多场协同下铝合金表面复合多尺度结构构筑及腐蚀磨损行为

Ocean engineering is the basic of a powerful country. Ocean engineering equipment is the tool for promoting the power of country. Aluminum is the one key supporting material for ocean engineering equipment. When facing the serve condition including the corrosion and wear, aluminum is easy to wear for the low hardness. Which becomes an obstacle for the deep application of aluminum in the ocean engineering. In the present project, a surface manufacturing method based on multi-field cooperation is proposed. A composite multi-scale structure was prepared on the aluminum surface under the synergistic effect of mechanical force, electric, heat and ultrasonic vibration. Finally, synthetical protection system with “high hardness and strong support” will be formed on the surface. The relationships between surface integrity, mechanical characteristics of the composite multi-scale structure and the parameters of the multi-field cooperation process will be investigated and established. The forming mechanism of nano-gradient multi-scale structure under multi-field cooperation will be revealed. The mechanisms of accelerated diffusion and solid-phase reaction of the element in multi-scale structure under multi-field cooperation will be investigated. The influence of multi-field cooperation on the forming uniformity and surface integrity of surface strengthening layer will be clarified. The mechanism of influence of multi-factor coupling on the defect control of composite multi-scale structure will be discussed. The corrosion wear behavior of composite multi-scale structure under marine environment will be investigated. The prediction model for accurately describing the rule of corrosion wear lifetime will be established. The intercross and coalescence among the multi disciplines will be conducted in this project. The aforementioned investigations will give the basic support for the application of aluminum under complex loading conditions in the ocean engineering.

海洋工程是强国之基，海洋工程装备是兴国之器。铝合金是海洋工程装备的基础支撑材料之一，但低硬度易磨损导致铝合金在腐蚀与磨损交割的苛刻环境下服役能力不足的问题，已成为其面向海洋深度应用的瓶颈。本项目提出通过多场协同表面制造的方式，综合机械力、电、热、超声振动在铝合金表面构筑复合多尺度结构，形成“高硬强支撑”表面综合防护体系。建立多场协同参数群与复合多尺度结构表面完整性及力学特征之间的映射关系；揭示多场协同下纳米梯度多尺度结构的成形机制；阐述多场协同下元素在多尺度结构中扩散的加速机制及对固相反应的推动机理；澄清多场协同作用对于强化层成形均匀性、表面完整性的影响机制；探讨多因素耦合对复合多尺度结构的缺陷抑制机理；研究海洋使役下复合多尺度结构的腐蚀磨损损伤行为；建立合理描述腐蚀磨损寿命演变规律的预测模型。本项目体现了多学科的交叉融合，为复杂载荷下铝合金涉海应用奠定了理论基础。

针对铝合金等低硬度易磨损的金属材料在苛刻的服役环境下服役能力不足的问题，自主设计制造了平面多珠滚压刀具和二维超声振动辅助加工系统。利用均匀设计试验方法设计二阶参数优化试验表，基于加工后的表面显微硬度和表面粗糙度构建二维超声振动滚压加工的回归模型，建立控制参数与目标参数的映射关系。二维超声振动滚压加工可实现表面强化和表面光整“一步法”加工，将表面硬度提升50%，表面粗糙度降低至原始态的2%达到镜面效果。二维超声振动的引入极大的改善了滚压加工的效率和质量，其中，垂向超声振动的引入可以显著降低加工时滚压力的大小，同时能进一步增加表面硬度；而横向超声振动可以显著降低加工时切向力的大小和抑制切向力的波动，同时能进一步降低表面粗糙度。铝合金等金属材料属于滞弹性体，其在超声振动作用下会发生模量亏损和能量损耗现象，这种现象主要是由于金属晶体在超声振动过程中弹性波与各种缺陷，如空位，间隙原子，位错等元激发的相互作用进而使超声振动能量损耗。进一步，超声振动能显著增大试样的势能，降低晶体的点阵阻力Peierls-Nabarro力，使位错更易发生滑移、湮灭和增殖，进而促使原始粗晶演化为细晶。材料表面在滚压刀具下发生单方向应变路径变形时，材料近表层的位错发生大量增殖进而产生位错胞、位错塞积、晶界等内应力源进而屏蔽了滚压力的影响。当材料近表层材料发生180°往复应变路径变形时，在几何必要为错产生的较大的背应力作用下发生包申格效应使材料屈服所需的外加应力降低。同时可以将加工产生的位错塞积和位错胞内的位错更均匀的分布在基体内部。进一步，随着更多滑移系适应变形，亚晶界发生连续重排，这导致滚压加工的影响深度大幅提升。二维超声振动滚压加工在表面构筑复合多尺度结构，形成“高硬强支撑”表面综合防护体系，显著了提升了材料的抗磨性能力，增强了其服役能力。