热压烧结法制备B_(4)C-CeB_(6)陶瓷材料微观结构及力学性能的研究

Microstructure and Mechanical Properties of B_(4)C-CeB_(6) Ceramics Fabricated by Hot Pressing Sintering

在温度为2050℃,压力为20 MPa的条件下,通过热压烧结的方法在碳化硼(B_(4)C)中分别添加2%~5%的CeO_(2)制备B_(4)C-CeB_(6)复合材料。通过原位反应在B_(4)C中引入CeB_(6)。详细研究了CeO_(2)添加量对B_(4)C-CeB_(6)复合材料的微观结构和力学性能的影响。结果表明:随着CeO_(2)添加量的增加(不超过4%),B_(4)C-CeB_(6)复合材料的相对密度和力学性能逐渐升高;但是当CeO_(2)添加量超过4%时,产生的CO增多会导致复合材料的相对密度和显微硬度下降;当CeO_(2)含量较低时,由于CeB_(6)的断裂韧性要比纯B_(4)C高,裂纹穿过CeB_(6)相断裂就会消耗更多的能量,使复合材料的断裂韧性得以提高;而当CeO_(2)含量较高时,CeB_(6)和B_(4)C热膨胀系数的不匹配造成裂纹偏转为主要的增韧机制,此外还发现有裂纹桥联、裂纹分支等机制。B_(4)C-CeB_(6)复合陶瓷相对密度、维氏硬度、抗弯强度和断裂韧性分别达到98.6%,39.5 GPa,396 MPa和5.96 MPa·m^(1/2)。

B_(4)C-CeB_(6) composites were fabricated by hot pressing sintering at 2050℃and 20 MPa,adding 2%to5%ceria(CeO_(2))to B_(4)C ceramics respectively.CeB_(6)was introduced into B_(4)C-CeB_(6) composites by in-situ reaction.The effects of CeO_(2)addition on the microstructure and mechanical properties of B_(4)C-CeB_(6) composites were studied in detail.The relative density and mechanical properties of B_(4)C-CeB_(6) composites increase with the increase of CeO_(2) content(no more than 4%).However,when the amount of CeO_(2) increases(more than 4%),the increase of CO gas will lead to the decrease of the relative density and hardness of the composites.When the content of CeO_(2) is low,the fracture toughness of CeB_(6) is higher than that of pure B_(4)C,more energy will be consumed when the crack passes through the CeB_(6) phase,which improves the fracture toughness of the composite;When the CeO_(2) content is high,the crack deflection caused by the mismatch of thermal expansion coefficients of CeB_(6) and B_(4)C is the main toughening mechanism.In addition,some toughening mechanisms such as crack bridging and crack branching were found.The relative density,Vickers hardness,flexural strength and fracture toughness of B_(4)C-CeB_(6) composite ceramics reach 98.6%,39.5 GPa,396 MPa and 5.96 MPa·m^(1/2)respectively.