Fedorchuk V. Technological strength of welded joints of aluminum alloys Al-Zn-Mg-Cu, alloyed with scandium

Thesis is devoted to the study of the weldability of high-strength aluminum alloys of the Al-Zn-Mg-Cu under the additional doping with by scandium. For the first time formulated criteria and rational limits for doping weld joints by scandium when welding aluminum alloys Al-Zn-Mg-Cu. It is shown that the maximum effect of the reinforcement weld joints is ensured with content of the scandium 0.35-0.4% at the expense shredding crystalline structure and solid solution hardening of the weld metal scandium. It is found that a prerequisite for enhancing the weldability is the presence of scandium in welded alloys and in the filler wire. It is shown that doping of alloys of Al-Zn-Mg-Cu scandium and use filler wires of Al-Mg alloys with scandium reduces the tendency to hot cracking during welding by 1.5-2 times and improve the strength characteristics of welded joints up to 20-30%. Study of the mechanical properties of welded joints also confirm the value of doping scandium not only filler wire but also welded alloys. It has been established that the use of a filler wire with scandium increases the tensile strength of welded joints by 15-20 MPa, while introduction of 0.3% scandium in weldable metal enhances the tensile strength by 100 MPa. Moreover, the ductility remains at the same level.