Microstructural Evolution of 7A04 Alloy Prepared by FE-ECAE in Semi-Solid State

Article Preview

Abstract:

In the paper, forward extrusion-equal channel angular extrusion (FE-ECAE), which is new strain-induced melt activation (SIMA) method, is introduced in making semi-solid billet of 7A04 alloy. The principle of the method is that by using FE-ECAE as strain induced step and semi-solid isothermal treatment as melt activation step. The results show that semi-solid billet with highly spheroidal and homogeneous refined grains can be prepared by FE-ECAE method. The equivalent strain in FE-ECAE before reheating has a great influence on its microstructural evolution. Grain size decreases and its shape also approaches to sphericity with increasing equivalent strain. The main mechanism of the initial semi-solid grains coarsening was coalescence. With the prolongation of isothermal holding time, the grains grew up and spheroidized, in which the mean diameter of grain and liquid volume fraction increased. In the meantime, the higher the reheating temperature, the faster the grain grew and spheroidized. Subsequently, the main mechanism of grains coarsening was Ostwald ripening. The suitable reheating temperature of 7A04 alloy was 610°C.

You might also be interested in these eBooks

Info:

Periodical:

Key Engineering Materials (Volumes 426-427)

Pages:

274-278

Citation:

Online since:

January 2010

Export:

Price:

Permissions CCC:

Permissions PLS:

Сopyright:

© 2010 Trans Tech Publications Ltd. All Rights Reserved

Share:

Citation:

[1] J.F. Jiang: Preparing semi solid billet by new SIMA method and research on thixotropic die forging of AZ91D (Harbin Institue of Technology, China 2005).

Google Scholar

[2] S. Nursen and Z. Metin: J. Mater. Process Technology Vol. 148 (2004) No. 1, pp.103-107.

Google Scholar

[3] S.J. Luo: Trans. Nonferrous Met. Soc. China Vol. 14 (2004) No. 6, pp.1074-1081.

Google Scholar

[4] H.S. Mahes, I.J. Beyerlein and C.N. Tome: Scripta. Mater. Vol. 53 (2005) No. 8, pp.965-969.

Google Scholar

[5] H. Conrad and K. Jung: Scripta. Mater. Vol. 53 (2005) No. 5, pp.581-584.

Google Scholar

[6] O.N. Sennonv, S.V. Senkova and J.M. Scott: Mater. Sci. Engineering (Series A) Vol. 393 (2005) No. 12, pp.12-21.

Google Scholar

[7] P.L. Sun, P.W. Kao and C.P. Chang: Scripta. Mater. Vol. 51 (2004) No. 6, pp.565-570.

Google Scholar

[8] W.H. Huang, L. Chang and P.W. Kao: Mater. Sci. Engineering (Series A) Vol. 307 (2001) No. 2, pp.113-118.

Google Scholar