark Al2(La,Ce) phase, the grey Al(La,Ce) phase and the bright amorphous matrix (Fig. 4a), and their volume fraction is estimated to be 47, 33 and 20%, respectively. For the alloy in which the rare-earth elements were substituted by Fe, their morphology and phase formation changed appreciably, as demonstrated in Figs. 4b and c. For the alloy doped with 5 at.% Fe, i.e., Al50(CoCu)5(LaCe)40Fe5, formation of the grey Al(La,Ce) phase was suppressed and a small portion of the black AlFe phase and the grey needle-like Al2Fe phase appeared instead. In addition, the volume fraction of the dark Al2(La,Ce) phase and the bright amorphous matrix is determined to be approximately 60 and 35%, respectively (Fig. 4b). With the increase of Fe, the alloy is still comprised of the black AlFe phase, the dark phase Al2(La,Ce) and the bright matrix (Fig. 4c), however, the volume fraction of the glass matrix was drastically decreased because of strong formation of AlFe and Al2(La,Ce).

Bottom Line: The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades.These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting.However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China.

ABSTRACT
The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades. In this paper, we reported formation of a series of BMG matrix composites which contain a high Al content up to 55 at.%. These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting. Our results indicate that proper additions of transition element Fe which have a positive heat of mixing with the main constituents La and Ce can appreciably improve the formability of the BMG matrix composites by suppressing the precipitation of Al(La,Ce) phase resulted from occurrence of the phase separation. However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys.

No MeSH data available.


Related in: MedlinePlus