Microstructure transition from lamellar eutectic to anomalous eutectic of Nb-Si based alloy powders by heat treatment and spark plasma sintering

作者：Guo, Yueling; Jia, Lina^*; Kong, Bin; Zhang, Shengnan; Sha, Jiangbo; Zhang, Hu

来源：Journal of Alloys and Compounds, 2017, 696: 516-521.

DOI：10.1016/j.jallcom.2016.11.236

• Nb-Si alloy
• High-temperature alloys
• Powder metallurgy
• Eutectic solidification
• Heat treatment
• Phase transitions

With a nominal composition of Nb-18Si-24Ti-2Cr-2Al (at%), pre-alloyed Nb-Si based alloy powders were fabricated by plasma rotating electrode processing (PREP). The phases and microstructures of the prealloyed powders subjected to spark plasma sintering (SPS) and heat treatments (HT) at 900 degrees C, 1000 degrees C, 1200 degrees C and 1400 degrees C for 1 h were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that main phases of the pre-alloyed powders were Nbss, beta Nb5Si3 and Nb3Si in the as-received state, but evolved into Nbss and alpha Nb5Si3 after either SPS or HT at > 1000 degrees C for 1 h. The as-received powders processed by PREP were distinguished by novel refined lamellar eutectic structures. The microstructure transition from lamellar eutectic to anomalous eutectic was triggered by either SPS or HT at > 1000 degrees C for 1 h, accompanied by a significant drop in hardness. The silicides in the anomalous eutectics were coarsened and smoothened after HT at a higher temperature. The corresponding microstructure transition mechanism was discussed.

• 出版日期2017-3-5
• 单位北京航空航天大学