摘要
6016铝合金板材主要制造汽车覆盖件，特别是乘用车内外罩、后行李箱和门框等汽车外板，是汽车轻量化的关键材料。而目前国内的铝合金板材仍存在着成形性、抗凹性及零件成形后质量差等问题，无法满足使用要求。因此开展6016铝合金板材关键的预时效工艺和冲压成形工艺研究，对提高板材的成形质量十分重要。
本文将545 o C固溶30 min的6016铝合金（Al-0.55%Mg-1.0%Si-0.18%Cu）板材水淬后，经60 o C~160 o C×5 min~30 min预时效，室温停放25天后，进行185 o C×20 min的模拟烤漆处理。采用硬度、拉伸试验，结合示差扫描量热法（DSC）、扫描电子显微镜（SEM）等分析技术，研究预时效工艺对合金的力学性能及微观组织的影响规律。通过数值模拟仿真实际的冲压过程，并预估零件成形后可能出现的质量缺陷，优化关键成形工艺参数。结果表明：
①固溶淬火后立即进行预时效可以抑制自然时效过程，T4P态合金的成形性和烘烤硬化性能都得到改善。烤漆前后的硬度随着预时效温度升高，出现先缓慢增加后迅速增加的趋势。预时效温度为100 o C，预时效时间为20 min合金烘烤前屈服强度低于120 MPa，延伸率在25%左右；烘烤后屈服强度高于180 MPa（预变形2%合金烘烤硬化值达到104 MPa），烘烤后的延伸率在22%左右，综合比较优于其他预时效工艺。
②结合DSC曲线对β”析出温度和激活能进行计算，研究发现，随预时效温度升高，β”析出峰左移，激活能也降低。说明预时效可以抑制合金自然时效过程，提高合金T4P态成形性能，而且促进烘烤过程中β”的析出，增强烘烤硬化效果。
③以铝制汽车发动机罩内板为对象，建立冲压CAE模型，对板料冲压过程仿真，研究了不同成形工艺对成形后最大减薄率、最大增厚率及最大回弹量的影响规律。
④对多因素的优化问题，首先通过灰关联分析法，获得较优的工艺参数为：压边力500 KN，摩擦系数0.1，凹凸模间隙1.1t（1.32 mm）、凸模速度3 m/s，仿真试验后出现了少量拉裂缺陷。进一步采用智能优化算法在连续空间内寻优，得到最优解：压边力243 KN，摩擦系数0.11，凹凸模间隙1.06t（1.272 mm）、凸模速度8.68 m/s。进行现场冲压实验，未出现破裂缺陷，法兰面出现起皱可在随后切边过程去除，成形质量较好，与仿真结果符合。
关键词：铝合金，预时效，数值模拟，参数优化
ABSTRACT
6016 aluminum alloy sheet is mainly used for the manufacture of automotive panels, especially automotive exterior and interior covers, rear luggage, door frames and other automotive exterior pan
els. It is the key material for lightweight vehicles. At present, the domestic aluminum alloy sheet still has the problems of formability, anti-concavity, and poor quality of parts after forming, and cannot meet the requirements for use. Therefore, it is very important to improve the forming quality of the plate by performing the key pre-aging process and the stamping forming process of the 6016 aluminum alloy plate.
In this paper, the 6016 aluminum alloy (Al-0.55%Mg-1.0%Si-0.18%Cu) plated in 545 o C solid solution for 30 min was water quenched, pre-aged at 60 o C~160 o C × 5 min~30 min, and kept at room temperature for 25 days, and conducted a 185 o C × 20 min simulated baking. Hardness and tensile tests were combined with differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) to study the influence of pre-aging techniques on the mechanical properties and microstructure of the alloy. The actual stamping process was simulated by numerical simulation to predict the quality defects that may occur after the part is formed, and the key process parameters of the forming are optimized. The results show:
①Pre-ageing immediately after solution quenching can inhibit the natural aging process. Both the formability and the bake hardening performance of the T4P alloy are improved. The hardness before and after baking increases with the pre-aging temperature, and it tends to increase rapidly after first i
ncreasing slowly. The pre-aging temperature is 100 o C, and the pre-aging time is 20 min. The yield strength of the alloy before baking is less than 120 MPa, the elongation is about 25%, and the yield strength after baking is higher than 180 MPa (pre-deformation 2% alloy bake hardening value Achieved 104 MPa), the elongation after baking is about 22%, comprehensive comparison is better than other pre-aging techniques.
②The β” precipitation temperature and activation energy were calculated with the DSC curve. It was found that with the increase of pre-aging temperature, the β”precipitation peak left shifted and the activation energy also decreased. This shows that pre-aging can inhibit the natural aging process of the alloy, improve the T4P formability of the alloy, and promote the precipitation of β” in the baking process, and increase the
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bake hardening effect.
③Aiming at the inner panel of aluminum automobile engine hood, a stamping CAE model was established to simulate the sheet metal stamping process. The effect of different forming processes on the maximum thinning rate, maximum thickening rate and maximum rebound volume after formin
g was studied. .
④For the optimization of multi-factors, the best process parameters are obtained through the grey relational analysis: blank holding force 500 KN, friction coefficient 0.1, concave and convex die clearance 1.1 t (1.32 mm), punch speed 3 m/ s After the simulation test, there was a small amount of cracking defects. The intelligent optimization algorithm is further used to optimize the continuous space to obtain the optimal solution: blank holder force 243 KN, friction coefficient 0.11, convex and concave die gap 1.06 t (1.272 mm), and punch speed 8.68 m/s. In-situ stamping test, no cracking defects occurred, and wrinkles on the flange surface could be removed in the subsequent trimming process. The forming quality was good and was in accordance with the simulation results.
Key words: aluminum alloy, pre-aging, numerical simu lation, parameter optimization
IV
目录
目录
中文摘要........................................................................................................ I 英文摘要..........................
............................................................................ III 1 绪论. (1)
1.1 引言 (1)
1.2 车身用铝合金板材的分类及特点 (2)
1.3 国内外铝合金汽车板应用发展现状 (3)
1.3.1 国外铝合金车身板材料的发展状况 (3)
1.3.2 国内铝合金车身板材料的发展现状 (6)
1.4 6000系铝合金板材的研究现状 (8)
1.4.1 固溶 (8)
1.4.2 预时效 (8)
1.4.3 车身用铝合金覆盖件冲压成形技术发展现状 (10)
1.5 金属板料成形数值模拟关键技术概述 (11)
1.5.1 金属板料成形有限元理论 (11)
1.5.2 冲压成形质量的影响因素 (13)
1.5.3 板料冲压成形过程中出现的缺陷 (13)
1.6 研究意义及内容 (17)
1.6.1 研究意义 (17)
1.6.2 研究内容 (17)
2 实验材料及方法 (19)
2.1 实验材料 (19)
2.2 热处理实验 (19)
2.3 实验分析方法 (19)
2.3.1 力学性能测试 (19)
2.3.2 差示扫描量热法（DSC） (22)
2.3.3 光学显微镜观察 (22)
2.3.4 SEM分析 (23)
3 预时效对6016铝合金组织和性能的影响 (25)
3.1 合金固溶态组织和性能 (25)
3.1.1 固溶态组织 (25)
3.1.2 自然时对6016铝合金性能的影响 (26)
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3.2 预时效对合金烘烤前性能的影响 (29)
3.2.1 预时效对合金的烘烤前硬度影响 (29)
3.2.2 预时效对合金烘烤前拉伸性能的影响 (30)
3.2.3 预时效合金烘烤前断口分析 (34)
3.3 预时效对合金烘烤后性能的影响 (35)
3.3.1 预时效对合金烘烤后硬度的影响 (35)
3.3.2 预时效对合金烘烤后拉伸性能的影响 (36)
3.3.3 预时效合金烘烤后的断口分析 (41)
3.4 预时效工艺对析出动力学的影响 (42)
3.4.1 DSC曲线分析 (42)
3.4.2 析出激活能计算 (43)
3.5 本章小结 (46)
4 汽车铝合金发动机罩盖内板成形数值模拟 (47)
4.1 前罩盖内板冲压成形有限元模型建立 (48)
4.1.1 网格划分与CAE模型 (48)
4.1.2 边界条件 (50)
汽车发动机盖
4.1.3 材料模型 (51)
4.1.4 求解器设置 (52)
4.2 工艺参数对内板成形质量的影响 (52)
4.2.1 试验方案设置 (52)
4.2.2 压边力的影响 (53)
4.2.3 摩擦系数的影响 (58)
4.2.4 凹凸模间隙的影响 (61)
4.2.5 凸模速度的影响 (63)
4.3 本章小结 (64)
5 汽车铝合金发动机罩盖内板冲压成形工艺优化 (67)
5.1 基于灰关联分析法的冲压工艺参数优化 (67)
5.1.1 试验因子与试验水平 (67)
5.1.2 拟定正交试验方案与仿真计算结果 (68)
5.1.3 计算灰关联度 (70)
5.1.4 仿真试验验证 (73)
5.2 基于智能优化算法的内板成形质量预测及控制 (75)
5.2.1 人工神经网络 (75)
5.2.2 铝合金发罩盖内板冲压工艺参数ANN模型建立 (76)
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