The microstructure and its effects on the high temperature mechanical behavior of Cu-2.7%Al_2O_3 （volume fraction） dispersion strengthened copper （ADSC） alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700℃. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 ℃ are lower than those at 700 ℃. The stress exponents at 400 ℃ and 700℃ are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.
探究一种无敏化和活化过程的石墨粉化学镀铜新工艺。研究石墨粉分别在酒石酸钾钠单络合剂、EDTA·Na_2单络合剂、酒石酸钾钠和EDTA·Na_2的双络合剂3种镀液配方中的化学镀铜行为,以及温度对镀层外观、镀覆速率、镀覆前后质量增加率的影响,并采用SEM分析方法表征施镀前后的石墨粉微观形貌。结果表明:石墨粉无敏化、活化处理条件下,可镀覆上完整的铜层。施镀反应在镀液pH值为12.5,甲醛浓度为35 m L/L条件下进行。镀覆温度为75℃,络合剂配方选择在乙二胺四乙酸二钠浓度c(EDTA·Na_2)为30 g/L时,镀覆速率1.32 g/h,镀覆效果最佳。镀覆后的石墨粉外观呈玫红色,且镀层连续致密。
