摘要
用OM、SEM和TEM等方法研究了超超临界电站用Sanicro25钢的蠕变机制。结果表明,这种钢的最小蠕变速率随着温度的升高和应力的增大而提高。根据最小蠕变速率特征得出表观应力指数为7.6~8.2,表观激活能为496.7~531.8 kJ/mol。在蠕变过程中在晶内弥散析出的纳米级Cu-rich相和MX相阻碍位错运动,导致蠕变门槛值应力的出现。用线性外延法求出的门槛值应力,随着温度的升高而减小。用门槛值将蠕变本构方程修正为ε̇_(min)=A_(2)[(σ-σ_(th))/G]^(n)exp(-Q/RT),可将不同温度下的最小蠕变速率归一化;同时确定真实应力指数(n=5)和真实表观激活能(Q=286.6 kJ/mol约等于γ-Fe自扩散激活能),从而判别出实验参数下材料的蠕变机制为点阵自扩散协助的位错攀移。
The creep behavior at 130~240 MPa/973~1023 K of Sanicro25 steel for ultra-supercritical power plants were investigated by OM,SEM and TEM.The results showed that the minimum creep rate increases with the increasing temperature and applied stress.Based on the characteristics of the minimum creep rate,the stress exponents of 7.6~8.2 and the apparent activation energy of 496.7~531.8 kJ/mol can be acquired for the creep process.Nano-scale Cu-rich phase and MX phase precipitated in the matrix imped the dislocation motion,thus resulted in the emerging of creep threshold stress.The creep threshold stresses can be estimated by the linear extrapolation method,and which decrease with the increase in temperature.By invoking the concept of the threshold stresses to modify the constitutive equation,ε̇_(min)=A_(2)[(σ-σ_(th))/G]^(n)exp(-Q/RT),the normalization of the minimum creep rate can be acquired at various temperatures;Meanwhile,the true stress exponent(n=5)and the true apparent activation energy(Q=286.6 kJ/mol approximately equal to theγ-Fe self-diffusion activation energy)can be identified.The creep rate-controlling mechanism was determined to be dislocation climbing mechanism assisted by lattice self-diffusion.
作者
吕德超
曹铁山
程从前
周彤彤
赵杰
LV Dechao;CAO Tieshan;CHENG Congqian;ZHOU Tongtong;ZHAO Jie(School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,China)
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2023年第11期846-854,共9页
Chinese Journal of Materials Research
基金
国家自然科学基金(U1610256和51901035)。
