The Effect Of C Ti Sr On Microstrcture And Performance Of Al-Si Casting Alloys

Based on the findings of TiC fining Al-Si alloys, especially on the experiments and theories of foreign scholars from ninety's up to now after Cibula put forward the "carbide theory", we bring forward a new method for adding C to Al-Si alloys to hope for obtain TiC particles which can fine the grain of Al-Si alloys. Then, adding Sr which is a longtime modification element for Al-Si alloys, we hope to change the shape of Si at the same time.Temperatures (720℃-900℃) and adding programs will affect the dissolution of C and Ti and the formation of TiC remarkably. During this range of temperature, C will be added to melt more easily as the temperature is higher. But the quantity of C in the melt is still very small. After adopting spinning nuzzle method, a lot of TiC particles were got even at 720 ℃, and AlTi10 master alloy will be dissolved more easily. In addition to that, C and Ti also affect the eutectic point and a phase of Al-Si alloys.Sr is a longtime modification element for Al-Si alloys. Sr wasn't poisoned by C after adding C and Ti, and still had perfect modification effect. If the quantity of Sr is over some value (0.02%-0.04%), the melt will absorb hydrogen, and result in the formation of cavities. We think the reason is that the dissociated Sr destroyed the compact oxide film of the melt. When the concentration of Sr is 0.02%, the shape of eutectic silicon will change to grain, and the ductibility of the alloy will be boostedgreatly. Otherwise, Sr still promote the quantity of a phase.Under analyzing the thermodynamics of CCl4, C, Cl2, TiC, Al4C and TiAl3, we illustrated the decomposing progress of CCl4 in the Al-Si alloys, discussed the possibility of the TiC formation by the reaction of C which came from the decomposing of CCl4 and dissociated Ti in the melt. The calculation indicated that TiC was more stable than Al4C3 and TiAl3 after the concentration of Ti was over 1%.