Abstract: The 2 mm-thick SiC_p/LD2 composite plates were electron beam welded at different heat inputs. The microstructures of welds were investigated by OM, TEM, SEM, and XRD, and the properties of welds were measured with MTS-810 testing system. The results show that the quantity and size of acicular Al₄C₃ precipitates (interfacial reaction product) decrease with the heat input decreasing. When the heat input lowers to 30 J/mm, the formation of needle-like Al₄C₃ can be prevented. The distributions of SiC in the fusion zones are more uniform than that in as-received composite. TEM analysis reveals that there are Al₄C₃ crystals on the surface of every survived particle, the needle-like Al₄C₃ observed under the optical microscope consists of many tabular Al₄C₃ crystals which have different orientations. With the increase of heat input, the fracture mechanism changes from ductile one to brittle one, the quantity of fractured particles on the fracture face decreases and the strength and ductility of the weld decrease.

Key words:  SiC_p/LD2 composite; electron beam welding; interfacial reaction