Precipitates Generation Mechanism and Surface Quality Improvement for Aluminum Alloy 6061 in Diamond Cutting

Abstract

To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning (SPDT) by studying influence of the precipitates generation of Al6061 on surface integrity and surface roughness. Based on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg₂Si and the scratches on the machined surface mostly come from the iron-containing phase (α-, β-AlFeSi). Moreover, the generated Mg₂Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg₂Si with the medium size (more than 1 µm and less than 2 µm) in Al6061.

Keywords

Al6061 / precipitates / aging treatment / diamond cutting / surface roughness

References

[1] DelRio F W, de Boer M P, Knapp J A, et al. The Role of Van Der Waals Forces in Adhesion of Micromachined Surfaces[J]. Nature Materials, 2005, 4(8): 629-634.

[2] Proudhon H, Fouvry S, Buffiere J. A Fretting Crack Initiation Prediction Taking into Account the Surface Roughness and the Crack Nucleation Process Volume[J]. International Journal of Fatigue, 2005, 27(5): 569-579.

[3] To S, Lee W B, Chan C Y. Ultraprecision Diamond Turning of Aluminum Single Crystals[J]. Journal of Materials Processing Technology, 1997, 63(1–3): 157-162.

[4] Cheung C F, Lee W B. Modelling and Simulation of Surface Topography in Ultra-precision Diamond Turning[J]. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2000, 214(6): 463-480.

[5] Cheung C F, Lee W B. Study of Factors Affecting the Surface Quality in Ultra-precision Diamond Turning[J]. Materials and Manufacturing Processes, 2000, 15(4): 481-502.

[6] To S, Cheung C F, Lee W B. Influence of Material Swelling on Surface Roughness in Diamond Turning of Single Crystals[J]. Materials Science and Technology, 2001, 17(1): 102-108.

[7] Kong M C, Lee W B, Cheung C F, et al. A Study of Materials Swelling and Recovery in Single-point Diamond Turning of Ductile Materials[J]. Journal of Materials Processing Technology, 2006, 180(1–3): 210-215.

[8] Jun M B G, Liu X, DeVor R E, et al. Investigation of the Dynamics of Microend Milling-Part I: Model Development[J]. Journal of Manufacturing Science and Engineering, 2006, 128(4): 893-900.

[9] Malekian M, Mostofa M G, Park S S, et al. Modeling of Minimum Uncut Chip Thickness in Micro Machining of Aluminum[J]. Journal of Materials Processing Technology, 2012, 212(3): 553-559.

[10] Zong W J, Huang Y H, Zhang Y L, et al. Conservation Law of Surface Roughness in Single Point Diamond Turning[J]. International Journal of Machine Tools and Manufacture, 2014, 84: 58-63.

[11] Wang S J, To S, Chen X. An Investigation on Surface Finishing in Ultra-precision Raster Milling of Aluminum Alloy 6061[J]. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2014, 229(8): 1 289-1 301.

[12] Chon K S, Takahashi H, Namba Y. Wear Inspection of a Single-crystal Diamond Tool Used in Electroless Nickel Turning[J]. Optical Engineering, 2014, 53(3): 34-102.

[13] Yoon H S, Ehmann K F. Dynamics and Stability of Micro-cutting Operations[J]. International Journal of Mechanical Sciences, 2016, 115–116: 81-92.

[14] Zhou Y, Tian Y, Jing X, et al. A Novel Instantaneous Uncut Chip Thickness Model for Mechanistic Cutting Force Model in Micro-end-milling[J]. The International Journal of Advanced Manufacturing Technology, 2017, 93(5–8): 2 305-2 319.

[15] Lu X, Zhang H, Jia Z, et al. Floor Surface Roughness Model Considering Tool Vibration in the Process of Micro-milling[J]. The International Journal of Advanced Manufacturing Technology, 2017, 94(9–12): 4 415-4 425.

[16] Cheung C F, Chan K C, To S, et al. Effect of Reinforcement in Ultra-precision Machining of Al6061/SiC Metal Matrix Composites[J]. Scripta Materialia, 2002, 47(2): 77-82.

[17] Gómez De Salazar J M, Barrena M I. The Influence of Si and Mg Rich Phases on the Mechanical Properties of 6061 Al-matrix Composites Reinforced with Al₂O₃[J]. Journal of Materials Science, 2002, 37(8): 1 497-1 502.

[18] Simoneau A, Ng E, Elbestawi M A. Surface Defects during Microcutting[J]. International Journal of Machine Tools and Manufacture, 2006, 46(12–13): 1 378-1 387.

[19] Rahman M A, Rahman M, Kumar A S. Material Perspective on the Evolution of Micro- and Nano-scale Cutting of Metal Alloys[J]. Journal of Micromanufacturing, 2018, 2(1): 97-114.

[20] Demir H, Gündüz S. The Effects of Aging on Machinability of 6061 Aluminum Alloy[J]. Materials & Design, 2009, 30(5): 1 480-1 483.

[21] Ozturk F, Sisman A, Toros S, et al. Influence of Aging Treatment on Mechanical Properties of 6061 Aluminum Alloy[J]. Materials & Design, 2010, 31(2): 972-975.

[22] Wang S J, To S, Chan C Y, et al. A Study of the Cutting-induced Heating Effect on the Machined Surface in Ultra-precision Raster Milling of 6061 Al Alloy[J]. The International Journal of Advanced Manufacturing Technology, 2010, 51(1–4): 69-78.

[23] Wang S J, Chen X, To S, et al. Effect of Cutting Parameters on Heat Generation in Ultra-precision Milling of Aluminum Alloy 6061[J]. The International Journal of Advanced Manufacturing Technology, 2015, 80(5–8): 1 265-1 275.

[24] Liu Y L, Kang S B. The Solidification Process of Al−Mg−Si Alloys[J]. Journal of Materials Science, 1997, 32(6): 1 443-1 447.

[25] Wang Q G, Davidson C J. Solidification and Precipitation Behavior of Al−Si−Mg Casting Alloys[J]. Journal of Materials Science, 2001, 36(3): 739-750.

[26] Sha G, O’Reilly K, Cantor B, et al. Growth Related Metastable Phase Selection in a 6xxx Series Wrought Al Alloy[J]. Materials Science and Engineering: A, 2001, 304–306: 612-616.

[27] Sha G, O’Reilly K A Q, Cantor B, et al. Quasi-peritectic Solidification Reactions in 6xxx Series Wrought Al Alloys[J]. Acta Materialia, 2003, 51(7): 1 883-1 897.

[28] Li X C. Microstructure and Metallographic Map of Aluminum Alloy Materials[M], 2010 Beijing: Metallurgical Industry Press.

[29] Zheng Z Q. Fundamentals of Materials Science[M], 2013 Changsha: Central South University Press.

[30] Samaras S N, Haidemenopoulos G N. Modelling of Microsegregation and Homogenization of 6061 Extrudable Al-alloy[J]. Journal of Materials Processing Technology, 2007, 194(1–3): 63-73.

[31] Chang C S T, Banhart J. Low-temperature Differential Scanning Calorimetry of an Al−Mg−Si Alloy[J]. Metallurgical & Materials Transactions A, 2011, 42(7): 1 960-1 964.