热处理对SiC/Ti-6Al-4V复合材料力学性能的影响

Effect of Heat Treatment on Mechanical Properties of SiC/Ti-6Al-4V Composites

摘要:

测定了经过900 ℃不同时间热处理的SiC/Ti-6Al-4V复合材料的拉伸强度，并采用全局载荷分配模型计算了复合材料的强度。发现长时间热处理后，复合材料强度的计算值与实测值吻合很好，但该模型对未经热处理的制备态试样的预测值偏高。扫描电镜和透射电镜微观分析表明，随着热处理时间的延长，SiC/Ti-6Al-4V复合材料的界面反应区增厚而SiC纤维的C涂层逐渐消耗，复合材料的界面结合强度逐渐增加但抗拉伸强度逐渐下降。界面反应形成的反应产物主要为TiC，在C涂层消耗完的区域还形成了Ti5Si3。界面反应是使复合材料力学性能变差的主要原因。

Abstract:

Tensile strength of the SiC/Ti-6Al-4V composites under the conditions of preparation and heat treatment at 900 oC for different time was measured and calculated by means of Global Load-Sharing model. It is found that after long-time heat treatment, the calculated strength is in accordance with the measured one. But the former is higher than the later for the as-prepared sample. SEM and TEM observations show that with prolonging the holding time at 900 oC, the interfacial reaction zone of the SiC/Ti-6Al-4V becomes thicker and the C-coating of the SiC fiber thinner, leading to the decrease of the tensile strength and the increase of the interfacial shear strength. It is identified that the main interfacial reaction product is TiC. However, when the C-coating is consumed entirely Ti5Si3 forms in the interfacial reaction zone adjacent to the SiC fiber. Interfacial reaction is the main reason for the decrease of mechanical properties of composites.