深海钛合金构件激光喷丸强化抗氢致开裂机理及性能调控

To avoid hydrogen embrittlement failure of key components in ocean engineering equipment under deep-sea environment, the aim of this proposal is to investigate the mechanism of preventing hydrogen induced cracking(HIC) and performance control of Ti-6Al-4V alloy subjected to laser peening (LP). (1)Effects of residual compressive stress (RCS) induced by super-high strain rate LP on hydrogen solubility and hydrogen diffusion driving force is analyzed firstly, and then an accurate model related to dislocation multiplication and hydrogen diffusion coefficient is established. Furthermore, the stress and structure strengthening mechanism for inhibiting hydrogen permeation on titanium alloy surface is explored. (2) RCS relaxation regulation under different temperatures, pressures and hydrogen concentrations is analyzed. What’s more, the stress field near the hydrogen induced crack tip is described, while the morphology and distribution of hydrogen atoms and hydride in the grain refining layer of crack tip is clarified. Furthermore, plastic damage behavior and crack propagation mode of crack tip are analyzed, and the interaction between RCS and grain refinement for preventing hydrogen embrittlement is revealed. (3) Six sigma method is utilized to analyze the multiple variables during LP, and then the incidence relation of laser parameter-residual stress/microstructure-HIC is established. Finally, the performance control model and process criterion of preventing HIC are obtained. These research achievements can not only enrich and develop the basic theory of surface modification technology, but also provide theoretical and technological references for anti-HIC of deep-sea components by LP process.

针对海洋工程装备关键结构件在深海环境中易发生氢脆失效的难题，开展典型Ti-6Al-4V钛合金激光喷丸强化抗氢致开裂机理及性能调控研究。(1)分析激光喷丸诱导的残余压应力对材料表层氢溶解度及氢扩散驱动力的影响规律，建立位错增殖与氢扩散系数关系模型，探索抑制表层氢渗透的应力强化和组织强化机制；(2)研究残余压应力在不同温度、压力及氢浓度下的松弛规律，准确描述裂纹尖端附近应力场，表征裂纹尖端晶粒细化层内原子氢及氢化物的形态与分布，分析氢致裂纹尖端的塑性损伤行为和裂纹扩展模式，揭示残余应力/晶粒尺寸协同的抗氢致开裂延寿机理；(3)采用六西格玛统计过程控制技术，建立激光工艺参数－残余应力/微观组织结构－抗氢致开裂特性强关联模型，获得激光喷丸抗氢致开裂性能调控模型及工艺准则。项目成果有望丰富和拓展塑性形变表面改性的基础理论，为深海关键结构件超高应变率作用下抗氢脆的工程应用提供理论和技术支撑。

针对海洋工程装备关键结构件在深海环境中易发生氢脆失效的难题，以典型钛合金和不锈钢为研究对象，开展激光喷丸强化抗氢致开裂机理及性能调控研究。（1）研究超高应变率动态塑性形变对材料表层氢溶解度和氢扩散驱动力的影响规律，揭示激光喷丸诱导的残余压应力抑制表层氢渗透的作用机制；探索金属材料在富氢环境中的微观结构响应特征，准确描述晶粒细化层内原子氢扩散及聚集过程，研究氢与位错运动交互作用模式，揭示激光喷丸阻碍表层氢渗透的微观组织强化机制；（2）开展不同激光功率密度下，典型试样激光喷丸强化、氢渗透、电化学充氢慢拉伸试验，探索激光喷丸诱导的高幅值残余压应力、高密度位错及细化晶粒与氢原子扩散的耦合作用对试样表面完整性和氢致塑性的影响机制；（3）开展典型试样的模态参数测试和振动疲劳试验，并对振动疲劳断口形貌各特征区（裂纹萌生区、裂纹扩展区和裂纹瞬断区）进行定性及定量分析，探讨氢致裂纹尖端的塑性损伤行为和裂纹扩展模式，揭示残余应力/晶粒尺寸协同的抗氢致开裂延寿机理；（4）以ABAQUS-MSC.Fatigue软件为平台，构建激光喷丸工艺参数-残余应力-氢扩散-振动疲劳特性集成的计算模型，系统分析不同激光喷丸工艺参数诱导的应力和组织强化效应对材料氢扩散行为、氢致塑性和振动疲劳性能的强化效果，从而获得激光喷丸抗氢致开裂性能调控模型及工艺准则。项目成果有望丰富和拓展塑性形变表面改性的基础理论，为深海关键结构件超高应变率作用下抗氢脆的工程应用提供理论和技术支撑。