Effects of ZrC content on the synthesis of MAX phase and mechanical properties of Cf-C-SiC-Ti3SiC2-ZrC composites

Abstract

In this research synthesis of Ti3SiC2 nano-laminate, effects of Al and ZrC on the amount and morphology of the synthesized MAX phase and mechanical properties of the Cf-C-SiC, Cf-C-SiC-Ti3SiC2 and Cf-C-SiC-Ti3SiC2-ZrC composites, fabricated by LSI method, were investigated. The infiltration process was conducted at 1500 °C for 30 min and then the samples were annealed at 1350 °C. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were utilized in order to investigate the phase composition and microstructure of the samples, respectively. The results showed that the sample containing Al, had the largest amount of synthesized MAX phase and also addition of ZrC led to the decrease of intensities of MAX phase peaks. Among the samples, Cf-C-SiC-Ti3Si(Al)C2 had the best mechanical properties compared to the others. Bending strength, interlaminar shear strength and fracture toughness of this sample were 505 MPa, 34 MPa and 19.1 MPa m1/2 respectively. The results confirmed that the mechanical properties were decreased by addition of ZrC. Among ZrC-containing samples, the sample containing 10 vol% ZrC has shown the least decrease properties including the bending strength of 369.11 MPa, interlaminar shear strength of 26 MPa and fracture toughness of 16.9 MPa m1/2. Addition of ZrC phase caused pseudo-plastic behavior appearance in the force-displacement curve and led to fibers pull-out and also displacement enhancement. Microstructural observations confirmed the plate-like morphology of synthesized MAX phases. Furthermore, the distance between layers decreased and MAX phase size increased respectively by addition of Al. Also MAX phase size decreased by increasing the ZrC content. It was confirmed that the MAX phase-containing samples can tolerate various micro-deformation mechanisms including: crack deflection, bending and delamination of lamellae, kink boundary and laminate fracture. These mechanisms led to the toughening of the composites.