(1. 北京科技大學(xué) 國家材料服役安全科學(xué)中心，北京 100083；
2. 上海大學(xué) 材料科學(xué)與工程學(xué)院，上海 200072)
摘 要: 采用取向成像顯微技術(shù)對鎳基690合金U彎樣品及經(jīng)退火處理后樣品進(jìn)行分析，研究對U彎樣品進(jìn)行表面晶界工程處理(GBE)的方法。結(jié)果表明：U彎樣品沿厚度方向上存在形變量梯度，致使退火后樣品的晶界網(wǎng)絡(luò)在厚度方向上產(chǎn)生規(guī)律變化，局部區(qū)域(約10%拉伸變形層區(qū)域)形成高比例低∑重合位置點(diǎn)陣(CSL, ∑≤29)晶界(約80%)。彎曲形變量對再結(jié)晶形核密度及孿晶形成幾率的影響決定GBE處理效果，GBE處理的合適變形量稍大于再結(jié)晶的臨界變形量：形變量過小時(shí)，不利于提高孿晶形成幾率，甚至不發(fā)生再結(jié)晶；形變量過大時(shí)，不利于形成大尺寸的晶粒團(tuán)簇，都不利于形成高比例低∑CSL晶界。
關(guān)鍵字: 鎳基690合金；晶界工程；U彎；低∑-CSL晶界；晶界網(wǎng)絡(luò)
（1. National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China;
2. School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China）
Abstract:The grain boundary networks of U-bended and annealed specimens were characterized using orientation image microscopy (OIM) in Ni-based alloy 690, the surface grain boundary engineering (GBE) was investigated. The results show that the deformation amount vary in thickness direction of the bended specimen, resulting in changes of the grain boundary network characteristics in the thickness direction. A region including high proportion of low-∑ coincidence site lattice (CSL, ∑≤29) boundaries (about 80%) is formed, which is the layer with about 10% tension of U-bending. Additionally, the deformation amount has a significant effect on the nucleus density and twinning frequency during recrystallization, furthermore influencing the grain boundary network after GBE. A deformation is slightly larger than the critical deformation condition of recrystallization, which can optimize the grain boundary network during GBE. Lower deformation will decrease the frequency of twinning, even avoiding recrystallization. Higher deformation will increase the recrystallization nucleus density, which results in smaller grain-cluster and higher random boundary density. Both the two conditions are disadvantageous factors for forming high proportion of low-∑CSL grain boundaries.
Key words: Ni-base 690 alloy; grain boundary engineering; U-bending; low-∑CSL grain boundaries; grain boundary network
