感应淬火条件下Cu-Ni低碳低合金钢的强化机制

采用电子背散射衍射(EBSD)、扫描电镜(SEM)、X射线衍射仪(XRD)和TEM原位拉伸试验等分析了含Cu-Ni低碳低合金钢经感应加热淬火+时效的显微组织及Cu粒子与强度的关系，并对强化机制进行了量化分析。结果表明，试验钢经980℃感应淬火+670℃时效的综合性能优于1030℃感应淬火+680℃时效；含Cu-Ni低碳低合金钢呈现多种强化机制，包括沉淀强化、晶界强化、位错强化、固溶强化和点阵阻力，其中沉淀强化与晶界强化为主要强化机制，二者占比超过70%;理论计算出Cu粒子在Orowan机制中最小临界尺寸为28.50 nm,在TEM原位拉伸中观测到位错在Cu粒子周围发生塞积，并按照绕过机制与尺寸为44.57 nm的Cu粒子发生交互作用。

Strengthening mechanism of Cu-Ni-bearing low-carbon low-alloyed steel under induction quenching treatment

Microstructure and the relationship between Cu particles and strength of the Cu-Ni-bearing low-carbon low-alloyed steel under induction-heat quenching and aging was analyzed by means of electron back-scatter diffraction(EBSD), scanning electron microscope(SEM), X-ray diffractometer(XRD) and in-situ tension in transmission electron microscope(TEM), and the quantitative analysis of strengthening mechanism was discussed. The results show that the comprehensive properties of the tested steel after induction quenching at 980 ℃ and aging at 670 ℃ is better than that induction quenching at 1030 ℃ and aging at 680 ℃.There are many strengthening mechanisms for the Cu-Ni-bearing low-carbon low-alloyed steel, including precipitation strengthening, grain size strengthening, forest dislocations strengthening, solid solution strengthening and lattice friction stress, among which precipitation strengthening and grain size strengthening are the main strengthening method, accounting for more than 70%. In theoretical calculation, the minimum critical size of Cu particles is 28.50 nm in Orowan mechanism, and the dislocation pile-up around the Cu particles, and they interact with a Cu particle with size of 44.57 nm according to the bypass mechanism during in-situ tension in TEM.