Organizer：State Key Laboratory of Explosion Science and Technology
Collaborative Innovation Center of Safety and Protection
Title： Metastable phases at interfaces of explosively welded materials
Reporter： A/Prof.Ivan Bataev
Novosibirsk State Technical University, Russia
Time： 10:00a.m., June 21, 2017
Venue： Meeting Room, 2nd Floor, State Key Laboratory of Explosion Science and Technology
Biography：
Ivan Bataev is currently an assistant professor since 2011. His research interest is materials science aspects of high speed and high energy phenomenon, including explosive welding, high-strain-rate deformation, laser and electron beam heating and multilayer composites. Prof. Ivan Bataev has published 39 scientific journal articles and conference papers. He has travelled and collaborated with many colleagues in Germany, France, UK and Japan.
Abstract:
Explosion welding is one of the most common techniques for the fabrication of bimetals and multilayer composites, consisting of dissimilar alloys. The high-speed oblique collision of workpieces caused by the detonation of explosive materials occurs during the welding process. If the collision angle and velocity are chosen correctly, the conditions for metallurgical bond formation are provided at the contact point. It is typically assumed that surface contaminations and thin oxide films are effectively removed from the surface of welded materials due to the formation of the so-called “jet, which moves ahead of the contact point. This process improves the welding tendency of materials. It is widely considered that virtually all combinations of metallic alloys can be explosively welded.During an explosion, the interfaces of welded materials experience fast heating due to high strain rate severe plastic deformation. This leads to the formation of local zones, where melting and mixing of welded materials is observed. These zones are frequently referred to as vortexes, eddies or swirls, due to the specific rotational movement of materials during mixing. This study is primarily devoted to the discussion of the structures that appear in these zones. Simple approaches to estimate the heating and cooling rates at the interfaces between explosively welded materials were proposed. It was concluded that the heating rate at the interfaces was of the order of 109 K/s, while the cooling rate achieved 107 K/s. Several combinations of explosively welded alloys (steel/steel, Ti alloy/steel, Zr/Cu, Zr/Ni, Ta/Cu, Al/magnesium alloy, Cu/brass, etc.) were thoroughly analyzed using scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. In most of these combinations, metastable crystalline, quasi-crystalline or glassy phases were observed. The formation of different types of metastable phases is discussed with respect to the compositions of the welded alloys. It was concluded that solidification conditions at the interfaces of explosively welded materials are similar to those during rapid solidification.
