| 摘要 |
An aluminium base-silicon hypereutectic casting alloy with Si 12-15 wt.% has (a) elements A in wt.%, Cu 1.5-5.5, Ni 1.0-3.0, Mg, Fe each 0.1-1.0, Mn 0.1-0.8, Zr 0.01-0.10, Zn 0-3.0, Sn, Pb each 0-0.2, Cr 0-0.1, Si modifiers Na 0.001-0.01 and/or Sr 0.01-0.10, B(elem.) 0.05<x>, Ca 0.03<x>, P 0.05<x>, others 0.05<x> each (<x> = max.); (b) at least one of elements X, namely, Cr, Mo, Nb, Ta, Ti, Zr, V and combinations thereof, with-without Al, each of which form stable nucleants such as carbides, borides, nitrides, phosphides and combinations thereof, subject to the exclusion of AlB in the presence of modifier Sr, (with which it reacts, with detriment to Al-Si eutectic modification). Each element X is present in wt.% 0.005-0.250; (c) at least one of elements Z, namely, Fe, Mn, Cr, Co, Li, Na, K, Rb, Cs, Ca, Sr, Y, Ce and other rare earth lanthanides and combinations thereof. Sr when used alone ranges 0.11-0.40. The remaining elements vary in terms of those selected, examples of which follow in wt.%, namely, Fe 1.5-2.0, Mn 1.0-2.0, Cr 0.5-1.0, Co 0.5-3.0, Na 0.1-0.4, Rb 0.5-2.0, Ca 0.9-2.0, Y, Ce, other rare earth lanthanide metals 0.5-3.0. The balance of the alloy is aluminium and incidental impurities, subject to the exclusion of Ti solely for X and Sr solely for Z. Elements Z are added for forming intermetallic phases, (e.g., Al2Si2Sr, Cr4Si4Al13), which form early during solidification and thus promote the nucleation of primary Si, which in turn promotes nucleation of the Al-Si eutectic, when the temperature drops below the Al-Si eutectic solidus, thus enhancing castability. The levels of elements X and Z may exceed predetermined respective levels in the alloy, because they function differently, either alone or when also present as A constituents. The final microstructure is predominantly an Al-Si eutectic matrix, in which any primary Si present is uniformly dispersed. |
