Residual stress, always existing in additive manufactured AlSi10Mg alloy, has negative effects on its application. Therefore, it is needed to be controlled or even eliminated by heat treatment. The microstructure, properties and residual stress of as built and annealed alloys are investigated using X ray diffraction, optical microscope, field emission scanning electron microscope, transmission electron microscope, electron backscattered diffraction, microhardness and Raman spectrum tests. The results show that as built alloy consists of supersaturated Al solid solution and Si phase. Additionally, the Si phase exists in the forms of cellular eutectic silicon and dispersed silicon nanoparticles. Meanwhile, the grain size of as built alloy is relatively fine, and the d50 value of grain size distribution is about 10.4 μm. Annealing treatments lead to the depositions of alloying elements from supersaturated Al solid solution, and formations of equilibrium phase Mg2Si and Si phase as the annealing temperature ranging from 250℃ to 300℃. With the increase of annealing temperature, the alloying elements precipitate out more thoroughly. Furthermore, the coarsening of cellular eutectic silicon and silicon nanoparticles, grain growth and recrystallization also occur owing to annealing treatment. Because of the decline of fine grain strengthening, solid solution strengthening and dispersion strengthening after annealing treatment, the microhardness decreases. The residual stress, however, can be significantly reduced by annealing process with a reduction of 60%~80%. Consequently, it is necessary to develop new heat treatment system according to the characteristic of additive manufactured aluminum alloy, in order to regulate and control the microstructure and properties.
[1] 张学军, 唐思熠, 肇恒跃, 等. 3D打印技术研究现状和关键技术[J]. 材料工程, 2016, 44(2):122-128.
[2] Orme M E, Gschweitl M, Ferrari M, et al. A holistic process-flow from concept to validation for additive manufacturing of light-weight, optimized, metallic components suitable for space flight[C]//58th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Texas, USA:AIAA SciTech Forum, 2017:1540.
[3] Orme M E, Gschweitl M, Ferrari M, et al. Designing for additive manufacturing:Lightweight through topology optimization enabled lunar spacecraft[J]. Journal of Mechanical Design, 2017, 139:100905-1-100905-6.
[4] Gobetz Z. Utilization of additive manufacturing for aerospace heat exchangers[D]. Pennsylvania:Pennsylvania State University, 2016.
[5] Maamoun A H, Elbestawi M, Dosbaeva G K, et al. Thermal post-processing of AlSi10Mg parts produced by selective laser melting using recycle powder[J]. Addictive Manufacturing, 2018, 21:234-247.
[6] 王华明. 高性能大型金属构件激光增材制造:若干材料基础问题[J]. 航空学报, 2014, 35(10):2690-2698.
[7] Buchbinder D, Schleifenbauum H, Heidrich S, et al. High power selective laser melting (HP SLM) of aluminum parts[J]. Physics Procedia, 2011, 12:271-278.
[8] Wei P, Wei Z Y, Chen Z, et al. The AlSi10Mg samples produced by selective laser melting:single track, densification, microstructure and mechanical behavior[J]. Applied Surface Science, 2017, 408:38-50.
[9] Delroisse P, Jacques P J, Maire E, et al. Effect of strut orientation on the microstructure heterogeneities in AlSi10Mg lattices processed by selective laser melting[J]. Scripta Materialia, 2017, 141:32-35.
[10] 余开斌, 刘允中, 杨长毅. 热处理对选区激光熔化成形AlSi10Mg合金显微组织及力学性能的影响[J]. 粉末冶金材料科学与工程, 2018, 23(3):298-305.
[11] Li W, Li S, Liu J, et al. Effect of heat treatment on AlSi10Mg alloy fabricated by selective laser melting:Microstructure evolution, mechanical properties and fracture mechanism[J]. Materials Science & Engineering A, 2016, 663:116-125.
[12] Aboulkhair N T, Maskery I, Tuck C, et al. The microstructure and mechanical properties of selectively laser melted AlSi10Mg:The effect of a conventional T6-like heat treatment[J]. Materials Science & Engineering A, 2016, 667:139-146.
[13] Girelli L, Tocci M, Gelfi M, et al. Study of heat treatment parameters for additively manufactured AlSi10Mg in comparison with corresponding cast alloy[J]. Materials Science & Engineering A, 2019, 739:317-328.
[14] Uzan N E, Shneck R, Yeheskel O, et al. Fatigue of AlSi10Mg specimens fabricated by additive manufacturing selective laser melting (AM-SLM)[J]. Materials Science & Engineering A, 2017, 704:229-237.
[15] Zhang C, Zhu H, Liao H, et al. Effect of heat treatments on fatigue property of selective laser melting AlSi10Mg[J]. International Journal of Fatigue, 2018, 116:513-522.
[16] Kempen K, Thijs L, Humbeeck J V, et al. Processing AlSi10Mg by selective laser melting:Parameter optimisation and material characterisation[J]. Materials Science & Technology, 2015, 31(8):917-923.
[17] Rosenthal I, Shneck R, Stern A. Heat treatment effect on the mechanical properties and fracture mechanism in AlSi10Mg fabricated by additive manufacturing selective laser melting process[J]. Materials Science & Engineering A, 2018, 729:310-322.
[18] Zhou L, Mehta A, Schulz E, et al. Microstructure, precipitates and hardness of selectively laser melted AlSi10Mg alloy before and after heat treatment[J]. Materials Characterization, 2018, 143:5-17.
[19] Rafieazad M, Mohammadi M, Nasiri A M. On microstructure and early stage corrosion performance of heat treated direct metal laser sintered AlSi10Mg[J]. Additive Manufacturing, 2019, 28:107-119.
[20] Zakay A, Aghion E. Effect of post-heat treatment on the corrosion behavior of AlSi10Mg alloy produced by additive manufacturing[J]. The Journal of the Minerals, Metals & Materials Society, 2019, 71:1150-1157.
[21] Rubben T, Revilla R I, De Graeve I. Influence of heat treatments on the corrosion mechanism of additive manufactured AlSi10Mg[J]. Corrosion Science, 2019, 147:406-415.
[22] Gu X, Zhang J, Fan X, et al. Abnormal corrosion behavior of selective laser melted AlSi10Mg alloy induced by heat treatment at 300℃[J]. Journal of Alloys and Compounds, 2019, 803:314-324.
[23] 雷振坤, 仇巍, 亢一澜. 微尺度拉曼光谱实验力学[M]. 北京:科学出版社, 2015:217-222.
[24] Wang M, Song B, Wei Q, et al. Effects of annealing on the microstructure and mechanical properties of selective laser melted AlSi7Mg alloy[J]. Materials Science & Engineering A, 2019, 739:463-472.
[25] 唐鹏钧, 何晓磊, 杨斌, 等. 激光选区熔化用AlSi10Mg粉末显微组织与性能[J]. 航空材料学报, 2018, 38(1):47-53.
[26] Fiocchi J, Tuissi A, Bassani P, et al. Low temperature annealing dedicated to AlSi10Mg selective laser melting products[J]. Journal of Alloys and Compounds, 2017, 695:3402-3409.
[27] 胡汉起. 金属凝固原理[M]. 2版. 北京:机械工业出版社, 2000:190-193.
[28] Gomes R M, Sato T, Kamio A. Microstructures and coarsening behavior of silicon particles in P/M Al-SiCu-Mg alloys containing Fe and Ni[J]. Journal of Japan Institute of Light Metals, 1997, 47(2):90-97.
[29] Thijs L, Kempen K, Kruth J P, et al. Fine-structured aluminium products with controllable texture by selective laser melting of pre-alloyed AlSi10Mg powder[J]. Acta Materialia, 2013, 61(5):1809-1819.
[30] Takata N, Kodaira1 H, Sekizawa K, et al. Change in microstructure of selectively laser melted AlSi10Mg alloy with heat treatments[J]. Materials Science & Engineering A, 2017, 704:218-228.
[31] Kolobnev N I, Ber L B, Khokhlatova L B, et al. Structure, properties and application of alloys of the Al-MgSi-(Cu) system[J]. Metal Science and Heat Treatment, 2012, 53(9-10):440-444.
[32] Riccardo C, Maurizio V. Aging response of an A357 Al alloy processed by selective laser melting[J]. Advanced Engineering Materials, 2018, 21(4):1800406.
