“…In recent years, several laser-assisted joining processes have received more attention; these include laser-assisted roll bonding, [4] laser pressure welding, [5] laser-induced reactive wetting without filler metal (only irradiating Al sheet to melt it), [6] laser brazing (only irradiating filler metal wire or steel sheet to melt filler metal by direct heating or heat conduction through the hot steel sheet), [7][8][9] and laser braze welding (irradiating both filler metal wire and Al sheet to melt and mix them). [10,11] For laser-assisted joining processes, shielding gas (argon) [6][7][8][9][10][11] or brazing flux (e.g., fluor-base anticorrosive brazing flux [6][7][8]11] ) is necessary, although satisfactory strength can be obtained by optimizing filler metal (e.g., using Zn filler metal instead of the Al base one [9,10] ) and process parameters. [8] On the other hand, friction stir lap welding (FSLW) of Al sheet to steel sheet has also been attempted in recent years, because a joint is produced in solid state and no cover gas or flux is used.…”