Impact of melt treatment on semi-solid metal processing

The concurrent presence of liquid and primary solid particles is the principal requirement for semisolid metal (SSM) processing. It is proposed that in addition to the temperature sensitivity of the solid fraction and the SSM temperature process window, partitioning of the solidification range is also essential. The solidification range of hypoeutectic Al–Si alloys is divided into two distinct temperature intervals of α-Al primary particles formation and eutectic and post-eutectic reactions zone. The primary particles are formed in three steps of α-Al nucleation, dendrite to rosette/globular transformation and coarsening of the primary α-Al particles over the entire solidification range. Furthermore the effects of inoculation and modification on these temperature intervals are discussed and elaborated for hypoeutectic Al–Si alloys.