Tailored formation of novel reinforcement in laser additive manufactured aluminum matrix nanocomposites and its strengthening mechanisms on mechanical properties

陶瓷颗粒增强铝基复合材料（AMCs）的一个显著缺点是塑性降低伴随着强度的增加。将钢筋尺寸减小到纳米级是解决碳纤维强度与延性矛盾的有效途径。本项目将基于粉末的激光增材制造（LAM）工艺，包括选择性激光熔化（SLM）和激光金属沉积（LMD），通过完整的熔化和凝固机制，应用于al基纳米复合材料的制备。为了实现再析出纳米级陶瓷增强材料的可控发展和分散，研究了再析出纳米级陶瓷增强材料高加热和高冷却速率的独特特性及其非平衡冶金机制。本项目从理论上研究了非平衡马兰戈尼流作用下激光诱导熔池中温度场、速度场和溶质场对纳米陶瓷增强相生长和分散的综合影响，提出了具有独特微观结构和分布特征的激光控制纳米增强相形成机制。定量研究了增强陶瓷和al基的种类和含量、粉末的物理性质以及应用的激光加工参数对纳米级陶瓷增强相结晶和生长行为的影响，提出了获得可控纳米级增强相的材料和工艺方法。研究了激光增材制造的AMCs零件的力学性能（特别是抗拉强度和延展性），并阐明了纳米级al基增强的潜在机理。因此，建立了过程-微观结构-性能关系，从而能够成功生产具有定制强化结构和改进机械性能的AMCs部件。本项目强调“设计材料”、“定制工艺”和“性能可控”的整合，为高性能amc组件的LAM提供科学的理论基础和关键策略。

One of the significant drawbacks for ceramic particle reinforced aluminum matrix composites (AMCs) is the decrease of ductility accompanied with the increase in strength. Decreasing the size of reinforcement to nanoscale is a promising approach to solve the contradiction between strength and ductility of AMCs. In the present project, powder-based laser additive manufacturing (LAM) processes including selective laser melting (SLM) and laser metal deposition (LMD) are applied to process Al-based nanocomposites through a complete melting and solidification mechanism. The unique feature of LAM of high heating and cooling rates and resultant non-equilibrium metallurgical mechanism are considered, in order to realize the controllable development and dispersion of re-precipitated nanoscale ceramic reinforcement. This project theoretically studies the temperature, velocity, and solute fields and their combined effect on the growth and dispersion of nanoscale ceramic reinforcing phases within laser-induced molten pool under the action of non-equilibrium Marangoni flow, thereby proposing the laser-controlled formation mechanisms of nanoscale reinforcing phases with unique microstructure and distribution features. The influence of the category and contents of reinforcing ceramics and Al-matrix, the physical properties of powder, and the applied laser processing parameters on the crystallization and growth behaviors of nanoscale ceramic reinforcing phases is quantitatively studied, in order to propose the material and process methods to obtain the controllable microstructures of nanoscale reinforcement. The mechanical properties (especially tensile strength and ductility) of laser additive manufactured AMCs parts are studied and the underlying strengthening mechanisms of nanoscale reinforcement to Al-matrix are elucidated. A process¿microstructure¿performance relationship is accordingly established to enable the successful production of AMCs parts with tailored reinforcement architecture and improved mechanical performance. The integration of 'designed material', 'tailored process', and 'controllable performance' is emphasized in this project, providing the scientific theoretical basis and key strategy for LAM of high-performance AMCs components.