The article describes the effect of friction stir processing (FSP) on the superplastic behaviour of the Al–4.5 Mg alloy containing Sc and Zr. The results yielded by the FSPed sheet were compared with the superplastic behaviour of the same alloy produced conventionally by cold rolling. The measurements of the superplasticty included the flow stresses and the maximum elongations of the alloy at initial strain rates ranging from 1×10−3 s−1 to 1 s−1, and at testing temperatures from 350 °C to 500 °C. The inclusion of the FSP step considerably enhanced the superplastic behaviour of the alloy in comparison with its rolled counterparts, which was reflected in higher elongations at higher strain rates and lower forming temperatures.
COBISS.SI-ID: 1315679
The paper describes the effect of minor additions of scandium and zirconium on the superplastic behaviour of the friction stir processed Al–5Mg based alloy. The measurements included the flow curves and tensile elongations of (in wt.%) Al–5Mg–0.1Zr, Al–5Mg–0.2Sc, and Al–5Mg–0.2Sc–0.15Zr alloys at initial strain rates ranging from 1×10-3 to 1×10-1 s-1, and at forming temperatures from 350 to 500 ℃. The inclusion of friction stir processing at tool rotation rates of 95 and 475 rpm considerably enhanced the superplastic behaviour of the Al–5Mg–0.2Sc–0.15Zr alloy, which was reflected in elongations without failure of over 1900 %. Other friction stir processed alloys, treated at lower tool rotation rates, did not achieve superplasticity due to abnormal grain growth. The results yielded by the friction stir processed alloys were compared with the superplastic behaviour of the same alloys produced conventionally by cold rolling.
COBISS.SI-ID: 1507423
A parametric study of friction stir spot welding (FSSW) of lap joints in aluminium alloy 5754 using a pinless tool with scrolled shoulder is presented. Experimental plan was done according to the response surface methodology (RSM), where tool rotation speed varied between 988 and 3511 rev/min, plunge rate between 24.4 and 150 mm/min and dwell time between 1 and 3.5 s. The plunge depth was held constant at 0.4 mm. During welding, the axial force and torque were monitored using a dynamometer. The welds were tensile shear tested, and the broken samples were visually examined. The weld bond line and microstructure were analysed using light optic microscope under polarised light, and SEM was used for examination of fractured surface. Mathematical models describing the relationship between welding parameters and joint strength, axial force and torque were developed. FSSW parameters, at which maximal joint strength was obtained, were considered as optimal. At these welding parameters, the axial force and torque were in the lower range among tested parameters. Material flow and joint formation are experimentally presented and schematically illustrated.
COBISS.SI-ID: 13806875
The paper presents an analysis of micro friction stir welding (mikroFSW) of electrolytic tough pitch copper (CuETP) in a lap and butt joint. Experimental plan was done in order to investigate the influence of tool design and welding parameters on the formation of defect free joints. From the welds samples for analysis of microstructure and samples for tensile tests were prepared. The grain size in the nugget zone was greatly reduced compared to the base metal and the joint tensile strength exceeded the strength of the base metal.
COBISS.SI-ID: 13473819
The paper presents an overview of different types of defects at friction stir welding. In order to explain the reasons for their occurrence a short theoretical background of the process is given first. The main emphasis is on the parameters that influence the process. An energy supply based division of defects into three disjoint groups was used. The occurring defects are demonstrated on various materials.
COBISS.SI-ID: 13744411