Si元素含量对激光快速成形制备Nb-Si二元合金显微组织演变的影响

Effect of Si content on microstructural evolution of Nb-Si binary alloys fabricated by laser rapid forming

关键词:  Nb-Si二元合金  激光快速成形  显微组织  显微硬度  硅含量

Key words:  Nb-Si binary alloys  laser rapid forming  microstructure  mirco-hardness  Si content

摘要:

以铌粉和硅粉为原料，采用双通道同轴送粉制备了四种不同Si元素含量的Nb-Si二元合金，通过扫描电镜（SEM）、能谱仪（EDS）及X射线衍射仪（XRD）等分析了合金的显微组织演变及维氏硬度.结果表明，硅含量由7%增加至25%，合金的显微组织由Nb_SS+Nb₃Si转变为初生Nb_SS+（Nb_SS/Nb₃Si）共晶，硅含量为18%时，呈Nb_SS/Nb₃Si全共晶组织，硅含量提高至25%，合金中出现初生β-Nb₅Si₃相，并仍存在Nb_SS/Nb₃Si共晶组织.铌和硅粉末在激光作用下原位反应并快速凝固，显著细化了Nb-Si合金的显微组织.随硅含量增加，硅化物含量逐渐增加，合金显微硬度由746 HV增至1 342 HV.

Abstract:

The high purity Nb powder and Si powder were used as raw powder and four kinds of Nb-Si binary alloys with different Si content were fabricated by laser rapid forming with double coaxial powder feeding. The microstructural evolution and the micro-hardness of these alloys were investigated by scanning electron microscope (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction spectrometer (XRD). The results showed that with the content of Si increasing from 7% to 25%, the microstructure of Nb-Si binary alloys was changed from NbSS+Nb3Si to primary NbSS+ (NbSS/Nb3Si) eutectic structure. When the content of Si was 18%, the fabricated alloy is almost 100% NbSS/Nb3Si eutectic structure. With the Si content reaching 25%, the primary β-Nb5Si3 phase appears and the NbSS/Nb3Si eutectic structure still existed. Moreover, under the high energy of laser beam, the in situ reaction between Nb and Si powder would occur and the microstructure of Nb-Si alloys could be refined significantly. With the content of Si increasing, the volume fraction of silicide increased gradually and the micro-hardness of the alloys increased from 746 HV to 1 342 HV.