Laser resolidification of Al-5Mg-0.1Sc alloy: Growth of cells and banded structures

Abstract

The versatility of Al-Mg alloys makes them well-suited for applications ranging from everyday items to cutting-edge fields like automotive, microelectronics, and aerospace. Moreover, although Al-Mg alloys hold promise for improved surface features in components, research on their laser surface remelting (LSR) remains scarce, presenting an open opportunity to create novel components with these materials. Understanding the growth modes and morphologies of laser surface remelted products is critical in this context. Using a laser instrument, optical microscopy, SEM, XRD, Vickers hardness and image analysis techniques, a correlative analysis of microstructure features and laser heat input is proposed in this research. Furthermore, the Al-5Mg-0.1Sc (wt%) alloy was remelted using two distinct original substrates, each exhibiting varying degrees of microstructure coarsening. Additionally, four distinct laser heat input conditions were applied to each case. All molten pools regions were formed either by cells or bands, with higher growth rates producing a higher fraction of bands. While the variation in the original microstructure of the substrate did not significantly impact both cellular spacings and band/cellular fractions, the microhardness varied remarkably with the reduction in energy input from 10.0 J/mm to 1.7 J/mm. Kurz and Fisher model provided an accurate prediction of the cell spacings formed at the laser molten pool.