【摘要】 激光粉末床熔融技术制备的陶瓷颗粒增强镍基复合材料由于具有质轻、高强、耐热腐蚀及可设计等特点而备受关注。然而，在已报道的研究中，陶瓷颗粒的质量分数大多在2%以下，且材料力学性能随陶瓷含量变化的规律尚未明确。以TiC/Inconel 718镍基复材为研究对象，进行了激光粉末床熔融成形实验，研究了微观组织特征和强化机理。结果表明：TiC颗粒均匀、弥散地分布在Inconel 718基体中，晶粒以外延生长的柱状晶为主。随着TiC含量的增加，TiC/Inconel 718复合材料熔合线上下组织差异减小。TiC颗粒的添加细化了TiC/Inconel 718复合材料的显微组织，等效晶粒尺寸从9.56μm细化到8.43μm。TiC/Inconel 718复合材料熔合线曲率半径的增大进一步诱导了枝晶的外延生长，使得TiC/Inconel 718复合材料织构强度由4.27上升到12.76。与打印态Inconel 718相比，TiC/Inconel 718复合材料的强度较大，这与纳米TiC颗粒阻碍位错运动及承载部分载荷有关。在变形过程中，TiC颗粒脱黏后造成的凹坑成为裂纹源和裂纹扩展的通道，使复合材料的延伸率下降。研究结果为优化TiC/Inconel 718镍基复合材料的性能提供了理论支持和实验依据。更多还原

【Abstract】 Objective Laser powder bed fusion(LPBF) technology for fabricating ceramic particle-reinforced nickel-based composites is one of the effective methods to enhance the mechanical properties of Inconel 718 alloy. In the reported studies, the ceramic mass fraction is predominantly below 2%. Although some studies have reported Ti C mass fraction up to 5% in Inconel 718 alloy, the impact of Ti C particles on mechanical properties has still not been thoroughly investigated. Consequently, the contribution of Ti C particles to the mechanical properties in high Ti C content Ti C/Inconel 718 composites remains ambiguous, and the influence of Ti C content on the microstructure is not yet well-defined.Methods In this study, Ti C/Inconel 718 composites with Ti C mass fraction of 1.5% and 3.0% were prepared by the LPBF technology. The effects of Ti C content on the microstructures and mechanical properties of the composites were systematically analyzed. In addition, the effect of Ti C particles on the tensile process of LPBF-Ti C/Inconel 718 composites was analyzed.Results and Discussions The thermal conductivity of Ti C is significantly higher than that of Inconel 718 alloy, which accelerates the cooling rate of the composite melt pool. This reduces the primary dendrite spacing in the LPBF-Ti C/Inconel 718 composite, leading to a more uniform microstructure. The layered structure becomes less pronounced, and the microstructure is significantly refined. Furthermore, as the mass fraction of Ti C increases, the curvature radius of the fusion line in the LPBF-Ti C/Inconel 718 composite gradually increases, and the melt pool becomes flatter. This further promotes the epitaxial growth of dendrites within the melt pool, enhancing the texture strength of the LPBF-Ti C/Inconel 718 composite. The addition of Ti C particles significantly improves the mechanical properties of the LPBF-Ti C/Inconel 718 composite and the yield strength increases when the mass fraction of Ti C particles increases. The effect of Ti C on the yield strength of the LPBF-Ti C/Inconel 718 composite can be analyzed from three aspects: coefficient of thermal expansion(CTE) mismatch strengthening, load strengthening, and fine grain strengthening. The results show that the contribution of these three strengthening mechanisms to the yield strength is positively correlated with the Ti C content. CTE mismatch strengthening and fine grain strengthening are the primary contributors to the increase in yield strength of the LPBFTi C/Inconel 718 composite, while the contribution of load strengthening is relatively minor. Additionally, during the tensile process of the LPBF-Ti C/Inconel 718 composite, Ti C particles may debond and spall, forming pits that act as crack initiation sites and propagation paths. This increases the numbers of potential failure initiation points, thereby reducing the elongation of the composite.Conclusions As the Ti C content in the composite increases, a notable transformation occurs in the microstructure of the Ti C/Inconel 718 composite. Specifically, the microstructure becomes more uniform, and the distinct layer-band structure becomes less pronounced and eventually indistinguishable. This uniformity is attributed to the consistent distribution of Ti C particles throughout the matrix, which facilitates a more homogeneous microstructure. The addition of Ti C particles does not fundamentally alter the asdeposited microstructure of the composite. Instead, it enhances the characteristic of columnar crystal epitaxial growth, which is a key feature of the as-deposited state. This enhancement is observed through the refinement of the microstructure, where the primary dendrite spacing is significantly reduced from 502.2 nm to 355.3 nm. This reduction in dendrite spacing is a direct result of the increased nucleation sites provided by the Ti C particles, leading to a finer and more uniform microstructure. Concurrently, the increased curvature radius of the fusion line in the Ti C/Inconel 718 composite plays a crucial role in the growth of dendrites within the melt pool. This directional growth is induced by the geometric changes in the melt pool, which in turn enhances the texture strength of the material. The texture strength increases from 4.27 to 12.76, indicating a significant improvement in the material anisotropic properties and overall mechanical performance. Compared to the as-deposited Inconel 718 composite, which serves as a baseline for comparison, the Ti C/Inconel 718 composite exhibits a marked enhancement in mechanical properties. This improvement is evident in the increased yield strength, ultimate tensile strength, and hardness of the composite. However, it is important to note that the elongation of each composite is reduced to varying degrees. This reduction in elongation is attributed to the presence of Ti C particles, which can act as stress concentrators and potential crack initiation sites. Despite this decrease in elongation, the overall mechanical performance of the Ti C/Inconel 718 composite is significantly superior to that of the as-deposited Inconel 718 composite, making it a promising material for applications requiring high strength and durability.更多还原