Effect of Welding Parameters on Microstructure and Mechanical Properties of Friction Stir Spot Welded of Titanium Alloy TiAl6V4

Document Type: Original Article

Authors

1 Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

2 Department of Mechanical Engineering, Tiran Branch, Islamic Azad University, Isfahan, Iran

3 Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran

Abstract

In this study, friction stir spot welding (FSSW) is applied to join the TiAl6V4 titanium alloy with 1.5 mm thickness and then the effect of rotational speed and tool dwell time on microstructure and mechanical properties is investigated. In this regard, the speed of the tool rotation was considered as 800, 1000, and 1200 rpm, as well as the tool dwell time was set at 7 and 12s. Microstructural evaluation was carried out using optical microscopy (OM) and scanning electron microscopy (SEM). In addition, tensile-shear and hardness studies were performed to analyze mechanical properties. The obtained results from microstructural evaluation show that the welded joints consist of two regions, namely the SZ and the HAZ-regions. Additionally, microstructure of the SZ-region was identified in the form of α/β layer within the initial β-phase. The results of tensile/shear tests and micro-hardness test indicated that the joint strength and hardness are enhanced with increasing the rotational speed and dwell time. The tensile/shear strength is increased from 2.7 to 15 KN with increasing the rotational speed at constant dwell time of 7s, and also is increased from 7.3 to 17.25 KN with increasing the rotational speed at constant dwell time of 12s. The maximum tensile/shear strength was achieved for the welded joint with the dwell time of 12s and rotational speed of 1250 rpm. The hardness of SZ, HAZ regions and base metal are measured around 380 to 420, 340 to 380, and 300 to 340, respectively.

Keywords


[1]     Aghajani, H., Elyasi, M., and Hoseinzadeh, M., “Feasibility study on Aluminum alloys and A441 AISI Steel joints by friction stir welding”, International Journal of Advanced Design and Manufacturing Technology, Vol. 7, No. 4, 2014, pp. 99-109.

[2]     Fari, A., Batalha, G. F., Prados, E. F., Magnabosco, R., and Delijaicov, S., “Tool wear evaluations in Fraction stir processing of commercial Titanium Ti-6Al-4V”, Wear, Vol. 302, 2012, pp. 1327-133.

[3]     Kurtulmus, M., “Friction stir spot welding parameters for Polypropylene sheets”, Scientific Research and Essays, Vol. 7, 2012, pp. 947-956.

[4]     Kemal Bilici, M., “Application of taguchi approach to optimize FSSW parameters of Polypropylene”, Materials and Design, Vol. 35, 2012, pp. 113-119.

[5]     Ramirez, A. J., Juhas, M. C., “Microstructural evolution in Ti–6Al–4V friction stir welds”, Materials Science Forum, Vols. 426-432, 2003, pp. 2999-3004.

[6]     Nader, S., Kasiri, M., and Shamanian, M., “Effect of dwell time on microstructure of friction stir spot welded of titanium alloy TiAl6V4”, Advanced Processes in Materials Engineering, Vol. 9, No. 2, 2015, pp.149-156.

[7]     Feng, Z., Santella, M. L., and David, S. A., “Friction stir spot welding of advanced high-strength steels a feasibility study”, Transactions Journal of Materials and Manufacturing, Vol. 114, 2005, pp. 1–7.

[8]     ASME Standard, Section IX, “Welding, brazing and fusing qualification”, QW-462.9, 2007 Edition.

[9]     ASTM: E384-11e1, “Standard test method for knoop and vickers hardness of materials”.

[10]  Zhang, Y., Sato, Y., Kokawa, H., Park, S.C., and Hirano, S., “Microstructural characteristics and mechanical properties of Ti-6Al-4V friction stir welds”, Material Science and Engineering: A., Vol. 485, 2007, pp.448-445, 2007.

[11]  Liu, H. J., Zhou, L., and Liu, Q. W., “Microstructural characteristics and mechanical properties of friction stir welded joints of Ti-6Al-4V titanium alloy”, Materials and Design, Vol. 31, 2009, pp. 1650-1655.

[12]  Zhou, L., Liu, H. J., and Liu, Q. W., “Effect of rotation speed on Microstructure and mechanical properties of Ti-6Al-4V Friction Stir Welded Joints”, Materials and Design, Vol. 31, 2010, pp. 2631-2636.

[13]  Lee, W. B., Lee, C. Y., and Chang, W. S., “Microstructural investigation of friction stir welded pure titanium”, Material Letters, Vol.59, 2005, pp. 3315-3318.

[14]  Mishra, R. S., Ma, Z. Y., “Friction stir welding and processing”, Material Science and Engineering: R, Vol. 50, 2008, pp. 1-78.

[15]  Rai, R., De, A., Bhadeshia, H. K. D. H., and Debroy, T., “Review: Friction stir welding tools”, Science and Technology of Welding and Joining, Vol.16, 2011, pp. 325-342.