Effect of oxide species on their particle dispersion behavior and the strength properties of mechanically alloyed ODS ferritic steels

本课题研究了氧化物种类和基体相组织对机械合金化氧化物弥散强化铁素体钢强度性能的影响，并阐明了机械合金化后的氧化物种类和热处理对氧化物颗粒弥散行为和基体相组织的影响。研究了MA加工后的Y_2O_3、ZrO_2、TiO_2、MgO和Al_2O_3 5种氧化物种类以及高温和低温两种热处理方式。结果表明，颗粒的分散行为是由氧化物的种类决定的，极小的Y_2O_3颗粒均匀分布在基体中。另一方面，ZrO_2、TiO_2、MgO和Al_2O_3的其他颗粒分布并不均匀，在一些地方存在大颗粒（直径200 ~ 300nm）。MA加工后的热处理不影响颗粒的分散行为，但对基体相的微观组织有很大的影响。在较高温度下的热处理使基体中出现了非常小的晶粒（包括亚晶粒）。细小的Y_2O_3颗粒分布均匀，晶粒尺寸非常小的微观组织使其具有最大的强度。

In the present research project, the effects of oxide species and microstructure of matrix phase on the strength properties of mechanically alloyed oxide dispersion strengthened ferritic steels were investigated and also the effects of oxide species and thermomechanical treatments just after the mechanically alloying procedure on the oxide particle dispersion behaviors and microstructure of matrix phase were clarified.Investigattion were made on the 5 kinds of oxide species of Y_2O_3, ZrO_2, TiO_2, MgO and Al_2O_3 and the 2 kinds of thermomechanical treatments after the MA processing, such as higher temeprature treatment and lower temperature one.It was clarified that the particle dispersion behavior was decided by the oxide specy and very tiny particles of Y_2O_3 distributed uniformly in the matrix. On the other hand, other particles of ZrO_2, TiO_2, MgO and Al_2O_3 did not necessarily distributed uniformly and in some places large particles (diameter : 200 to 300nm) existed. The thermomechanical treatments after the MA processing did not affect the particle dispersion behaviors, but had very large effects on the microstructure of matrix phase. The thermomechanical treatment at higher temperature introduced very small grains (including sub-grains) in the matrix. Uniform distribution of tiny partilces of Y_2O_3 and microstructure of very small grain size gave the largest strength.