采用激光熔注(LMI)技术在Ti-6Al-4V表面制备了WCp/Ti-6Al-4V梯度复合材料(MMC)层，对其形成机制进行了研究。研究结果表明，WC颗粒在复合材料层中的分布与其初始速度v0、穿越熔池表面最小临界速度vmin以及熔池粘度η有关。由于WC陶瓷颗粒密度大，在激光熔注过程中具有较高的动能，熔池粘度不再是决定梯度复合材料层形成的关键因素。对于WC/Ti材料体系，熔池凝固前沿是形成WCp/Ti-6Al-4V梯度复合材料层的重要因素，复合材料层不同深度范围内WC颗粒的数量由这一深度熔池凝固前沿长度所决定。WC颗粒注入位置对其在复合材料层中的分布有很大影响。在WC颗粒由熔池后部“拖尾”注入的情况下，该区域熔池深度较浅，WC颗粒遇到的熔池凝固前沿位于较高的位置，大多数WC颗粒被“冻结”在复合材料层的上部，进而形成了WCp/Ti-6Al-4V梯度复合材料层。

WCp/Ti-6Al-4V graded metal matrix composites (MMC) layer was produced by the laser melt injection (LMI) process and the formation mechanism of the graded layer was studied. The results show that the initial speed of the particle (v0), the minimum velocity of injected particles necessary for penetrating through the melt surface (vmin) and the viscosity of the melt pool (η) play key roles in the distribution of the WC particle. With big density, the WC particle has high kinetic energy during the laser melt injection process, and therefore the viscosity of the melt pool is not a critical factor anymore. The solidification front of the solid-liquid interface of the melt pool is the most sensitive factor that determines the formation of the graded layer when the WC particle is used as injection particle. Meanwhile, the total amount of WC particle at different depth of the MMC layer is dominated by the length of the solidification front in this depth. The injection location plays an important role in the distribution of WC particles. When the WC particles are injected into the extended part of melt pool, the depth of this region is low ,and the WC particles meet the solidification front at higher position. In that case, most WC particles are trapped at the top part of the melt pool and therefore a WCp/Ti-6Al-4V graded metal matrix composites layer is formed.