AIP Conference Proceedings [Author(s) MECHANICS, RESOURCE AND DIAGNOSTICS OF MATERIALS AND STRUCTURES (MRDMS-2018): Proceedings of the 12th International Conference on Mechanics, Resource and Diagnostics of Materials and Structures - Ekaterinburg, Russia (21–25 May 2018)] - Contribution of intermetallics to the formation of the stress-strain state of tensile welds on the AISI 321 steel and the grade 2 titanium alloy with a copper insert