激光增材制造高强高韧TC11钛合金力学性能及航空主承力结构应用分析

Laser additive manufactured high strength-toughness TC11 titanium alloy:Mechanical properties and application in airframe load-bearing structure

随着损伤容限设计理念发展和轻量化要求提高,高强高韧钛合金逐渐成为航空装备关键主承力构件主要结构材料。激光增材制造制备钛合金大型主承力构件具有数字化、短周期、低成本等技术优势,特别是激光增材制造过程超常固态相变动力学条件为制备高强高韧钛合金提供了新的机会。本文根据航空主承力结构选材性能要求,对激光增材制造TC11钛合金静强度、疲劳和损伤容限特性进行测试与分析,在此基础上对其在航空主承力结构的应用前景进行分析。结果表明,激光增材制造TC11钛合金力学性能具有显著的高强高韧和低屈强比特征,其疲劳缺口敏感性和裂纹扩展速率低,性能分散性小,综合性能满足航空主承力结构选材要求。与目前航空主承力结构广泛应用的TC4-DT损伤容限型钛合金相比,激光增材制造TC11高强高韧钛合金损伤容限特性相当、疲劳性能有所改善、许用应力提高23%,结构具有进一步减重优势。激光增材制造TC11钛合金优异的强韧性匹配在提高结构许用应力的同时可避免大厚度结构发生脆性断裂,其低疲劳缺口敏感性和优异的疲劳裂纹扩展特性对于结构服役安全具有重要意义。

With the development of damage tolerance design concept and increasing requirement for lightweight,the high strength-toughness titanium alloy has been the main airframe material of load-bearing structure.Laser additive manufacturing has the advantages of digitization,short period and low cost in deposition of the large load bearing structure.Especially,the dynamics of solid phase transformation in the laser additive manufacturing process provide a new opportunity for the preparation of high strength-toughness titanium alloy.In this paper,the static strength,fatigue and damage tolerant properties of the laser additive manufactured TC11 titanium alloy were reported and analyzed according to the design requirements of airframe load-bearing structure.The prospects of using the alloy for the airframe load-bearing structure are then discussed.The results show that the alloy is characterized by high strength-toughness and low yield strength ratio.With low fatigue notch sensitivity,low fatigue crack growth rate and small dispersibility,the alloy can meet the requirements of mechanical properties of the airframe load-bearing structure.Compared with the damage tolerant TC4-DT titanium alloy that is now widely used for the airframe load-bearing structure,the laser additive manufactured TC11 titanium alloy shows similar damage tolerant properties,better fatigue performance,and improved static strength(by 23%).The excellent strength/toughness matching of the laser additive manufactured TC11 titanium alloy can avoid the occurrence of low stress brittle fracture in large thickness components,and low fatigue notch sensitivity and fatigue crack growth rate of the alloy are critical for ensuring service safety of the airframe load-bearing structure.