The combustion behavior and mechanism of Ti14 titanium alloy are studied by promoted ignition combustion tests at different oxygen pressures in this paper. The burning velocity increases at higher oxygen pressures and also increases with longer burning times instead of a constant at the same pressure. The Cu atoms are found enriched in two zones—i.e., the heat affected zone and melting zone during the combustion process—which can prevent the diffusion process of oxygen atoms. The different combustion behavior of Ti14 and Ti-Cr-V alloys is basically controlled by the characteristics of phase structures and chemical reactions.

In this paper, a new type of hot-work die steel with excellent high-temperature mechanical properties at 700 °C was designed based on the traditional 25Cr3Mo3NiNb steel with the help of Thermo-calc software. The effects of C, Cr, Mo, W and V on the types and mass fractions of carbides were studied. Phase diagram calculation revealed that with the increase of V and W contents and the decrease of Cr content, the precipitation temperature and the mass fraction of M₂₃C₆ carbides decreased. Meanwhile, the mass fraction of MC carbides increased as the Mo content decreased. Based on the thermodynamic calculation, new material 25Cr3Mo2NiWVNb steel was designed. Compared to the 25Cr3Mo3NiNb steel, more finely dispersed MC and M₂C carbides with high thermal stability, as well as fewer M₂₃C₆ carbides with low thermal stability, were precipitated in the new steel. The high-temperature tensile showed that the new steel showed high thermal stability and strength even at 700 °C. The high-temperature strengthening effect might be ascribed to the fine and stable nano-scale MC and M₂C carbides which precipitated during tempering.