High-Temperature Compressive Properties of TiC-Added Mo-Si-B Alloys

High-temperature compressive properties of two TiC-added Mo-Si-B alloys with nominal compositions of Mo-5Si-10B-7.5TiC (70Mo alloy) and Mo-6.7Si-13.3B-7.5TiC (65Mo alloy) (at.%) were investigated. The alloys were composed of four constituent phases: Mo solid solution (Mo-ss), Mo5SiB2, (Mo,Ti)C, and (Mo,Ti)(2)C. The primary phases of the 70Mo and 65Mo alloys were Mo-ss and T-2, respectively. The compressive deformability of the 65Mo alloy was significantly limited even at 1600A degrees C because of the elongated, coarse primary T-2 phase, whereas the 70Mo alloy had good compressive deformability and a high strength in the test-temperature range of 1000-1600A degrees C; the peak stresses were 1800 MPa at 1000A degrees C, 1230 MPa at 1200A degrees C, and 350 MPa at 1600A degrees C. At and above 1200A degrees C, the peak stress values were more than double those of Mo-6.7Si-7.9B, Ti-Zr-Mo, and Mo-Hf-C alloys. The plastic strain in the 70Mo alloy at temperatures lower than the ductile-brittle transition temperature of T-2 was generated by plastic deformation of not only Mo-ss but also of (Mo,Ti)C and (Mo,Ti)(2)C. This work indicates that (Mo,Ti)C and (Mo,Ti)(2)C play an important role in determining the high-temperature strength and deformation properties of TiC-added Mo-Si-B alloys.