Inhibition of cracking in pulsed laser welding of aluminium alloys

[摘要] Pulsed laser welding of Aluminium Silicon alloys has been investigated experimentally to discover the causes of welding cracking which affect these alloys and a means for its prevention. Cracking was observed in conduction and non-conduction limited modes of welding, being more severe in the latter because of higher quenching rates induced in the fused material. The specimen alloys chosen were a heat-treatable type-6082-T6 and a non-heat-treatable type-5251-H24. Welds were generated with a high pulse repetition frequency ND3+:YAG laser, capable of operating with a mean power of 500W. The power intensity in the weld was selected by variation of the pulse parameters to achieve the desired welding modes. Control was exercised over the degree of overlap present between successive weld spots by appropriate variations of the pulse repetition frequency and the velocity of translation of the incident beam. Cross sections of weld were examined microscopically; a scanning electron microscope was employed to analyse variations in the concentrations of the alloying elements in the fused zone. With there results, cracking was attributed to tensile failure in the last alloy to freeze which was weakened by the segregation of silicon consequent upon non-equilibrium freezing of the volatile components was another caused factor. A complete solution was found by the inclusion of a high silicon content wire in the weld preparation. By this means, the silicon content in the last metal was raised, in the conduction limited mode, and spatial radients of the temperature were reduced.

[发布机构] University:University of Glasgow

[关键词] Materials science