Unveiling the Intricacies of a Ductile‐Phase Toughened Intermetallic: An In‐Depth Exploration of a Eutectic Mo–Si–Ti Alloy and its Mechanical Behavior

Herein, the development of directional solidification for a novel high‐temperature Mo–20Si–52.8Ti (at%) ternary alloy using a modified Bridgeman type apparatus is presented. The resulting alloy exhibits a microstructure consisting of a body‐centered cubic solid solution (BCC_ss) and a hexagonal silicide (Ti,Mo)₅Si₃ with approximate volume fractions of 50% for each phase. The phases exhibit a crystallographic orientation relationship with and . Different solidification velocities are imposed, which reveal an inverse relationship to the lamellar spacing according to a Jackson–Hunt type scaling. Mechanical characterization using Vickers indentation demonstrates that the BCC_ss accommodates plasticity through dislocation motion, while the silicide phase exhibits high hardness and brittleness, serving as a crack initiation site. Crack propagation is arrested and deflected at the interface to the BCC_ss. Fracture toughness measurements via indentation yield a fracture toughness of 3.7 MPa√m for the silicide, somewhat higher than previously reported values for Nb‐, Mo‐, and Cr‐based silicides at room temperature. The directionally solidified specimens show an enhanced fracture toughness attributed to a greater BCC_ss length scale; thus, combining the ductile and hard phases results in a ductile‐phase toughened intermetallic composite. The findings open up new possibilities for the design of advanced intermetallic composites with improved toughness performance.