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Experiments were carried out to study the influence of surface condition on expulsion during the spot welding ofAZ31B Mg alloy. A general electrical contact resistance theory for conductive rough surfaces and the relation betweenmaximum temperature Tm in the contact and voltage-drop V across interface of two surfaces were employed tounderstand the reason of expulsion in Mg alloy spot welding. The main reason of expulsion is that the high electricalcontact resistance induced by large roughness of the surface and oxide film covered on the surface leads to localmelting of metal in the interface of two surfaces, and liquid metal of the local area ejected from the specimen underelectrode force forms expulsion.
Experiments were carried out to to study the influence of surface condition on expulsion during the spot welding of AZ31B Mg alloy. A general electrical contact resistance theory for conductive rough surfaces and the relation between max temperature Tm in the contact and voltage-drop V across interface of two surfaces were employed tounderstand the reason of expulsion in Mg alloy spot welding. The main reason of expulsion is that the high electricalcontact resistance induced by large roughness of the surface and oxide film covered on the surface leads to localmelting of metal in the interface of two surfaces, and liquid metal of the local area ejected from the specimen underelectrode force forms expulsion.