Industrial fluxless laser weld-brazing process of steel to aluminium athigh brazing speed

Abstract

tAA6016-T4 aluminium and DX56D + Z140M steel sheets were joined by fluxless laser weld-brazing pro-cess in industrial conditions and at high brazing speed reaching 6 m/min with ER4043 AlSi5filler wire. Theconfiguration studied corresponds to an automotive roof/body-side bond application. For each configu-ration the energy and feeding rate are computed. The resulted intermetallic layer at the Fe–Al interfaceand its morphology are investigated through hardness, optical microscopy, EDS and EBSD analysis. Themaximum thickness of the intermetallic layer is measured for each configuration. The associated mechan-ical strength is quantified to evaluate the potential of different configurations for an high brazing speedindustrial application. Both, thin and thick intermetallic layer presents specific crystallographic orienta-tion. Thin layer presents a small grains microstructures in the opposite of thick layer with bigger grains.For some samples, specific orientations of the intermetallic needles are observed. The configuration withenergy of 600 J/cm and a feeding rate of 1.125 (unit-less) stands out as the most significant with anaveraged mechanical strength of 101% of the mechanical properties of the filler wire and intermetalliclayer with thickness bellow 2 m. Mechanical fractures are no longer observed at the Fe–Al interface butoccurred in the welded area, between the seam and the aluminium sheet.