Synthesis of W-Y2O3 alloys by freeze-drying and subsequent low temperature sintering:Microstructure refinement and second phase particles regulation  

作　　者：Weiqiang Hu Zhi Dong Liming Yu Zongqing Ma Yongchang Liu 

机构地区：[1]State Key Lab of Hydraulic Engineering Simulation and Safety,School of Materials Science and Engineering,Tianjin University,Tianjin 300072,China

出　　处：《Journal of Materials Science & Technology》2020年第1期84-90,共7页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.51822404 and 51574178);the Science and Technology Program of Tianjin(No.18YFZCGX00070);the Natural Science Foundation of Tianjin(No.18JCYBJC17900);the Seed Foundation of Tianjin University(Nos.2018XRX-0005 and 2019XYF-0066)。

摘　　要：In this work,W-Y2 O3 alloys are prepared by freeze-drying and subsequent low temperature sintering.The average size of reduced W-Y2 O3 composite powders prepared by freeze-drying method is only 18.1 nm.After low temperature sintering of these composite nanopowders,the formed W-Y2 O3 alloys possess a smaller grain size of 510 nm while maintaining a comparatively higher density of 97.8%.Besides a few submicron Y2 O3 particles(about 100-300 nm)with a W-Y-O phase diffusion layer on their surface distribute at W grain boundaries,lots of nano Y2 WO6 particles(<20 nm)exist in W matrix.Moreover,many Y6 WO12(<10 nm)particles exist within submicron Y2 O3 particles.The formation of these ternary phases indicates that some oxygen impurities in the W matrix can be adsorbed by ternary phases,resulting in the purification of W matrix and the strengthening of phase boundaries.The combined action of the above factors makes the hardness of the sintered W-Y2 O3 alloys in our work as high as 656.6±39.0 HV0.2.Our work indicates that freeze-drying and subsequent low temperature sintering is a promising method for preparing high performance W-Y2 O3 alloys.In this work,W-Y2 O3 alloys are prepared by freeze-drying and subsequent low temperature sintering.The average size of reduced W-Y2 O3 composite powders prepared by freeze-drying method is only 18.1 nm.After low temperature sintering of these composite nanopowders,the formed W-Y2 O3 alloys possess a smaller grain size of 510 nm while maintaining a comparatively higher density of 97.8%.Besides a few submicron Y2 O3 particles（about 100-300 nm） with a W-Y-O phase diffusion layer on their surface distribute at W grain boundaries,lots of nano Y2 WO6 particles（<20 nm） exist in W matrix.Moreover,many Y6 WO12（<10 nm） particles exist within submicron Y2 O3 particles.The formation of these ternary phases indicates that some oxygen impurities in the W matrix can be adsorbed by ternary phases,resulting in the purification of W matrix and the strengthening of phase boundaries.The combined action of the above factors makes the hardness of the sintered W-Y2 O3 alloys in our work as high as 656.6±39.0 HV0.2.Our work indicates that freeze-drying and subsequent low temperature sintering is a promising method for preparing high performance W-Y2 O3 alloys.

关 键 词：W-Y2O3 ALLOYS FREEZE-DRYING Low temperature SINTERING ULTRAFINE grains 

分 类 号：TG146.411[一般工业技术—材料科学与工程]