真空热压烧结温度对TiBw/TC4复合材料微观结构及性能的影响

The effect of vacuum hot-press sintering temperature on the microstructure and properties of TiBw/TC4 composites

  • 摘要: 钛基复合材料(TMCs)在航空航天等领域具有重要的应用前景,但其强度与塑性的协同优化仍是挑战。本文以细晶TC4为基体、粗晶TC4为软区,采用两步低能球磨结合真空热压烧结(HPS)工艺,制备了双峰异构TiB晶须增强TC4(TiBw/TC4)复合材料,系统研究了1100℃、1150℃、1200℃和1250℃四种热压烧结温度对材料致密化、微观组织、相组成、力学性能及断裂行为的影响。结果表明,随着热压烧结温度从 1100℃ 升高至 1250℃,复合材料的致密度先升高后趋于平稳,TiBw 分布趋于均匀,α 晶粒尺寸略有增大,β 相含量增加。然而,过低温度(1100℃)导致致密度不足,且 TiBw 易沿原始粉末边界偏聚,温度升高后原子扩散充分,团聚占比会显著下降;过高温度(1250℃)则引起晶粒粗化、界面弱化和TiBw长大粗化。相比之下,1200℃ 热压烧结能够在高致密基础上保持良好的界面结合与适中的晶粒尺寸,有利于形成异质界面和背应力强化效应。因此,该温度下制备的复合材料实现了强度与塑性的协同提升,综合力学性能最优,其平均抗拉强度达 1129.5±8.2 MPa,延伸率为 4.3±0.3%,表观断裂韧度为 37.9±1.7 MPa·√m。

     

    Abstract: Titanium matrix composites (TMCs) exhibit promising application prospects in aerospace and other fields, yet the synergistic optimization of their strength and ductility remains a challenge. In this paper, bimodal heterogeneous TiB whisker-reinforced TC4 (TiBw/TC4) composites were fabricated using fine-grained TC4 as the matrix and coarse-grained TC4 as the soft region via a two-step low-energy ball milling combined with vacuum hot pressing sintering (HPS) process. The effects of four hot pressing sintering temperatures (1100℃, 1150℃, 1200℃ and 1250℃) on the densification, microstructure, phase composition, mechanical properties and fracture behavior of the materials were systematically investigated. The results show that as the hot-press sintering temperature increases from 1100℃ to 1250℃, the density of the composite first rises and then levels off, TiBw becomes more evenly distributed, α grain size slightly grows, and the β phase content increases. However, too low a temperature (1100℃) leads to insufficient density, and TiBw tends to cluster along the original powder boundaries. When the temperature rises, atomic diffusion is sufficient, and the amount of agglomeration drops significantly. On the other hand, Excessively high temperatures (1250℃) cause grain coarsening, interface weakening, and TiBw growth and coarsening. In comparison, hot-press sintering at 1200℃ can maintain good interface bonding and moderate grain size on a high-density basis, which helps form heterogeneous interfaces and back-stress strengthening effects. Therefore, composites prepared at this temperature achieve both improved strength and ductility, with the best overall mechanical performance: average tensile strength of 1129.5±8.23 MPa, elongation of 4.3±0.3%, and apparent fracture toughness of 37.9±1.7 MPa·√m.

     

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