退火工艺对Cu基体中Al2O3-Ce协同效应的抑制

Decrease of Al2O3-Ce Co-Strengthening Effect in Cu Matrix after Annealing Process

采用高能球磨、结合放电等离子烧结（SPS）的方法制备Al2O3和Ce协同增强Cu基复合材料。研究了不同退火温度和时间对Cu-Al2O3和Cu-Al2O3-Ce复合材料微观组织、Al2O3弥散颗粒分布、复合材料硬度和电导率的影响。结果表明：Cu基体中Al2O3和Ce具有明显的协同作用,具体表现为Cu基复合材料的硬度和电导率都显著提高。扫描电镜（SEM）分析结果表明Al2O3和Ce协同效应的机制为Ce的加入优化了Al2O3的分布,减弱了Al2O3的团聚。在退火过程中Ce明显抑制了Al2O3的团聚。退火温度的升高会导致Al2O3颗粒尺寸增加。在固定的退火时间下,通过拟合Al2O3颗粒的平均尺寸与退火温度的关系,发现二者近似符合阿伦尼乌斯关系。由于较大的Al2O3颗粒对弥散强化和自由电子传播都有不利影响,高于400℃退火会显著抑制Al2O3和Ce的协同效应,降低复合材料的硬度和电导率。400℃下退火2 h以上会降低复合材料的电导率和硬度,但是不显著影响Al2O3和Ce协同效应。Cu-0.5%Al2O3-0.02%Ce复合材料的最佳热处理温度为400℃下退火1-3 h。

Cu based composite co-strengthened by Al2O3 and Ce was prepared via high-energy ball milling and spark plasma sintering （SPS）. Effec.ts of annealing time and temperature on the microstructure, aggregation of A1203 particles, hardness and electrical conductivity of Cu-Al2O3 and Cu-Al2O3-Ce composite were studied. The results proved the co-strengthening effect of Al2O3 and Ce in Cu matrix. The mechanism of co-strengthening effect was the optimized distribution and decreasing aggregation of Al2O3 , which led to extra increase of hardness and electrical conductivity. In annealing process, the existence of Ce weakened the aggregation of Al2O3. The increasing annealing temperature led to larger particle size of AI：O3. For fixed annealing time, the average particle size of AI203 and annealing temperature met the Arrhenius relationship by fitting the relationship between the two. Considering larger particles weakening dispersion strengthening and motion of free electron, annealing above 400 ℃ would weaken the co-strengthening effect of Al2O3 and Ce, which meant a lower hardness and eleetrical conductivity. Annealing at 400 ℃ over 2 h had almost no impaet on eo-strengthening effect, only decreasing electrical conductivity and hardness. The optimum heat treatment process of Cu-0.5% Al2O3-0. 02% Ce composite was annealing at 400 ℃ for 1 - 3 h.