| High-silicon aluminum alloy possesses many advantages such as low density, light weight, good thermal conductivity, low heat expansion coefficient, volume stability, good abrasion resistance and good corrosion resistance, which can be broadly used as auto engine piston and rotor materials. The development of modern auto industry advances more demanding requirements on the heat resistance and abrasion resistance properties of materials, while the coarse silicon phase and other second phases of high-silicon aluminum alloy limits its application. The second phases of high-silicon aluminum alloy can be refined by rapid solidification technology, which further improves the alloy properties and meets the requirement of auto industry on the material properties. Based on hyper-eutectic Al-Si-Cu-Mg alloy, Al-15Si-5Fe-2Ni-3.5Cu-1Mg-1.5Mn-1V alloy was prepared by the addition of the alloying elements Fe,Ni,Mn,V and with the spray-deposition technology. The microstructures, thermal stability and mechanical properties of the alloy were studied in this paper. The main research results were as follows:Compared with the cast alloy microstructure, the microstructure of spray-deposition alloy was much smaller and more homogeneous, and the second phase shapes were granular or clump-like, and the size of primary Si phase was about 4.86μm. The microstructure of the alloy after hot extrusion was very compact and the second phases distributed dispersively on the substrate, moreover, the primary Si phase was refined effectively. When the extrusion ratio was 14:1, the average size of the primary Si phase was about 2μm, and the tip solution of the primary Si phase made the shape become smooth. The volume fraction of the second phases in the alloy by T6 heat treatment increased and the size didn't change obviously. The XRD result showed that the phase structures of as-spray deposited, as-extruded and as-solid solution aging treated for high-silicon aluminum alloy were similar. The as-extruded alloy was composed ofα-Al,β-Si,Al13(Fe,V)3Si,Al7Cu4Ni and AlCu2Mn phases with the EDS analysis of the second phases. Cu and Mg elements were consumed due to the addition of Fe,Mn,V,Ni elements, which inhibited the formation of Al2Cu and Mg2Si. At the same time, the addition of Mn and V inhibited the formation ofδ-Al4FeSi2 andβ-Al5FeSi, moreover, the Al13(Fe,V)3Si phase formed by the prior solution of V in the Al-Si-Fe phase.The thermal stability of the alloy was systemically investigated in the paper. After the as-extruded alloy was isothermally treated at 300℃for different time, there was no evident growth of the primary Si, furthermore, the size of primary Si increased a little till above 400℃for 20h. In addition, the influence of Al,Fe,Mn,V,Ni,Cu,Mg elements on electron structure of Si was calculated by EET. The influence of alloy elements on thermal stability of Si was explained firstly using the statistical value S' of the structure formation factor and statistical value nA' of the strongest bond covalent electron pairs, statistical value FS′i Dof FS Di, considering that the dissolution of alloying elements Fe,Mn,Ni,V,Mg,Cu and Al inβ-Si form substitutional solid solution, which made nA' and S' increasing; at the same time, showing that Fe and Ni became interstitial atoms more easily than that of Si element, which made the the statistical value S' increase, all of these prevented Si phase from aggregating and growing owing to the diffusion of Si atoms. The dissolution of Fe,Mn,Ni,V,Mg and Cu elements inα-Al matrix made FS′i D value increase and the diffusion resistance of Si inα-Al matrix, furthermore prevented primary Si phase from growing and coarsening during heating.The tensile test of the alloy under solid solution and aging treatment indicated that the maximum strength reached 581MPa at room temperature, 376MPa at 200℃and 228MPa at 300℃. The elongation ratio was 1.8% at room temperature, and the value increased with the temperature increasing.The strengthening mechanism of the alloy showed that was by the high volume fraction dispered phases and precipitated phases anchored the dislocation and increased the resistance of dislocation slipping, which was the main reason strengthening the alloy. The dispersed primary silicon phase was also a strengthening phase. At high temperature the main reasons for the strength decrease and plasticity increase were the increasing of the dislocation motion and the dissolving of some precipitated phases. The fracture research of the alloy showed that the crack source of the as-extruded alloy appeared on the Si phase. The crack in the alloy as-heat treated appeared at the bonding position between Si phase and the matrix besides on the Si phase. The crack mainly appeared at the interface between the second phase and matrix at high temperature, furthermore, the segregation of the second phase and matrix increased with the rupture of Si decreasing.
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