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金属学报  2022, Vol. 58 Issue (6): 760-770    DOI: 10.11900/0412.1961.2021.00017
  研究论文 本期目录 | 过刊浏览 |
预拉伸变形对欠时效7N01铝合金板材疲劳断裂的影响
田妮1,2(), 石旭1, 刘威1, 刘春城3, 赵刚1,2, 左良2,4
1.东北大学 材料科学与工程学院 沈阳 110819
2.东北大学 材料各向异性与织构教育部重点实验室 沈阳 110819
3.东北大学 工程训练中心 沈阳 110819
4.中国科学院金属研究所 沈阳 110016
Effect of Pre-Tension on the Fatigue Fracture of Under-Aged 7N01 Aluminum Alloy Plate
TIAN Ni1,2(), SHI Xu1, LIU Wei1, LIU Chuncheng3, ZHAO Gang1,2, ZUO Liang2,4
1.School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China
2.Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China
3.Engineering Training Center, Northeastern University, Shenyang 110819, China
4.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
引用本文:

田妮, 石旭, 刘威, 刘春城, 赵刚, 左良. 预拉伸变形对欠时效7N01铝合金板材疲劳断裂的影响[J]. 金属学报, 2022, 58(6): 760-770.
Ni TIAN, Xu SHI, Wei LIU, Chuncheng LIU, Gang ZHAO, Liang ZUO. Effect of Pre-Tension on the Fatigue Fracture of Under-Aged 7N01 Aluminum Alloy Plate[J]. Acta Metall Sin, 2022, 58(6): 760-770.

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摘要: 

针对工业化生产的7N01铝合金板材,采用拉伸实验、疲劳实验和微观组织结构表征等手段研究了预拉伸变形对欠时效态7N01铝合金板材疲劳性能和疲劳断裂特征的影响。结果表明,预拉伸变形量增大至20%,欠时效态7N01铝合金板材中合金相粒子的形状、尺寸、数量、分布以及薄带状晶粒的尺寸和形状基本保持不变。然而,板材表现出明显的加工硬化效应,其屈服强度、抗拉强度和显微硬度分别由181 MPa、233 MPa和95 HV增大至254 MPa、271 MPa和117 HV,延伸率从23.2%降低至5.2%。在应力175 MPa、应力比R = 0的疲劳循环加载条件下,随预拉伸变形量的增加,欠时效态7N01铝合金板材的疲劳寿命呈现出先缩短再延长又缩短的趋势。未预拉伸变形试样的疲劳寿命为6.06 × 105 cyc,5%预拉伸变形可将铝板的疲劳寿命延长75%,达到了1.06 × 106 cyc,而3%和20%的预拉伸变形将铝板的疲劳寿命分别缩短至4.21 × 105和2.89 × 105 cyc。5%~16%预拉伸变形使欠时效态7N01铝合金板材基体中形成均匀分布的高密度位错或位错胞的显微组织,可将合金板材的疲劳寿命延长23%以上。

关键词 7N01铝合金板材预拉伸变形欠时效位错疲劳    
Abstract

7N01 aluminum alloy is the main load-bearing structure material for bullet train bodies due to its high specific strength, high specific stiffness, good magnetic-shielding ability, strong corrosion resistance, and good formability and weldability. The fatigue performance of materials and components used in bullet trains determines their security. It is unavoidable that there is pre-deformation during the assembly process of aluminum alloy components, which will influence the active service and fatigue performance of the aluminum alloy. It is important not only to clarify the relationship between pre-deformation and fatigue performance but also to reveal the mechanism of pre-deformation on the fatigue fracture of 7N01 aluminum alloy, to ensure the security of the bullet train. In this study, the effect of pre-tensile deformation on the fatigue property, fatigue fracture initiation, and fatigue crack propagation characteristics of a commercial 7N01 aluminum alloy plate at under-aged conditions was studied using tensile and fatigue tests combined with microstructure analysis. As the pre-tensile deformation increased to 20%, the results showed that the shape, size, number, distribution of second phase particles, as well as the size and morphology of thin strips grain of under-aged 7N01 aluminum alloy plate were almost the same. However, the under-aged 7N01 aluminum alloy plate has a significant strain-hardening effect after pre-tensile at room temperature, with the yield strength, tensile strength, and hardness increased from 181 MPa, 233 MPa, and 95 HV (without pre-tensile deformation) to 254 MPa, 271 MPa, and 117 HV (after 20% pre-tensile deformation), while the elongation decreased from 23.2% to 5.2%. Under the 175 MPa pulsating tensile load condition (stress ratio R = 0), the overall fatigue life of the under-aged 7N01 aluminum alloy plate first reduced, then prolonged, and then decreased as pre-tensile deformation increased. Without pre-tensile deformation, the fatigue life of under-aged 7N01 aluminum alloy plate is about 6.06 × 105 cyc, and when prolonged by about 75%, it reaches about 1.06 × 106 cyc after 5% pre-tensile deformation. However, the fatigue life of the under-aged 7N01 aluminum alloy plate is decreased to 4.21 × 105 and 2.89 × 105 cyc after 3% and 20% pre-tensile deformation, respectively. The evenly distributed high-density dislocations or dislocation cells resulted in 5%-16% pre-tensile deformation in the under-aged 7N01 aluminum alloy plate, which can prolong the fatigue life of the alloy plate by over 23%.

Key words7N01 aluminum alloy plate    pre-tensile deformation    under-aged    dislocation    fatigue
收稿日期: 2021-01-14     
ZTFLH:  TG146.2  
基金资助:国家自然科学基金项目(51871043);中央高校基本科研业务费项目(180212010);辽宁省自然科学基金项目(2019-MS-113)
作者简介: 田 妮,女,1975年生,副教授,博士
图1  拉伸及疲劳试样尺寸
图2  欠时效态7N01铝合金板材及其经不同程度预拉伸变形后显微组织的OM像(纵截面,未腐蚀)
图3  欠时效态7N01铝合金板材及其经不同程度预拉伸变形后的晶粒OM像(纵截面)
图4  欠时效态7N01铝合金板材经不同程度预拉伸变形后组织的TEM像
图5  欠时效态7N01铝合金板材经不同程度预拉伸变形量后的力学性能
图6  欠时效态7N01铝合金板材经不同程度预拉伸变形后的疲劳寿命
图7  欠时效态7N01铝合金板材经不同程度预拉伸变形后的疲劳断口表面裂纹源处SEM像
图8  欠时效态7N01铝合金板材经不同程度预拉伸变形后的疲劳断口表面裂纹扩展区形貌的SEM像
Term0%3%5%8%12%16%20%
λi+ + ++ ++ + + ++ + + ++ + + ++ + + + ++
λp+ ++ ++ + + + ++ + + ++ + +++
λ+ + + + ++ + + ++ + + + + + + + ++ + + + + + + ++ + + + + + ++ + + + + ++ +
表1  不同程度预拉伸变形后,欠时效态7N01铝合金板材中疲劳裂纹萌生阻力贡献值(λi)、疲劳裂纹扩展阻力贡献值(λp)及疲劳寿命贡献值(λ)的分析结果
图9  欠时效态7N01铝合金板材经不同程度预拉伸变形后的疲劳裂纹扩展示意图
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