Controlled melting process of off-eutectic alloy

For optimization of semi-solid processing (SSP), differential scanning calorimetry (DSC) and quenching experiments were employed to investigate the effect of heating rate on the evolution of microstructure and volume fraction of the solid phase of the as-cast Al-5.8wt%Cu alloy during controlled heating process. It is shown that near-spherical α-phase surrounded by the liquid can be directly obtained from the dendrite when the heating process is properly controlled. Slow heating to a temperature between solidus and liquidus followed by an isothermal holding process are favorable for the spheroidization of the grains. Based on the Scheil equation, mathematical models of the solid fraction versus temperature for the off-eutectic alloy during melting process are presented for the cases with and without consideration of solid diffusion. The evaluated solid fractions for the melting of Al-5.8wt%Cu alloy with the models were coincident with the experimental results.