奥氏体钢中不同尺寸纳米析出相对晶界的钉扎机制

项目名称： 奥氏体钢中不同尺寸纳米析出相对晶界的钉扎机制

项目编号： No.51501114

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 一般工业技术

项目作者： 赵冰冰

作者单位： 上海交通大学

项目金额： 25万元

中文摘要： 析出相对晶界的钉扎作用可以抑制晶粒长大，进而提高材料的力学性能。随着析出相尺寸达到纳米级，晶界析出相三叉线的影响变得显著，会改变析出相与晶界的作用方式。但迄今，纳米析出相对晶界的钉扎机制尚不清晰。本项目选择新型氧化铝保护层自发形成的奥氏体(Alumina-Forming Austenitic)耐热钢为模型材料，针对其中两种小于50纳米的析出相进行研究。通过不同温度下再结晶处理和蠕变测试，获得不同尺寸的纳米析出相，采用聚焦离子束定点加工的技术，制备含有所需晶界区域的样品，利用TEM显微表征，揭示MC析出相对晶界的钉扎方式和具有L12结构的含铜析出相在晶界上的形貌随尺寸变化的关系，区分三叉线影响下纳米析出相对晶界的不同钉扎机制，统计分析纳米析出相在晶界上的尺寸和间距与晶粒中尺寸和体积分数的关系，从而建立符合实际情况的钉扎力解析式，为利用纳米析出相调控材料微观结构及其力学性能提供科学依据。

中文关键词： 析出相；晶界；钉扎机制；三叉线

英文摘要： Introducing second-phase precipitates is one of the most commonly used methods to inhibit grain growth and achieve better mechanical properties in polycrystalline materials. With decreasing of the precipitate size, the impact of grain boundary-precipitate triple line is pronounced and can change the interaction between precipitates and grain boundaries. However, the pinning mechanism of nanoscale precipitates on the grain boundaries is not clear so far. This project will choose a new class of alumina-forming austenitic (AFA) heat-resistant steel as the model material, to study the interaction of grain boundaries with precipitates smaller than 50 nm. Nanoscale precipitates of different sizes will be achieved by different recrystallization and creep testing conditions. The specific areas containing grain boundaries will be prepared by focused ion beam (FIB) technique. With TEM characterization, this project will clarify the size-dependent pinning mechanism of MC-type and Cu-containing L12-type precipitates, distinguish different pinning mechanisms under the effect of grain boundary-precipitate triple line, and statistically analysis the size and distribution of nanoscale precipitates on the grain boundaries and within the grains. According to the experimental results, an analytical equation of the pinning force will be derived, and it is helpful for controlling the microstructure and improving mechanical properties by nanoscale precipitates.

英文关键词： Precipitate;Grain boundary;Pinning mechanism;Triple line