Study On Thermal Behavior Of Ti-3573 And Ti-3873 Alloys

Titanium and titanium alloys have been selected by the aerospace industry for their high temperature and corrosion resistance.At present,conventional titanium alloys are gradually unable to meet the required performance requirements.In this paper,TA2,TC4,Ti-3573 and Ti-3873 alloys are mainly used for experiments.The microstructure and mechanical properties of titanium alloys are studied by changing the cold-rolling and heat treatment process parameters and using various analysis methods.The main work of the experimental part in this article is as follows: First,the three types of alloys are treated separately according to the different properties of the three types of alloys,and the microstructure and performance characteristics of the new metastable ?-type titanium alloy are compared and studied.Secondly,different cold rolling and annealing process parameters are designed for Ti-3573 and Ti-3873 alloys,and their microstructures are controlled through different thermal behaviors after cold rolling to improve their comprehensive mechanical properties.Finally,an aging treatment process was developed based on the aging temperature interval and time interval to investigate the thermal behavior and the number and shape of the precipitated phases of the two new titanium alloys at different temperatures and different time periods,and to further improve their comprehensive mechanical properties.The results show that:(1)Compared to TA2 and TC4 alloys,due to the effect of ?-phase stabilizing elements,Ti-3573 and Ti-3873 alloys can maintain a single ?-phase during rapid cooling after ?-phase transformation,and with the alloy as the molybdenum equivalent in the composition increases,hardness and strength increase.(2)A large number of slip bands and twin bands are generated in the microstructure of Ti-3573 and Ti-3873 alloys after cold rolling.When annealing the two alloys in the ? + ? phase region,A small amount of ? phase is preferentially precipitated on the slip bands and twin bands.These slip bands,twin bands,and primary ? phase increase their Vickers hardness,yield and tensile strength.When the two alloys are annealed in the ? phase region,the average grain size of the two alloys after complete recrystallization is smaller.Due to the effect of fine grain strengthening,the yield and tensile strength are significantly improved compared to before cold-rolling.(3)After aging treatment,the two alloys annealed in the phase region of ? + ? phase precipitate a large amount of granular or spherical ?,and the band-shaped structure and grain boundaries grow into needle-like or lamellar ?.The mechanical properties are significantly improved.The Ti-3573 alloy has a higher Vickers hardness of 446.8 HV,a tensile strength of up to 1733.2 MPa,and an excellent plasticity of 15.9%.The Ti-3873 alloy has a Vickers hardness of 442.6 HV and a tensile strength of 1569.7 MPa with 12.1% plasticity.In the aging treatment of the two alloys in the annealed state in the ? phase region,the ? phase precipitates at the grain boundaries to form flaky ?GB first,then precipitates granular ? in the grains and grows into V-shaped fine needles.Ti-3573 alloy's maximum hardness is up to 438.9 HV,the tensile strength is up to 1569.3 MPa,and at the same time,it has a strength plasticity match with an elongation of 10.1%.The Ti-3873 alloy has a Vickers hardness up to 440.5 HV and a tensile strength up to 1466.7 MPa with an elongation of 12.9%.