Microstructure and properties of Cu-Ni-Si-Zr alloy after thermomechanical treatments

The effect of thermomechanical treatments on the microstructures and properties of Cu-2.1Ni-0.5Si- 0.2Zr alloy was investigated. The hot-rolled plates were solution treated at 920 ℃ for 1.5 h, quenched into water, cold rolled by 70 % reduction in thickness, and then aged at 400, 450 and 500 ℃for various times. The variation in tensile strength and electrical conductivity of the alloy was measured as a function of the aging time. The results show the peak strength value of 665 MPa for the alloy aged at 450 ℃ for 2 h. However, the electrical conductivity is observed to reach a maximum of 47 % IACS aged at 450℃for 8 h. OM, SEM, and TEM were used for microstructural inspection of the alloy. Precipitation occurs preferentially at deformation bands in the cold-rolled alloy. Properties behavior is discussed in the light of microstructural features.

六价铬对大鼠学习记忆的影响

目的观察六价铬[Cr(VI)]对大鼠学习记忆的影响。方法母鼠哺乳期分别给予双蒸水(对照组)、低(0.8 mg/kg)、中(4.0 mg/kg)、高(20 mg/kg)重铬酸钾溶液(低、中、高剂量重铬酸钾组)。断乳后仔鼠灌胃与其母鼠相同剂量的重铬酸钾溶液,共6个月。石墨炉原子吸收光谱法测定大鼠脑组织中铬含量;Morris水迷宫实验测试大鼠学习记忆能力;尼氏染色和免疫组织化学等方法观察大鼠海马神经细胞及星形胶质细胞的形态学改变;高效液相色谱法测定谷胱甘肽(GSH)含量。结果低、中、高剂量重铬酸钾组脑组织中铬含量与对照组比较,差异有统计学意义(P<0.05)。随着染毒剂量增加,大鼠平均逃避潜伏期和第1次寻找平台的潜伏期延长,穿越原平台次数减少,在原平台象限停留时间缩短(P<0.05)。与对照组比较,重铬酸钾组大鼠海马组织出现损伤、神经元排列紊乱及细胞核浓染固缩。星形胶质细胞GFAP阳性表达现象随剂量的增加而加重。与对照组比较,铬暴露组大鼠海马组织的GSH含量下降(P<0.05)。结论重铬酸钾可引起大鼠海马神经元结构及其功能损伤,学习记忆能力降低,其机制可能与Cr(VI)所诱导的氧化应激有关。