B_(4)C-NbB_(2)复相陶瓷的SPS反应烧结及固溶强化

Reactive spark plasma sintering and solid solution strengthening of B_(4)C-NbB_(2) composite ceramics

以NbC和无定形B粉为原料,采用放电等离子烧结(SPS)法在2000℃/50 MPa条件下制备B_(4)C-NbB_(2)复相陶瓷,研究摩尔分数为0.1的TiC或ZrC替代NbC对复相陶瓷物相组成、致密度、显微结构和力学性能的影响。结果表明:以0.1的TiC或ZrC替代NbC后,反应烧结形成的TiB_(2),ZrB_(2)可与NbB_(2)分别固溶形成Nb 0.9 Ti 0.1 B_(2),Nb_(0.9)Zr_(0.1)B_(2)相。Ti,Zr固溶可有效提升复相陶瓷的烧结致密度,细化组织,获得优异的力学性能,且Zr固溶产生的效果更佳。B_(4)C-Nb_(0.9)Zr_(0.1)B_(2)复相陶瓷的致密度、三点抗弯强度、维氏硬度和断裂韧度分别为99.5%,676 MPa,31.0 GPa和5.5 MPa·m 1/2。致密度的提高、固溶强化和细晶强化是复相陶瓷性能提升的主要原因。

The B_(4)C-NbB_(2) composite ceramics were prepared by reactive spark plasma sintering(SPS)at 2000℃/50 MPa using NbC and amorphous B powders as raw materials.The effects of the partial replacement of NbC with 0.1 mole fraction of TiC or ZrC on the phase composition,relative density,microstructure,and mechanical properties of prepared ceramics were investigated.The results show that TiB_(2),ZrB_(2) formed during the reactive sintering process can be dissolved with NbB_(2)to form Nb 0.9 Ti 0.1 B_(2),Nb_(0.9)Zr_(0.1)B_(2) phases respectively.The formation of these solid solutions greatly improves the densification and mechanical properties of the composite ceramics with refined microstructure.The solution of ZrB_(2) has a better effect than that of TiB_(2).The relative density,3-point bending strength,Vickers hardness and fracture toughness of the prepared B_(4)C-Nb_(0.9)Zr_(0.1)B_(2) composite ceramics reach 99.5%,676 MPa,31.0 GPa and 5.5 MPa·m 1/2,respectively.The improved mechanical properties are attributed to the relative density enhancement,solid solution strengthening and microstructure refinement caused by the formation of solid solution.