Investigations about the influence of the time-temperature curve on the formation of intermetallic phases during electron beam welding of steel-aluminium material combinations

Electron beam welding of square butt joints has been used for the joining of the low-alloy steel DC05 and the aluminium alloy AlMg3 without filler materials. To this end, a clamping device which allows free expansion and shrinking of the plates and also in situ heating by the electron beam has been developed. In order to examine the influence which the time-temperature curve at the edge exerts on the formation of the intermetallic phases, in a test series, the preheating temperature of the steel plate has been successively increased from 100 to 500 degrees C. It has been possible to identify two intermetallic phases by EBSD analysis-on the steel side, the eta-phase (Al5Fe2) and, on the aluminium side, the T-phase (Fe4Al13). Through the correlation of the measured individual phase widths, the evaluation of the temperature curves and the results from the quasi-static tensile tests, the factors which exert influence on the development of various intermetallic phases have been identified. A maximum tensile strength of 200 MPa with a total phase width of 2.3 mu m has been achieved.