摘要
以TaC、Ta和Ni粉为原料,采用热压法制备名义成分为TaC_(0.3)-20%(体积分数)Ni的复合材料,研究热压温度在1 100~1 900℃范围内变化对TaC+Ta反应进程、物相、显微组织和力学性能的影响。根据压头位移,致密化过程可分为四个阶段,反应致密化主要发生在第二阶段950~1 700℃,充分反应后,生成平衡物相Ta_2C和Ni_3Ta相。在1 600℃/30 MPa/30 min条件下热压,材料能够完全致密,并形成均匀的细晶组织(平均晶粒尺寸小于5μm),测量的抗弯强度和断裂韧性分别为(689±71) MPa和(5.72±0.57) MPa·m~(1/2)。当热压温度超过Ni_3Ta熔点(约1 500℃)较多时(例如T=1 700℃),熔化的Ni_3Ta被挤出而获得几乎单相的Ta_2C陶瓷材料。1 900℃条件下制备的复合材料中晶粒长大到40~50μm,虽然断裂韧性值可达到(6.96±0.38) MPa·m~(1/2),但粗大晶粒作为结构缺陷诱发裂纹扩展,使抗弯强度略降低到(546±44) MPa。
Ta 2C ceramic based composites with a nominal composition TaC 0.3-20%Ni were prepared by hot pressing,using TaC,Ta and Ni powders as starting materials.Effects of hot-pressing temperatures in range of 1100~1900℃on densification,phase formation,microstructure and mechanical properties of the composites were investigated.The hot press ram travel showed a four-stage densification process,in which the largest proportion of densification took place in the second stage corresponding to a temperature window from 950 to 1700℃.After complete reaction,the constituent phases in equilibrium were Ta 2C and Ni 3Ta.The sample prepared by hot pressing at 1600℃for 30 min under 30 MPa evidenced the equilibrium phases and the microstructure of this material was consisted of uniformly fine grains with an average grain size of about 5μm to reach a flexural strength and fracture toughness value of(689±71)MPa and(5.72±0.57)MPa·m 1/2,respectively.Hot pressing at temperatures too much higher than the melting point of Ni 3Ta(~1500℃),for instance at T=1900℃,complete Ni 3Ta loss due to squeezing out of the Ni 3Ta liquid could result in a Ta 2C single-phase material;Significant enlargement of the Ta 2C grains(average diameter~40~50μm)at high temperatures may have caused premature crack initiation and propagation,slightly decreasing flexural strength while preserving or even increasing fracture toughness.The flexural strength and fracture toughness of the 1900℃sample was(546±44)MPa and(6.96±0.38)MPa·m 1/2,respectively.
作者
魏彦博
管政
刘利盟
Wei Yanbo;Guan Zheng;Liu Limeng(School of Materials Science and Engineering,North Minzu University,Yinchuan 750021,China)
出处
《山东化工》
CAS
2023年第5期5-10,共6页
Shandong Chemical Industry
基金
国家自然科学基金(52062001)
宁夏青年拔尖人才项目
国家民委中青年英才项目。
