Research on semi-solid slurry of a hypoeutectic Al-Si alloy prepared by low superheat pouring and weak electromagnetic stirring

The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.

EFFECT OF GRAIN REFINING ON PRIMARYαPHASE IN SEMI-SOLID A356 ALLOY PREPARED BY LOW SUPERHEAT POURING AND SLIGHT ELECTROMAGNETIC STIRRING

The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.

Microstructural characteristics of in situ Mg_2Si/Al-Si composite by low superheat pouring

To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rheo-casting of this type of material,three Al-Si matrix composites reinforced by 5wt.%,9wt.%and 17wt.%Mg2Si with hypoeutectic,eutectic and hypereutectic compositions were prepared by the low superheat pouring(LSP)process.The effects of the pouring temperature(superheat)on the morphology and size distribution of primary phases(primaryα-Al and Mg2Si),binary(α-Al+Mg2Si)eutectic cell and eutectic Mg2Si were investigated.The experimental results show that low pouring temperature(superheat)not only refines the grain structure of the primaryα-Al and binary(α-Al+Mg2Si)eutectic cell in three composites and promotes the formation of more nondendritic structural semi-solid metal(SSM)slurry of these phases;but also refines the primary and eutectic Mg2Si phases,which seems to be attributed to the creation of an ideal condition for the nucleation and the acquisition of a high survival of nuclei caused by the LSP process.