Thermodynamic Modeling and Mechanical Testing for the Multiphase Mo-Si-B-X (X=Ti, Zr, Hf) Alloy for High Temperature (1300ºC-1500ºC) Services

CompuTherm, LLC in collaboration with Oak Ridge National Laboratory proposes to develop a modeling tool that can be used to understand the effect of Ti, Zr, and Hf addition on the improvement of ductility of the (Mo) phase in the Mo-Si-B system. The tool will be developed by integrating thermodynamic modeling with mechanical testing. Thermodynamic descriptions of the Mo-Si-B-X (X=Ti, Zr, Hf) systems will be developed using the state-of-art Calphad approach. Using these descriptions, we can calculate phase equilibrium and related information and determine the Si solubility in the (Mo) phase as a function of Ti, Zr, or Hf concentration, which will lead us finding ways of reducing the embrittle silicon concentration in the (Mo) phase. Such calculations will also reveal new heterogeneous phase equilibria that will form other than (Mo)+Mo3Si-T2-Mo5SiB2 due to the addition of Ti, Zr, or Hf. Quaternary alloys with potential combined optimum properties will be identified for experimental study including alloy fabrication and homogenization, microstructural characterization, and mechanical testing. This work will provide key input for the development of deformation model, and is critically needed in accelerating alloy design and property optimization of the Mo-Si-B-X (X=Ti, Zr, Hf) alloys.