Microstructure and mechanical properties of friction pull plug welding for 2219-T87 aluminum alloy with tungsten inert gas weld

Abstract

The friction pull plug welding (FPPW) of the 2219-T87 tungsten inert gas (TIG) welded joint was investigated, and the microstructures, precipitate evolution, mechanical properties, and fracture morphologies of this joint were analyzed and discussed. In this study, defect-free joints were obtained using a rotational speed of 7000 r/min, an axial feeding displacement of 12 mm, and an axial force of 20–22 kN. The results indicated that within these welding parameters, metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains. The microstructural features of the FPPW joint can be divided into different regions, including the heat-affected zone (HAZ), thermomechanically affected zone (TMAZ), recrystallization zone (RZ), heat-affected zone in the TIG weld (TIG-HAZ), and the thermomechanically affected zone in the TIG weld (TIG-TMAZ). In the TIG-TMAZ, the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process. The main reason for the softening in the TMAZ is determined to be the dissolution of θ′ and coarsening of θ precipitate particles. In a tensile test, the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa. The locations of cracks and factures in the TIG-TMAZ were identified. The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.

Keywords

friction pull plug welding / tungsten inert gas weld / microstructures / constituent particles / mechanical properties

References

[1] R. Takeshita and T.L. Hibbard, Friction Plug Welding, United States Patent, Appl. US6213379.B1, 2001.

[2] J.A. Littell, Friction Pull Plug and Material Configuration for Anti-Chatter Friction Pull Plug Weld, United States Patent, Appl. US9452491.B1, 2016.

[3] S.A. Brooke and V. Bradford, Friction pull plug welding in Aluminum alloys, [in] TWI Conference the Welding Institute, Huntsville, 2012, p. 1795.

[4] Wang GQ, Zhao YH, Zhang LN, Bai JB, Zhu RC. A new weld repair technique for friction stir welded aluminum structure: inertia friction pull plug welding. China Welding, 2017, 26(4): 56

[5] Metz DF, Barkey ME. Fatigue behavior of friction plug welds in 2195 Al-Li alloy. Int. J. Fatigue, 2012, 43, 178.

[6] D.F. Metz, E.R. Weishaupt, M.E. Barkey, and B.S. Fairbee, A microstructure and microhardness characterization of a friction plug weld in friction stir welded 2195 Al-Li, J. Eng. Mater. Technol. Trans. ASME, 134(2012), No. 2, art. No. 021005.

[7] Du B, Cui L, Yang XQ, Wang DP, Sun ZP. Weakening mechanism and tensile fracture behavior of AA 2219-T87 friction plug welds. Mater. Sci. Eng. A, 2017, 693, 129.

[8] Cui L, Lu P, Li WK, Wang HM, Wang DP, Zhang ZP, Song JL. Influence of axial force parameters to the quality of friction pull plug welding for 2219-T87 aluminium alloy sheets. Sci. Technol. Weld. Joining, 2019, 24(1): 27.

[9] Gao JY, Yang LJ, Cui L, Lu P, Yang J, Gao YJ. Improving the weld formation and mechanical properties of the AA-5A06 friction pull plug welds by axial force control. Acta Metall. Sinica Engl. Lett., 2020, 33, 828.

[10] P. McGill and J. Burkholder, Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy, [in] Ninth International Symposium on Friction Stir Welding, Huntsville, 2012, p. 1188.

[11] P. McGill and J. Burkholder, Damage tolerance behavior of friction stir welds in aluminum alloys, [in] National Space and Missile Materials Symposium, Tampa, 2012, p. 1017.

[12] Du B, Sun ZP, Yang XQ, Cui L, Song JL, Zhang ZP. Characteristics of friction plug welding to 10 mm thick AA2219-T87 sheet: Weld formation, microstructure and mechanical property. Mater. Sci. Eng. A, 2016, 654, 21.

[13] Feng XL, Liu HJ, Lippold JC. Microstructure characterization of the stir zone of submerged friction stir processed aluminum alloy 2219. Mater. Charact., 2013, 82, 97.

[14] Son SK, Takeda M, Mitome M, Bando Y, Endo T. Precipitation behavior of an Al-Cu alloy during isothermal aging at low temperatures. Mater. Lett., 2005, 59(6): 629.

[15] Chu Q, Li WY, Yang XW, Shen JJ, Vairis A, Feng WY, Wang WB. Microstructure and mechanical optimization of probeless friction stir spot welded joint of an Al-Li alloy. J. Mater. Sci. Technol., 2018, 34(10): 1739.

[16] Li H, Zou JS, Yao JS, Peng HP. The effect of TIG welding techniques on microstructure, properties and porosity of the welded joint of 2219 aluminum alloy. J. Alloys Compd., 2017, 727, 531.