Effect of Novel Thermomechanical Treatment on Microstructure and Properties of 6156 Alloy

Abstract:

A novel thermomechanical treatment (TMT) was proposed for increasing the strength of 6156 aluminum alloy while maintaining a high elongation, which is based on artificial aging at low temperature, cold rolling and natural aging. The corresponding tensile properties and microstructure of 6156 aluminium alloy under different treatments were investigated. The yield strength and the ultimate tensile strength are increased by over 50 MPa over those of T3, while a high elongation rate is maintained. The fracture mechanism of T4 and TMT state alloy are typical ductile fracture, while that of T6 and T8 state alloy is a mixture of ductile fracture and shear fracture. For the TMT processed 6156 alloy, though no obvious precipitates can be observed in the matrix, tangled dislocations around primary phase in the matrix, as well as a high density of dislocations piled up at the grain boundary were observed. The mechanism of the novel TMT, by which the mechanical properties of the alloy is greatly improved, is the synergistic effect of composite structures, including dislocation substructures, the complex of Mg-Si clusters/vacancies, as well as GP zones.

• Periodical: Materials Science Forum (Volume 877)
• Pages: 275-280
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.877.275
• Online since: November 2016
• Authors: Jie Ke Ren, Zhi Guo Chen*, Ji Qiang Chen, Shuai Feng, Jing Peng
• Keywords: Al-Mg-Si Alloy, Mechanical Properties, Microstructure, Thermomechanical Treatment

References

[1] W.S. Miller, L. Zhuang, J. Bottema, et al, Recent development in aluminium alloys for the automotive industry, Mat. Sci. Eng. A. 280 (2000) 37-49.

[2] J. Hirsch, Aluminium in innovative light-weight car design, Mater. Trans. 52 (2011) 818-824.

DOI: 10.2320/matertrans.l-mz201132

[3] L.B. Ber, Accelerated artificial ageing regimes of commercial aluminium alloys. II: Al-Cu, Al-Zn-Mg- (Cu), Al-Mg-Si-(Cu) alloys, Mat. Sci. Eng. A. 280 (2000) 91-96.

DOI: 10.1016/s0921-5093(99)00661-9

[4] C. Cayron, P.A. Buffat, Transmission electron microscopy study of the β' phase (Al-Mg-Si alloys) and QC phase (Al-Cu-Mg-Si alloys): ordering mechanism and crystallographic structure, Acta Mater. 48 (2000) 2639-2653.

DOI: 10.1016/s1359-6454(00)00057-4

[5] C.D. Marioara, S.J. Andersen, J. Jansen, et al, The influence of temperature and storage time at RT on nucleation of the β" phase in a 6082 Al-Mg-Si alloy, Acta Mater. 51 (2003) 789-796.

DOI: 10.1016/s1359-6454(02)00470-6

[6] O.R. Myhr, Ø Grong, S.J. Andersen, Modeling of the age hardening behaviour of Al-Mg-Si alloys, Acta Mater. 49 (2001) 65-75.

DOI: 10.1016/s1359-6454(00)00301-3

[7] S. Esmaeili, X. Wang, D.J. Lloyd, et al, On the precipitation-hardening behavior of the Al-Mg-Si-Cu alloy AA6111, Metall. Mater. Trans. A. 34 (2003) 751-763.

DOI: 10.1007/s11661-003-0110-4

[8] H. Li, Q. Mao, Z. Wang, et al, Simultaneously enhancing the tensile properties and intergranular corrosion resistance of Al–Mg–Si–Cu alloys by a thermo-mechanical treatment, Mater. Sci. Eng. A. 617 (2014) 165-174.

DOI: 10.1016/j.msea.2014.08.045

[9] Z. Martinova, G. Zlateva, Microstructure development during thermomechanical treatment of Al-Mg-Si alloy, J. Min. Metall. B. 38 (2002) 153-162.

DOI: 10.2298/jmmb0204153m

[10] Z.H. Ismail, Microstructure and mechanical properties developed by thermomechanical treatment in an Al-Mg-Si alloy, Scripta Mater. 32 (1995) 457-462.

DOI: 10.1016/s0956-716x(99)80082-x

[11] Y. Birol, Pre-straining to improve the bake hardening response of a twin-roll cast Al-Mg-Si alloy, Scripta Mater. 52 (2005) 169-173.

DOI: 10.1016/j.scriptamat.2004.10.001

[12] R.S. Yassar, D.P. Field, H. Weiland, The effect of predeformation on the β" and β' precipitates and the role of Q' phase in an Al-Mg-Si alloy; AA6022, Scripta Mater. 53 (2005) 299-303.

DOI: 10.1016/j.scriptamat.2005.04.013