Influence of Multi-pass Friction Stir Processing on Microstructure and Mechanical Properties of Die Cast Al-7Si-3Cu Aluminum Alloy

doi:10.1007/s40195-016-0405-2

Abstract

Abstract:

The influence of overlap multi-pass friction stir processing on the microstructure and the mechanical properties, in particular, strength, ductility and hardness of die cast Al-7Si-3Cu aluminum alloy was investigated. It was observed that increase in the number of overlap passes friction stir processing resulted in significant refinement and redistribution of aluminum silicon eutectic phase and elimination of casting porosities. The microstructural refinement by the friction stir processing not only increases the ultimate tensile strength from 121 to 273 MPa, but also increases the ductility as observed by the increase in fracture strain from 1.8% to 10%. Analysis of the fractured surface reveals that the microstructural refinement obtained by friction stir processing plays a vital role in transforming the fracture mode from completely mixed mode to the ductile mode of the fracture with increasing number of passes. The change in the size, shape, morphology and distribution of eutectic silicon particles and elimination of the porosities are the main reasons for the increases in tensile strength and ductility due to friction stir processing.

Key words: Friction stir processing, Overlap multi-pass, Microstructure, Mechanical properties

L. John Baruch, R. Raju, V. Balasubramanian, A. G. Rao, I. Dinaharan. Influence of Multi-pass Friction Stir Processing on Microstructure and Mechanical Properties of Die Cast Al-7Si-3Cu Aluminum Alloy[J]. Acta Metallurgica Sinica (English Letters), 2016, 29(5): 431-440.

Figures/Tables 9

Table 1 Chemical composition (wt%) of cast AS7U3G aluminum alloy

Si	Fe	Cu	Mn	Mg	Zn	Cr	Ti	Al
7.7	0.48	3.24	0.31	0.19	0.09	0.02	0.05	Bal.

Fig. 1 Friction stir processing setup and tool: a workpiece and tool; b tool dimensions (all dimensions in mm)

Fig. 2 Cast alloy a, a1, one-pass FSP stir b, b1, two-pass FSP stir c, c1 and three-pass FSP stir d, d1 zone SEM micrographs and corresponding energy-dispersive spectra of the FSP stir zones

Fig. 3 SEM micrograph a, EDS result a1 of three-pass FSP stir zone with HT

Fig. 4 Tensile test results of base metal and friction stir processed materials

Fig. 5 Microhardness profile across the as-cast and FSPed region of one, two and three pass

Fig. 6 Microhardness profile across the as-cast, three-pass FSPed region before and after precipitation hardening treatment

Fig. 7 SEM fractographs of the tensile specimens for the as-cast alloy a, one-pass FSP b, two-pass FSP c, three-pass FSP d, three-pass FSP with HT e

References 27

[1]	D.L. Zhang, L. Zheng, Metall. Mater. Trans. A 27, 3983 (1996)
[2]	Y.B. Yu, P.Y. Song, S.S. Kim, J.H. Lee, Scr. Mater. 41, 767(1999)
[3]	G. Atxang, A. Pelayo, A.M. Irrisarri, Mater. Sci. Technol. 17,446(2001)
[4]	K.T. Kashyap, S. Murali, K.S. Raman, K.S.S. Mater.Sci. Technol. 9, 189(1993)
[5]	J. Jiang, Y. Wang, J. Qu, Mater. Sci. Eng. A 560, 473 (2013)
[6]	J. Jiang, Y. Wang, Z. Du, J. Qu, Y. Sun, S. Luo, J. Mater.Process. Technol. 210, 751(2010)
[7]	W.M. Thomas, US Patent Patent Application No. 9125978.8(1991)
[8]	Z.Y. Ma, S.R. Sharma, R.S. Mishra, M.W. Mohaney, Mater.Sci.Forum2891, 426-432 (2003)
[9]	Z.Y. Ma, S.R. Sharma, R.S. Mishra, Metall. Mater. Trans. A 37,3323 (2006)
[10]	Z.Y. Ma, S.R. Sharma, R.S. Mishra, Scr. Mater. 54, 1623(2006)
[11]	S.R. Sharma, Z.Y. Ma, R.S. Mishra, Scr. Mater. 51, 237(2004)
[12]	M.L. Santella, T. Engstrom, D. Storjohann, T.Y. Pan, Scr.Mater. 53, 201(2005)
[13]	F. Nacimento, T. Santos, P. Vilaca, R.M. Miranda, L. Quintino, Mater. Sci. Eng. A 506, 16 (2009)
[14]	A.G. Rao, B.R.K. Mater. Lett. 63, 2628(2009)
[15]	K. Nakata, Y.G. Kim, H. Fujii, T. Tsumura, T. Komzaki, Mater.Sci. Eng. A 437, 274 (2006)
[16]	M.M.E. J. Mater. Process. Technol. 212,1157(2012)
[17]	G.R. Cui, D.R. Ni, Z.Y. Ma, S.X. Li, Metall. Mater. Trans. A 45,5318 (2014)
[18]	N. Nadammal, S.V. Satish, S. Suwas, Mater. Des. 65, 127(2015)
[19]	S. Tutinchilar, G.M.K.Mater. Sci. Eng. A 534, 557 (2012)
[20]	D. Yadav, R. Bauri, Mater. Sci. Eng. A 539, 85 (2012)
[21]	R. Bauri, D. Yadav, G. Suhas, Mater. Sci. Eng. A 528, 1326(2011)
[22]	K. Surekha, B.S. Murty, K.P. Rao, Surf. Coat. Technol. 202,4057(2008)
[23]	Z.Y. Ma, S.R. Sharma, R.S. Mishra, Mater. Sci. Eng. A 433, 272(2006)
[24]	K. Elangovan, V. Balasubramanian, Mater. Charact. 59, 1168(2008)
[25]	F.Y. Tsai, P.W. Kao, Mater. Lett. 80, 40(2012)
[26]	L. Karthikeyan, V.S. Senthilkumar, V. Balasubramanian, S.Natarajan, Mater. Des. 30, 2237(2009)
[27]	D. Lu, S. Wei, M. Zhou, Y. Jiang, R. Zhou, Adv. Mater. Res.1689, 148-149 (2010)