SCANDIUM EFFECT ON THE PROPERTIES AND STRUCTURE OF ALLOYS OF Al-Zn-Mg-Cu SYSTEM AND THEIR WELDED JOINTS

摘要

The effect of scandium additives on structure and mechanical properties of cast metal, sheet semi-finished products and butt joints made by nonconsumable electrode argon-arc welding of aluminum alloys of Al-Zn-Mg-Cu alloying system was studied. It is shown that scandium-containing alloys, both in the cast metal, and in their sheet semi-finished products, all the structural components have smaller dimensions, than in the alloys without scandium, that ensures the ultimate strength of the sheets on the level of 640-700 MPa, depending on content of main alloying elements in them. It is established that in nonconsumable argon-arc welding of 3 mm sheets from scandium-containing alloys the total length of the softening zone is reduced by 20% at simultaneous increase of weld metal hardness that provides higher mechanical properties of such joints. Complex addition of scandium to base material and filler wire simultaneously that ensures its content in the weld metal on the level of 0.30-0.35% allows significantly increasing the resistance of welded joints of Al-Zn-Mg-Cu system to hot solidification cracking.