Effects of aging treatment on the microstructure and superelasticity of columnar-grained Cu₇₁Al₁₈Mn₁₁ shape memory alloy

Abstract

The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu₇₁Al₁₈Mn₁₁ shape memory alloy (SMA) at the temperature ranging from 250°C to 400°C was investigated. The microstructure evolution during the aging treatment was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that the plate-like bainite precipitates distribute homogeneously within austenitic grains and at grain boundaries. The volume fraction of bainite increases with the increase in aging temperature and aging time, which substantially improves the martensitic transformation critical stress of the alloy, whereas the bainite only slightly affects the superelasticity. This behavior is attributed to a coherent relationship between the bainite and the austenite, as well as to the bainite and the martensite exhibiting the same crystal structure. The variations of the martensitic transformation critical stress and the superelasticity of columnar-grained Cu₇₁Al₁₈Mn₁₁ SMA with aging temperature and aging time are described by the Austin–Rickett equation, where the activation energy of bainite precipitation is 77.2 kJ·mol⁻¹. Finally, a columnar-grained Cu₇₁Al₁₈Mn₁₁ SMA with both excellent superelasticity (5%–9%) and high martensitic transformation critical stress (443–677 MPa) is obtained through the application of the appropriate aging treatments.

Keywords

copper aluminum manganese alloys / shape memory effect / columnar grains / aging / bainite / superelasticity

References

[1] Otsuka K., Wayman C.M. Shape Memory Materials, 1999, Cambridge, Cambridge University Press, 97.

[2] Lexcellent C. Shape-Memory Alloys Handbook, 2013, London, John Wiley & Sons, 37.

[3] Oliveira J.P., Panton B., Zeng Z., Omori T., Zhou Y., Miranda R.M., Braz F.M. Fernandes, Laser welded superelastic Cu–Al–Mn shape memory alloy wires. Mater. Des., 2016, 90, 122.

[4] Oliveira J.P., Zeng Z., Omori T., Zhou N., Miranda R.M., Braz F.M. Fernandes, Improvement of damping properties in laser processed superelastic Cu–Al–Mn shape memory alloys. Mater. Des., 2016, 98, 280.

[5] Liu J.L., Huang H.Y., Xie J.X. The roles of grain orientation and grain boundary characteristics in the enhanced superelasticity of Cu_71.8Al_17.8Mn_10.4 shape memory alloys. Mater. Des., 2014, 64, 427.

[6] Liu J.L., Huang H.Y., Xie J.X. Superelastic anisotropy characteristics of columnar-grained Cu–Al–Mn shape memory alloys and its potential applications. Mater. Des., 2015, 85, 211.

[7] Jani J.M., Leary M., Subic A., Gibson M.A. A review of shape memory alloy research, applications and opportunities. Mater. Des., 2014, 56, 1078.

[8] Sutou Y., Omori T., Okamoto T., Kainuma R., Ishida K. Effect of grain refinement on the mechanical and shape memory properties of Cu–Al–Mn base alloys. J. Phys. IV, 2001, 11(PR8): Pr8-185.

[9] Prado M.O., Tolley A. Hardness of Cu–Mn–Al alloys as a function of the annealing temperature in the β phase. Mater. Sci. Eng. A, 1999, 273-275, 590.

[10] Sutou Y., Koeda N., Omori T., Kainuma R., Ishida K. Effects of ageing on bainitic and thermally induced martensitic transformations in ductile Cu–Al–Mn-based shape memory alloys. Acta Mater., 2009, 57(19): 5748.

[11] Sutou Y., Koeda N., Omori T., Kainuma R., Ishida K. Effects of aging on stress-induced martensitic transformation in ductile Cu–Al–Mn-based shape memory alloys. Acta Mater., 2009, 57(19): 5759.

[12] Adorno A.T., Carvalho T.M., Magdalena A.G., dos Santos C.M.A., Silva R.A.G. Bainitic precipitation in the Cu–9wt.%Al–4wt.%Mn–5wt.%Ag alloy. J. Alloys Compd., 2014, 615(S1): S153.

[13] Kennon N.F., Dunne D.P., Middleton L. Aging effects in copper-based shape memory alloys. Metall. Trans. A, 1982, 13, 551.

[14] Tabuchi M., Marukawa K., Sato H. Process of bainitic precipitation and successive transformation in Cu–Zn–Al alloy. J. Jpn. Inst. Met., 1997, 61(1): 1.

[15] Takezawa K., Sato S. Nucleation and growth of bainite crystals in Cu–Zn–Al alloys. Metall. Trans. A, 1990, 21(6): 1541.

[16] Zou W.H., Gui J.N., Wang R.H., Tang C.H., Xiang M.Z., Zhang D., Sun W.H., Yang D.Z. Bainitic precipitation and its effect on the martensitic transformation in the Cu–Al–Ni–Mn–Ti shape-memory alloy. J. Mater. Sci., 1997, 32(19): 5279.

[17] Benke M., Mertinger V., Barkóczy P. Investigation of the kinetic of a bainitic reaction upon heating in a CuAlNiMn and a CuAlNiMnFe shape memory alloy. Mater. Sci. Forum, 2013, 752, 3.

[18] Benke M., Mertinger V., Pekker P. Investigation of the bainitic reaction in a CuAlNiMnFe shape memory alloy. J. Min. Metall. Sect. B, 2013, 49(1): 43.

[19] Kurz W., Fisher D.J. Fundamentals of Solidification, 1998, Stafa-Zurich, Switzerland, Trans Tech Publications Ltd., 56.

[20] Otsuka K., Ohba T., Tokonami M., Wayman C.M. New description of long period stacking order structures of martensites in β-phase alloys. Scripta Metall. Mater., 1993, 29(10): 1359.

[21] Starink M.J. Kinetic equations for diffusion-controlled precipitation reactions. J. Mater. Sci., 1997, 32(15): 4061.

[22] Planes A., Romero R., Ahlers M. The martensitic transition temperature in ternary Cu–Zn–Al alloys. Influence of the L2₁ structure. Acta Metall. Mater., 1990, 38(5): 757.