项目名称： 基于动态调控原位ＸＲＤ激光沉积制造显微组织/应力演化规律研究

项目编号： No.51505010

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 机械、仪表工业

项目作者： 吕俊霞

作者单位： 北京工业大学

项目金额： 20万元

中文摘要： 高性能金属构件激光增材制造是当前先进制造领域的国际前沿和竞争热点，其工艺特点决定的快速凝固和周期性热循环导致成形零件物相组成以及显微结构和力学性能发生显著变化。因此，揭示激光加热材料凝固组织显微结构/应力演化机理，探索原位动态调控微观组织演变是本领域当前尚未解决而又亟待解决的基础科学问题。我们提出一种全新的思路：基于X射线衍射的实验方法，在线研究凝固相结构在激光沉积过程中动态转变行为，以广泛应用的Ti6Al4V为对象，结合透射电子衍射技术、EBSD技术等结构表征手段，阐明该过程中Ti6Al4V物相转变、应力发展机理。并且探索添加辅助热源通过原位XRD实时监控相变及应力变化，调节辅助热源参数以实时调控激光沉积凝固组织显微结构演变和应力行为，为激光直接制造材料可控沉积提供一种全新的方法。本项目的研究不仅具有重要的理论意义，也具有深远的工程应用背景。

中文关键词： 激光沉积制造；显微组织；应力；原位XRD；辅助热源

英文摘要： Laser direct metal deposition (LDMD) is an advanced additive manufacturing (AM) technology, which is also called laser deposition manufacturing (LDM). It has tremendous potential for producing high-value, complex, individually customized parts and also can be used to repair and rebuild worn or damaged components by forming the wear and corrosion resistance coatings. LDM is a process by layer-by-layer deposition directly from a 3-D digital model. In this process, the solidification characteristics for metal-based materials are very different from those formed under the equilibrium condition. This is due to the rapid cooling speed and the periodic thermal recycling inducing the obvious change of the microstructure and stress. Therefore, it is necessary to study the microstructure and stress evolution behavior during the LDM heating and solidification process. At the present, the study of the phase transformation and stress evolution are mainly based on the solidification microstructure analysis under the room temperature according to the equilibrium phase diagram speculation. In this project, we propose a new idea to in situ study of the phase transformation and stress evolution during the laser manufacturing process. The phase transformation and the stress evolution can be identified directly from the characteristic lines change of the X-ray diffraction spectrum. We chose the extensively used Ti6Al4V alloy. The mechanism of phase transformation and stress evolution was investigated in LDM by in situ XRD and TEM and EBSD characterization. Finally, we explore a new method to change the phase transformation behavior by using an auxiliary heat source. By adjusting the processing parameters, such as laser power, scanning speed and input speed of powder, the microstructure can be controlled on real time directly. The study of this project will be very important for not only the theoretical significance of LDM material but the engineering application.

英文关键词： Laser deposition manufacturing;microstructure;stress;in situ XRD;auxiliary heat source