(1. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083；
2. 中南大学 航空航天学院，长沙 410083)
摘 要: 采用原位电阻法测得以不同速率连续冷却2A12铝合金的电阻率—温度曲线，根据曲线斜率变化确定相变点及临界冷却速率，利用透射电镜观察连续冷却过程特征温度点的淬火组织，绘制出实验合金的连续冷却转变曲线(CCT图)。结果表明：2A12合金连续冷却相变主要集中在220~400 ℃的温度区间，随着冷却速率的增加，相变结束温度一直呈下降的趋势，但相变开始温度在达到某冷却速率时骤升，然后继续降低，抑制相变的临界冷却速率稍大于38 ℃/s。慢速连续冷却实验合金时，固溶度减小是引起电阻率变化的主要原因，固溶体脱溶的动力学行为与等温相变规律相似，可较好地用Johnson−Mehl−Avrami (JMA)方程描述。
关键字: 2A12铝合金；原位电阻；相变；连续冷却转变
studied by using in-situ electrical resistivity measurement
（1. Educational Key Laboratory of Non-ferrous Metal Material Science and Engineering,
Central South University, Changsha 410083, China;
2. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China）
Abstract:The electric resistivity versus temperature curves of 2A12 aluminum alloy were recorded during continuous cooling using the in-situ electrical resistivity measurement. The phase transformation temperatures and critical cooling rate without phase transition of the alloy can be obtained from the relationships of electrical resistivity vs temperature curves. TEM was applied to the microstructure observation during the continuous cooling process. CCT diagrams of the tested samples can be established. The results show that the phase transformations of the tested alloy mainly take place between 220 ℃ and 400 ℃. The phase transformation finishing temperature decreases with the increase of cooling rates. While the phase transformation starting temperature increases suddenly until the cooling rate reaches some value, then decreases with the increase of cooling rates. The critical cooling rate for preventing phase transformation is above 38 ℃/s. The decrease of solid solubility is the main reason for variation of electric resistivity with a low cooling rate of the alloy. The decomposition of solid solution of the alloy is similar with the isothermal phase transformation, which can be well described by the Johnson−Mehl−Avrami (JMA) equation.
Key words: 2A12 aluminum alloy; in-situ electric resistivity; phase transformation; continuous cooling
