Researches Of Impact Dynamics Problems And Prepared Bulk Metallic Glass Composite By Explosive Welding

Metallic glass composite materials have some properties in mechanics and physics better than crystal metals, so it can be widely used in civil and national defense industry as structural material. But because of the rapidly solidified limitation of cooling rates, at present the actual application was restricted by its three dimensions size. At present, preparing bulk metallic glass composite is the research focus, so extensive and further researches have been done at home and abroad, and developed some prepared methods. As a result, bulk metallic glass composites were larger in size. Explosive welding is one of the most important method, people pay more attention on it. This method is a classical impact kinetics method, in this paper, series studies have been developed.The explosive welding of preparing bulk metallic glass composites by amorphous foils is first to be discussed. It can be deduced by theory of elasticity that the experiment can not lay as metal plate with macro clearance between layers. And because its surface roughness can provide acceleration, it can be laid as superposition which is the style that put one upon another without macro clearance. Then the relationship between initial density and impact temperature was analyzed. Second, prosperities of amorphous foils higher surface hardness and temperature sensitivity, they make the explosive welding low limitation higher and upper limitation lower respectively, so window is narrower. Considering difficulties mansion above, it has been done that coated with another metal at amorphous foils to reduce its surface hardness. Besides, based on the theory of stress wave transformation and reflection, we introduced ideas of damage mechanics to set defects on experiment device. These defects can accelerate the attenuation of tension wave, so the strength of tension wave which arrive at welding interface is weaker. And the upper limit was increased. In researches of impact response, the motion differential equation of integral compressible by detonation products was given out, and gained its numerical results which were used to draw curves of displacement, density and velocity. Besides, based on finite elements theory, the EPIC-2D computer program was modified to make sure it suitable for simulating impaction between layers during explosive welding. By its result, we can analysis stress, strain and temperature field of welding interfaces. Lastly, bulks metallic glass composite materials were prepared by multilayer explosive welding. Samples were cut to test, and results were explained by impact dynamics and crystallization kinetics. Results show out that the impact temperature of multilayer amorphous foils explosive welding can not be neglected, and it can be controlled by adjustment of density of amorphous foils. The coated metal not only decreased its low limitation, but also improved the heat situation of amorphous matrix. These effects are beneficial to protect amorphous as metastable state. Defects on experiment device can accelerate the attenuation of tension wave, so can protect welding interfaces from cracks and increased upper limitation. Lower low limitation and higher upper limitation make the welding window wider. In curves of impact response, characters of inertial and strain rate effect in dynamic mechanics were reflected, and by cloud pictures of stress, strain and temperature field of welding interfaces, it can be concluded that the interfaces and matrix can be preserved well. Both of curves of XRD and DSC confirmed that the amorphous foils matrixes metastable state was maintained in bulk. SEM images reflected conditions of welding interfaces and coating interfaces. It can be concluded by images information that foils didn't crack and interfaces combined each other very well. We believe that strain, strain rate and adiabatic shear energy were all concentrated on coated metal, and detonation products were isolated, these make sure amorphous matrixes didn't transform to liquid, so can not occur structural relaxation. And because of characters of transient physics in explosive welding, temperature and pressure were attenuated in few minutes, the time isn't enough to diffuse for atom, so can not form nucleus and crystallize.