ANALYSIS OF THE PROPERTIES OF ELECTRON BEAM WELDED JOINTS OF ALUMINIUM LITHIUM ALLOY LATEST GENERATION

摘要

Electron beam welded joints made on AW2099 aluminium lithium alloy with the thickness of 4 mm were analysed. The third generation of aluminium lithium alloys was developed to improve the drawbacks of the second one. Various electron beam welding parameters (beam current, welding speed) were tested. Accelerating voltage was constant, i.e., 55 kV. Defect free welded joints were produced under optimized welding parameters. Weld metal microstructure and welded joints mechanical properties were investigated. Microstructure of weld metal matrix consists of α-aluminium solid solution. Inter-dendrite areas were enriched in alloying elements due to segregation. Narrow equiaxed zone was observed at the location close to the fusion boundary being characteristic for welded joints made on aluminium lithium alloys. The character of the grains changed in the direction towards weld metal centre to columnar dendritic and equiaxed dendritic. Microhardness values reduction in the weld metal was observed which is associated to the dissolution of strengthening precipitates.