V. G. Burov

Structure and Fatigue Crack Resistance of Multilayer Materials produced by Explosive Welding

Multilayer materials produced by explosive welding of low carbon steel were investigated. Non-uniform structure of interlayer boundary was characterized using visible light microscopy, SEM and TEM. It was shown that 4 zones with different structure and mechanical properties present in the welded seams. To estimate fatigue properties of the multilayer materials kinetic diagram of fatigue failure were used. It was revealed that larger boundary waves give more significant contribution to fatigue crack resistance. In experiments carried out in the current research number of cycles to failure of multilayer materials was higher than those for bulk materials.

Microstructure and fracture behaviour of flash butt welds between dissimilar steels

Abstract Flash butt welds between high carbon steel and chrome–nickel steel were studied in this article. Light and electron microscopic studies have shown that the welded joints have a complex structure consisting of several phases. In addition to pearlite colonies, austenite microvolumes and regions of high strength martensite, the welds contain brittle inclusions of titanium sulphide and carbide particles. The mechanical behaviour of the welded joints is negatively influenced by the dramatic change in hardness in the weld zone. Fractographic analysis of dynamically fractured welds between carbon steel and stainless steels has shown that the fracture in the weld samples occurs in both steels. This behaviour of the material is caused by the non-uniform distribution of martensitic regions within the weld. The formation of martensitic regions in the structure of the material is a major cause of the reduction in the fatigue crack resistance of the welded joints.

Equipment for In Situ Studies of the Surface Structure of Thin Surface Layers in the Process of their Formation

The widespread use of polymeric semiconductor compositions for creating flexible and inexpensive solar cells can be achieved by providing the higher values of the coefficient of efficiency. The cost-effective production of polymer solar cells is expected at the efficiency of them not less than 10 %, while now its real level does not exceed 4 %. Many laboratories work to develop semiconductor compositions of organic materials as donors and acceptors which are fullerene derivatives or nanosize particles of semiconductor inorganic compounds [1-6]. The prospect of polymer used depends on the photovoltaic materials and the polymer purity and to a greater extent on the structure of the films formed from the compositions under development. In the search for ways to achieve higher performance of solar cells it is essential to optimize the technology of polymeric composition preparation, of which the active layer is formed, as well as optimization of the layer formation. In order to get information about the relationship between the structure of formed layer and its photovoltaic characteristics it is suggested to analyze the structure of the active layer simultaneously with the monitoring of its current-voltage characteristics. The study of the material structure directly in the process of its evolution seems an urgent task, since the majority of modern methods of structure investigation (light and electron microscopy, X-ray analysis) is not able to detect structural changes occurring in a short period of time. The most useful tool for monitoring the structure of polymer active layer is high intensity X-ray diffraction.

Features of the Fine Structure of the Active Layers of Organic Solar Cells

The article is devoted to investigation of fine structure of the active layers of organic solar cells. By using atomic forth microscopy (AFM) and transmission electron microscopy (TEM) it is clearly shown that thermal treatment of active layers at 150 °C for 10 minutes leads to increasing their crystallinity. During annealing processes of diffusion redistribution of the film components are activated, and this is accompanied by both the growth of the original crystalline phase and the formation of new crystals.

Impact of Local Weld Pool Zones on the Heterogeneous Material Structure

This work is devoted to formation of the Widmanstatten ferrite in the zone of complete recrystallization of the base metal during welding of low-carbon steels and cladding of hard coatings on the surface of low-carbon steels. The methods to reduce the brittleness of the ferrite in the overheated zones are proposed.