【作者】 薛松；

【导师】 周杰；

【作者基本信息】 重庆大学 ， 材料加工工程， 2011， 博士

【摘要】 钛合金作为当代飞机结构设计的重要选材之一,其应用水平的高低甚至已成为衡量飞机结构设计选材先进程度的重要标志之一。钛合金对于减轻飞机整体结构重量、提高结构设计效率、改善结构可靠性、提高机体寿命、满足高温和高载以及腐蚀环境要求等方面能够发挥其他金属无法比拟的作用。目前航空器上应用的钛合金结构件正朝着整体化、大型化方向发展。而对于钛合金,锻造工艺是应用最广泛的成形方法,能够通过变形和热处理精确改变合金的显微组织和性能。因此,研究大型钛合金航空结构件的锻造成形特性与工艺有着重要的现实意义。TA15钛合金整框模锻件是具有典型代表的大型钛合金航空结构件,通过研究TA15钛合金的热变形特性并结合锻造生产工艺参数的优化研究,可以为这类大型钛合金结构件的模锻生产提供相关生产基础数据和工艺经验。为了研究TA15钛合金的热变形特性,本文首先利用Gleeble-1500D材料热/力模拟试验机对TA15钛合金在800℃、850℃、900℃、950℃、1000℃、1050℃温度条件下采用应变速率为0.01s-1、0.1 s-1、1 s-1、10 s-1进行热压缩试验,通过热压缩试验数据分析了其高温流变特性并建立了基于Arrhenius流动模型的本构方程以及基于Fields-Backofen流动应力方程及并加入了软化因子的本构方程;对建立的本构方程进行了验证和讨论。基于动态材料模型加工图的理论,采用TA15钛合金高温压缩试验数据建立了实验条件下应变为0.2、0.4、0.6时的热加工图,对该合金的高温变形能力进行了综合分析,对热加工工艺参数进行了优化。运用塑性有限元分析软件DEFORM-2D,对TA15钛合金热物理模拟压缩实验方案进行了模拟仿真。通过对TA15钛合金韧性损伤力学行为的数值模拟研究,从材料临界损伤因子角度探讨了TA15钛合金的加工工艺性能。确立了TA15钛合金临界损伤因子随着变形温度和应变速率变化规律。针对TA15钛合金大型整框模锻件,采用数值模拟技术研究了其成形工艺过程。通过对坯料外形、尺寸的的研究获得了在对击锤上模锻的最佳工艺坯料方案。对锻造成形过程中的锻造温度、打击速度、变形载荷对锻件成形的影响进行了全面分析,获得了对钛合金整框锻造合理的工艺参数。通过采用基于热压缩实验的本构方程对整框锻件数值模拟研究,验证了该模型的可靠性。在基础理论和数值模拟研究的基础上,对TA15钛合金大型整框模锻件在1MJ对击锤上进行了试制。对锻件坯料的工艺,模锻工艺参数进行了验证,通过对成形锻件组织和力学性能的测试和评估,结果达到了相关标准对锻件的要求。通过试制验证了本文所建立的流变应力模型和数值模拟结果。总结了大型钛合金锻件质量现场生产控制技术,即“组织准备+锻造变形量和变形温度协调控制+组织监控”诸过程的严格控制是钛合金大锻件成功研制的重要保证。在试制过程中,还研究了碳化物分布对H13模具用钢的组织及性能的影响。研究结果对于制定大型钛合金锻件锤上模锻生产工艺具有指导意义。更多还原

【Abstract】 Titanium alloy, as the most important selectable structural material in modern aircraft, its application level in design even become the most important mark to measure the extent of advanced in selection of aircraft structural material. Titanium alloy can play the role that other metals can not match on such aspects, to decrease the total weight of aircraft, to raise the design efficiency of aircraft structure, to improve the structural reliability, to enhance the life of aircraftbody, to meet the requirements that worked under high temperature, high load and corrosive condition. At present the application of titanium aircraft structural parts are moving in the overall and large-scale direction. Forging process is the most applied forming method to titanium alloy; it can change the microstructure and mechanical properties accurately by deformation and heat treatment. So, it has the most practical significance to research the forming features and process of large-scale titanium alloy aircraft structural parts.TA15 titanium alloy whole frame die forging part was the typical large scale titanium alloy aircraft structural part. By study on the hot deformation features and combined with the reaserch on forging process parameters optimization, it can provide the base pudution data and process experience to die forging process of this type of large scale titanium alloy structural part.To study the hot deformation features of TA15 titanium alloy, a series of hot compression tests which were tested on Gleeble-1500D material thermal / power simulation test machine were carried out. In the test, TA15 titanium alloy pecimence were compressed under the heating temperature of 800℃、850℃、900℃、950℃、1000℃and 1050℃by strain rates of 0.01s-1、0.1 s-1、1 s-1、10 s-1 respectively. By the hot compression test results data, the high temperature rheological behavior of TA15 were analysised and the constitutive equation based on Arrhenius flow model and Fields-Backofen flow stress model were established. The constitutive equation were verified and discussed.Based on the theory of dynamic material modeling (DMM), processing map of TA15 were established with the hot compression test data that the strain were 0.2,0.4,0.6 respectively. The hot deformation ability of this alloy was analysised and the hot working process parameters were optimized.Plastic finite element analysis software DEFORM-2D was apllied to simulate the TA15 titanium alloy hot compression test plan. The hot process performance of it was discussed in terms of material critical damage factor by study on the mechanical behavior of ductile damage with numerical simulation. The law that the material critical damage factor varied with the deforming temperature and strain rate changing was established.With the large scale TA15 titanium alloy whole frame die forging, numerical simulation technology was carried out to study its hot forming process. The optimized scheme of forging blank piece was obtained by study on the outline and size of it. Forging temperature, stroke speed, and deformation power effect on the forging forming process were anlysised comprehensively, the reasonable parameters of titanium alloy whole frame part forging process were obtained. The reliability of the constitutive model that eatablished using hot compression test data was verified by using it in whole frame forging part numerical simulation research.The large scale TA15 titanium alloy whole frame die forging was trialed on 1MJ counter-blow hammer based on the study of basic theory and numerical simulation. The process of forging blank piece and parameters of die forging were verified in the trial. The microstructure and mechanical properties of the finished forging were tested and evaluated; the results show that the forging had reached the demand of standards. The trial verified the results of numerical simulation and flow stress model which established by hot compression test also. The site production quality control technology of large titanium forging were summaried, that is the critical control of the process“microstructure preparation+coordination and control of forging deformation and forming temperature+microstructure monitoring”is the important guarantee for the successful development of large scale titanium alloy forging. In the trial process, the die steel H13 was researched in terms of carbides. The research results are instructive to the development of large-scale forging on hammer.更多还原