(1. 江苏大学 材料科学与工程学院，镇江 212013；
2. 上海交通大学 金属基复合材料国家重点实验室，上海 200240)
摘 要: 采用熔体直接反应法，以工业7055铝合金为基体，利用K2TiF6和K2ZrF6多组元制备Al3(Ti0.5Zr0.5)原位颗粒强化铝基复合材料，再将复合材料经过挤压、固溶时效处理后进行深冷时效循环处理。采用正交实验设计法研究降温速度、处理时间和循环次数对复合材料显微组织和力学性能的影响。采用差示热分析仪对复合材料进行低温热分析，采用SEM和TEM对材料显微组织进行观察。结果表明：材料从液氮温度77 K升温至165 K左右时出现了明显的放热峰，此温度处出现了相变。热计算结果表明该温度下大量析出了S相(Al2CuMg)。深冷处理后复合材料内部细小析出相数量增多，主要组分是η(MgZn2)相和η′(MgZn2′)相；随着降温速度、处理时间和循环次数增加，性质不稳定且硬度高的η′相数量减少，性质稳定硬度较低的η相数量增加。与未冷处理试样相比，深冷时效循环处理后试样的平均抗拉强度提高14.7%，冲击韧性提高10.9%，伸长率提高50%，断裂机制为韧窝型断裂机制。当试样具有高强度、高韧性时，对应的最优冷处理参数为：降温速度v为1 ℃/min、保温时间t为24 h、循环次数N为1或2。当试样的伸长率最高时，对应的参数为：v为10 ℃/min、t为36 h、N为1。复合材料强化机制为析出相强化、位错强化和细晶强化等。
关键字: 铝基原位复合材料；深冷时效循环处理；显微组织；力学性能
（1. School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China;
2. The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China）
Abstract:The in-situ Al3(Ti0.5Zr0.5) composite was synthesized using K2TiF6 and K2ZrF6 components in 7055 aluminum alloy by melt direct reaction method. Cryogenic aging circular treatment (CACT) was performed after extrusion deformation and solution-aging heat treatment. The effects of cooling rate (v), processing time (t) and circular index (N) on the microstructure and mechanical properties of composites were studied by orthogonal experimental method. The composite was studied by differential scanning calorimetry (DSC) under cryogenic condition, and the microstructure of composite was studied by SEM and TEM. The result shows that when the specimen is heated from the cryogenic temperature (77 K) to about 165 K, there will be an obvious exothermic peak. The phase transforms from matrix to S phase (Al2CuMg). There are amounts of fine precipitates in the composites, the main components are regarded as η (MgZn2) and η′(MgZn2′) phases. With increasing the v, t and N, the amount of η′ phase that is unstable but hard will decrease, while the stable but soft η phase will increase. Compared with the sample without CACT, the average tensile strength (σb), impact toughness (ak) and elongation (δ) of the sample with CACT have been enhanced by 14.7%,10.9% and 50%, respectively. The main fracture mechanism is dimple one. When the samples with high σb and ak are acquired, the optimal CACT parameters are: v=1 ℃/min; t=24 h and N=1 or 2. When the samples with superior elongation are acquired, the corresponding CACT parameters are: v=10 ℃/min, t=36 h and N=1. The strengthening mechanisms of CACT composite are precipitation strengthening, dislocation strengthening and fine crystalline strengthening.
Key words: in-situ aluminum matrix composite; cryogenic aging circular treatment; microstructure; mechanical property
