Microstructure and Mechanical Properties of the ZrC-Added Mo-Si-B Alloys Prepared by Arc-Melting

ZrC-added Mo-Si-B alloys were prepared by arc-melting. After heat-treatment at 1800 degrees C for 24 h, their density and elastic moduli were measured, and their microstructure was evaluated. Moreover, high-temperature compression tests at 1400 degrees C and four. point bending tests with a Chevron notch at room temperature were conducted to investigate their mechanical properties. The primary phase was Mo solid solution (Mo-ss) or ZrC depending on Mo/ZrC compositional ratio. After the primary phase crystallization, Mo2B, Mo5SiB2 (T-2), Mo-ss+ ZrC eutectic, Mo-ss+ T-2 eutectic and/or Mo-ss+ Mo3Si+ T-2 eutectic were crystallized out during solidification. Mo2B and/or Mo3Si dissolved during the heat treatment in some alloys. The ZrC-added Mo-Si-B alloys had higher high-temperature strength compared with the ternary Mo-Si-B alloys even though ZrC-added Mo-Si-B alloys contained less volume fraction of the T2. Besides, the ZrC-added Mo-Si-B alloys exhibited better fracture toughness than that of ternary Mo-Si-B alloys, reaching 20.2 MPa(m)(1/2). Therefore, this study found that ZrC plays a significant role in improving high-temperature strength and fracture toughness in Mo-Si-B alloys.