Research On Interface Meso-mechanics And Microdefect Control Of Explosive Welding

As a convenient and efficient composite material processing technology,explosive welding technology has successfully prepared hundreds of different metal composite materials and is widely used in industrial production.However,in this technology,the welding process is difficult to control due to the complexity and danger in this process,in addition,improper selection of welding parameters will lead to poor interface morphology,and even makes the formation of a variety of interface defects or cracks and other undesirable phenomena.The interface defects could reduce the strength,toughness,stability and air tightness of the composite materials,and even scrap the workpieces,which will greatly reduce the comprehensive performance and economy of explosive welding composite materials.In this paper,explosive welding experiments and numerical simulation were used to research the effect of various factors on explosive welding in order to better predict and control the interface morphology,and to suppress the formation and development of interface defects,as well as to further explore and improve the relevant mechanism of explosive welding.The main research content and conclusions are as follows:First,a large number of explosive welding experiments were carried out on carbon steel materials with different strengths and hardness,and the welding process was numerically simulated using SPH algorithm to study the effect of material strength on explosive welding.According to the results,it can be seen that the effect of material strength on the interface morphology is very obvious,and the numerical relationship between the interface specific intensity and the specific wavelength is established.The characterization of the interface morphology revealed that microscopic defects such as shear bands,pores,and shrinkage cracks were formed on the interface of some samples.The formation of shear bands is caused by thermal instability on the interface,and most of these defects occur in high-strength materials;the formation of pores and shrinkage cracks is caused by excessive melting of the interface,and most of these defects appear in low-strength materials.In addition,combined with the numerical simulation results,it is found that the formation of waves is due to the instability of the interface caused by the accumulation of disturbances,and Bahrani indentation mechanism is more realistic in qualitative description of the formation process.Secondly,the titanium alloy was selected as flyer plates in order to study the effect of material density on explosive welding.The welding experiment results show that a flat interface appears in a large proportion of the samples.The results indicate that the lower flyer plate density lead to insufficient impact penetration ability at the collision point,making it difficult for the interface to be unstable.In the specimens with wavy interface,brittle lumpy impurities and element transition layers are formed on the interface due to the chemical reaction of dissimilar metals and the oxidation reaction of molten metal during the welding process.In addition,by analyzing the relationship between specific intensity and specific wavelength it can be found that the results is very close to the previous carbon steel experiments,which shows that the specific intensity of the interface is the most critical factor affecting the interface morphology no matter what kind of material it is.Finally,the theory of the "pipe effect" of explosive welding is proposed by analyzing the role and impact of the gas between the two plates during the welding process,and the pipeline effect intensity of different kinds of gases is calculated through theoretical derivation.According to the calculation results and the chemical reaction phenomenon of the active metal in the welding process,the explosive welding scheme using helium as the replacement gas was determined,and titanium/steel as well as magnesium/aluminum composite plates were manufactured.The experimental results show that the performance of each welding sample has been improved to varying degrees,so the new welding scheme is very feasible and worth promoting.