Study On Smelting Preparation And Properties Of β-series Titanium Alloys

Ti alloy is widely used in aerospace,Marine equipment,modern new energy equipment and other fields because of its advantages such as low density,good corrosion resistance,medium and high strength,good plasticity and toughness.However,due to the harsh working environment,theβ-series titanium alloy based on titanium molybdenum is prone to oxidation and corrosion in different environments,which leads to the failure of parts and restricts its application.In this paper,Ti-15Mo-Cux titanium alloy ingots（x=2,4,6,8,11,13,15,20,25mass ratios）were prepared by adding Cu elements to Ti-15Mo asβmatrix,and their microstructure,hardness,corrosion resistance and oxidation resistance in the as-cast and after heat treatment were investigated.First,the alloy preparation process was studied by melting in a water-cooled copper crucible non-self-consuming vacuum arc melting furnace in combination with the existing melting process of titanium alloys and the corresponding conditions in the laboratory,and the Ti-15Mo-Cux（2,4,6,8,11,13,15,20,25）series alloys were completed,numbered（Cu2,Cu4,Cu6,Cu8,Cu11,Cu13,Cu15,Cu20,Cu25）10 alloys were prepared.Secondly,the effects of the microstructure of the alloys in the as-cast state and after solid solution ageing treatment and the mass ratio of Cu on the phase transformation of the alloys were compared by applying X-ray diffraction（XRD）,optical microscopy（OM）,scanning electron microscopy（SEM）and energy spectroscopy（EDS）,and it was found that the Ti-15Mo-Cux alloy gradually formed a metallic compound cytosolic phase from a singleβphase with the increase of Cu mass.It was found that the Ti-15Mo-Cux alloy gradually formed a metallic compound cellular phase with the increase of Cu mass,and the alloy changed from coarseβgrains and fineαorganization to long ordered rod organization after solid solution ageing treatment;the trend of hardness change of Ti-15Mo-Cux alloy after as-cast and solid solution ageing treatment was discussed.The results showed that the microstructure and hardness of Ti-15Mo-Cux alloy were significantly refined and improved after solid solution ageing treatment,and the alloy composition Ti-15Mo-Cu4 had the highest hardness in the Ti-15Mo-Cux system.Again,through high-temperature oxidation experiments,the oxidation performance of the eight alloys of（Cu2,Cu4,Cu6,Cu8,Cu11,Cu13,Cu15）at 700°C,750°C,and800°C,respectively,was studied,and it was concluded that the oxidation kinetics of the alloys conformed to the parabolic and linear laws;XRD analysis of the oxidized oxide films of the alloys after oxidation was performed,and it was pointed out that they were mainly composed of Ti O₂,Cu₂O composition;the high-temperature Gibbs free energy equation for oxide change was derived to reveal the alloy oxidation law.The results show that the three alloy ratios of Ti-15Mo-Cu2,Ti-15Mo-Cu4 and Ti-15Mo-Cu6 have good oxidation resistance at three temperatures.Finally,the microstructures of the eight alloys（Cu2,Cu4,Cu6,Cu8,Cu11,Cu13,Cu15）after corrosion under different corrosive solution conditions were studied by corrosion resistance experiments,and the corrosion rates were calculated.The results show that the Ti-15Mo-Cux system alloy has certain corrosion resistance,and the two combinations of Ti-15Mo-Cu2 and Ti-15Mo-Cu4 have the best corrosion resistance under acidic conditions.In conclusion,among the Ti-15Mo-Cux series alloys,Ti-15Mo-Cu4 alloy has the best hardness,corrosion resistance and oxidation resistance.