Effect Of High Frequency Vibration On Microstructure And Mechanical Properties Of TIG Welding Joints Of AZ31

Vibration welding is a new welding technique which is based on common weldingprocess and vibration aging.It is common practice to superimpose a certain frequencyand amplitude vibration on workpieces during the common welding process.Someresearch showed that vibration would have some influence on welding pool.The grainsize of the weld and heat affected zone decreased remarkably,especially by usingmechanical vibration.But research on vibration welding magnesium alloy is still few sofar,and some related issues are lack of awareness.In addition,the frequency of ordinaryvibration welding is generally low,ranging from a few hertz to several hundredhertz.Therefore,this paper developed a device for superimposing vibration onworkpieces during the TIG welding process so that it could reveal that how did highfrequency vibration influence the microstructure and mechanical properties of thewelding joints’ each area,and that could establish the theory and application foundationfor using high frequency vibration welding to improve the weldability of AZ31magnesium alloy.The main work of this paper included the following aspects.①Overseas and domestic research status of vibration welding was summed upand summarized.②Based on the relevant theory of sound wave transmission,this paper analyzedthe characteristics of high frequency vibration wave during the transmission in the meltand mechanism of action between the melt. When the high frequency vibration wavetransmitted the interface of two phase,the reflection and refraction occurred.Thereflection of the longitudinal wave and shear vertical wave would influence the thewelding process.The mechanism of action between high frequency vibration wave andmelt included acoustic streaming,cavitation effect,mechanical effect,heating effect andso on.All these effects produced by high frequency vibration wave would impact onwelding process.③High frequency vibration welding experiment was designed and done.AZ31sheets with thickness of3and1mm were used in the vibratory welding.From the microperspective,this paper compared the microstructure and grain size of high frequencyvibration welding joints’ each part under different vibration direction,groove angle andamplitude;From the aspects of mechanical properties,this paper measured themicro-hardness and did the tensile testing at ambient temperature.The law of different process parameters influencing the welding process was summarized.④Based on the high frequency vibration welding experiment and combined withthe existing theory,this paper analyzed and discussed the law which summarized fromthe experiment.Through the research of this project,we preliminary mastered the law that highfrequency vibration influenced the microstructure,micro-hardness and tensile propertiesof welding joints,and we had some knowledge of the essence that the high frequencyvibration impacted the welding process.All of these established a solid foundation forthe deeper theoretical research and practical application.