Microstructures and mechanical properties of carbon-added Ti composites fabricated by laser powder bed fusion or spark plasma sintering

The densification process plays a critical role in determining the microstructure and performance of Ti matrix com posites (TMCs). Herein, a comparative study was performed on a graphene oxide (GO)/Ti-6Al-4V composite fabricated by laser powder bed fusion (L-PBF) and spark plasma sintering (SPS). The flexible GO sheets were homoge neously decorated onto the Ti-6Al-4V powders via an electrostatic self-assembly without significantly changing the particle size or sphericity. Under high-energy laser irradiation, the GO sheets were completely dissolved into the matrix. The L-PBF-produced composite was composed of fine α ʼ martensite structures due to the rapid solidification and the solute carbon atoms. In contrast, the GO was reacted with Ti matrix and completely transformed into sub-micron TiC particles during SPS; the composite consisted of α ＋ β phases with randomly dispersed TiC. Moreover, the L-PBF-produced composite exhibited a higher hardness of 481 HV as compared with the SPS-produced one of 367 HV, attributing to the fine α ʼ microstructures and high residual stresses. The present work offers deep under-standing on the structural evolution of GO during high-temperature densifications, and shows new insights for fab rication of high-performance TMCs with tailored microstructures.