Stir zone material flow patterns during friction stir welding of heavy gauge AA5056 workpieces and stability of its mechanical properties

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 4 2021 Fig. 11. Comparison of the ultimate tensile strength of test samples cut from different areas of the stir zone with the base metal one Conclusion The conducted studies show that despite inhomogeneities in the structure of the samples produced by friction stir processing of 35 mm thick workpieces, the mechanical properties of the stir zone material exceed the base metal values in all directions relative to the processing line. Material structure heterogeneities after friction stir welding/processing have no determining in fl uence on the material properties of the stir zone. There is no clear correlation between the strength values and the direction of load application, nor is there any signi fi cant difference in mechanical properties depending on the location of the specimens within the stir zone. The average ultimate tensile strength values in the vertical, transverse, and longitudinal directions are 302 MPa, 295 MPa, and 303 MPa, yield strength – 155 MPa, 153 MPa, and 152 MPa, and ductility – 27.2 %, 27.5 %, and 28.7 % respectively. The deformation behavior of the specimens during the tests is similar, and only small differences in the process of plastic deformation and fracture can be distinguished for each group of ones. Microhardness values are also quite close and show no tendency to increase or decrease in the stir zone by more than 31 %, while the scatter of microhardness values for the sample as a whole is about 40 %. The obtained data allow concluding the high degree of applicability of friction stir welding and friction stir processing technologies to produce permanent joints and hardened surface structures of workpieces made of aluminum-magnesium alloy AA5056 , including heavy gauge ones. References 1. Mishra R.S., Ma Z.Y. Friction stir welding and processing. Materials Science and Engineering: R: Reports , 2005, vol. 50, iss. 1, pp. 1–78. DOI: 10.1016/j.mser.2005.07.001. 2. Threadgill P.L., Leonard A.J., Shercliff H.R., Withers P.J. Friction stir welding of aluminium alloys. Inter- national Materials Reviews , 2009, vol. 54, iss. 2, pp. 49–93. DOI: 10.1179/174328009X411136. 3. Balasubramanian V. Relationship between base metal properties and friction stir welding process parameters. Materials Science and Engineering: A ., 2008, vol. 480, iss. 1–2, pp. 397–403. DOI: 10.1016/j.msea.2007.07.048. 4. Deng Y., Peng B., Xu G., Pan Q., Yin Z., Ye R., Wang Y., Lu L. Effects of Sc and Zr on mechanical property and microstructure of tungsten inert gas and friction stir welded aerospace high strength Al-Zn-Mg alloys. Materi- als Science and Engineering: A. , 2015, vol. 639, pp. 500–513. DOI: 10.1016/j.msea.2015.05.052. 5. Han M.S., Lee S.J., Park J.C., Ko S.C., Woo Y.B., Kim S.J. Optimum condition by mechanical characteristic evaluation in friction stir welding for 5083-O Al alloy. Transactions of Nonferrous Metals Society of China , 2009, vol. 19, pp. 17–22. DOI: 10.1016/S1003-6326(10)60238-5.