激光冲击双相钛合金的微结构响应及动态塑性变形行为

To solve the large deformation generated by laser shock peening (LSP) and short fatigue life of the dual-phase titanium alloy, the aim of this proposal is to address the micro-structural response mechanism and dynamic plastic deformation behavior of dual-phase titanium alloy under the mechanical effect of massive LSP impacts. This research can be used to ensure the longlife and reliable service of some key components used in aero-engine. The following issues will be involved. The first is to investigate the dislocation configuration distribution of α-phase, β-phase and α/β interface, and reveal the micro-structural response mechanism of dual-phase titanium alloy subjected to LSP. The second is to describe the plastic deformation process of dual-phase titanium alloy subjected to LSP, develop the analytical expression of plastic deformation depth of dual-phase titanium alloy subjected to LSP, and obtain the cumulative macroscopic deformation rule of dual-phase titanium alloy generated by microscopic plastic defoemation. The third is to describe the evolution process of the dynamic grain under the mechanical effect, gain the micro-structural evolution in the depth direction, and reveal the grain refinement mechanism of dual-phase titanium alloy subjected to LSP. The last is to explore the effect between deformation energy and microstructure, and obtain the technic principle of dual-phase titanium alloy subjected to LSP. As a result, the surface mechanical properties and plastic deformation of dual-phase titanium alloy can be predicted and controlled during massive and overlapping LSP impacts. The above researches involve many new scientific issues, and these research achievements can not only enrich and develop the surface modification technology and basic theory of dual-phase alloys, but also provide theoretical guidance for their large-scale industrial applications of fan blade strengthened by massive LSP impacts.

面向航空发动机长寿命可靠运行的需求，针对钛合金叶片疲劳寿命短和强化变形大的难题，本项目拟以α+β双相钛合金叶片为研究对象，开展激光冲击钛合金微结构响应机制和动态塑性变形行为研究，主要包括：⑴研究双相钛合金双相及界面的位错组态分布，揭示激光冲击双相钛合金的微结构响应机制；⑵描述大面积多点搭接冲击的微观塑性变形过程，建立激光冲击钛合金塑性形变深度的解析表达式，获得微观塑性变形导致的累积宏观变形规律；⑶描述力学效应下动态晶粒演变过程，获得深度方向的微观结构演化规律，揭示超激光冲击双相钛合金的晶粒细化机制；⑷探索激光冲击双相钛合金的形变能量-微观结构效应，获得激光冲击强化双相钛合金的工艺准则，从而实现激光冲击双相钛合金强化效果及表面塑性变形控制。相关内容涉及众多全新科学问题，研究成果可以丰富和发展双相合金表面改性理论和技术，为激光冲击强化钛合金叶片的大规模工业应用提供理论依据。

面向航空发动机长寿命可靠运行的需求，针对钛合金叶片疲劳寿命短和强化变形大的难题，本项目以α+β双相钛合金叶片为研究对象，开展了激光冲击双相钛合金微结构响应机制和动态塑性变形行为研究，主要取得了以下进展：① 对于密排六方(HCP)结构的α-Ti合金，多次激光冲击波导致光斑范围微观区域应力和结构分布不同，通过(亚)微米量级多方向机械孪晶交叉，和纳米量级二次孪晶与位错墙交叉两种晶粒细分模式并行细分原始粗晶；② 激光温喷丸可大大降低TC4金属(类似Ti-6Al-4V)的屈服强度，从而显着增加塑性应变，高温激光喷丸诱导的残余压应力稳定性显著提高，其疲劳寿命远高于室温LSP试样，这是由于裂纹长度增加和残余压应力释放速率下降；③ 服役温度对激光冲击工业纯钛微观结构有重要的影响作用：在超高应变率低温下位错运动被抑制，塑性变形主要形式为孪生变形；在超高应变率高温下会激活位错运动，使变形孪晶在塑性变形层中消失；高温改变了TA2工业纯钛的断裂机制，断裂模式由20 °C的脆性断裂变为混合断裂模式，350 °C时为韧性断裂。高温导致了晶粒生长和断裂表面的拉伸颈缩，同时激光冲击强化也显著提高了TA2工业纯钛的塑性；④ 表征激光冲击力学效应下双相钛合金双相及界面的位错组态分布，揭示激光冲击双相钛合金的α相、β相对超高应变率激光冲击波的微观响应机制，主要体现在随着冲击层数增加，β相微观响应机制为“位错运动→位错胞、条状次生α相(首次发现)→DRX→细化晶粒/纳米晶”；⑤ 获得冲击波力学效应下典型双相钛合金的表面完整性、微观组织结构和力学性能的基本数据，建立双相钛合金多层梯度激光冲击强化工艺准则。.在项目执行期内，圆满完成计划任务书的各项任务。研究成果获2015年江苏省科学技术奖二等奖1项，出版中文专著《激光冲击波强化技术及微观塑性变形机制》1部，主要研究成果发表论文7篇，其中SCI收录6篇，EI收录1篇(不含SCI收录)。获美国授权发明专利1件、中国授权发明专利2件，申请美国发明专利1件，获得软件著作权2件。参加国际/国内会议交流37人次，做邀请报告3次。研究执行期内，项目组主要成员晋升教授1名，培养博士研究生1名、硕士研究生4名，获省优博1篇、省优硕1篇。

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