【作者】 门向南；

【导师】 童国权；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2010， 硕士

【摘要】 超塑成形/扩散焊接(简称SPF/DB)工艺,是南南南天领域成形研究的重要内容之一。钛合金多层板南心结构件由于其良好的结构形态、较轻的零件重量和简化的零件数量,一直以来是工艺应用的重点。目前钛合金SPF/DB工艺虽己进入使用阶段,但我国在SPF/DB技术上与发达国家相比还存在较大的差距。因此,开展钛合金等先进材料的SPF/DB技术研究,对降低成本,提高构件性能,增加飞机推重比具有非常重要的意义。本文结合数值模拟,采用先扩散焊接后超塑成形的方法,开展TC4三层板结构超塑成形/扩散焊接工艺研究和探讨。本文首先依据超塑成形和扩散焊接基本原理和变形机理,确定TC4三层板结构SPF/DB的实验方案,提出显微组织分析焊合率和晶粒尺寸的方法,分析了超塑成形/扩散焊接过程的影响因素。在理论和实验工艺的基础上,利用MARC软件对TC4三层板结构的超塑成形过程进行数值模拟,优化成形零件结构,预测成形零件的壁厚分布,讨论应变速率对成形结果与成形时间的影响,证明1x10-3 s-1为最佳成形应变速率,并获得最大应变速率恒定条件下的超塑成形压力—时间(p-t)曲线。对成形零件壁厚分布情况及成形结果进行分析,根据不同扩散焊接部位的显微组织计算焊接接头的焊合率及晶粒尺寸,讨论不同变形量对晶粒尺寸影响。结果表明:成形零件整体壁厚均匀,最大减薄率为32%;扩散焊接接头的焊合率较高,最大值为100%;成形后晶粒尺寸较原始晶粒尺寸明显长大,并且芯板的左、右肋和成形圆角处的晶粒尺寸较其余部位小;成形零件上面板质量较好,下面板出现一处明显的沟槽,芯板成形较好。对比数值模拟结果与实验结果,表明二者吻合较好,数值模拟可靠。更多还原

【Abstract】 Superplastic Forming and Diffusion Bonding (SPF/DB) process is one of the most important research subjects in the area-space engineering field. The titanium alloy multilayer sandwich structure is an important application in SPF/DB because of its perfect frame, low weight and few components. At present, the titanium alloy SPF/DB process has been taken into applied use in China, but there is a great gap compared with developed countries in the SPF/DB technology. So the research for titanium alloy and other advanced materials is carried out with SPF/DB process, which has extraordinarily magnitude significance to reduce costs, improve component performance and increase the aircraft thrust-weight ratio. In this thesis, the SPF/DB for three-sheet structure of Ti-6Al-4V titanium alloy was investigated combining numerical simulation by the method of SPF after DB.Beginning with mechanism and deforming path of SPF/DB were investigated. Then the experimental project about the SPF/DB for three-sheet structure of Ti-6Al-4V was established, the method of microstructure analysis for the area-bonding ratio and grain side was advanced and the factors influencing process was discussed in this thesis.Based on the theoretic and experiment, finite element simulation for SPF process was carried out on the software MARC which could optimize the forming part structure and predict the thickness distribution. The impact of strain rate on forming results and forming time was discussed, which also showed 1x10-3 s-1 was the best value of optimal strain rate. At the same time, the optimal SPF pressure-time curve was generated with the maximum constant strain rate control.The SPF/DB for three-sheet structure of Ti-6Al-4V was investigated. The thickness distribution and forming result was analyze. The impact of different transmutation on grain side was discussed. At one time, the area-bonding ratio and grain side was computed. The results show that the thickness of forming part is uniformity on the whole and the maximum thinning rate is 32%. The area-bonding ratio is grate overall and the maximum value is 100%. Compared with the formed grain side, the original one is much smaller. The grain side of the left or right rib of the middle sheet and the forming fillet is least. The quality for the upper sheet of forming part is very good, while the lower sheet takes on mark-off and the profile of the middle sheet is perfect. In the end, comparing the numerical simulation result with the forming one, it proved that the numerical simulation was correct.更多还原