Microstructure and tensile behavior of hybrid nano-micro SiC reinforced iron matrix composites produced by selective laser melting

The fully dense nano/micro-scaled SiC reinforced iron matrix composites parts were fabricated by selective laser melting (SLM). Scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were used to investigate surface morphology, phase structure and microstructure of the SLM parts. It was found that after addition of SiC into the Fe matrix, the obvious liquid front disappeared and some small particles were seen at the surface, due to the change in local melt instability and viscosity. The crystalline structure of iron was not changed after SiC addition. But the diffraction peaks of Fe/SiC composite exhibits much broadening and much decrease in intensity and other peaks like (2 0 0) disappear. With the hybrid SiC particulates, structural modification has been observed with the formation of transformation products. Moreover, the presence of nanosized iron grains and amorphous iron was observed, besides the retained micro-scaled and nanosized SiC particles. The tensile tests of the SLM-fabricated specimens were measured. The tensile results showed that SLM-fabricated Fe/SiC specimens display much higher strengths than pure iron, with a yield strength 302 ± 11 MPa and ultimate tensile strength up to 764 ± 15 MPa.