Effects of melt thermal treatment on hypoeutectic Al–Si alloys

A new refining method—melt thermal treatment without additive to melt is studied in this paper. Microstructure analysis and property evaluation of hypoeutectic Al–Si alloys treated with this method show that the solidification microstructure can be refined significantly with a considerable increase in elongation ratio and strength. Effects such as cooling rate, holding time and alloy composition on the solidification microstructure and mechanical properties have been evaluated. It is shown that the strengthening and toughening effects on the treated samples vary with alloy composition. The property increment of the alloy rich of iron is relatively more remarkable than those rich of Cu or Mg element. Specifically, the structure of the low temperature melt is identified as a primary factor, on which the solidification structure of the treated melt is dependent.