The broad range applications of Ultra-Fine Grained metals is substantially limited by the lack of a welding method that allows them to be joined without losing the strong refinement of structure. From this point of view, the solid state welding processes are privileged. Friction welding tests were carried out on UFG 316L stainless steel. A joining process at high temperature activates the recrystallization, therefore the friction welding parameters were selected according to the criterion of the lowest degree of weakness due to recrystallization in the heat affected zone. In order to characterize the structure of basic material and selected areas of the obtained joint, were performed SEM, TEM and metallographic examinations in terms of hardness and range of softening of the material and tensile test. Despite the short time and relatively low welding temperature, results of the test by scanning electron microscopy and transmission electron microscopy confirmed the loss of the primary ultrafine structure in the Heat Affected Zone of welded joint.

One of important resistance parameters introduced into engineering calculations for selection of materials and evaluation of their operating properties is material crack resistance. Contrary to the stationary fracture toughness K1c, J," the dynamic fracture toughness K,d, J,d, ~ is also an important parameter. In this paper, the authors have evaluated the relation between the parameters of the dynamical fractures toughness and the structure as well as impact resistance in chosen frictionally welded joints. The above-mentioned joints are made of the following steel parts: N9E-45, 18G2A-St3S, St3S-45, 40H-45, 18G2A-40H. In this experiment, the instrumented bending impact test was used.

The results of experimental study of solid state joining of tungsten heavy alloy (THA) with AlMg3Mn alloy are presented. The aim of

these investigations was to study the mechanism of joining two extremely different materials used for military applications. The

continuous rotary friction welding method was used in the experiment. The parameters of friction welding process i.e. friction load and

friction time in whole studies were changed in the range 10 to 30kN and 0,5 to 10s respectively while forging load and time were constant

and equals 50kN and 5s. The results presented here concerns only a small part whole studies which were described elsewhere. These are

focused on the mechanism of joining which can be adhesive or diffusion controlled. The experiment included macro- and microstructure

observations which were supplemented with SEM investigations. The goal of the last one was to reveal the character of fracture surface

after tensile test and to looking for anticipated diffusion of aluminum into THA matrix. The results showed that joining of THA with

AlMg2Mn alloy has mainly adhesive character, although the diffusion cannot be excluded.

In the paper the modelling of thermo-mechanical effects in the process of friction welding of corundum ceramics and aluminium is presented. The modelling is performed by means of finite element method. The corundum ceramics contains 97% of Al2O3. The mechanical and temperature fields are considered as coupled fields. Simulation of loading of the elements bonded with the heat flux from friction heat on the contact surface is also shown. The heat flux was modified in the consecutive time increments of numerical solutions by changeable pressure on contact surface. Time depending temperature distribution in the bonded elements is also determined. The temperature distribution on the periphery of the cylindrical surfaces of the ceramics and Al was compared to the temperature measurements done with a thermovision camera. The results of the simulation were compared to those obtained from the tests performed by means of a friction welding machine

Present study introduces effect of forge application and elimination on microstructural and mechanical properties of AISI 316 during friction welding. Temperature measurements, microstructure, micro-hardness, tensile test, scanning electron microscopy and X-ray diffraction were evaluated. Maximum temperature recorded was 819°C while forge was applied between 357°C-237°C. Thermo-mechanically affected zone and highly plastically deformed zone were created at the interface at elimination and application of forge respectively. Ultimate tensile strength decreased and ductility increased when forge elimination compared to forge application. Tensile fracture was occurred adjacent to the welding interface for both cases, though, after forge application, ductile fracture mode and cleavage features through the fingerprints were observed in the fracture morphology. Redistribution and concentration of gamma iron in 111 level after forge application and heat treated of AISI 316.

To investigate the solid state weldability on SUS316L alloy, this work was carried out. Friction welding as a solid state welding was introduced and conducted at a rotation speed of 2,000 rpm and a friction pressure of 25 MPa on tube typed specimens. After this work, the grain boundary characteristic distributions such a grain size, shape and misorientation angle of the welds were clarified by electron backscattering diffraction method. The application of friction welding on SUS316L resulted in a significant refinement of the grain size in the weld zone (6.03 μm) compared to that of the base material (57.55 μm). Despite the grain refinement, the mechanical properties of the welds indicate relatively low or similar to the base material. These mechanical properties are due to dislocation density in the initial material and grain refinement in the welds.