W/Ti含量对钢铁基复合材料微观组织和相变的影响规律

Effect of W/Ti Content on the Microstructure and Phase Transformation of Iron Matrix Composites

摘要:

以Fe、Ti、W和石墨粉为原料，采用真空烧结技术制备铁基复合材料。通过改变粉末中的W/Ti原子比，探究其对复合材料组织和相变的影响规律。结果表明：球磨后的粉末活性有所增加，并出现Ti_xW_1-x不稳定过渡相；材料的相变反应温度会随着粉末中W含量增加而升高，DSC曲线尖锐的放热峰会逐渐变宽、变缓，剧烈的反应得到控制；粉末经烧结后会生成TiC、WC和Ti₄WC₅等增强相，当粉末的W/Ti比从2∶8增加至4∶6时，反应产物中3种增强相的占比从84.09%增加至93.07%，生成物中WC的占比从32.45%迅速增加到78.5%。此外，由于复合材料组织中多种物相的存在，彼此间的取向差异会引起组织中出现微应变。随着粉末中W/Ti比的增加，复合材料组织中的微应变逐渐增大；与粉末W/Ti比为2∶8制得的复合材料相比，粉末的W/Ti比为4∶6时制备的复合材料组织中的微应变提高了2.84倍。因此，通过调节W/Ti含量可实现对钢铁基复合材料微观组织和增强相的优化。

Abstract:

Using the Fe， Ti， W and graphite powders as raw materials， the iron matrix composites were prepared by vacuum sintering technology in this study. By changing the W/Ti atomic ratio in the mixed powders， the effects on the microstructure and phase transition of the composites were investigated. The results showed that the activity of the powders increased after ball milling， and the unstable transition phase of Ti_xW_1-x appeared. The phase transition reaction temperature of the material increased with the increase of W content in the powder， and the sharp exothermic peak gradually became wider in the DSC curves， and the violent reaction could be well controlled. Reinforcing phases such as TiC， WC and Ti₄WC₅ were formed after the sintering processes. When the W/Ti ratio of the powders increased from 2：8 to 4：6， the proportion of the three reinforcing phases in the reaction product increased from 84.09% to 93.07% and the proportion of WC in the reactant increased rapidly from 32.45% to 78.5%. Furthermore， due to the presence of multiple phases in the microstructure of the composites， the difference in orientation between them could cause micro-strains in the microstructure. The micro-strains in the composite structure gradually increased with the increase of the W/Ti ratio in the powder. Compared with the composites prepared with powder W/Ti ratio of 2∶8， the micro-strains in the microstructure of the composites prepared with powder W/Ti ratio of 4∶6 increased by 2.84 times. Thus， the microstructures and phases of the iron matrix composites could be tailored by adjusting the W/Ti ratios.