Mierostruetural development of a commercial 7055 （Al-Zn-Mg-Cu）alloy is studied by transmission electron mieroseope（TEM） during the process of single-ageing for up to 48 h. It is observed that Guinier-Preston （GP） zones are formed on { 111} planes when the sample is aged for a short time and grows up gradually with increase of ageing time. η＇ phase is formsed after ageing for 4 h at 120℃, having the orientation relationship with the matrix as[0 0 0 1]η＇//[1 1^- 1]Al and （1 0 1^- 1）η＇//（1 1 0）Al.η phase starts to occur after 24 h ageing and has an orientation relationship with matrix as [1^- 1 0 0]η//[1 1 0]Al and （0 0 0 1）η// （1 1 1）Al. Since the density of both η＇ phase and η phase particles is much lower than that of GP zone on aged alloy, GP zones are important to control the properties of the alloy.
The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constraint model and the Bishop ＆ Hill maximum work principle. Results show that when the rolling direction （RD） is parallel to a certain direction of a grain, the large localized shear occurs on one slip plane, thus generating microbands in the grain because of the high localized shear strain. The angle between the RD and the shear band is about 30°. The plate-like structure of the microband is formed because of the dislocation double cross slip. The transmission electron microscope （TEM） observation of the microband in the cold rolled BCC metal confirms the formation mechanism of the microband.
针对纳米ZnO在制备以及使用的过程中极易发生团聚从而影响其抗菌性能这一缺点,设计实验使得纳米ZnO在溶胶凝胶过程中与多孔SiO2进行复合。通过扫描电子显微镜(Scanning electron microscope, SEM)以及透射电子显微镜(Transmission electron microscopy, TEM)等可以发现,ZnO很好地复合在多孔SiO2的骨架上并且分散得较为均匀。通过表面积测试(Brunner-emmet-teller measurement, BET)以及光致发光光谱(Photoluminescence spectrum,PL)的测试可以发现,复合材料的比表面积得到提高且光学性能加强。通过菌落计数法探究复合材料与单组分纳米ZnO的抗菌性能差异以及复合材料中纳米ZnO含量的变化导致的抗菌性能的变化。结论证明,当纳米ZnO与多孔SiO2进行复合之后,材料的抗菌性能得到了极大的提高,抑菌率超过了99%。
