激光/电解组合精确成形关键基础问题研究

In order to solve the difficulty on the manufacturing of the large high performance metallic parts with the high precision and efficiency by the traditional processing methods, the present project will focus on a new laser/electrochemical hybrid precision forming technology, which combined the high efficiency near-net shape additive manufacturing by laser solid forming and the high efficiency net shape subtractive manufacturing by electrochemical machining. In present work, the evolution behavior, formation and controlling mechanism on the surface residual stress, surface morphology, surface macro-microstructure and grain boundary characteristic will be investigated during laser solid forming of high performance hard-processing metallic materials including titanium alloy and superalloy et al. Their influence laws and mechanisms on the local electromagnetic field and electrochemical dissolution field in electrochemical machining process will be revealed. The nonlinear hereditary mechanism of geometric error in laser solid formed parts on the electrochemical machining process will be also analyzed. Based on the above mentioned researches, the present project will try to explore the matching control criterion of the morphology, stress and geometric error and the optimized forming strategies during laser/electrochemical hybrid precision forming process, to obtain the key processing principles in laser/electrochemical hybrid precision forming of high performance hard-processing metallic materials, lay an important science foundation for the development and application of laser/electrochemical hybrid precision forming of the large high performance metallic parts with the complex shape.

本项目针对大型高性能金属构件成形无法同时兼顾高精度与高效率的制造难题，将激光立体成形的高效近形增材制造与电解加工的高效近净去材加工相结合，发展激光/电解组合精确成形新工艺。重点研究钛合金、高温合金等高性能难加工金属构件激光立体成形过程中表层残余应力、表面形貌及表层宏微观组织和晶界特征的演化行为、形成机制和调控机理，揭示其对电解加工过程中局部电磁场和电化学溶解场的影响规律和作用机制，探讨激光立体成形构件形位误差在电解加工工程中的误差非线性遗传机制，探索激光/电解组合精确成形过程中的组织、应力及形位误差的匹配控制准则和成形加工策略的优化方法，获得高性能难加工金属材料激光/电解组合精确成形过程中的关键工艺原理，为大型高性能金属材料复杂构件激光/电解组合精确成形工艺的发展和应用奠定重要的科学基础。

本项目针对传统大型高性能金属构件成形无法同时兼顾高精度与高效率的制造难题，将激光立体成形的高效近形增材制造与电解加工的高效近净去材加工相结合，理清了TC4钛合金和GH4169高温合金构件激光/电解组合精确成形所涉及的关键科学问题，确定了激光立体成形TC4钛合金和GH4169高温合金复杂构件激光/电解组合精确成形加工策略，发展了激光/电解组合精确成形新工艺。取得的主要成果有：.（1）发现激光立体成形TC4合金构件所具有的外延生长的柱状晶以及顶部的等轴晶组织特征，以及残余应力水平对后续电解加工行为具有重要影响：1）等轴晶的耐腐蚀性能要优于柱状晶；对于柱状晶来说，横截面优于纵截面；2）对于晶粒尺寸和晶内相组成来说，粗大晶粒优于细小晶粒；电化学溶解时α相优先溶解；3）通过热处理降低激光立体成形TC4构件的残余应力水平有利于提升电化学溶解的均匀性；.（2）发现对于激光立体成形GH4169构件所具有的沿沉积方向外延生长的柱状晶以及顶部的等轴晶组织特征和残余应力水平对后续电解加工影响不大，而其晶内的γ基体和二次相（Laves相，MC相）组成和形态对电化学行为具有更为重要的影响：1）富铌枝晶干优先发生电化学溶解而二次相没有溶解直接剥落；2）γ基体直接决定了沉积态GH4169的钝化行为，二次相的分布影响表面产物电阻；.（3）激光立体成形构件的表面形貌对后续电化学溶解行为具有重要影响：沉积态表面形貌主要由搭接率和扫描策略决定，电化学整平来自于溶解过程中表面凸起处溶解速率高于低洼处。.（4）发展了激光立体成形件复杂型面电解液束加工工艺，发现液流反冲对成形质量有决定性作用；优化工具阴极出液孔设计可提高加工精度和表面质量；同时，采用激光成形/电解铣磨工艺显著改善遗传误差的传递，从而提高加工精度。.本项目共发表SCI收录论文38 篇，申请专利7 项。项目研究团队中入选“长江学者”特聘教授1 人，英国皇家学会“牛顿学者”1 人，陕西省创新人才推进计划中青年科技创新领军人才1 人。