INVESTIGATION OF INFLUENCE OF PARAMETERS OF LASER WELDING ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AL-4.7%MG -0.32%MN-0.21%SC-0.09%ZR ALLOY

 The influence of laser beam welding on mechanical properties will be investigated. The material used in the present work was 1545 K alloy with the chemical composition (Al-4,7%Mg-0,3%Mn-0,2%Sc-0,09%Zr-0,001%Be-The laser welding conditions were voltage range from 310 to 350 V, laser defocusing is -2, duration 14 ms, and filler metals of (same alloy, Al-3%Ti-1%B) were used.The investigations of the structure, mechanical properties before and after annealing were carried out. There are two different type of the structure has found the first type is a mix of equiaxed grains zone (at the center) and columnar grains zone (the edges) with the same alloy as a filler metal the second type is small grains with 3,9±0,2 µm with Al-3%Ti-1%B filler metal​ Fig.1

The best of the mechanical properties of the samples in regards to the base metal were welded using filler metal Al-3Ti-1B. The best yield stress of welded joint and the base metal both after annealed 370 °C for 6 hours was 260,280 MPa respectively. The ratio between UTS for welded sample and base metal was (420 MPa/490 MPa) 0,85 and after rolling thickness changed from 1 to 0.8mm which deformation equal ln(L-δL/L)=0.2 and from 1.75 to 1 mm deformation was 0.6

       Finally, it can be observed that using filler metal Al-3Ti-1B for welding 1545k alloy was given good mechanical properties compared to the mechanical properties of the 1545k alloy after the same heat treatment (annealing 370°c for 6 hours).there are two welded sheets were rolled, one of them was rolled from 1 to 0.8 mm which have UTS 324.87 Mpa and elongation 1.6% and the other was rolled from 1.75 to 1 mm with the same condition of welding and heat treating which have UTS 420 MPa with elongation 1.9 %, microhardness 160 HV in the middle of welding area and 165 HV for base metal Fig.2 . There were some phases of AL₃ZrSc appeared and the alloying elements diffuse through all base metal and fusion zone were equal due to the annealing process