Preparation of two-scale network-structured (TiC+(TiZr) 5Si3 )/TA15 composites using polycarbosilane derived ceramic phases

In this study, a (TiC+(TiZr)5Si3)/TA15 composite was fabricated using polycarbosilane (PCS) and TA15 alloy powder as raw materials through spark plasma sintering (SPS). The high-temperature decomposition products of PCS reacted with the TA15 matrix, forming in-situ reinforcements: TiC particles distributed along the original boundaries of the TA15 powder and (TiZr)5Si3 particles located at the alpha/(3 interfaces. The composite with 0.5 wt % PCS exhibited notable improvements in tensile strength, ductility, and uniform elongation, achieving values of 1085 MPa, 10.5 %, and 6.7 %, respectively-representing enhancements of 10.6 %, 26.5 %, and 139.3 % compared to pure TA15 alloy. However, further increases in PCS content resulted in reduced ductility; at 1.5 wt% PCS, the tensile strength reached a peak of 1254 MPa, while elongation dropped to 4.1 %. When the PCS content reached 2 wt%, the composite exhibited brittle fracture behavior, primarily due to excessive in-situ reinforcement, which caused significant dislocation accumulation and a reduction in colony size. Additionally, at elevated temperatures, the composite demonstrated substantial strength improvement, with the composite containing 2 wt% PCS achieving a strength of 704 MPa, a 48.2 % increase compared to TA15 alloy, while retaining a tensile elongation of 9.3 % due to matrix softening.