机械合金化和添加微量Y2O3对制备细晶钨合金

采用机械合金化、添加微量Y2O3和冷等静压、液相烧结工艺制备Ф25mm的晶粒度为3～4μm的细晶93W-4.9Ni-2.1Fe(质量分数%,下同)合金棒材,研究粉末机械合金化、添加微量Y2O3、烧结温度和保温时间对合金棒材烧结致密化和显微组织的影响。结果表明:在1480℃液相烧结时钨晶粒发生明显球化,在此温度下降低保温时间对控制钨晶粒长大有较大影响,保温时间为30min时,钨晶粒尺寸为5～8μm;保温时间为60min时,钨晶粒为8～10μm。添加微量稀土氧化物Y2O3可以进一步有效地抑制晶粒的长大,降低合金的钨晶粒尺寸和提高组织均匀性,在1480℃烧结60min时,钨晶粒为3～4μm,而且晶粒尺寸分布更均匀。

Effect of Mechanical Alloying and Trace Y2O3 Addition on Microstructure of Fine-Grain Tungsten Heavy Alloy Rods

Fine-grained 93W-4.9Ni-2.1Fe tungsten heavy alloy rods with diameter of 25 mm were fabricated by mechanical alloying (MA), trace Y_2O_3 adding, cold isostatic pressing and sintering. The tungsten grain size of the as-sintered alloy was 3-4 μm. The effects of MA, addition of trace Y_2O_3 and sintering process on the densification and microstructure of the alloy were studied. It is indicated that the tungsten grains were spheroidized during liquid phase sintering at 1480 oC, and at this temperature the sintering time greatly affects the control of tungsten grains growth. The grain size of the tungsten alloy sintered at 1480 ℃ for 30 min was 5-8 μm. The grain size of the tungsten alloy was 8-10 μm when the sintering time was 60 min at 1480 ℃. The addition of trace Y_2O_3 further prevents the tungsten grain growth, effectively refining the tungsten grain and inducing a homogeneous microstructure. The tungsten grain size of tungsten alloy sintered at 1480 ℃ for 60 min with addition of Y_2O_3 was 3-4 μm and more uniform.