摘要
目的 以选区激光熔化(SLM)制备的核用316L奥氏体不锈钢为研究对象,探究不同热处理工艺对其微观结构的调控机制,为设计新型的核用不锈钢材料提供实验依据。方法 使用X射线衍射仪、扫描电镜、透射电镜和电子背散射衍射等设备和技术手段,对600℃和1 050℃热处理后的SLM样品的合金成分、物相、晶粒形貌等开展表征和分析。结果 SLM技术成形的核用316L不锈钢内部无明显的裂纹和空洞,柱状及胞状亚晶粒清晰可见,各合金元素分布均匀;热处理温度的升高促进了亚晶粒中的应变能释放,导致部分亚晶界消失;当热处理温度为1 050℃时,小角度晶界比例急剧下降,亚晶粒发生重结晶。相比于传统的加工技术,SLM技术通过急速升温与降温的方法引入了高密度亚晶粒,利用位错强化和析出相强化机制提高了材料的硬度。结论 升高热处理温度可以提高激光增材制造核用316L不锈钢中大角度晶界的比例和铁素体相的含量。位错密度大幅度减小是不锈钢硬度降低的主要原因。
The work aims to take the 316L austenitic stainless steel fabricated by selective laser melting(SLM) as the research object to study the modification mechanisms of different heat treatment technologies on the microstructure and provide experimental evidence for the design of novel nuclear austenitic stainless steel. Equipment and technologies such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron backscattered diffraction were used to characterize and analyze the alloy composition, phase and grain morphology of SLM specimens after heat treatment at 600 ℃ and 1 050 ℃. There were no obvious cracks and cavities in 316L stainless steel formed by SLM technology, the columnar and cellular sub-grains were clearly visible, and the alloying elements were distributed uniformly. With the increase of heat treatment temperature, the strain energy in those sub-grains was released and a large number of sub-grain boundaries disappeared. When the heat treatment temperature increased to 1 050 ℃, the proportion of small-angle grain boundary decreased sharply, and sub-grains gradually recrystallized. In addition, compared with traditional casting 316L stainless steel, the rapid heating and cooling during the SLM process introduced high-density-sub-grains, thus improving the hardness of this material through dislocation strengthening and precipitation strengthening. As the heat treatment temperature increases, the proportion of large-angle grain boundary and the content of ferrite phase in nuclear 316L stainless steel by laser additive manufacturing also increase. The sharp decrease of dislocation density is the main reason for the decrease of stainless steel hardness.
作者
吕稀
王云鹏
王曦
高瑞
LYU Xi;WANG Yun-peng;WANG Xi;GAO Rui(Nuclear Power Institute of China,Chengdu 610000,China;School of Nuclear Science and Technology,Xi'an Jiaotong University,Xi'an 710049,China)
出处
《精密成形工程》
北大核心
2022年第7期77-85,共9页
Journal of Netshape Forming Engineering
基金
国家自然科学基金(12005256)
西安市科技计划(21ZCZZHXJS–QCY6–0007)。
关键词
激光增材制造
316L不锈钢
微观结构
强化机制
laser additive manufacturing
316L stainless steel
microstructure
strengthening mechanism
