Microscopic characterization of semi-solid aluminium alloys

Abstract

The microstructural evolution and element distribution of the Al-4Cu-Mg alloy during semi-solid compression were investigated, and the precipitate behavior and dislocation morphology were discussed. The experimental results show that the microstructure, the number of CuAl₂ (θ phase) precipitates, and the dislocation density of the Al-4Cu-Mg alloy depend apparently on the process parameters. More segregation of Cu at the grain boundary happens with an increase of deformation temperature and a decrease of strain rate, leading to an increase in the number of θ phase. With an increase of height reduction, Cu segregation at the grain boundary decreases gradually. Moreover, unique dislocation morphologies including helical dislocations and dislocation loops appear at different process parameters and evolve to reduce the stored energy.

Keywords

aluminum alloys / semi-solid state / microstructural evolution / dislocation

References

[1] Flemings M.C. Behavior of metal in the semi-solid state. Metall. Trans. A, 1991, 22(5): 957.

[2] Laxmanan V., Flemings M.C. Deformation of semi-solid Sn-15pctPb alloy. Metall. Trans. A, 1980, 11(12): 1927.

[3] Charreyron P.O., Flemings M.C. Rheology of semi-solid deformation Sn-Pb alloys at low strain rates: application to forming process. Int. J. Mech. Sci., 1985, 27(11–12): 781.

[4] de Freitas E.R., Ferracini E.Jr. Ferrante M. Microstructure and rheology of an AA2024 aluminum alloy in the semi-solid state, and mechanical properties of a back-extruded part. J. Mater. Process. Technol., 2004, 146(2): 241.

[5] Lee B.S., Joo D.H., Kim M.H. Extrusion behavior of Al-Cu alloys in the semisolid state. Mater. Sci. Eng. A, 2005, 402(1–2): 170.

[6] Liu D., Atkinson H.V., Kapranos P., et al. Microstructural evolution and tensile mechanical properties of thixoformed high performance aluminium alloys. Mater. Sci. Eng. A, 2003, 361(1–2): 213.

[7] Kim W.Y., Kang C.G., Kim B.M. The effect of the solid fraction on rheological behavior of wrought aluminum alloys in incremental compression experiments with a closed die. Mater. Sci. Eng. A, 2007, 447(1–2): 1.

[8] Seo P.K., Kim D.U., Kang C.G. The effect of the gate shape on the microstructural characteristic of the grain size of Al-Si alloy in the semi-solid die casting process. Mater. Sci. Eng. A, 2007, 445–446(1): 20.

[9] Lee B.S., Joo D.H., Kim M.H. Textures and mechanical properties of extruded Al-Cu alloys in the semisolid state. J. Mater. Process. Technol., 2008, 198(1–2): 366.

[10] Lu Y.L., Li M.Q., Li X.C. Experimental investigation and modelling of microstructural variables of Al-4Cu-Mg alloy. Mater. Sci. Technol., 2008, 24(7): 815.

[11] Kang C.G., Choi J.S., Kim K.H. The effect of strain rate on macroscopic behavior in the compression forming of semi-solid aluminum alloy. J. Mater. Process. Technol., 1999, 88(1–3): 159.

[12] Van Haaften W.M., Kool W.H., Katgerman L. Tensile behaviour of semi-solid industrial aluminium alloys AA3104 and AA5182. Mater. Sci. Eng. A, 2002, 336(1–2): 1.

[13] Atkinson H.V., Liu D. Microstructural coarsening of semi-solid aluminium alloys. Mater. Sci. Eng. A, 2008, 496(1–2): 439.

[14] Atkinson H.V., Burke K., Vaneetveld G. Recrystallisation in the semi-solid state in 7075 aluminium alloy. Mater. Sci. Eng. A, 2008, 490(1–2): 266.

[15] Shan W.W., Luo S.J. Mechanical behavior and microstructure during compression of semi-solid ZK60-RE magnesium alloy at high solid content. Mater. Sci. Eng. A, 2007, 465(1–2): 247.

[16] Li J.Y., Sumio S., Jun Y. Microstructural evolution and flow stress of semi-solid type 304 stainless steel. J. Mater. Process. Technol., 2005, 161(3): 396.

[17] Seidl I., Kopp R. Semi-solid rheoforging of steel. Steel Res., 2004, 75(8–9): 545.

[18] Yan H., Zhou B.F. Thixotropic deformation behavior of semi-solid AZ61 magnesium alloy during compression process. Mater. Sci. Eng. B, 2006, 132(1–2): 179.

[19] Song R.B., Kang Y.L., Zhao A.M. Semi-solid rolling process of steel strips. J. Mater. Process. Technol., 2008, 198(1–3): 291.

[20] Zhang Y.F., Liu Y.B., Zhang Q.Q. Microstructural evolution of thixomolded AZ91D magnesium alloy with process parameters variation. Mater. Sci. Eng. A, 2007, 444(1–2): 251.

[21] Yim C.D., Shin K.S. Semi-solid processing of magnesium alloys. Mater. Trans., 2003, 44(4): 558.

[22] Jiang H.T., Lu Y.L., Huang W.C., Li X.L. Microstructural evolution and mechanical properties of the semisolid Al-4Cu-Mg alloy. Mater. Charact., 2003, 51(1): 1.

[23] Jiang H.T., Li M.Q. Microscopic observation of cold-deformation Al-4Cu-Mg alloy samples after semi-solid heat treatments. Mater. Charact., 2005, 54(4–5): 451.