纳米晶W-Ni-Fe复合粉末及其烧结过程中的固溶特性

采用溶胶喷雾干燥-热还原法制备了50W-35Ni-15Fe(质量分数,%,下同)纳米晶复合粉末。利用X射线衍射及微区组织的能谱(EDAX)分析,揭示了纳米晶W-Ni-Fe复合粉末及其烧结过程中的固溶特性。研究发现:纳米晶50W-35Ni-15Fe复合粉末中,W在γ-(Ni,Fe)相中的固溶度达到了15%,Ni、Fe元素在W中的固溶度达到了2.4%,形成了超饱和固溶体;随着温度的升高,W的超饱和固溶体W(Ni,Fe)发生Ni、Fe元素的脱溶。而W在γ-(Ni,Fe)相中的固溶度随温度的升高而进一步增加,在1300℃以后基本维持在29%左右;稀土La的加入在低温阶段对W在γ-(Ni,Fe)相中的固溶度影响不大,在1200℃以上使固溶度有一定的降低。

Solid Solution Characteristics of Nano-crystalline W-Ni-Fe Powders during the Preparation and Sintering Processes

Nano-crystalline 50W-35Ni-15Fe(mass fraction,similarly hereinafter) composite powders were synthesized by sol-spray drying and subsequent hydrogen reduction process.The solid solution characteristics of the nano-crystalline powder during the preparation and sintering processes were characterized by XRD and EDAX analysis.The result shows that the solubility of W in γ-(Ni,Fe) phase is approximately 15% in the final obtained nano-crystalline 50W-35Ni-15Fe composite powders,while only 2.4% Ni and Fe atoms are dissolved in W lattice,forming the supersaturated solid solution W(Ni,Fe).With the sintering temperature increasing,Ni and Fe atoms precipitate from the metastable W(Ni,Fe) phase.The solubility of W in γ-(Ni,Fe) is elevated a lot with further increasing the sintering temperature and eventually reaches a stable solubility of about 29% at 1300℃.In addition,the solubility of W into γ-(Ni,Fe) is independent on the addition of La during the low temperature sintering,but the solubility will exhibit a decreasing tendency if the sintering temperature is above 1200 ℃.