Sr对Al-13%Si合金共晶凝固冷却曲线特征温度的影响

The Effects of Sr on the Characteristic Temperatures of the Cooling Curve of Al-13%Si Alloy During Eutectic Solidification

在冷却速度约为2℃/s条件下,考察了不同Sr量对Al-13%Si合金共晶凝固冷却曲线特征温度的影响。结果表明,随着Sr含量增加,形核温度TN、再辉前最低温度TM与再辉温度TG降低,共晶过冷度!TE增加,共晶团细化;分析认为,Sr的加入改变了-αAl+Si共晶体的形核和生长,一方面,使TN与TM值下降,在凝固过程中,形核过冷度显著增大,因而潜在的形核基底被激活,导致形核率提高,共晶体晶粒数增多,另一方面,"TE=TE-TG(TE为共晶反应平衡温度)增大,表明Sr抑制了共晶体的生长。二者的共同作用导致共晶团细化。

The influence of the addition of strontium in A1-13% Si alloy on the characteristic temperature of the eutectic reaction was investigated, whereas the average cooling rate of the melt prior to solidification was about 2 ℃/s. The result showed that the addition of strontium resulted in a decrease of the nucleation temperature, TN, the minimum temperature prior to recalescence, TM and the growth temperature, TG. It was thought that the addition of strontium changed the mode of the nucleation and growth of the eutectic （α-Al＋Si）. On the one hand, it led to a considerable decrease of TN and TM, and hence there was a remarkable increase in the undercooling of the nucleation of the eutectic, which caused a great number of potential nucleation substrates be activated, so the nucleating rate was increased. On the other hand, the increased undercooling, ΔTE=TE-TG （ TE, the equilibrium temperature of the eutectic reaction ）, with the addition of strontium, indicated the growth of the eutectic was restrained. The combination of the above two roles of strontium resulted in the refinement of the eutectic cells.