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定向凝固制备Al-5.3%Zn-5.3%Mg合金,在生长速率为4~500μm/s、温度梯度为25 K/cm的条件下,采用改进的晶体生长Bridgman技术研究该合金的形貌转变和溶质分布。结果表明,在生长速率为6.5~9.5μm/s的条件下,产生了晶胞。在速率下限时,界面前沿向晶胞组织转变,而在速率上限时晶胞组织转变为柱状枝晶。在30~500μm/s速率下凝固的合金,其微观组织主要由柱状枝晶组成,然而在大于500μm/s速率下凝固的合金,其微观组织为等轴晶。多元合金枝晶凝固的溶质分布实验结果与Rappaz和Boettinger模型预测的相吻合。根据溶质分布结果,可以得到τ相的沉淀分数,采用τ相作为铝牺牲阳极能提高合金的电化学性能。
Al-5.3% Zn-5.3% Mg alloy was prepared by directional solidification. The growth of the Al-5.3% Zn-5.3% Mg alloy was investigated by using the improved Bridgman technique at a growth rate of 4-500μm / s and a temperature gradient of 25 K / Solute distribution. The results show that under the condition of the growth rate of 6.5 ~ 9.5μm / s, the unit cell is produced. At the lower rate limit, the interface front transitions to unit cell organization, and at the rate upper limit, the unit cell structure changes to columnar dendrite. The microstructure of the alloy solidified at 30-500μm / s consists mainly of columnar dendrites. However, the alloy solidified at the rate of more than 500μm / s has the microstructure of equiaxed grains. The experimental results of the solute distribution of the dendrite solidified by the multi-element alloy coincide with that predicted by the Rappaz and Boettinger models. According to the results of solute distribution, the precipitation fraction of τ phase can be obtained. Using τ phase as the sacrificial anode for aluminum can improve the electrochemical performance of the alloy.