核反应堆压力容器模拟钢中纳米富Cu相的变形特征

提高了Cu含量的核反应堆压力容器(reactor pressure vessel,RPV)模拟钢样品,经过880 cC水淬、660℃调质处理和400℃1000～4000 h的等温时效处理,观察到纳米富Cu相的析出;随后进行20%～30%冷轧变形,采用萃取复型(extractionreplica,ER)和高分辨透射电镜(high resolution transmission electron microscopy,HRTEM)的方法研究纳米富Cu相的变形特征.研究结果表明,镶嵌在α-Fe基体中的纳米富Cu相,在冷轧变形时的变形机制较为复杂,存在多种变形方式.当纳米富Cu相的晶体处于有利取向时,可以跟随基体一起发生滑移变形,表现为"软"颗粒的特性;当晶体处于不利取向时,会发生孪生变形,甚至诱发马氏体相变,有时生成"轮毂辐条"状的孪晶结构,大大提高了纳米富Cu相继续变形时的抗力,表现为"硬"颗粒的特征,因而析出纳米富Cu相会产生明显的强化作用.

Deformation Characterization of Nano-Scale Cu-Rich Precipitates in Reactor Pressure Vessel Model Steel

The nano-scale Cu-rich precipitates in reactor pressure vessel(RPV) model steel after water quenching,tempering and thermal aging at 400℃has been investigated by extraction replica(ER) and high resolution transmission electron microscopy(HRTEM ).Samples were cold-rolled by 20%～30% after aging to study the deformation characterization of Cu-rich precipitates.The results show that the deformation characterization of the nanometer Cu-rich precipitates is complicated due to the restriction of a-Fe matrix.Different deformation mechanisms are detected.When the Cu-rich precipitates are located in a favorable orientation,they will be deformed by slipping together with the deformation of a-Fe matrix to show the particles of "soft" characteristic.When the Cu-rich precipitates are located in an unfavorable orientation,they will be deformed by twinning to form the spoke-like twins within a Cu-rich precipitate, even a martensitic phase transformation induced by strain.In this case,the Cu-rich precipitates show the particles of "hard" characteristic.Therefore the precipitation hardening occurs after the formation of Curich precipitates inα-Fe matrix.