Effect of Thermal-cold Cycling Treatment on Mechanical Properties and Microstructure of 6061 Aluminum Alloy

Abstract

The influence of thermal-cold cycling treatment on mechanical properties and microstructure of 6061 aluminum alloy was investigated by means of tensile test, optical microscopy(OM), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The cryogenic treatment mechanism of the alloys was discussed. The results show that thermal-cold cycling treatment is beneficial since it produces a large number of dislocations and accelerates the ageing process of the alloy and yields the finer dispersed β″ precipitates in the matrix. This variation of microstructural changes leads to more favorable mechanical properties than the other investigated states, while grain boundary precipitation is coarse and distributed discontinuously along grain boundaries, with a lower precipitation free zone (PEZ) on the both sides of precipitated phase. As a result, the tensile strength, elongation and conductivity of 6061 aluminum alloy after thermal-cold cycling treatment are 373.37 MPa, 17.2% and 28.2 MS/m, respectively. Compared with conventional T6 temper, the mechanical properties are improved significantly.

Keywords

thermal-cold cycling treatment / microstructures / tensile properties / aluminum alloys

References

[1] Albert M. Cutting Tools in the Deep Freeze[J]. Mod. Mach. Shop, 1992, 64(8): 55-61.

[2] Kamody D J. Cryogenics Process Update[J]. Adv. Mater. Process., 1999, 155(6): 67-69.

[3] Amini K, Nategh S, Shafyei A. Influence of Different Cryotreatments on Tribological Behavior of 80CrMo12 5 Cold Work Tool Steel[J]. Materials & Design, 2010, 31(10): 4 666-4 675.

[4] Dhokey N B, Dandawate J V. Study of Wear Stabilization in Cryoprocessed Cobalt-Based High Speed Steel[J]. Transactions of the Indian Institute of Metals, 2012, 65(4): 405-412.

[5] Wang J J, Xue X D, Yang Z Q, et al. Effect of Cryogenic Treatments on Mechanical Properties of 2A11 Aluminum Alloy [J]. Advanced Materials Research, 2011, 146–147: 1 646-1 650.

[6] Asl K M, Tari A, Khomamizadeh F. Effect of Deep Cryogenic Treatment on Microstructure, Creep and Wear Behaviors of AZ91 Magnesium Alloy[J]. Materials Science and Engineering: A, 2009, 523(1–2): 27-31.

[7] Gu K, Hong Z, Bing Z, et al. Effect of Cryogenic Treatment and Aging Treatment on the Tensile Properties and Microstructure of Ti-6Al-4V Alloy[J]. Materials Science and Engineering A: Structural Materials:Properties, Microstructure and Processing, 2013, 584(1): 170-176.

[8] Murtha S J. New 6XXX Aluminum Alloy for Automotive Body Sheet Applications[J]. Journal of Materials Processing and Manufacturing Science, 1995, 104: 657-666.

[9] Abis S, Boeuf A, Caciuffo R, et al. Investigation of Mg₂Si Precipitation in an Al-Mg-Si Alloy by Small Angle Neutron Scattering[J]. Journal of Nuclear Materials, 1985, 135: 181-189.

[10] Buha J, Lumley R N, Crosky A G, et al. Secondary Precipitation in an Al-Mg-Si-Cu Alloy[J]. Acta Mater., 2007, 55: 3 015-3 024.

[11] Ozturk F, Sisman A, Toros S, et al. Influence of Aging Treatment on Mechanical Properties of 6061 Aluminum Alloy[J]. Materials and Design, 2010, 31: 972-975.

[12] Demir H, Gunduz S. The Effects of Aging on Machinability of 6061 Aluminum Alloy[J]. Materials and Design, 2009, 30: 1 480-1 483.

[13] Ghulam H, Muhammad I, Lemopiisidore B B, et al. Mechanical Properties and Microstructure Evolution in Incremental Forming of AA5754 and AA6061 Aluminum Alloys[J]. Transactions of Nonferrous Metals Society of China, 2020, 30(1): 51-64.

[14] Kim H H, Cho S H, Kang C G. Evaluation of Microstructure and Mechanical Properties by Using Nano and Micro-indentation and Nano-scratch during Aging Treatment of Rheo-forged Al 6061 Alloy[J]. Materials Science and Engineering A, 2008, 485: 272-281.

[15] Maisonnette D, Suery M, Nelias D, et al. Effects of Heat Treatments on the Microstructure and Mechanical Properties of a 6061 Aluminium Alloy[J]. Materials Science & Engineering A, 2011, 528(6): 2 718-2 724.

[16] Andersen S J, Zandbergen H W, Jansen J, et al. The Crystal Structure of the β″ Phase in Al-Mg-Si Alloys[J]. Acta Materialia., 1998, 46(9): 3 283-3 298.

[17] Li Z H, Xiong B Q, Zhang Y A, et al. Ageing Behavior of an Al-Zn-Mg-Cu Alloy Pre-stretched Thick Plate[J]. Journal of University of Science and Technology Beijing, 2007, 14(3): 246-250.

[18] Chen G Q, Fu X S, Zhao F, et al. Microstructure and Mechanical Properties of 2A12 Aluminum Alloy after Age Forming[J]. Transactions of Nonferrous Metals Society of China, 2012, 22(8): 1 975-1 980.

[19] Xu Z Y, Li L. Thermodynamics of Materials[M], 2000 Beijing: Science Press.

[20] Liu H W. Material of Mechanics[M], 2004 Beijing: Higher Education Press.

[21] Dutta I, Allen S M. A Calorimetric Study of Precipitation in Commercial Aluminum Alloy 6061[J]. Journal of Materials Science Letters, 1991, 10: 323-326.