Formation mechanism of coronal composite secondary phase in titanium-zirconium-molybdenum alloy

The coronal composite secondary phase has a high mismatch tolerance with the molybdenum matrix. TiO₂ particles located within the coronal structure that provide a semi-coherent interface with a mismatch degree of 8.70%, and ZrO₂ particles located outside the coronal structure that provide an incoherent interface with a mismatch degree as high as 41.61%. The ZrO₂ particles of the coronal composite secondary phase are partially attached to the TiO₂ in a coronal structure, which endows the ZrO₂ with the molybdenum matrix's higher interfacial bonding force. Titanium sulfate and zirconium nitrate are realized the mixing of Ti/Zr, TiO₂/ZrO₂ molecules at atomic levels. Compared with Ti, Zr is more easily combined with oxygen, which leads to Zr in Ti/Zr solid solution being attracted by oxygen at high temperature to form ZrO₂. The small addition of zirconium element lacks nucleation particles to form of ZrO₂, so ZrO₂ can only adhere to more TiO₂ particles and nucleate, forming the second phase of the coronal composite structure. This study can guide the design of high-performance secondary phase strengthening alloys.