含Nb-Ti低碳微合金钢纳米碳化物析出行为

采用热膨胀仪、显微硬度计和透射电镜研究了等温温度对Nb-Ti微合金钢组织性能及析出行为的影响规律.结果表明,在不同温度下等温淬火均得到铁素体与马氏体的双相组织,且随着等温温度的降低,铁素体的体积分数逐渐增大.实验钢中存在两种主要的析出形态,分别为相间析出和弥散析出,且随着等温温度的降低,析出形态逐渐从相间析出向弥散析出转变.通过HRTEM确定相间析出碳化物具有Na Cl型晶体结构,晶格常数为0.432 nm,且与铁素体基体满足Baker-Nutting(B-N)关系.铁素体相的维氏硬度随着等温温度的降低而逐渐增大.

Precipitation Behaviors of Nanometer-sized Carbides in a Niobium-Titanium Contained Low-Carbon Steel

The microstructure， mechanical properties and precipitation behaviors in a low carbon Nb-Ti micro-alloyed steel were investigated using the dilatometer， Vickers-hardness tester and transmission electron microscope. The results showed that the microstructure of the experimental steel treated by an isothermal quenching process under different temperatures all mainly consisted of ferrite and martensite phases. The volume fraction of ferrite phase increased with the decrease of the isothermal temperature. Both of the interphase precipitation and supersaturated precipitation of carbides appeared in the samples treated by the isothermal quenching process. Along with the decrease of isothermal temperature， the precipitation form gradually changed from the interphase precipitation to supersaturated precipitation. Furthermore， the interphase-precipitated carbides had a NaCl-type crystal structure with a lattice parameter of 0.432nm and obeyed the Baker-Nutting (B-N) orientation relationship with respect to the ferrite matrix which confirmed by HRTEM. The Vickers-hardness of the ferrite increased with the decrease of the isothermal temperature.