The 12th TIMA21 which was held in Timișoara, Romania, by videoconference (November 25-26, 2021), paid particular attention to practical problems in the area of new joining technologies, mechanical and structural characterization of advanced materials and joints, corrosion and assessment of damage state. The volume includes selected papers in which the authors reveal the results of their own research and development activity, carried out in the frame of their institutes, universities and economic field from Romania, Hungary, Serbia, Ukraine, Bulgaria, and Latvia. Friction Stir Welding, Ultrasonic Welding, Arc Welding, Inert Gas Environment, Heat Treatment, Alloy, Steel, Polymer, Composite, Wire Electrical Discharge Machining, Soldering, Corrosion, Fatigue Behaviour, Thermal Stresses, Additive Manufacturing, Shape Memory Alloy, Mechanical Properties, Concrete Materials Science, Building Materials.