摘要
研究了ЭП866钢650℃下经最长2 000 h时效处理后组织和力学性能的变化规律,并运用Thermo-Calc热力学软件研究了钢中铬质量分数变化对σ相平衡析出的影响。结果表明,650℃长期时效后,钢中的析出相主要为M_（23）C_6、MX、Laves和σ相,同时发生了马氏体板条回复及析出相的粗化。材料的强度和硬度在500 h时效时间内下降较快,主要受析出相粗化和组织回复共同作用的影响;时效时间延长后,由于硬脆的σ相大量析出,强度和硬度缓慢下降。冲击吸收能量在1 000 h时效时间内呈下降趋势,主要受Laves相粗化和链状分布的M_（23）C_6的影响,时效时间延长后,组织回复引起软化的作用增强,冲击吸收能量又略有升高。Thermo-Calc计算结果表明,时效过程中σ相的析出与铬元素在晶界上的偏聚有关。
Effect of aging at 650 ℃ for up to 2 000 h on microstructure and mechanical properties of ЭП866 steel was investigated,and Thermo-Calc software was used to study the effect of Cr content on the equilibrium precipitation behavior of σ phase. The results showed that after long-term aging at 650 ℃,precipitation phases in the steel consist of M_（23）C_6、MX、Laves and σ phase. In addition,martensitic lath recovery and the coarsening behavior of precipitates also occurred.The sharp decrease of hardness and strength after aging for 500 h could be attributed to the combined effects of the coarsening of precipitates and the recovery of microstructure. However,these two properties decreased slowly with longer aging time,due to the large number of precipitation of σ phase,which was characterized as a hard and brittle phase. The impact energy decreased during aging for 1 000 h,resulting from the coarsened Laves phase and M_（23）C_6 particles distributed in chain-shape. Additionally,the softening effect by microstructure recovery brought about higher impact energy after longer aging time. Results from Thermo-Calc calculations show that the precipitation of the σ phase in this steel is related to segregation of Cr in the vicinity of grain boundaries during aging.
出处
《钢铁》
CAS
CSCD
北大核心
2018年第2期60-66,共7页
Iron and Steel
基金
国家重点研发计划资助项目(2016YFB0300203,2016YFB0700505)
关键词
ЭП866
长期时效
组织
力学性能
ЭП866
long term aging
microstructure： mechanical properties
