激光增材制造金属功能材料及其原位同步辐射研究(特邀)

Laser Additive Manufacturing of Metallic Functional Materials and In-Situ Synchrotron Radiation Research(Invited)

近年来,基于激光增材制造技术的先进结构材料和构件制备及应用取得了重要进展,并由此带动了该技术在金属功能材料制备与调控方面的发展。作为金属功能材料典型代表的形状记忆合金兼具形状记忆、超弹性和弹热效应等新奇特性,这些特性与合金的微观组织、微结构演化高度相关,但难以通过传统制备和表征手段实现精细化调控和实时相变测量,因而通过激光增材制造技术调控微结构并进行原位同步辐射观测成为形状记忆合金性能提升的重要手段。本文综述了基于激光增材制造的形状记忆合金设计、微结构调控、工艺-结构-性能关系以及国内外研究现状,并从技术原理、材料特性、工艺优化、结构调控和原位表征等方面对形状记忆合金激光增材制造研究进展进行了介绍,归纳整理了现阶段激光增材制造形状记忆合金的主要性能。另外,本文介绍了激光增材制造过程的原位X射线衍射表征方法以及该表征方法的典型应用,对增材制造过程中合金的相变动力学测量及单晶原位表征方法进行了梳理,并对该技术的未来发展趋势进行了展望。

Significance Laser additive manufacturing is a technology that utilizes a laser beam to melt and mold powders layer by layer based on a 3D model.It has made outstanding progress in the molding of metallic structural materials such as large and complex structural parts in the aerospace industry.Laser additive manufacturing has also achieved remarkable progress in the fabrication of metallic functional materials.Shape memory alloys are a type of metallic functional materials that exhibit shape memory,superelasticity,and elastocaloric effects.Through design and optimization of the process strategy,shape memory alloys with excellent functional properties and complex shapes could be fabricated by laser additive manufacturing.Laser additive manufacturing offers an effective method to research metallic functional materials with outstanding performance that can meet the application requirements.Progress In this paper,we systematically summarize the research on laser additive manufacturing of metallic functional materials and their characterization by insitu synchrotron radiation.We further introduce the research progress on laser additive manufacturing of highperformance shape memory alloys as well as the latest progress of metal LPBF and LDED technologies for synchrotron radiationbased insitu Xray diffraction(XRD)research.In the first part of this paper,the dominant types of laser additive manufacturing and their basic principles are introduced.On this basis,the relationship between the functional properties of shape memory alloys and the parameters of the process strategy is revealed.This relationship offers a guideline for how to fabricate a shape memory alloy with targeted properties.In the next part,the research progress on highdensity shape memory alloys fabricated through laser additive manufacturing is introduced.The guidance of results predicted by computer is convenient for selecting the combinations of parameters that could be used to fabricate shape memory alloys with high density.The final part presents the research progress on synchrotron radiationbased insitu Xray characterization in the laser additive manufacturing process.This part introduces the characterization platform and typical applications of insitu XRD in the laser additive manufacturing process of metallic materials.We describe some scenarios involving the phase transition dynamics measurement and insitu characterization methods of single crystals in additive manufacturing.We also present the future development trends.Conclusions and Prospects The molten pool in LPBF and LDED metal additive manufacturing processes has the characteristics of nonequilibrium and rapid solidification,and the microstructure of metallic functional materials can be controlled by adjusting the parameters of these processes.The additive manufacturing process may produce microdefects such as keyholes and lack of melting,and it also tends to form columnar crystals with a certain orientation.Based on the EagerTsai model,a fabricationquality distribution map can be predicted,with the parameters as the coordinates.On this basis,the process strategy can be adjusted to obtain a columnar crystal alloy with high orientation and high quality,and the mechanical properties can be further optimized.Synchrotron radiationbased insitu XRD can effectively characterize the phase transition dynamics,texture evolution,and grain size changes in the additive manufacturing process,which provides insights into the control of the process parameters in additive manufacturing of metallic functional materials.The application of synchrotron radiationbased insitu XRD can provide a key reference for additive manufacturing in terms of improving the functional characteristics and optimizing the component quality.By delving deeper into the microscopic evolution of the additive manufacturing process,researchers can better understand the properties of metallic materials,so that they can precisely manipulate the process parameters to achieve precise controlling of metal functional materials.