亚稳相对定向凝固Ni-Si共晶腐蚀行为的影响

Effect of Metastable Phase on Corrosion Behavior of Direc-tionally Solidified Ni-Si Eutectic Composites

摘要:

采用改进的Bridgman定向凝固技术制备了凝固速率为25 μm/s的Ni-Si共晶复合材料。由于在凝固过程中不可避免地会产生亚稳相Ni₃₁Si₁₂，采用退火工艺以减少亚稳相的含量，并利用电化学阻抗谱和电位动力学极化技术分析了材料在25 ℃、7%（质量分数）H₂SO₄溶液中的耐腐蚀性，并进行了等效电路分析。结果表明，退火处理（1050 ℃、4 h）改善了亚稳相Ni₃₁Si₁₂的含量和分布，退火后Ni-Si共晶的钝化性能和耐腐蚀性提升。亚稳相的含量越少，耐腐蚀性能越强。

Abstract:

The modified Bridgman directional solidification technique was used to prepare the Ni-Si eutectic composites at solidification rate of 25 μm/s. However, the formation of metastable phase Ni₃₁Si₁₂ was inevitably during solidification process. Annealing treatment was conducted to reduce the number of metastable phases. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used to analyze the corrosion resistance of Ni-Si eutectic composites in the 7wt% H₂SO₄ solution at 25 °C. The equivalent circuit was analyzed. Results show that the passivation performance and corrosion resistance behavior of Ni-Si eutectic composites are improved after annealing at 1050 °C for 4 h, which is mainly attributed to improvement of content and distribution of metastable phase Ni₃₁Si₁₂. The less the content of metastable phase, the stronger the corrosion resistance.