TiAl合金与镍基高温合金激光焊接头组织与性能关联性及调控机制研究

This project focuses on the great demands of the state in the fields of aerospace, automobile and national defense, etc., aiming at the correlation and regulation mechanism of microstructures and properties of laser-welded joint of TiAl alloy and Ni-based superalloy (TiAl/Ni alloy). The welding process, microstructure characteristics, intermetallics properties, distribution and variation, room-temperature/high-temperature properties, rack initiation and propagation characteristics and fracture morphology, etc. are studied systematically for revealing the essential corelation between joint microstructures and mechanical properties. Effects of transition layer on the microstructures and properties of the joint are studied, and their affecting mechanisms and regulation mechanism are revealed and the composition and structure of the transition layer are optimized for improving the joint property. Effects of laser welding parameters and processing conditions on the microstructures and properties of the joint are studied, and their affecting mechanisms and regulation mechanism are revealed and the welding process is optimized for improving the joint property. Based on the optimal transition layer, the mathematics relation between joint properties and welding parameters is established for optimizing welding parameters, Further clarifying the internal relations of the welding parameters, joint microstructures and joint mechanical properties，and achieving the joint microstructure and mechanical properties forecast and joint quality control. Finally, high quality dissimilar joint of TiAl alloy and Ni-based spueralloy will be obtained.

本项目聚焦于国家在航空航天、汽车和国防等领域的迫切需求，针对TiAl合金与镍基高温合金激光焊接头组织与(室温/高温)性能的关联性及调控机制开展研究。系统地研究激光焊接头的形成过程、微观组织结构特征、脆性金属间化合物性质、分布状态及变化规律、室温/高温力学性能特点、裂纹萌生、扩展特点及断口形貌特点等，揭示接头组织结构与力学性能的本质关联。研究过渡层对TiAl/镍基高温合金激光焊接头组织与性能的影响规律，揭示其影响机理及调控机制，优化过渡层成分与结构，提高接头性能；研究激光焊参数与工艺条件耦合控制对接头组织与性能的影响规律，揭示其影响机理基调控机制，优化焊接工艺过程，提高接头性能。基于优化过渡层建立接头力学性能与焊接参数关系数学模型，优化参数，进一步明确焊接参数、微观组织和力学性能三者之间的内在联系，实现接头组织与性能的预测和接头质量控制，最终实现TiAl合金与镍基高温合金异质材料的优质连接。

TiAl基高温合金被认为是21世纪极具应用前景的新型轻质高温结构材料，其与镍基高温合金的连接在航空航天、国防等高科技领域具有潜在应用前景。本项目系统地研究了TiAl基合金与镍基高温合金激光焊接头的微观组织与力学性能特点及二者中间的关联性。. 研究结果表明，不加中间层条件下，二者无法形成有效的激光焊接头，AlNi2Ti和Al0.35Ni0.30Ti0.35是主要的致裂相。通过设计填加多种形式的中间过渡层材料，探索改善二者焊接性的途径和方法，揭示了中间过渡层材料对接头组织与性能的影响规律及作用机制。. 采用单一中间层材料（Ti, Nb, V, Cu）作为冶金调控元素对TiAl基合金与镍基高温合金激光焊接头焊接头微观组织和力学性能改善程度有限，接头抗拉强度最高仅为158MPa（0.4mmCu中间层），接头脆性金属间化合物仍是导致接头力学性能不高的原因。. 为进一步控制TiAl基合金与镍基高温合金激光焊过程中的冶金反应，抑制脆性金属间化合物的形成，基于元素冶金相容性原理及热力学分析设计多种复合中间过渡层，获得了连接质量较好的TiAl基合金与镍基高温合金异质材料激光焊接头。采用V/Cu复合中间层，焊缝区主要由V基固溶体、Cu基固溶体及(V,Ti)/AlCu2Ti片层组织组成，有效的降低了焊缝区脆性，接头室温和高温抗拉强度平均为230MPa和145MPa。复合中间层结构优化后，接头的室温和高温（873K）抗拉强度均有所提高，分别达255MPa和206MPa。. 通过数值模拟方法分析了不填加中间层和填加中间层的激光焊接头温度场和应力场，进一步阐明了激光焊热物理过程、微观组织结构和力学性能三者之间的内在联系，明确了改善接头组织和提高接头性能的方向.为实现TiAl基合金与镍基高温合金异质材料激光焊的成功应用提供了基础理论依据和技术支持。