ВЛИЯНИЕ ФОРМЫ ИНСТРУМЕНТА ДЛЯ СВАРКИ ТРЕНИЕМ С ПЕРЕМЕШИВАНИЕМ НА ФИзИКО-МЕХАНИЧЕСКИЕ СВОйСТВА СВАРНЫХ СОЕДИНЕНИй АЛЮМИНИЕВОГО СПЛАВА EN AW 6082-T6

The paper presents the results of studying the formation of macrostructure and distribution of mechanical properties in welded joints of flat samples from aluminium alloy EN AW 6082-T6 8 mm thick, produced by the method of friction stir welding with application of three types of specially designed pins with shoulders: C - cylindrical threaded pin and shoulder with a spiral groove; T - cylindrical threaded pin with three grooves and shoulder with a spiral groove; S - smooth cylindrical pin without thread and flat shoulder. Friction stir welding was conduced in the equipment of the Institute of Welding in Gliwice (Poland), and treatment and mechanical testing were conducted at PWI. Mechanical testing by indentation was performed in Microngamma instrument, which allows experimental identification of the structural state of metal after refinement and determination of the presence of strain ageing by limit values of the ratio of hardness to Young’s modulus of elasticity. It is found that for all the three samples HAZ hardness decreases, and in the thermomechanical impact zone hardness increases. Maximum hardness values are inherent to the central part of welded joint nugget, as well as to light-coloured oval concentrated fragments of the structure in the nugget upper and lower part. Judging by the presence of nanosized strengthened structure and uniformity of its distribution in the nugget, as well as good dispersion of oxide films and absence of discontinuities, friction stir welding with C-type tool can be regarded as the optimum variant. An assumption was made that formation of a uniform structure in welds can be achieved at three-four rotations of the tool in friction stir welding in one spot. [ABSTRACT FROM AUTHOR]