【作者】 葛荣山；

【导师】 张永安；

【作者基本信息】 北京有色金属研究总院 ， 材料科学与工程， 2011， 硕士

【摘要】 2524铝合金作为重要的航空材料,主要应用于飞机的蒙皮、机翼下壁板等关键部位,2E12铝合金是国内在2524合金基础上进一步降低Fe、Si杂质含量研制而出。本论文采用OM、SEM (EBSD)、TEM、EDS、DSC、硬度测试、电导率测试、室温拉伸性能测试和疲劳裂纹扩展速率测试等分析手段,研究了国产2E12-T3和进口2524-T3铝合金微观组织、常规力学性能、疲劳裂纹扩展速率以及微观裂纹扩展路径等,得出影响国产2E12-T3铝合金疲劳裂纹扩展性能的主要因素,并提出工艺优化方案,并对优化工艺2E12-T3铝合金进行疲劳裂纹扩展性能评价,从而获得疲劳性能基本达到进口2524-T3铝合金水平的国产2E12-T3铝合金,获得如下实验结果和结论：国产2E12-T3合金晶粒明显细小、均匀,近似呈等轴晶,发生了更高程度的再结晶,进口2524-T3合金晶粒呈典型轧制纤维状；两种合金基体内均分布有少量未溶的AlCu、AlCuMg和富Fe等粗大第二相；国产2E12-T3合金晶内的Al20Cu2Mn3棒状相数量略多于进口2524-T3合金,且棒状粒子间距更密；两种合金都为T3态,时效析出强化相皆为与基体相共格的GP区结构。国产2E12-T3合金的疲劳裂纹扩展速率明显高于进口2524-T3合金,且两者的断口形貌具有明显的差异,2E12-T3合金较平坦,辉纹间距较大,韧窝数量较少,而2524-T3合金断口较粗糙,辉纹间距较小,韧窝数量较多。国产2E12-T3与进口2524-T3合金在微观组织方面的最主要区别为再结晶程度大小,为了降低国产2E12-T3合金的再结晶程度,可在最后一道轧制之前添加一道低温退火,充分释放材料内部累积的过高形变能,同时可以保留形变组织。优化工艺2E12-T3合金晶粒组织发生非常明显的改变,获得了与进口2524-T3合金相似的纤维状状组织,尤其是1.2mm厚优化工艺2E12-T3铝合金纤维状特征更加突出,基本达到进口2524-T3合金水平。通过对优化工艺2E12-T3铝合金进行疲劳裂纹扩展性能评价,发现添加中间退火工艺能够有效地降低2E12-T3合金的裂纹扩展速率,并延长2E12-T3合金的剩余疲劳寿命,其中1.2mm厚优化工艺2E12-T3合金疲劳裂纹扩展速率曲线与2524-T3合金基本重合,且其剩余疲劳寿命高达4.10×104周,比进口2524-T3合金的4.24x 104周仅低约为3%,疲劳性能基本达到进口水平。更多还原

【Abstract】 As an important aviation materials,2524 aluminum alloy was mainly used in the aircraft’s skin, the wing lower panels and other key positions, and successfully applied in the Boeing 777, Airbus A380 aircrafts,2E12 aluminum alloy was developed at the basis of 2524 by further reducing the impurity content of Fe and Si. The microstructure, conventional mechanical properties, fatigue crack growth rate and micro-crack growth path of domestic 2E12-T3 and imported 2524-T3 alloy were evaluated by OM, SEM (EBSD), TEM, EDS, DSC, Hardness Testing, Conductivity Testing, Tensile performance testing at room temperature, fatigue crack growth rate testing and other methods, etc, and obtained the main reasons of effect on the fatigue property of pre-made 2E12 aluminum alloy, then proposed the optimize program of the preparation process, and took a evaluation of fatigue crack propagation performance for the improved 2E12-T3 aluminum alloy, and obtained the domestic 2E12-T3 aluminum alloy which basically achieved the imported 2524-T3 fatigue level, the test results and conclusions obtained are as follows:The grains of domestic 2E12-T3 alloy were homogeneous and minute with more seriously recrystallized, and were approximately equiatxed, but the imported 2524-T3 alloy presented the rolled fibrous tissue, which were approximately equiatxed, the former was more seriously recrystallized; both of them were distributed with a little undissolved coarse second phase in the matrix, AlCu or AlCuMg and iron-rich phase; more middle-size Al20Cu2Mn3 club-shaped particles were observed in 2E12-T3 alloy with more close space in them; And with the same heat-treatment state for T3 state, the aging precipitated strengthening phase was the GP zone, which was coherent with the matrix.The fatigue crack growth rate of domestic 2E12-T3 alloy was significantly higher than imported 2524-T3 aluminum alloy, and the fractures had the significant differences, the fracture of 2E12-T3 alloy was relatively flat with the small striation space and a few of dimples,2524-T3 alloy was more rough and obviously rugged with the bigger striation space and more dimples at the fracture.The main difference between domestic 2E12-T3 and imported 2524-T3 alloy was the degree of recrystallization in microstructure, in order to reduce the recrystallization of domestic 2E12-T3, a low temperature annealing process could be added the front of the last one cold rolling annealing, the high accumulated strain energy would be fully released, while the deformation structure was reserved.By comparison with imported 2524-T3 alloy, the grains characteristic of improved 2E12-T3 aluminum alloy had come about an obvious change, and obtained the same fibrous-like tissues with 2524-T3 alloy, then a more prominent phenomena was observed in the improved 1.2mm-thick 2E12-T3 aluminum alloy, whose length-width ratio was about 6. Therefore, the microstructure of improved 2E12-T3 alloy had basically achieved the level of imported 2524-T3 alloy. By the evaluation of fatigue crack growth performance for the improved 2E12-T3 aluminum alloy, adding intermediate annealed process could effectively slow the crack growth rate and extend the remained fatigue life of domestic 2E12-T3 alloy, particularly, the fatigue crack growth rate curve of 1.2mm-thick improved 2E12-T3 alloy was almost coincided with 2524-T3 alloy, whose remained fatigue life reached up to 4.10×104cycles, it was only lower than the imported 2524-T3 alloy about 3%. Therefore, the fatigue performance of improved 2E12-T3 alloy basically achieved the level of imported 2524-T3 alloy.更多还原