高温退火温度对ODS-316L钢微观组织的影响

Effect of High Annealing Temperatureon Microstructure of ODS-316L Steel

氧化物弥散强化316L(ODS-316L)钢作为第4代核裂变反应堆候选高温结构材料之一,其热处理工艺将影响基体中纳米析出相的状态。本文采用机械合金化-放电等离子体烧结工艺制备了ODS-316L钢,研究了两种温度的高温退火处理对ODS-316L钢微观组织的影响。结果表明:经1100℃/1 h退火后,ODS-316L样品中部分长大为微米晶的晶界处出现了百纳米尺寸的Si—O析出相;而经1150℃/1 h退火后,ODS-316L样品中纳米晶几乎全部长大为微米晶,除粗化的Si—O析出相外,晶界处还出现了部分百纳米尺寸的Y—Si—O与Ti—O析出相。纳米晶的长大改善了材料的塑性,但在晶界或三叉晶界处粗化的析出相则破坏了材料的拉伸失稳特征。

Oxide dispersion strengthened 316L(ODS-316L)steel is one of the candidate high-temperature structural materials for the generationⅣnuclear reactors.The heat treatment process of ODS-316L steel will affect the nano-sized precipitates in the matrix.In this study,ODS-316L steel was fabricated with the mechanical alloying and spark plasma sintering processes,and annealed at two temperatures respectively.After the ODS-316L samples annealed at 1100℃/1 h,part of the ultrafine grains grow into the micron-sized grains,hundred-nanometer sized Si—O precipitates appear at the grain boundaries of the micron-sized grains.While for the ODS-316L samples annealed at 1150℃/1 h,the ultrafine grains almost grow into micron-sized grains.In addition to the coarsened Si—O precipitates,some hundred-nanometer sized precipitates of Y—Si—O and Ti—O also appear at the grain boundaries.The growth of ultrafine grains improves the plasticity of ODS-316L steel,while the precipitates coarsen at the grain boundaries or the trigeminal grain boundaries will give high damage to the tensile instability characteristics of ODS-316L steel.