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<p>A novel method for fabricating W<sub>2</sub>B<sub>5−<i>x</i></sub>-based ceramics was developed using in situ SPS of W and B<sub>4</sub>C mixed powders with various molar ratios (1.6:1, 1.8:1, and 2:1). The results revealed a primary reaction between W and B<sub>4</sub>C yielding W<sub>2</sub>B<sub>5−<i>x</i></sub> and graphite, alongside a minor residual B<sub>4</sub>C phase. All compositions achieved near-full densification, featuring a uniform microstructure composed of coarse B<sub>4</sub>C grains and fine graphite particles dispersed within the boride matrix. Quantitative phase analysis indicated that increasing the W/B<sub>4</sub>C molar ratio led to a progressive increase of the W<sub>2</sub>B<sub>5−<i>x</i></sub> phase and a slight increase of graphite but a marked decrease of the residual B<sub>4</sub>C. Mechanically, Vickers hardness declined from 15.63 GPa  ± 0.40 GPa to 14.28 GPa  ± 0.34 GPa (under a 30&#xa0;kg load) as the W/B<sub>4</sub>C ratio increased, attributable to the diminished content of high-hardness B<sub>4</sub>C and the grain coarsening of the W<sub>2</sub>B<sub>5−<i>x</i></sub>. The flexural strength exhibited a similar downward trend, with a maximum value of 620.4&#xa0;MPa ± 45.4&#xa0;MPa achieved at a W/B<sub>4</sub>C ratio of 1.6. Remarkably, fracture toughness improved from 7.94&#xa0;MPa·m<sup>1/2</sup> ± 0.04&#xa0;MPa·m<sup>1/2</sup> to 9.21 MPa·m<sup>1/2</sup> ± 0.08&#xa0;MPa·m<sup>1/2</sup>, primarily because of graphite-induced toughening mechanisms such as crack deflection, branching, and bridging.</p>

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One-Step In Situ Spark Plasma Sintering (SPS) Synthesis of Dense W2B5−x Composites with High Strength and Toughness

  • 期刊论文

  • 发表日期：

    2025年11月26日

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  • Xiao-Hui Yang,
  • Kai-Fei Wang,
  • Guo-Hua Zhang

摘要

A novel method for fabricating W2B5−x-based ceramics was developed using in situ SPS of W and B4C mixed powders with various molar ratios (1.6:1, 1.8:1, and 2:1). The results revealed a primary reaction between W and B4C yielding W2B5−x and graphite, alongside a minor residual B4C phase. All compositions achieved near-full densification, featuring a uniform microstructure composed of coarse B4C grains and fine graphite particles dispersed within the boride matrix. Quantitative phase analysis indicated that increasing the W/B4C molar ratio led to a progressive increase of the W2B5−x phase and a slight increase of graphite but a marked decrease of the residual B4C. Mechanically, Vickers hardness declined from 15.63 GPa  ± 0.40 GPa to 14.28 GPa  ± 0.34 GPa (under a 30 kg load) as the W/B4C ratio increased, attributable to the diminished content of high-hardness B4C and the grain coarsening of the W2B5−x. The flexural strength exhibited a similar downward trend, with a maximum value of 620.4 MPa ± 45.4 MPa achieved at a W/B4C ratio of 1.6. Remarkably, fracture toughness improved from 7.94 MPa·m1/2 ± 0.04 MPa·m1/2 to 9.21 MPa·m1/2 ± 0.08 MPa·m1/2, primarily because of graphite-induced toughening mechanisms such as crack deflection, branching, and bridging.