Deformation And Damage Of Explosive Welded Steels Under Gas Gun Shock Loading

Explosive welded materials have the advantages of strong adhesion,good processing performance and low cost,which have been widely applied in national defense,aerospace,transportation,shipbuilding and other fields.At present,the research on explosive welding materials mainly focuses on the effects of welding parameters and interface shapes on welding quality,as well as the tensile,shear,and bending resistance of different metal welding interfaces.There are few studies on the response of explosive welding materials under high strain rate loading,and the evolution of microstructure is not yet clear.With the extensive use of explosive welding materials in the fields of national defense and aerospace,their service environment is getting worse and worse.It is necessary to consider the dynamic response and damage evolution of explosive welding materials under high strain rate loading,which are important scientific issues in the field of materials science and physics.Therefore,the research on dynamic response and damage deformation of explosive welding materials not only has important scientific significance,but also can provide reliable experimental and theoretical data for improving the explosive welding materials.Q235 and #45 are carbon steels,which are cheap and widely used.In this work,the method of explosive welding has been used to weld the Q235 and #45 together,the light gas gun was used to conduct experiments on the sample,and dynamic macro response and microscopic damage and deformation characteristics were studied.The main work and innovation points are summarized as follows:(1)The spallation and compression experiment of explosive welding steel Q235/#45 were conducted by light gas gun.The free surface velocity of samples were measured by the Doppler Pin System(DPS).Hugoniot elastic limit(HEL)and spallation strength of the sample at different impact velocity were obtained,which were compared with the matrix material Q235's.The damage and deformation characteristics of explosive welding steel were analyzed.In the spallation experiment,the crack propagation can be hindered by the explosion welding interface,resulting in passivation or deflection of cracks,which reduced the stress concentration effect at the crack tip.This is the reason why the crack strength and Hugoniot elastic limit of the explosive welding material is higher than that of Q235 at high speed and low velocity loading.In the compression experiment,the explosive welding steel and the matrix material Q235 show obvious difference in the elastic-plastic transition.Free surface velocity of the explosive welding steel increases slowly,while the free surface velocity of the Q235 increases quickly after a period of time at the Hugoniot elastic limit.(2)The mechanical properties and microscopic damage deformation characteristics of the compressed explosive welding steel were analyzed by the Victor hardness tester,scanning electron microscope(SEM)and electronic backscatter diffraction(EBSD).The SEM and EBSD characterization results showed that a large number of dislocations appeared in the fine crystal zone of the explosive welding interface after the impact compression,and a large number of twins and subgrain boundaries appeared in the severe deformation zone,which increased the hardness of these regions.(3)The micro damage characteristics of explosive welding steel under dynamic tensile loading were analyzed.With the increase of tensile stress,the micro damage was first nucleated at the ultra-fine grain area near the interface,forming small voids.The small voids grew up and connected with each other to form cracks and expand along the wavy interface,which eventually leads to the complete cracking of the interface.The tensile stress duration in #45 steel is longer than that in Q235,due to the different of wave impedance between the interface and basis material,so there are more cracks and voids in #45 steel,while almost no cracks occur in the Q235.