Microstructure and Novel Properties of Nanocrystalline and Nanoquasicrystalline Alloys Prepared in Al-based Systems by Rapid Solidification

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This paper aims to review our recent results on the microstructure and mechanical properties of nanocrystalline and nanoquasicrystalline alloys in Al-based system obtained by rapid solidification. The nanocrystalline alloys consist of nanoscale fcc-Al particles with a particle size of 3 to 5 nm embedded in an amorphous matrix. The homogeneous dispersion of the nanoscale fcc-Al particles caused the remarkable increase in tensile fracture strength (σ_f) by about 1.4 times as compared with those for the corresponding amorphous single phase and the highest value reached as high as 1560 MPa. The high σ_f has been interpreted to result mainly from the extremely high σ_f of the Al particles caused by the absence of internal defects, based on the result that no internal defects are observed in the nanoscale Al particles. The nanoquasicrystalline alloys are composed of spherical icosahedral (I) particles with a particle size of 10 to 50 nm surrounded by an Al layer with a thickness of about 10 nm and the volume fraction of the I-phase is as high as about 70 %. The nanoquasicrystalline base alloys exhibit high σ_f reaching 1350 MPa combined with good bending ductility. The internal structure is interpreted to consist of a new nonequilibrium phase with a short-range disorder and long-range I-structure by high-resolution TEM. The formation of the unique nonequilibrium structure is presumed to be the origin for the achievement of high σ_f and good ductility. It is also shown that the bulk I-based alloys produced by extrusion of the atomized I-based powders exhibit high σ_f of 500 to 850 MPa and large ε_f of 6 to 25 %. These properties are excellent enough to demonstrate the validness of the structure control to nanocrystalline and nanoquasicrystalline phases.nanocrystalline alloynanoquasicyrstalline alloyaluminum base alloyshigh specific tensile strengthrapid solidification
東北大学の論文
1996-03-28

Microstructure and Novel Properties of Nanocrystalline and Nanoquasicrystalline Alloys Prepared in Al-based Systems by Rapid Solidification

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