Hf对ODS-FeCrAl合金微观组织及性能的影响

为研究少量添加的Hf对ODS-FeCrAl合金微观组织及性能的影响，通过机械合金化和后续的热等静压工艺研制两种14Cr ODS FeCrAl合金，对其进行微观结构、力学性能、1 200 ℃空气抗氧化性能和1 200 ℃水蒸气抗腐蚀性能测试。TEM结果表明，两种合金中YAlO3氧化物析出相细小弥散，而Hf的添加促进合金基体中生成颗粒尺寸更加细小的Y2Hf2O7纳米氧化物。由于纳米氧化物Orowan的强化机制，两种合金均具有优异的室温与高温力学性能。XRD和SEM结果表明，两种合金经过1 200 ℃空气氧化与1 200 ℃水蒸气腐蚀后，表面均形成均匀致密的α Al2O3膜，对合金起保护作用。Hf添加有利于合金在1 200 ℃水蒸气腐蚀条件下形成更加均匀的α Al2O3膜，抑制Al3+的向外扩散，避免合金内部晶界处形成空穴。

Effect of Hf on Microstructure and Property of ODS-FeCrAl Alloy

In order to study the effect of a small amount of Hf on the microstructure and property of ODS FeCrAl alloy, two kinds of 14Cr ODS FeCrAl alloys were prepared by mechanical alloying and subsequent hot isostatic pressing. The microstructure, mechanical property, air oxidation resistance at 1 200 ℃ and steam corrosion resistance at 1 200 ℃ were tested. TEM results show that the oxide precipitate phases of YAlO3 oxide in the two kinds of alloys are fine and dispersed, while the addition of Hf promotes the formation of Y2Hf2O7 nano oxide with finer particle size in the alloy matrix. Due to the Orowan strengthening mechanism, the two kinds of alloys have excellent mechanical property at room temperature and high temperature. The results of XRD and SEM show that the surface of the two kinds of alloys form uniform and dense α Al2O3 film after air oxidation at 1 200 ℃ and steam corrosion at 1 200 ℃, which protects the alloy. The addition of Hf is beneficial to form more uniform α Al2O3 films under the condition of 1 200 ℃ steam corrosion, to inhibit the outward diffusion of Al3+, and to avoid the formation of cavities at the internal grain boundary of the alloy.