The paper focuses on an experimental topic relating to the field of friction welding process of a nodular cast iron. The microstructures, phase transformation, temperature distributions, microhardness, and tensile test are all studied within the framework of the paper in question. Maximum temperature measurements in the axial center and periphery of the analyzed joints were equal to 950 and 840°C, respectively. Both temperature and increasing temperature gradient at the axial center were higher than those at the periphery. The maximum tensile strength of the examined friction-welded nodular cast iron joints was 53% of that of the parent metal. The welding region was composed of deformed graphite nodules, coarse pearlite, proeutectoid ferrite, and acicular martensite. Highly deformed graphite nodules were distributed along the weld interface due to the material flow in the thermo-mechanically affected zone (TMAZ). In the central zone, graphite displayed a striped configuration and ferrite transformed into a martensite structure. In the peripheral region, graphite surrounded by martensite kept the form of individual granules. Maximum hardness at the interface in the TMAZ and the heat-affected zone reached 603 HV and 345 HV, respectively. The executed microstructure analysis showed that the cracks started occurring mostly at the interface of the deformed graphite nodules and then spread through the grain boundaries of metal matrix. The fracture surface appearance showed a cleavage fracture in the peripheral zone and a little dimple fracture around graphite nodules in the central zone.
The temperature distributions, microstructure, and mechanical properties of tungsten composite with aluminum alloy friction-welded joints are presented in this paper. The effects of welding parameters on flash diameter, shortening, joint efficiency, microhardness, and microstructure were studied. Empirical temperature models for heating and cooling phases are proposed in this study. The predicted maximum temperatures at the periphery and in the axis of aluminum specimens were close to 550 °C and 480 °C at the interface, respectively. Moreover, the peak temperature in the weld zone was studied analytically. A maximum tensile strength of 234 MPa was reached for the following welding parameters: friction time of 3.5 s and friction force of 12.5 kN. The efficiency of the welded samples decreased after reaching the maximum value, with an increase of friction time and force. Maximum hardness at the interface and the half-radius reached 100 HV and 80 HV in the aluminum alloy joints, respectively. Dynamic recrystallisation areas on the aluminum alloy side were observed. Transmission electron microscopy observations of the microstructure in the aluminum alloy revealed the presence of a high dislocation density compared to the parent material.
The paper presents an investigation of the bainite morphology in two experimental Mo-Cr and Mo-Cr-V-Ti steels using TEM, high speed dilatometry backed by thermodynamic analysis. The microstructure was investigated using metallography and TEM method. After austenitisation at 1200 o C followed by bainitic reaction in upper and lower temperatures of isothetmal transformation the bainite was in the form of classical sheaves. The amont, distribution and morphology of retained austenite and bainitic ferrite depend on prior austenitisation and isothermal transformation temperatures within the bainitic range.
The friction rotary welding (FRW) of magnesium alloy to aluminum alloy was presented in a paper due to significant interest in the manufacturing industry. A genetic algorithm (GA) method for optimizing FRW process parameters of dissimilar light alloys was presented. After obtaining the welding parameters by GA method, it was possible to determine the best tensile strength of the friction joint. The obtained joints were subjected to tensile strength. The highest tensile strength TS = 178 MPa was found using a genetic algorithm for the following friction welding parameters: friction force FF = 16 kN, friction time FT = 4 s, and upsetting force UF = 44 kN. The optimized values were compared with the experimental results. The application of the genetic algorithm method allowed increasing the tensile strength joint from 88 to 180 MPa. The maximum tensile strength of the friction welded magnesium alloy-aluminum alloy joints was 73% of the base AZ31B metal. The relationship between welding parameters and strenght of welds was also demonstrated in this study.
The article shows the video-optical system for to recognition of location and size of weld groove. Was used special system equipped with two USB cameras (VGA resolution) and red laser laser. First of camera was used to recognition of groove location and second one with laser as mobile scanner was used to size of groove analyse. For proposed conception was prepared in Visual Basic 6.0 special software WELD_REC, which calculate the angle of groove location and the groove parameters: width, depth and angle of opening. Presented system is used for experiments using PC controlled IRb –60 industrial robot. The differences of location of groove: between well-known and video-optical measured have the highest of 3% .
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