Nb-V低碳微合金钢等温淬火过程析出行为

Carbide Precipitation in Ferrite in Nb-V-Bearing Low-carbon Steel During Isothermal Quenching Process

利用透射电镜和纳米压痕仪对Nb-V低碳微合金钢中纳米碳化物的析出行为进行研究.研究结果表明,在700℃等温60 min试样中,可同时观察到相间析出和弥散析出,在其余试样中均未观察到相间析出,此规律可以通过相变过程中的扩散准则和台阶机制来解释.另外,纳米压痕结果显示在600℃等温20 min试样中,平均硬度为3. 87 GPa,650℃等温20 min试样中,平均硬度为4. 10 GPa,且通过TEM观察可以看出,650℃等温20 min中试样析出物数量密度较大且分布均匀.利用Ashby-Orowan机制对析出强化量进行计算,可以得出在650℃等温20 min试样中,析出强化对整个屈服强度的贡献量可以达到110 MPa.

Precipitation behavior of carbides in Nb-V HSLA steel during isothermal quenching process and its strengthening effect were studied using TEM and nanoindentation tests.The results indicated that interphase precipitations and dispersed precipitations could occur simultaneously in the specimen treated at 700℃ for 60 min,while in other specimens,only random precipitations were observed.This phenomenon can be explained by mass balance criterion and ledge mechanism during diffusional phase transformation.It was also found that the average hardness of the specimen held at 600℃ for 20 min was 3.87 GPa and was 4.10 GPa at 650℃ for 20 min.Moreover,the TEM results illustrated that carbide precipitations in the specimen holding at 650℃ for 20 min were dispersed more uniformly and the volume fraction of the precipitations was greater than that treated at 600℃ for 20 min.The strengthening contributed by the precipitations was 110 MPa in the specimen treated at 650℃ for 20 min,evaluated by the Ashby-Orowan mechanism.