Improved wear resistance of Al-15Si alloy with a high current pulsed electron beam treatment |
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Authors: | Y HaoB Gao GF TuSW Li C DongZG Zhang |
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Affiliation: | a School of Materials and Metallurgy, Northeastern University, Shenyang 110004, China b Key Laboratory of the Ministry of Education of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024, China |
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Abstract: | A hypereutectic Al-15Si alloy (Si 15 wt.%, Al balance) was irradiated by high current pulsed electron beam (HCPEB). The HCPEB treatment causes ultra-rapid heating, melting and cooling at the top surface layer. As a result, the special “halo” microstructure centering on the primary Si phase is formed on the surface due to interdiffusion of Al and Si elements. The composition of the “halo” microstructure is distributed continuously from the center to the edge of the “halo”. Compared to an untreated matrix, the remelted layer underneath the surface presents single contrast because of the compositional homogeneity after HCPEB treatment. The thickness of the remelted layer increases slightly from 4.4 μm (5 pulses) to 5.6 μm (25 pulses). HCPEB treatment broadens and shifts the diffraction peaks of Al and Si. The lattice parameters of Al decreases due to the formation of a supersaturated solid solution of Al in the melted layer. Through analysis of Raman spectra and transmission electron microscopy (TEM), the amorphous Si (a-Si) and nanocrystalline Si are formed in the near-surface region under multiple bombardments of HCPEB. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 9, which can be attributed to the formation of metastable structures. |
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Keywords: | Hypereutectic Al-15Si alloy High current pulsed electron beam &ldquo Halo&rdquo microstructure Supersaturated solid solution Amorphous Si Nanocrystalline Si |
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