Papers by Author: Vjacheslav I. Mali

Abstract: In current research composite copper/tantalum were used as interlayer for explosive welding of titanium and Ni-based alloy sheets. Defects such as cracks coupled with brittle intermetallics compounds were not detected at the interface of dissimilar materials by metallographic analysis. Strength test of obtained composite material reveals growth of yield strength in 2 times in comparison with Ni-based alloy.

Abstract: 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.

Abstract: The structure and mechanical properties of the laminates produced by explosive welding of low carbon steel were investigated. The maximum number of layers in the composites was 21. It was shown that the structure of the composite is not uniform across the thickness of the layers and along the boundaries in the shape of the wave. Transmission electron microscopy revealed that the sizes of the grain-subgrain clusters forming in the weld adjacent zones are about 100…400 nm. The maximum temperature was reached in the areas of the vortices. High-strength martensite was formed in these zones in the process of cooling. The strength properties and toughness of the com-posite is almost 2 times higher compared with the properties of the original plates. It was shown that the boundaries of welds are the barriers inhibiting the development of fatigue cracks.

Abstract: TiB2-Cu composites in a nanostructured state are candidates for high-strength conductive and erosion-resistant materials. In this work, we studied formation of nanostructured TiB2-Cu composites under shock wave conditions. We investigated the influence of preliminary mechanical activation (MA) of Ti-B-Cu powder mixtures on the peculiarities of the reaction between Ti and B under shock wave. In the MA-ed mixture the reaction proceeded completely while in the nonactivated mixture the reagents remained along with the product – titanium diboride. The size of titanium diboride particles in the central part of the compact was 100-300 nm. This research shows that shock wave synthesis in mechanically activated powder mixtures with simultaneous compaction of the composite is a promising way to materials with submicron and nanostructures.