目的 针对汽车轻量化背景下A356铝合金缸盖在服役过程中面临的热失效风险,揭示T6态合金在250~385 ℃内微观组织的热稳定性与力学性能的衰退机理,为缸盖的抗热老化设计提供定量理论支撑。方法 在250、325、385 ℃下进行45 h热暴露试验,模拟发动机工况。利用SEM和EDS分析相组织转变;结合TEM及GPA（几何相位分析）技术,从原子尺度阐明其相变序列、共格性丧失及应变场演化规律;通过室温拉伸与硬度试验验证性能变化。结果 A356铝合金宏观力学性能受温度影响变化明显,且随保温时间的延长表现出明显的非线性变化特征。在250 ℃时,组织相对稳定,仅发生轻度过时效,屈服强度微降6.7%,延伸率小幅提升。325 ℃为性能转折临界点,粗化速率常数K激增至13.455 03,析出相与基体共格关系被破坏,位错钉扎能力下降40%,导致屈服强度骤降27%。在385 ℃极端条件下,基体Mg含量（原子数分数）耗尽至0.52%,亚稳态强化相完全转变为粗大平衡相,位错强化贡献率降至10%以下,致使屈服强度暴跌45%至130.35 MPa,硬度下降41%;同时,共晶Si的完全球化促使断裂模式由准解理断裂彻底转变为微孔聚集型韧性断裂,延伸率激增至17.16%。结论 A356铝合金的热失效主要由Mg2Si强化相的粗化失稳及共格性丧失主导。合金在250 ℃及以下可维持性能稳定,而在325 ℃及以上将产生不可逆的强度损伤。研究明确了250 ℃为安全服役的临界温度阈值,直接服务于高强铝合金复杂构件的寿命预测与可靠性评估。
Abstract
Against the background of automotive lightweighting, A356 aluminum alloy cylinder heads face thermal failure risks during service. The work aims to reveal the thermal stability of microstructures and the degradation mechanism of mechanical properties of T6-treated alloy within the temperature range of 250-385 ℃, providing quantitative theoretical support for the thermal aging resistance design of cylinder heads. Thermal exposure tests were conducted at 250 ℃, 325 ℃ and 385 ℃ for 45 hours to simulate actual engine service conditions. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were adopted to characterize phase microstructure evolution. Combined with Transmission Electron Microscopy (TEM) and Geometric Phase Analysis (GPA), the phase transformation sequence, loss of coherency and evolution law of strain field were clarified at the atomic scale. Room-temperature tensile tests and hardness measurements were performed to verify the variations in mechanical properties. The macroscopic mechanical properties of A356 aluminum alloy were significantly temperature-dependent and exhibited distinct nonlinear characteristics with prolonged thermal exposure time. At 250 ℃, the microstructure remained relatively stable with only slight overaging, resulting in a marginal reduction of 6.7% in yield strength and a moderate increase in elongation. 325 ℃ served as the critical transition temperature for mechanical properties. The coarsening rate constant K rose sharply to 13.455 03, the coherent relationship between precipitates and the matrix was destroyed, and the dislocation pinning capacity decreased by 40%, leading to a sharp drop of 27% in yield strength. Under the extreme condition of 385 ℃, the magnesium content in the matrix was depleted to 0.52%. Metastable strengthening phases completely transformed into coarse equilibrium phases, and the contribution rate of dislocation reinforcement dropped below 10%. Consequently, the yield strength plummeted by 45% to 130.35 MPa, with a 41% reduction in hardness. Meanwhile, the full spheroidization of eutectic silicon fundamentally changed the fracture mode from quasi-cleavage fracture to micropore-aggregated ductile fracture, and the elongation surged to 17.16%. The thermal failure of A356 aluminum alloy is predominantly dominated by the coarsening, destabilization and coherency loss of Mg2Si strengthening phases. The alloy maintains stable mechanical properties at 250 ℃ and below, while irreversible strength degradation occurs at 325 ℃ and above. This work defines 250 ℃ as the critical temperature threshold for safe service, which can directly support the life prediction and reliability evaluation of complex high-strength aluminum alloy components.
关键词
A356铝合金 /
热暴露 /
微观组织演变 /
力学性能
Key words
A356 aluminum alloy /
thermal exposure /
microstructure evolution /
mechanical properties
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参考文献
[1] 中国汽车工程学会. 节能与新能源汽车技术路线图 2.0[M]. 北京: 机械工业出版社, 2020.
Chinese Society of Automotive Engineers. Technology Roadmap of Energy-Saving and New Energy Vehicles 2.0[M]. Beijing: China Machine Press, 2020.
[2] 乐银强. 铝合金缸盖倾转浇注工艺设计与应用[J]. 中国铸造装备与技术, 2024, 59(6): 89-94.
LE Y Q.Design and Application of Aluminum Alloy Cylinder Head Tilting Pouring Process[J]. China Foundry Machinery & Technology, 2024, 59(6): 89-94.
[3] WANG Q G, BOBEL A, WALKER M, et al.Evaluation of Two New Cast Aluminum Alloys for High Performance Cylinder Heads[J]. International Journal of Metalcasting, 2025, 19(1): 52-58.
[4] ANGELONI M, RUCHERT C O T R, BOSE FILHO W W, et al. Fatigue Life Assessment of A356 Aluminum Alloy Used for Engine Cylinder Head[J]. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2025, 47(4): 175.
[5] ZHANG H, ZHAO Y, LIU C, et al.Microstructure and Mechanical Properties of A356 Aluminum Alloy Wheels Fabricated by Low Pressure Die Casting[J]. Journal of Materials Engineering and Performance, 2021, 30: 2027-2036.
[6] ZHU S, YANG Z, YAN F, et al.Effects of T6 Heat Treatment on the Microstructure and Mechanical Properties of A356 Alloy Wheels[J]. Materials Testing, 2020, 62(6): 621-627.
[7] SJÖLANDER E, SEIFEDDINE S. The Heat Treatment of Al-Si-Cu-Mg Casting Alloys: A Review[J]. Journal of Materials Processing Technology, 2010, 210(10): 1249-1259.
[8] YANG S G, CHEN J M, JIN L, et al.Effect of T6 Heat Treatment on Microstructure and Mechanical Properties of A356 Aluminum Alloy[C]//Light Metals 2025. Cham: Springer, 2025: 403-410.
[9] SIVANANTHAM A, DEVARAJ J, SANDURU B, et al.Study on the Failure Effect Analysis of IC Engine Cylinder Head[C]//E3S Web of Conferences. 2024, 563: 02010.
[10] LUMLEY R N, DEEVA N, KITTISAK R.The Performance of A356 Alloy at Elevated Temperatures[J]. Metallurgical and Materials Transactions A, 2013, 44(2): 1074-1086.
[11] CASARI D, MERLIN M, GARAGNANI G L.The Effect of Microstructure on the Fracture Toughness of A356 Casting Alloy[J]. Journal of Materials Science, 2014, 49(3): 1235-1250.
[12] NNAKWO K C, NWAJIOKE C T, CHUKWUNEKE J L, et al.Microstructure Evolution in A356 Alloy Subjected to Controlled Heat Treatment Regimes Processes[J]. Discover Applied Sciences, 2024, 6(10): 497.
[13] CHEN X, GUO E, ROMETSCH P, et al.Coarsening Behavior of Eutectic Si in A356 Alloy Modified by Sb and Sr during Solution Treatment[J]. Transactions of Nonferrous Metals Society of China, 2023, 33(8): 2251-2263.
[14] DANG B, LIU C C, LIU F, et al.Effect of Solidification Microstructure Characteristics of A356 Aluminum Alloy on Solution Treatment Process[J]. Transactions of Nonferrous Metals Society of China, 2016(3): 634-642.
[15] VIDYA S, KUMAR S, KUMAR P.Effect of Solution Treatment on Microstructure and Mechanical Properties of A356 Alloy[J]. Materials Today: Proceedings, 2021, 46: 8718-8722.
[16] 何兵, 李建, 张勇. Sr和La复合添加对A356铝合金铸态组织及力学性能的影响[J]. 特种铸造及有色合金, 2024, 44(12): 1389-1394.
HE B, LI J, ZHANG Y.Effects of Sr and La Composite Addition on As-cast Microstructure and Mechanical Properties of A356 Aluminum Alloy[J]. Special Casting & Nonferrous Alloys, 2024, 44(12): 1389-1394.
[17] QIU J, WU S, WAN L, et al.Solidification Process of Squeeze Casting and Effect of Heat Treatment on Properties of A356 Aluminum Alloy[J]. Special Casting & Nonferrous Alloys, 2024, 44(2): 189-197.
[18] 邱谨, 曹杨婧, 罗晓梅, 等. A356铝合金挤压铸造凝固过程及热处理对其性能的影响[J]. 特种铸造及有色合金, 2024, 44(2): 189-197.
QIU J, CAO Y J, LUO X M, et al.Solidification Process of Squeeze Casting and Effect of Heat Treatment on Properties of A356 Aluminum Alloy[J]. Special Casting & Nonferrous Alloys, 2024, 44(2): 189-197.
[19] 刘亚刚, 胡奖品, 吴晓成, 等. A356铝合金衬套外管挤压铸造工艺研究[J]. 精密成形工程, 2026, 18(1): 46-56.
LIU Y G, HU J P, WU X C, et al.Extrusion Casting Process of Outer Bushing Tubes for A356 Aluminum Alloy[J]. Journal of Netshape Forming Engineering, 2026, 18(1): 46-56.
[20] JIN C K.Microstructures and Mechanical Properties of A356 Alloy and A6061 Alloy through Rheo, Upsetting, Thixo, Forming Process, and T6 Heat Treatment[J]. Metals, 2022, 12(12): 2051.
[21] ZHANG L, LIU Y, WANG S, et al.Evolution of Mg2Si Phase and Mechanical Properties of A356 Alloy during Aging Treatment[J]. China Foundry, 2018, 15(6): 436-442.
[22] LEE W B, KIM S H, PARK Y H.Effect of Solution Treatment on Microstructure and Mechanical Properties of A356 Alloy Casting[J]. Materials, 2023, 16(4): 1332.
[23] WANG J, ZHANG J, LIU Y, et al.Effect of Er on Microstructure and Mechanical Properties of A356 Aluminum Alloy during Thermal Exposure[J]. Journal of Alloys and Compounds, 2023, 960: 170654.
[24] LI Y, LIU X, ZHANG H, et al.Enhanced High- temperature Strength of A356 Alloy via Zr and V Alloying[J]. Materials Science and Engineering: A, 2023, 880: 145321.
[25] 汪峰, 任玲玲, 王帅, 等. SiC颗粒对WAAM 2319铝合金高温组织与性能的影响[J]. 精密成形工程, 2025, 17(8): 68-76.
WANG F, REN L L, WANG S, et al.Effect of SiC Particles on the High Temperature Microstructure and Properties of WAAM 2319 Aluminum Alloy[J]. Journal of Netshape Forming Engineering, 2025, 17(8): 68-76.
基金
国家外专项目（H20240023）; 陕西省教育厅青年创新团队; 陕西省重点研发计划（2025CY-JJQ-120）
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