利用放电等离子烧结制备Al-4.5Cu(质量分数,%)合金,并对其进行固溶、淬火和时效处理。通过 X 射线衍射、扫描电镜和透射电镜进行结构表征以及拉伸力学性能测试,研究颗粒界面结构和界面析出行为及其对力学性能影响。结果表明：放电等离子烧结Al-4.5Cu合金颗粒界面由Al2O3纳米颗粒、粗大CuAl2相和纳米微孔组成。热处理后,Al-4.5Cu合金颗粒界面附近析出尺寸为150~600 nm的CuAl2相,同时形成宽度为 40~60 nm 的无析出区。屈服强度和抗拉强度分别从95 MPa 和229 MPa增加至280 MPa和378 MPa,断后伸长率从11.8%下降为6.0%。强度增加主要归因于热处理过程中析出相的弥散分布,以及材料的致密化;塑性下降主要是由于拉伸变形过程中,无析出区率先发生塑性变形,导致位错从无析出区向颗粒界面附近的 CuAl2相堆积,造成应力集中,促使裂纹沿颗粒界面扩展,材料伸长率下降。
Al-4.5Cu (mass fraction, %) alloy was prepared by spark plasma sintering (SPS) followed by solution, quenching and aging. The X-ray diffraction, scanning electron microscopy, transmission electronmicroscopy and tensile tests were carried out. The effect of interparticle boundary (IPB) and precipitation behavior on mechanical properties of the Al-4.5Cu alloy were investigated in detail. The results show that the IPB consists of Al2O3 nanoparticles, CuAl2 phase and residual nanopores. After T6 aging, coarse CuAl2 phases with a diameter of 150-600 nm precipitate at the IPB, and the precipitation free zone (PFZ) with a width of 40-60 nm is formed. An improvement of yield strength and ultimate tensile strength from 95 MPa and 229 MPa to 280 MPa and 378 MPa is achieved respectively after T6 aging, while the elongation to fracture decreases from 11.8% to 6%. The increase in strength is mainly due to the well dispersion of precipitates and the densification of the material during T6 aging. The decrease in plasticity may result from the earlier plastic deformation in the PFZ during tensile deformation, leading to the accumulation of dislocations from PFZ to CuAl2 phase nearby the IPB, as a result, stress concentrationis formed, which consequently promotes cracksexp and along the IPB and decreases the ductility of the material.
[1] 李京京, 李晨光, 梁加淼, 等. TiB2含量对TiB2/Al-3.8Zn- 1.85Mg-1.32Cu复合材料微观组织与力学性能的影响[J]. 中国有色金属学报, 2020, 30(6): 1221-1229.
LI Jingjing, LI Chenguang, LIANG Jiamiao, et al.Influence of TiB2 particles content on microstructure and mechanical properties of TiB2/Al-3.8Zn-1.85Mg-1.32Cu composites[J]. The Chinese Journal of Nonferrous Metals, 2020, 30(6): 1221-1229.
[2] SU J, LI Y, DUAN M G, et al.Investigation on particle strengthening effect in in-situ TiB2/2024 composite by nanoindentation test[J]. Materials Science and Engineering A, 2018, 727(6): 29-37.
[3] LI S, SU Y, OUYANG Q B, et al.In-situ carbon nanotube- covered silicon carbide particle reinforced aluminum matrix composites fabricated by powder metallurgy[J]. Materials Letters, 2016, 167(3): 118-121.
[4] 谢娇雅, 刘如铁, 陈洁, 等. 镁含量对粉末冶金Al-3.9Cu-Mg合金组织与力学性能的影响[J]. 粉末冶金材料科学与工程, 2018, 23(6): 547-552.
XIE Jiaoya, LIU Rutie, CHEN Jie, et al.Effects of the magnesium content on the microstructure and mechanical properties of Al-Cu-Mg sintered alloy[J]. Materials Science and Engineering of Powder Metallurgy, 2018, 23(6): 547-552.
[5] REDDY M P, SHAKOOR R A, PARANDE G, et al.Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques[J]. Progress in Natural Science: Materials International, 2017, 27(5): 606-614.
[6] 赵凡, 刘祖铭, 吕学谦, 等. 粉末冶金Cu-Cr-Zr合金的形变热处理组织及性能[J]. 粉末冶金材料科学与工程, 2019, 24(4): 385-390.
ZHAO Fan, LIU Zuming, LÜ Xueqian, et al.Microstructure and properties of powder metallurgy Cu-Cr-Zr alloy by heat-treatment and deformation[J]. Materials Science and Engineering of Powder Metallurgy, 2019, 24(4): 385-390.
[7] ZHANG J, SHI H, CAI M, et al.The dynamic properties of SiCp/Al composites fabricated by spark plasma sintering with powders prepared by mechanical alloying process[J]. Materials Science and Engineering A, 2009, 527(1): 218-224.
[8] BISWAS A, SIEGEL D J, WOLVERTON C, et al.Precipitates in Al-Cu alloys revisited: Atom-probe tomographic experiments and first-principles calculations of compositional evolution and interfacial segregation[J]. Acta Materialia, 2011, 59(15): 6187-6204.
[9] SHANMUGASUNDARAM T, HEIMAIER M, MURTY B S, et al.On the Hall-Petch relationship in a nanostructured Al-Cu alloy[J]. Materials Science and Engineering A, 2010, 527(29): 7821-7825.
[10] TRUNOV M A, SCHOENITZ M, ZHU X, et al.Effect of polymorphic phase transformations in Al2O3 film on oxidation kinetics of aluminum powders[J]. Combustion and Flame, 2005, 140(4): 310-318.
[11] RUFINO B, BOULCH F, COULET M V, et al.Influence of particles size on thermal properties of aluminium powder[J]. Acta Materialia, 2007, 55(8): 2815-2827.
[12] ZHANG Z H, LIU Z F, LU J F, et al.The sintering mechanism in spark plasma sintering-proof of the occurrence of spark discharge[J]. Scripta Materialia, 2014, 81(6): 56-59.
[13] ZHOU D, WANG X, MURANSKY O, et al.Heterogeneous microstructure of an Al2O3 dispersion strengthened Cu by spark plasma sintering and extrusion and its effect on tensile properties and electrical conductivity[J]. Materials Science and Engineering A, 2018, 730(7): 328-335.
[14] CAO L, ZENG W, XIE Y H, et al.Effect of powder oxidation on interparticle boundaries and mechanical properties of bulk Al prepared by spark plasma sintering of Al powder[J]. Materials Science and Engineering A, 2019, 742(1): 305-308.
[15] OKUDA H, OCHIAI S.The effects of solute and vacancy depletion on the formation of precipitation-free zone in a model binary alloy examined by a monte carlo simulation[J]. Materials Transactions, 2004, 45(5): 1455-1460.
[16] OGURA T, HIROSAWA S, CEREZO A, et al.Atom probe tomography of nanoscale microstructures within precipitate free zones in Al-Zn-Mg(-Ag) alloys[J]. Acta Materialia, 2010, 58(17): 5714-5723.
[17] HIROSAWA S, OGURI Y, SATO T.Experimental and computational investigation of formation of precipitate free zones in an Al-Cu alloy[J]. Materials Transactions, 2005, 46(6): 1230-1234.
[18] RAGHAVAN M.Microanalysis of precipitate free zones (PFZ) In Al-Zn-Mg and Cu-Ni-Nb alloys[J]. Metallurgy Transactions A, 1980, 11(6): 993-999.
[19] HOYT J J.A mean field description of the knetics of precipitate free zone formation[J]. Scripta Materialia, 1997, 37(12): 2033-2039.
[20] OGURA T, HIROSAWA S, SATO T.Quantitative characterization of precipitate free zones in Al-Zn-Mg(-Ag) alloys by microchemical analysis and nanoindentation measurement[J]. Science and Technology of Advanced Materials, 2004, 5(4): 491-496.
[21] RADMILOVIC V, TAYLOR C, LEE Z, et al.Nanoindentation properties and the microstructure of grain boundary precipitate-free zones (PFZs) in an AlCuSiGe alloy[J]. Philosophical Magazine, 2007, 87(26): 3905-3919.
[22] YIWEN M O U, HOWE J M, STARKE E A. Grain-boundary precipitation and fracture behavior of an Al-Cu-Li-Mg-Ag alloy[J]. Metallurgical and Materials Transactions A, 1995, 26(6): 1591-1595.
