B4C含量对ZrB2陶瓷微观结构及力学性能的影响

针对ZrB₂陶瓷粉末在球磨时易掺入ZrO2,影响ZrB₂陶瓷烧结致密化的问题,添加B₄C作为烧结助剂,采用无压烧结法制备ZrB₂陶瓷材料,研究B₄C含量(w(B₄C),下同)对材料微观形貌、硬度与抗弯强度的影响。结果表明,B₄C通过与晶粒表面的ZrO2发生反应,抑制ZrB₂晶粒粗化,减小晶粒尺寸,从而提高烧结致密度。随B₄C含量增加,ZrB₂陶瓷的晶粒尺寸和相对密度逐渐增大,抗弯强度和硬度先升高后降低。当w(B₄C)为7%时,ZrB₂晶粒细小,材料的抗弯强度和硬度(HV)达到最大,分别为242 MPa和12.65 GPa。w(B₄C)增加至9%时,出现晶粒异常长大,材料力学性能下降。

Effects of B4C content on the microstructure and mechanical properties of ZrB2 ceramics

Aiming at the problem that ZrB₂ ceramics powder were easily mixed with ZrO2 during ball milling,which affected the sintering denstification of ZrB₂ ceramics,B₄C was introduced as sintering additive,and ZrB₂ ceramics were prepared by pressureless sintering.The effects of B₄C content on the microstructure and mechanical properties of the materials were investigated.The results show that B₄C can inhibit grain coarsening and reduce grain size by reacting with ZrO2 on the grain surface.With the increase of B₄C content,the grain size and relative density of the ZrB₂ ceramics increase gradually,while the flexural strength and hardness first increase and then decrease.When the mass fraction of B₄C is 7%,the grain size of ZrB₂ are fine,and the flexural strength and hardness of the material reach the maximum value,which are 242 MPa and 12.65 GPa respectively.As increasing the content of B₄C to 9%,the grains grow abnormally and the mechanical properties decrease.