Solidification structure of melt mixture of hypoeutectic/semisolid hypereutectic Al–Si alloy

Abstract

Through mixing the hypoeutectic and semisolid hypereutectic Al–Si alloy melts at different temperatures, this paper studies the changes in solidification microstructure of the melt mixture. It is indicated that the microstructure of the solidified melt mixture has the structural characteristics of both hypoeutectic and hypereutectic Al–Si alloys, i.e. the primary silicon is distributed in the matrix composed of primary α(Al) phase and eutectic ( α+Si) phase and has undergone apparent refinement and passivation. Higher temperature of hypoeutectic melt and longer holding time of melt will be more favourable for the refinement and passivation of primary silicon and meanwhile, its quantity decreases. The solidification structure of the melt mixture can be controlled through controlling the mixing temperature and holding time.

Numerical analysis of liquid fraction in solid–liquid phase transformation of semisolid alloy

“…For closed system dH~C P dT (3) where C P is average constant pressure heat capacity (J uC 21 g 21 ), T is heating temperature (uC) and H is enthalpy. Since DS5DH/T…”

“…1 The liquid fraction of semisolid slurry is important not only to the quality of semisolid slurry but also to the rheology and thixotropy of semisolid processing. 2,3 At present, liquid fraction of semisolid slurry is basically measured by electric resistance measurement, thermal analysis [differential scanning calorimetry (DSC)] and optical image observation. 4 The solid fraction of 7075Al alloy was studied by Lu.…”