Elevated temeprature annealing of novel aluminium-silicon gradient alloy produced by semi-continuous casting

摘要

A novel Al-Si gradient alloy is prepared by semi-continuous casting using double-stream-pouring method.The microstructures and property of the alloy annealed at elevated temeprature are investigatee.The results show that the Rockwell hardness decreases remarkaly and the gradient distribution of ht ehardness value in cross section becomesflat after elevaled temeprater annealing,however,prolonged holding after annealing at 500 deg C for 24h,the Rockwell hardness has little change because of the dissolution and spheroidization of eutectic silicon.On the contrary,the silicon composition distribution of the alloy annealed at high temeprature for a long time has no obvious difference from that of the alloy in as-cast state because hte interfacial energy of eutectic silicon which plays a key role in the morphology variation of silicon prevents long distance diffussion of silicon atoms.