Transient Local Melting in Al 7075-T6 Friction Stir Spot Welds

Abstract:

Article Preview

Transient local melting can account for the remarkable decrease in the strain rate when the tool rotational speed, heating rate and cycle time produce temperatures exceeding the 475 °C in Al 7075-T6 spot welds. The calculated strain rate is about 20 s-1 in Al 7075-T6 spot welds produced using tool rotational speeds from 1500 RPM to 3000 RPM and dwell time of 4 s. However, the peak temperature is less than less than 475 °C when a low tool rotational speed setting (1000 RPM) is used; transient local melting and tool slippage are precluded and the calculated strain rate is high (about 650 s-1). It is proposed that transient local melted films directly influence formation of the stir zone microstructure in Al 7075- T6 spot welds. It is suggested that the stir zone microstructure in spot welds made using high tool rotational speed settings are determined by a combination of grain boundary sliding and the limitation of cavity interlinkages when transient local melted films form.

Info:

Periodical:

Materials Science Forum (Volumes 539-543)

Main Theme:

Edited by:

T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran

Pages:

3826-3831

Citation:

T.H. North et al., "Transient Local Melting in Al 7075-T6 Friction Stir Spot Welds", Materials Science Forum, Vols. 539-543, pp. 3826-3831, 2007

Online since:

March 2007

Export:

Price:

$38.00

[1] P. Su, A. Gerlich, T.H. North and G.J. Bendzsak: in press, Sci. Tech. Welding and Joining, (2006).

[2] P. Su, A. Gerlich and T.H. North: SAE Technical Series, 2006-01-0971.

[3] A. Gerlich, G.A. Cingara, P. Su, T. H. North and G.J. Bendzsak: submitted for publication, Metall. Trans., January (2006).

[4] A. Gerlich, P. Su, T.H. North and G.J. Bendzsak: Materials Forum Vol. 29 (2005), p.290.

[5] A. Gerlich, P. Su and T.H. North: Sci. Tech. Welding and Joining, Vol 10(6) (2005), p.647.

[6] A. Gerlich, P. Su and T.H. North: in press, J. Materials Science, Vol. 40, p.6473.

[7] T.H. North, G.J. Bendzsak, A. Gerlich and P. Su: AWJT'2005 Conference, Dalian, China, (2005).

[8] T.H. North, G.J. Bendzsak, P. Su, G.A. Cingara and C. Maldonado: Proc. InterUniversity Research Seminar (IURS 2000), Tsinghua University, Beijing, China, (2005).

[9] G.J. Bendzsak, T.H. North and C.B. Smith, TWI Conf., Gothenburg, Sweden, (2000).

[10] T.H. North, G.J. Bendzsak, C.B. Smith, G.H. Luan: Proc. of the 7 th Int. Symp., JWS, Kobe, Japan (2001), p.621.

[11] A. Gerlich, G.A. Cingara and T.H. North: submitted to Materials Science Forum, January (2006).

[12] Y.S., Sato, M., Urata, and H. Kokawa: Metall. Mater. Trans A. (2002), vol. 33A, p.625.

[13] G.J. Bendzsak, unpublished research Dept. of Mat. Sci. Eng. University of Toronto, (2006).

[14] T.G. Nieh and J. Wadsworth: Scripta. Metall. and Materialia, (1992), Vol. 26, p.703.

[15] T.G. Nieh and J. Wadsworth: Superplasticity in Aerospace Aluminum, (1985), edited by R. Peace and L. Kelly, Ashford Press, Curdridge, Southampton, Hampshire, p.194.

[16] M. Mabuchi, K. Higashi and T.G. Langdon: Acta Mater., (1994), Vol. 42, p.1739.

[17] M. Mabuchi, K. Higahsi and T.G. Langdon: J. of Materials Research, (1996), Vol. 11, p.1755.

[18] P. Colegrove and H. Shercliff: Sci. and Tech. of Weld. and Joining, (2003), Vol. 8, p.360.