Mo-MoSi_2功能梯度材料的三点弯曲行为

Three point bending behavior of Mo-MoSi_2 functionally gradient material

采用渗硅工艺制备了Mo-MoSi2功能梯度材料,并利用扫描电镜、X射线衍射以及弯曲强度试验观察并分析Mo-MoSi2功能梯度材料的微观结构和断裂行为。结果表明,梯度材料由表及里的结构变化形式为表层MoSi2晶粒(尺寸为6.8μm)+少量Si→MoSi2柱状晶粒(长度为15μm)→过渡层(2μm)→Mo基体。该Mo-MoSi2功能梯度材料具有组织致密,MoSi2晶粒细小,梯度层与Mo基体界面结合良好等特点。Mo-MoSi2梯度材料具有良好的弯曲性能,弯曲强度为1025 MPa,断裂挠度为1.87 mm,弹性模量为26.6 GPa。在保证Mo基体强度的同时,MoSi2功能梯度涂层显著提高了Mo基体塑性性能。Mo-MoSi2梯度材料的弯曲断裂形式主要为沿晶断裂和穿晶断裂两种形式。过渡层和MoSi2涂层形成是Mo-MoSi2功能梯度材料断裂韧性提高的主要原因。

Mo-MoSi2 functional gradient material( FGM) was prepared by siliconizing technology on Mo substrate. Microstructure and fracture behavior of the Mo-MoSi2 functional gradient material was investigated by scanning electron microscopy,X-ray diffraction and bending test. The results show that the microstructure of Mo-MoSi2 functionally gradient coating from outside to inside is MoSi2 crystalline grains( 6. 8 μm) and Si→MoSi2columnar grains( 15 μm) →transition layer→Mo substrate. The Mo-MoSi2 functionally gradient material has compact structure,fine grain size and the metallurgical bonding between Mo substrate and MoSi2 functional gradiental layer is obtained. The Mo-MoSi2 gradient material has good bending performance and its flexural strength can reach 1025 MPa,also its fracture bending deflection and elastic modulus is 1. 87 mm and 26. 6 GPa,respectively. Meantime,MoSi2 functional gradient coating significantly improve the plastic properties of Mo substrate and no decreasing of its strength is observed. The bending fracture mechanism of Mo-MoSi2 functionally gradient material is characterized by intergranular fracture and transgranular fracture. The fracture resistance of the Mo-MoSi2 gradient material is improved by the formation of transition layer and MoSi2 coating.