engleski

Testing of mechanical properties of AlMg4.5Mn alloy welded by MIG procedure and impact of hydrogen on mechanical properties of the welded joint

Good mechanical properties, corrosion resistance and relatively low density make aluminium and its alloys widely used structural material in many applications. Rapid development of aluminium structures induced also development of solutions for resolving of aluminium joining problems. This included development of welding processes, welding consumables and supporting equipment. Appropriate selection of welding process and filler material allows avoiding specific technical problems. Particular difficulty is welding of thick aluminium sections, due to possible occurrence of incomplete fusion caused by high thermal conductivity of aluminium. Also, appearance of reduced strength values within the heat-affected zone is characteristic phenomenon. Mentioned factors impose complex requirements in optimization of welding parameters and selection of welding technology if specified mechanical properties of welded joint are required. Process of MIG welding of EN AW 5083 (AlMg4, 5Mn) aluminium alloy has been reported in this contribution. Alloy has been delivered in as- cast condition. Base material has been supplied in the form of 32 mm thick plates. Edges of plates have been machined to make X-shaped groove ready for welding. Detailed investigations of micro- and macro-structure have been made. Specimens for tensile and bending test were cut out. Samples that were welded applying MIG process meet requirements stipulated in HRN EN ISO 15614-2 standard. It can be concluded that applied technology produced acceptable mechanical and structural properties. In this paper the influence of hydrogenation on mechanical properties and microstructure of MIG double-side welded EN AW- 5083 aluminium alloy was also investigated. Detachment between base metal and weld started at the weldroot and afterwards the main crack continues spreading along the fusion line characterized by as-cast microstructure with fine equiaxed columnar grains. A great number of grain boundaries could be considered as H-traps and the sites from where initial microcracks start.

AlMg4.5Mn ; MIG welding ; hydrogen ; metallographic investigation ; mechanical properties ; welded joint

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